CLIMATE CHANGE

August 15, 2022

SUPERFORECASTING

LONG-TERM RISKSAND CLIMATECHANGE

Report prepared by Good Judgment Inc

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Good Judgment Inc is the outgrowth of a four-year, $20 million research project run by
the US O ice of the Director of National Intelligence to see whether crowd-sourced
forecasting approaches could deliver more accurate forecasts than existing approaches.
The result was decisively positive, with Good Judgment’s methodology generating up to
an 85% increase in accuracy.1 In 2013-2014, Good Judgment was compared to 4,300
members of the US Intelligence Community (IC). On the same set of 139 geopolitical
forecasting questions, Good Judgment was 34.7% more accurate, although the IC had
access to classi ied information while making their forecasts.2 Good Judgment continues
to work with clients and partners to push the frontiers of forecasting accuracy even further.

METHODOLOGY
To generate the most accurate forecasts available, Good Judgment works with some 180
Superforecasters from around the world whose forecasting accuracy placed them in the
top 1-2% of the more than 100,000 forecasters who took part in the US Government
research project or on the public forecasting platform Good Judgment Open.
These Superforecasters are a diverse group, with professions ranging from inance tointelligence, management to medicine, and psychology to archaeology. Most have one ormore graduate degrees, and a third have doctorates. A third of Superforecasters live
outside of the United States and most speak two or more languages.
Good Judgment’s Superforecasters analyzed 22 questions related to the long-term risk ofclimate change. The questions were presented to the Superforecasters under thefollowing categories: future levels of emissions, number of deaths caused by severe
weather events (heat, storms, loods, and drought), food (cereal yields and food prices),
future of the Amazon biome, cost of solar energy, and the risk of extinction where climatechange is a cause thereof. These questions were examined irst through a narrower set ofobjectively falsi iable forecast metrics, followed by a wider discussion of the overarchingquestions and alternative scenarios.
Halfway through the project, ten subject matter experts examined the initial forecasts
and provided the Superforecasters with feedback and additional sources, after which the
1 https://journals.sagepub.com/doi/abs/10.1177/1745691615577794
2 http://www.sjdm.org/journal/17/17408/jdm17408.pdf

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Superforecasters had the opportunity to consider and react to the expert feedback. Thiskind of exchange between subject matter experts and forecasting experts leads to themost accurate, well-considered forecasts. We are grateful for the expert feedback from
Matthew Burgess, Matthew Ives, Linus Blomqvist, Katrin Burkart, Patrick Kinney, Kieran
Hunt, Ertug Ercin, Benjamin I Cook, Chris A Boulton, Andrew Watson. Over the course ofthis project, 51 Superforecasters made a total of 1,377 forecasts and 1,821 extended
comments. This summary is accompanied by 22 comment-format reports that include all
Superforecaster commentary for each question.
This summary is structured as follows:• Each category of questions is presented in a
separate section.

• Each section starts with the question, or theforecast metric—a suf iciently narrow,speci ic, and actionable question that can beobjectively and unambiguously resolved
with an answer in the given time frame. It isfollowed by resolution criteria.

• Accompanying each forecast metric is atable with two to ive potential outcomesto which the Superforecasters assigned

numeric probabilities. Those probability
values are aggregated3 and are called the“consensus forecast.”• The consensus forecast and the key

arguments are then summarized, includingarguments behind the Superforecasters’
forecasts, key areas of uncertainty, anddevelopments that, if they occurred, would
make the Superforecasters change theirforecasts. Examples of Superforecaster
commentary are set o with quotation
marks.

Good Judgment’s team of Superforecasters for this project included a smaller “RedTeam”—Superforecasters who did not themselves forecast, but rather who critiqued theteams’ thinking and suggested alternative arguments for consideration. Red Team
members highlight new details or new arguments that, in their view, forecasters had not
fully considered. This results in forecasts that are better informed by multiple data sets
and perspectives.
Superforecasters are not required to agree with each other on their forecasts or theirreasoning. Our report, therefore, is an e ort to describe the main lines of thinking of adisparate group of forecasting experts.

3 Aggregation of probability estimates of many individuals to form a consensus probability estimate was shown to resultin more accurate forecasts (wisdom-of-the-crowd e ect). For further information, please see our journal articles onaggregation algorithms here.

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TABLE OF CONTENTS
Methodology

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Table of Contents

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EMISSIONS ...............................................................................................................................6
Q1: What will be the total carbon dioxide emissions in the world in 2023, according to Our
World in Data (OWiD)?
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Q2: What will be the total carbon dioxide emissions in the world in 2050, according to
Our World in Data (OWiD)?

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FOOD .......................................................................................................................................13
Q3: What will be the yield of cereals per hectare in the world in 2023, according to the
Food and Agriculture Organization (FAO)?
13
Q4: What will be the yield of cereals per hectare in the world in 2050, according to the
Food and Agriculture Organization (FAO)?
16
Q5: Assuming that the Earth’s global average surface temperature increases by 7°C in
2100 as compared to 1880, what will be the yield of cereals per hectare in the world in
2100, according to the Food and Agriculture Organization (FAO)?
19
Q6: What will be the FAO Food Price Index value for 2023?

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Q7: What will be the FAO Food Price Index value for 2050?

24

Q8: Assuming that the Earth’s global average surface temperature increases by 7°C in
2100 as compared to 1880, what will be the FAO Food Price Index value for 2100?
28
HEAT .......................................................................................................................................30
Q9: How many heat-related deaths will there be in the world in 2023?

30

Q10: How many heat-related deaths will there be in the world in 2050?

33

Q11: Assuming that the Earth’s global average surface temperature increases by 7°C in
2100 as compared to 1880, what will be the decadal average of annual heat-related
deaths in the world from 2091 to 2100?
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FLOODS ..................................................................................................................................39
Q12: How many deaths will be caused by loods in the world in 2023, according to Our
World in Data (OWiD)?
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Q13: How many deaths will be caused by loods in the world in 2050, according to Our
World in Data (OWiD)?
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Q14: Assuming that the Earth’s global average surface temperature increases by 7°C in
2100 as compared to 1880, what will be the decadal average of annual deaths caused byloods in the world from 2091 to 2100, according to Our World in Data (OWiD)?
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STORMS ..................................................................................................................................47
Q15: How many deaths will be caused by storms in the world in 2023, according to Our
World in Data (OWiD)?
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Q16: What will be the decadal average of annual deaths caused by storms in the worldfrom 2041 to 2050, according to Our World in Data (OWiD)?
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DROUGHT ...............................................................................................................................52
Q17: What will be the decadal average of annual deaths caused by drought in the worldfrom 2041 to 2050, according to Our World in Data (OWiD)?
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Q18: Assuming that the Earth’s global average surface temperature increases by 7°C in
2100 as compared to 1880, what will be the decadal average of annual deaths caused bydrought in the world from 2091 to 2100, according to Our World in Data (OWiD)?
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FUTURE OF THE AMAZON BIOME ..........................................................................................57
Q19: What percentage of the current Amazon biome will transition to savannah or
grassland as of 2100?

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COST OF SOLAR ENERGY.......................................................................................................61
Q20: What will be the midpoint for unsubsidized solar photovoltaic levelized cost ofenergy (LCOE) in 2023, according to Lazard?

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EXTINCTION ...........................................................................................................................65
Q21: Will climate change be a cause of human extinction by 2100?

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Q22: Will climate change be a cause of human extinction by 2300?

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EMISSIONS
Q1: WHAT WILL BE THE TOTAL CARBON DIOXIDE EMISSIONS IN THE
WORLD IN 2023, ACCORDING TO OUR WORLD IN DATA (OWID)?

Resolution Criteria: The outcome will be determined using data as reported by OWiD. In
2020, total carbon dioxide emissions in the world were 34.81 billion tonnes.

Base Rate
Prior to a decrease induced by the Covid-19 global pandemic, total CO2 emissions
increased every year in 2016-2019, from 35.45 billion tonnes in 2016 to 36.7 billion
tonnes in 2019. The top 10 emitters are: China, US, EU, India, Russia, Japan, Iran, South
Africa, Indonesia, Canada and Brazil.

“

2019 was the last Covid-free year, and it was 36.7 (answer option C). I assume that this year, we
will roughly revert to the post-Covid norm, after a Covid-related fall, and so option C is themost likely. Even with the Covid fall in 2020, we were barely into option A, so I think option A canbasically be ruled out, even if there is a recession. Option E would require a very rapid rise relative
to past rises, so it is unlikely as well.”6f“China emits more than one-quarter of the total global CO2 emissions and its trend is de initely
upward, so it is key to this forecast.”

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Upward Pressures(i.e., factors that would lead to higher total emissions)
Availability of and demand for fossil fuels: The Superforecasters expect continued
reliance on fossil fuels in the developing world and China and a temporary increase in
the use of such energy sources in Europe in 2023.

““

Chinese coal plants are running to make goods that are sold to the US/Europe, shiftingemissions from West to East. Chinese energy usage will depend on the West’s demand.”The large increase in natural gas prices is a key factor. Coal plant retirements are being
postponed. Analysts at ICIS projected 5% higher electricity emissions in Europe as a result.
Given that the EU power sector accounts for just over 1 billion tonnes, that means an increase of
0.05 billion tonnes. Chinese mine output is also planned to expand. All in all, I am assuming that2022 will be a small increase as coal use outweighs economic slowdown, leading to somewherearound 37. I guess that 2023 would then be anywhere between a 2% decrease or a 2% increase.”“

The ambitious plans to shift away from the dependency on Russia will take at least three years,
and in the meantime, dirtier alternatives are being used, e.g., life extension for mothballed coalplants.”“A recession and higher energy costs may be o set by more use of cheaper, dirtier fuels in
2023.”

Lack of policy focus: Geopolitical instability in Europe, political battles in the US, andin lation in much of the world will lead to less focus on climate-focused measures inthis period.

““

Given that Europe is going back to using coal, a war rages in which Russia is involved, andin lation is eating budgets worldwide, it appears climate ixes are on the backburner.”

Positive impacts will be increasing political pressure and increasing technology solutions(minor in this time frame). Negative impact will be China/Russia vs US/Europe political battles
giving cover to inaction/increasing fossil fuel usage.”

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Downward Pressures(i.e., factors that would lead to lower total emissions)
Economic slowdown: A recession, and especially a downturn in the Chinese economy,e.g., due to Covid lockdowns, could lead to lower CO2 emissions.

““

A modest increase from the estimated 36.4 tonnes in 2021 is likely, but not certain. A recession,
paired with changing consumer behavior due to high energy costs, could result in a decline.”

While it is true that Europe in particular is taking desperate measures to keep the lights on,which mostly include more coal- ired power, we will probably see a major contraction ineconomic growth in the developed world and even China. And that will be especially true inenergy-intensive industries.”“

The inal result of this question will depend on how much China’s energy usage has been andwill be a ected by its Covid lockdowns.”

General trend toward clean energy: Green transition is not expected to have a majore ect in this period.

“

It only takes 3% annual growth to get to answer option D. Serious reductions in CO2 emissions
won’t happen for another 10 years or so.”

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Q2: WHAT WILL BE THE TOTAL CARBON DIOXIDE EMISSIONS IN THE
WORLD IN 2050, ACCORDING TO OUR WORLD IN DATA (OWID)?

Resolution Criteria: The outcome will be determined using data as reported by OWiD. In
2020, total carbon dioxide emissions in the world were 34.81 billion tonnes.

Base Rate
Business-as-usual projections put the increase in global carbon dioxide emissions in
2050 to just over 43 billion tonnes. Status quo is around 35 billion, with an upward
trend.

“

I’m having a hard time imagining this not resolving in (at least) answer option D. The only
factors that have slowed down growth in the last 30 years were a global recession and a global
pandemic. I think it would take some kind exogenous shock to shift away from oil.”“

Compared to year 2000, in 2019, according to OWiD, Europe and the US were down about 12%,
while India and China were up about 170% and 205%, respectively. Asia on the whole is also up
about 125%.”

Upward Pressures(i.e., factors that would lead to higher total emissions)
Increased demand for energy: Economic growth, population growth, higher global
temperatures all suggest an increased demand for energy, much of which comes fromfossil fuels.

“

If you look at the list of the largest producers of oil, gas, or coal, some countries don’t seem tohave a choice in this timeframe to substantially reduce their domestic consumption of fossil
fuels. In those places, a growing population and growing domestic demand for energy are going

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to continue, while foreign demand for fossil fuels will slowly fall. Growing incomes will drive moredemand for energy. Heat will increase the need for air conditioning. What will make poorer
countries invest massive amounts to convert away from cheap and abundant domestic energy
sources? The less the rest of the world buys their fossil fuels, the cheaper fossil fuel energy will
become on their domestic markets and the stronger the incentive for them to continue to use
them.”“

I’m taking it as a given there will be an increased need for energy by 2050. And it’s still going tobe easier to use coal and drill for oil than use cleaner energy sources. Even with pronounced
and dangerous consequences in severe weather and whatever else unpredictable will happen by
2050, it won’t be enough to outweigh the need already baked in.”““Coal usage in lower-income countries will not be reduced. The capacity de icit is so large thatwhile I expect an increase in renewables, I do not expect a decrease in fossil fuels.”With China planning to peak CO2 emission in 2030, and India and other countries with large
populations certainly following that path, I’d say even under the best circumstances, spending
some time in >40 billion territory (answer option E) in the next 10 years is a virtual certainty.”

Positive feedback loops: One source of uncertainty that could push emission levels
higher is the potential triggering of positive feedback loops in some areas of the world.

“

I think a major uncertainty is the behavior of major carbon sinks. Tundra, bogs, the oceans, etc.
Global warming could trigger outgassing from carbon sinks in a positive feedback loop.”

Lack of political will to reduce emissions: Many Superforecasters expect politicalfragmentation, polarization, and lack of international cooperation to continue in thisperiod (NB: dissenting arguments are o ered in the Downward Pressures section
below).

“I am fairly skeptical about how seriously governments will attempt to lower emissions, so for astarting estimate, I’m just going to take the ’stated/current policies’ forecasts, average them,and then move it down a bit to re lect the fact that only some attempts at lowering emissions will
likely occur. Averaging them gets us 38 billion, which would be the upper end of answer option D,
but not that far from answer option E.”

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Short of external actors forcing lower-income countries to switch over, and paying for it, I don’t
see how large parts of the world transition to renewables by 2050. My guess is that at some

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point we reach a tipping point where that happens; and that tipping point will be further in the
future than seems reasonable today.”“

China’s active and dramatic cooperation would be much needed to get to C. Is that a serious
possibility? I would need to see them ceasing to add capacity before I could even entertain
that, and they are currently doing the opposite.”““

If the decrease in emissions depends on our leaders’ actions, one has to wonder if other needs
will push climate down the list of priorities.”
Economic constraints, imposed by a period of global slowdown, or tensions caused byinequality, could use up the political capital needed to sustain and intensify climate policy.”

Downward Pressures(i.e., factors that would lead to lower total emissions)Technological advancement: As technologies continue to develop, many
Superforecasters expect the issue of renewable intermittency to be addressed and thecost of renewable energy to decrease signi icantly. This, in turn, will incentivize andspeed up the green transition.

““

Green energy is getting cheaper than fossil fuels and batteries are getting better. The
acceleration of the energy transition is inevitable and key milestones are now in sight.”

Energy projections have generally underestimated clean energy cost declines (as well as actual
deployment). Decarbonization is becoming cheaper than previously expected, which alsomeans that government pledges have become much easier to meet.”International commitment to reduce emissions: A minority of just under one third ofSuperforecasters believe climate policies, propelled by cheaper clean energy and by ageneration of climate-conscious voters and policymakers, will help curtain CO2emissions by 2050.

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Steel and cement account for about 15% of global CO2 emissions; I would expect
technological gains here in reducing the carbon emissions quite substantially by 2050.”

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The overall trend is toward more climate policy, not less, despite temporary setbacks. This
includes policies that are not explicitly about climate change but about local bene its. One
example of a climate action co-bene it that may be the actual driver of emission reductions is air
quality, which has been important in China, India, and other nations that prioritize quality of life
for their growing middle classes. To wit, before 2015, we were headed for a warming of around
4C. Paris put us on track to 2.7C. Glasgow is about 2.4C.”“

I think the war in Ukraine will be a strong driver of better energy security, and renewables will
form a good part of this. I also felt at COP26 for irst time a real urgency was palpable among
political leaders. Covid took this away, but I expect it to have returned well before 2050, so thatmeaningful actions will be in place by then.”“

We could see a dramatic increase in commitments to reduce CO2 emissions, combined withcheap clean energy. Clean energy has consistently beaten ambitious cost reduction
projections.”

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FOOD

Q3: WHAT WILL BE THE YIELD OF CEREALS PER HECTARE IN THE
WORLD IN 2023, ACCORDING TO THE FOOD AND AGRICULTURE
ORGANIZATION (FAO)?

Resolution Criteria: The outcome will be determined using data as reported by the FAO.
In 2020, the yield of cereals per hectare was 4.07 tonnes.

Base Rate
A linear upward trend with stochastic variations around it has been the norm in thepast 60 years. The Superforecasters, therefore, have identi ied 4.1-4.25 tonnes/ha as
their baseline.

“

When I plug the data into Excel from the past ten years available (2011-20) and extend thetrendline from the past 10 years to 2023, I get a value of ~4.25. So if 2023 is a good year, I see a
D bin resolution as entirely possible.”

The trend has been up due to advances in agricultural inputs and techniques.

“

The graph shows the FAO Total Cereals worldwide in tonnes per hectare from 1961-2020. The
plot is disarming in that it shows six decades of improvement in the world’s ability to increase
its cereals output. This is nearly a threefold increase over time due to better seeds, bettermethods, better equipment and likely because of better storage and distribution.”f

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Downward Pressures(i.e., factors that would lead to lower yields)
Because this question focuses on a single year, the outcome is susceptible to outlier
events. For instance, yield losses on already planted areas are possible due to severe
weather events.

“

Mitigating the upward trend have been, over the last three decades, a drier climate and more
extreme temperatures and weather events, e.g., loods and storms. The war in Ukraine will no
doubt disrupt the results for 2022, and the pandemic for both 2021-2022. 2023 could very well bea recovery year from the war and the pandemic. On the negative side, drier and more extreme
weather will likely weigh against crop results.”

Other disruptive developments could play a role, including the war in Ukraine,
although its impact will be smaller and less direct than might be expected at irst
glance (in particular because the relative size of Ukraine’s grain production is only asmall fraction of the global igure).

“

It has been mentioned that yields in Ukraine are higher than average, so a decrease of
production there can be expected to lower average yields; however, Ukraine is not that far fromthe average. A bigger impact would come from a hypothetical change in production in the US,
where yields are very high.”“

While the war in Ukraine will continue, its global impact on cereal yields will be real but
modest.”Higher prices for fertilizer and fuel, on the other hand, as a result of Russia’s invasionof Ukraine, may have a larger impact.

“

Long-term cereals production per hectare is increasing, and it makes sense to think it willcontinue in at least the near future. That said, Russia’s invasion of Ukraine is harming
production in both countries due to the con lict and sanctions. There are also impacts around theworld as other farmers can’t get inputs like fertilizer, normally provided by those countries. Even if
the con lict ends this year, disruptions will ripple out for some time, and this makes me think 2023
will not be a good year either.”

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Fertilizers use natural gas, which has seen a price spike in the wake of the invasion of Ukraine.
Fertilizer prices have risen accordingly. Prices of gasoline and diesel impact farming
economics as well.”“

Sanctions on Russia could limit supplies of pesticides, seeds, and fertilizer, leading to lower
yields. FAO also has a more extreme scenario: if the war continues, and fertilizers become
scarce, higher costs of energy could also reduce yields.”

Upward Pressures(i.e., factors that would lead to higher yields)
The Superforecasters point out the impact of higher fertilizer costs may not be
unidirectional because yield per hectare can remain stable, or even increase, evenwhen the overall cultivated area decreases.

“

A key unknown I am wondering about is whether the current cost issues will in fact have theopposite e ect and actually increase yields (rather than the currently hypothesized reduction).
What if farmers respond to the price spikes by planting less and focusing on making the most of asmall area of land?”“Fertilizer shortage, supply chain issues, and potential increased climate shifts are factors thatshould reduce production, but could they actually increase the yield? For example, farmers
may plant less and spend their resources on getting the most out of the land they choose tocultivate in 2023.”“

A low yield in Ukraine alone would not impact the world yield signi icantly. Fertilizers can be abigger issue worldwide, but it may have e ect in the longer term and may not have adevastating e ect in the irst year.”

Ongoing technological advancement is likely to o set many of the negative trends.

“

While climate change has tremendous potential to reduce yields of speci ic crops, such as
wheat and maize, other crops, such as millet, will experience few impacts. Additionally,
identi ication and implementation of strategies to mitigate climate impacts (breeding, irrigation,
fertilization, and increasing the cultivation area of tolerant crops) will potentially minimize any
reduction in yields. Localized weather events that devastate yields in a speci ic region will likely
be o set by improved yields elsewhere, at least in the time period of this question.”

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Q4: WHAT WILL BE THE YIELD OF CEREALS PER HECTARE IN THE
WORLD IN 2050, ACCORDING TO THE FOOD AND AGRICULTURE
ORGANIZATION (FAO)?

Resolution Criteria: The outcome will be determined using data as reported by the FAO.
In 2020, the yield of cereals per hectare was 4.07 tonnes.

Base Rate
The upward trend has been remarkably consistent in the past 60 years, with someluctuations due to, e.g., yield losses (down) or bumper crops (up).

“The trendline for cereals production has been surprisingly linear and given that it incorporates
60 years of history, I have no reason to think that the next years can signi icantly alter it,
barring some large, unforeseen, and global crises or technological innovation that revolutionizes
cereals yield. Thus, extrapolating to 2050, the trend would indicate 5.44 tonnes per hectare.”Upward Pressures(i.e., factors that would lead to higher yields)
Population growth: Increases in yield have so far been correlated with population
growth, and many Superforecasters expect the world to continue being able to feeditself in 2050.

“

In the last 30 years, the increase in yield is much aligned to the increase in population. The
world population of 5.3 billion in 1990 has increased by 47% to 7.8 billion, while yield has
increased by 46%. The correlation has been stronger or weaker, but present throughout the last
25-30 years. Based on UN latest projection for 2050, there will be 9.7 billion people, an increase of
25% vs 2020. A 25% increase in yield would mean 5.09 tonnes per hectare.”

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“

People will do whatever is needed to eat, so adaptation here will be as fast as necessary.
Costly, yes. Disruptive, yes. Impact on crop yields? Not sure.”
Necessity is the mother of invention: yields will need to improve to feed the masses.”

Technological development, including in lower-income countries (LIC): To ful ill thegrowing demand for food, particularly in the face of increasing climate change e ects,
humanity will continue to devise solutions, such as better seeds or more e icientfarming techniques. Innovation may have its limits, and yields may plateau where its
e ects have maxed out, but the Superforecasters see enough room for advances inthis timeframe.
There are still crops and regions utilizing their capacity at 45-70%, meaning that opportunities
remain to boost yields in some areas.”
The greatest gains in productivity will come from increased farm sizes and economies of scalein LIC. Migration will control the speed, as it did during the industrial revolution.”

To reach Bin E, the global yield would have to approximate the current yield in the US. I expect
yields in Africa to increase substantially. Investment in African agriculture from China and the
Gulf states will be made both as sound inancial decisions and a need to feed their own
populations through imports. An example of potential rapid increase through technology is
Romania. From 1991 until 2016, their yield was between 2 and 4 tonnes, but shot up to 6.006 by
2018. A change in the type of seeds used and farming methods have dramatically increased
production.”“

The straight-line regression of the very consistent trend of the last 60 years would estimate
5.40 in 2050. In 2050, increasing farm technology will likely still be able to overcome andadapt to climate change. But the rate of linear increase has been so consistent for so long that I
don’t think we will be able to exceed it by much.”

Downward Pressures(i.e., factors that would lead to lower yields)
Climate change: Climate change e ects can limit the extent to which technologicaldevelopment will improve yields. Not all climate change e ects will be negative,

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however (e.g., CO2 fertilization e ect). While overall net negative, climate change will
not be catastrophic in 2050, according to most Superforecasters.

“

On the one hand, global warming-caused heat stress, crop diseases, drought, looding,erosion, pests, and unpredictable weather (climate weirding) will reduce output per hectare.
On the other hand, CO2 fertilization, warmer climates, and longer growing seasons will bene itsome crops in some regions of the world. Agricultural regions near the equator will be devastatedwhile the Global North will see some modest gains in agricultural productivity. This forecast is myguess about how these countervailing trends will balance out in the end. We should see increased
productivity of C3 (rice) and C4 crops (wheat, maize) in a high emissions scenario before the full
negative e ects of climate change start kicking in.”“

The likelihood of catastrophic climate impacts in the 30-year timeframe is not as high, so I
don’t think we’ll see much of a deviation from the recent trend. I could see technologicalimprovements drive a faster pace, but also some headwinds from climate change.”

Outlier events: Because this question focuses on yields in a single year, much like the2023 question, it is susceptible to outlier events in that year.

“

Given that this is another one of those ’point-in-time’ forecasts, it’s still possible for some
unexpected shock that happens to throw o the numbers for 2050 such that they’resigni icantly di erent from 2048 and 2049. And at this point, I think that any shock that could
occur is more likely to result in a Bin A resolution than a Bin E resolution.”

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Q5: ASSUMING THAT THE EARTH’S GLOBAL AVERAGE SURFACETEMPERATURE INCREASES BY 7°C IN 2100 AS COMPARED TO 1880,
WHAT WILL BE THE YIELD OF CEREALS PER HECTARE IN THE WORLDIN 2100, ACCORDING TO THE FOOD AND AGRICULTURE
ORGANIZATION (FAO)?

Resolution Criteria: Measurements of global average surface temperature haveincreased since the 1880. The outcome will be determined using data as reported by the
FAO. In 2020, the yield of cereals per hectare was 4.07 tonnes.
In a scenario envisioning a global average surface temperature increase of 7°C in 2100
above the 1880 levels, the Superforecasters still expect a trendline level of yields(55% probability) with 35% probability for downside risk (5.00 tonnes per hectare or
lower). Accounting for this forecast is, in part, the calculus behind the FAO yield igure:
The land in use in 2100, while undoubtedly smaller in area, may have been made atleast as productive as it is today.

“

The development of heat-tolerant grain varieties, automation, and precision farming become
only more essential/critical if humanity is to cope with a 7°C increase in temperature on top of
population growth. The alternative is increasing levels of food scarcity, starvation, and civil
unrest.”“Given sea level rise impacts, there will likely be less money and fewer resources available forresearch and more devoted towards relocation, and many more wars/mass refugee
movements as a result. There also might be a population collapse as a result of disruption, which
actually might increase yields if production is focused in the most hospitable areas, so really avery wide range of outcomes here.”At 7°C, there probably won’t be much land left to cultivate, but I imagine our technology will besuch that what we still have is extremely productive.”

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Such a change may rather increase yields. I think that in such conditions, there would befurther shift from extensive to intensive farming. It would be much harder for individual farmers
or smaller companies whose yields are lower as they have less capital and use less mechanization
to maintain production in unfavorable conditions. Low-yield areas will be abandoned while newareas for farming will use much more capital and newest technologies as land there will beacquired by huge farming conglomerates which will bring yields up to speed.”On the other hand, con lict is likely to increase under such conditions, and not all
Superforecasters are convinced global cooperation will improve.

“

There’s no question climate change will have a strong negative impact on crop yields under
this scenario. Then there’s the likely human response to the decline in crop yields. I think asociety that allowed a 7°C warmer planet to happen in the irst place isn’t going to be one thatengages in responsible, sustainable, and e icient farming practices. Nor will it be one that assists
the most vulnerable populations.”“

Human con lict is likely to be much more extreme, but whether a major war will be playing out
in 2100 is impossible to accurately forecast. Whether the rising temperatures will beaccompanied by a global breakdown in order and civilized society or helps unify us around acommon threat is also an unknown. The global and national responses to Covid, including
polarization along political lines, however, suggest current lack of cooperation is likely tocontinue.”

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Q6: WHAT WILL BE THE FAO FOOD PRICE INDEX VALUE FOR 2023?

Resolution Criteria: The outcome will be determined using data as reported by the FAO.
For 2021, the real Food Price Index was 125.1.

Base Rate
The index average has been around 100, although it has exhibited some short-term
volatility, including its current level of 125.1 for 2021 on an annual basis. The
Superforecasters expect it to remain elevated in 2023 but moderate somewhat from its
recent highs.

“

We are currently in Bin D, uncharted territory, which is the highest it’s ever been in the 60-year
history of the index. Furthermore, the monthly numbers are coming down. I don’t see things
getting much worse, and I don’t see us sitting above 150 for prolonged periods.”“

While world food prices will moderate in real terms for 2023, they will still remain elevatedrelative to the decades-long trend. That said, the index is bouncy, and a new war, a deadlier
Covid variant, a new lu pandemic, unrest in China, a worsening situation in Ukraine, a run of bad
weather (whether climate related or not) are factors that each could send the index soaring again—or rather keep it up where it is. Whereas smooth geopolitical/pandemic sailing, paired with the
dynamic where high pricing drives increased crop yields and increases in arable land, could
swing the index back to the A Bin—as it traditionally reverted to after spikes.”

Upward Pressures(i.e., factors that would keep food prices high)E ects of the war in Ukraine: The war in Ukraine has reduced the global wheat cropand has led to increased cost of natural gas, which a ects fertilizer and fuel costs. As

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the Superforecasters as a group do not expect the situation to be resolved prior to2023, geopolitical factors will continue to exert upward pressures on food prices.

“

The cost and availability of natural gas will likely rise through the winter, as will instability inEurope. Reaching Bin A would require two consecutive years of drops that near the limits of therecent historical record. In 2009, the price dropped ~25, but there were never back-to-back years
like that. Supply shortages will continue to keep prices high. Bin E is unlikely, but the situation isalready fragile so an expansion of the war or serious unrest in major food producing regions of
the world make me hesitant to completely discount another jump.”“

The resumption of grain export from Ukraine happened faster than I expected. On the other
hand, I expect natural gas prices to stay elevated into 2023, as a knock-on e ect of the current
disruptions. This is because even if gas lows increase in 2023, I expect storages to be very low as
Europe draws down during winter (the severity of which is one factor here). High gas prices will
bleed into fertilizer pricing, which will likely lower yields or be passed on to consumers and thus
exert upward pressure on food prices.”

New shocks: Adverse weather conditions, or indeed any new shocks to the system,
would keep the price index level above the historical norm.

“

As long as there isn’t a new disruption in the next 12-18 months, the FAO index should begin to
decrease. Will it go all the way back below 100 like it was in 2020? Probably not. However, I
think it’s more likely that it goes down below 100 than it goes up over 170.”

Downward Pressures(i.e., factors that would reduce food prices in this timeframe)
Reversion to the mean: Many Superforecasters expect a reversion to the mean has
started as the existing risks are becoming priced in.

“

The index value has shot up due to Covid and now Russia’s invasion of Ukraine and subsequent
supply chain shocks. However, I think the shocks have now happened, and the global foodsystem is adapting, and this explains the slow but steady fall in the last three months.”

Recession: A recession, now increasingly expected in late 2022-2023, would have a
cooling e ect on prices, including prices of fertilizer and fuel, leading to a drop in thefood price index.

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The main driver of the food price index in 2023 will be the price of fuel and energy sources,
which will probably fall due to global recession or at least slowdown in economy. It willprobably not get to sub-50 USD per barrel levels, which would guarantee sub-110 food priceindex, but if oil falls to 60-80 USD, food price index level of 110-130 is possible.”“

Cereals price is the most highly correlated with the total index. Although wheat and othergrains have come down in the last couple months, there is still plenty of risk from Ukraine. A
recession in 2023 might bring down prices, but food prices are very inelastic. A new normalmight be in the 120-140 range that we saw from 2011 to 2014.”

Possible end of active hostilities in Ukraine: Some of the e ects of the war in Ukraine
are smaller than might appear at irst glance, but a resolution of the crisis could be adownward pressure on food prices.

“

Lion’s share of world’s cereals production is consumed locally in countries of origin and only
17% is traded internationally. Of those 17%, roughly 10% has been originating in Ukraine. So, aloss of entire Ukrainian export would result in loss of 1.7%-2% of world’s demand. And ups anddowns of 2% in cereals production due to various reasons are not something unusual, and theworld is generally prepared for it keeping stock-to-use ratio at 30% levels.”
If the Ukraine situation is resolved, there might very well be a glut next year.”

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Q7: WHAT WILL BE THE FAO FOOD PRICE INDEX VALUE FOR 2050?

Resolution Criteria: The outcome will be determined using data as reported by the FAO.
For 2021, the real Food Price Index was 125.1.

Base Rate
The index average has been around 100, although it has exhibited some short-term
volatility. The Superforecasters are almost evenly split between two answer options:“Between 80.0 and 115.0, inclusive” (which includes the historic base rate; 35%
probability) and “More than 115.0 but less than 150.0” (which includes current level;
37% probability), with a 22% probability in total for upside risks (i.e., higher foodprices).

“

While there was a long period of stability between 1990 and 2003, the trend since then has
been higher. There have been no years below 80 since 2005, and no years below 90 since2006. Nine of the past 15 years have been above 100. While I believe we will continue to see
cycles of both increase and decrease, I think the general trend during this period will keep theindex above 100, with occasional peaks above 180 due to higher energy prices, extreme weather
events, general in lation in the short term, and con licts leading to reduced supply.”“

I’m guessing the higher post-2007 prices will persist and even modestly increase by 2050. My
underlying assumptions driving that forecast are: (1) crop yield e iciencies will continue to be
driven by industrial agriculture in countries with enough political stability and underlying
infrastructure to sustain them; (2) while this has the potential to exert downward pressure on
pricing, the consolidation also means food prices will remain more vulnerable than in decades
past to storms, looding, and heatwaves, as well as supply chain issues and spikes intransportation costs; (3) there will also likely be 20-30% more people on the earth by 2050, which
will exert upward pressure on (real) pricing both by increasing demand for food and because it
may impact the cost and availability of land. That said, the food price index is bouncy, and even if
the trendline suggests a certain value is likely, that 2050 could be an anomalous year.”

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Upward Pressures(i.e., factors that would keep food prices high)Climate change e ects: Some of the climate change e ects will be felt by 2050, andcan lead to higher levels of the food price index.

“

There will be some climate change impacts by 2050: increased drought, hotter temperatures,some sea level rise, and maybe more severe storms. Vulnerable crops like corn might alreadystart to shift north. I don’t think 100 is the base to which prices will return; there’s probably a
general upward trend. Prices are more volatile than yield, and can jump around quite a bit. Energy
and fertilizer prices will also likely increase, which will also drive the FPI up.”“

There is no question that climate change will impact food prices in 2050. Warming past 2C by
2050 (the likely scenario) will devastate agriculture in the world’s most fertile regions not
simply because drought will become more common but also because farming will become anincreasingly unpredictable enterprise thanks to weird weather (’climate weirding’). Climate
weirding and failed harvests will wreak havoc on food prices.”

Lag in technology: Technological development will need to keep pace with climatechange and growing world population. Any lag will put an upward pressure on foodprices.

“New acreage is less likely due to climate change. Labor-saving machines may continue toimprove, albeit more slowly. Fertilizers will likely become more expensive but not likely better.
Purpose designed crops are one vector that may continue to improve over the next 30 years. It
thus will likely be a race between the changing climate and bioengineers’ ability to redesign crops
to meet new climate realities. Human inertia to change will likely slow down the acceptance of
new crops or new versions of existing crops. Thus, there will likely be a lag, which forces the foodindex upward over a period of time. If bioengineering is very successful and new crops are
accepted by the public quickly, the Food Price Index could moderate in spite of climate changes
and reduced arable crop land. Public acceptance may be the wildcard, however, if there iscontinued resistance to GMO foods.”“

Vegetable oils is the component I worry about because of their dependence on bees. Theseoils may become more expensive if the number of pollinators is reduced due to climatechange. Dairy and meat may also still be struggling in 28 years. They can be selectively bred tosurvive climate changes, but it will take longer to do so. I think those prices could still be high in
28 years.”

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Lack of international cooperation: Continued trend toward deglobalization is another
risk.

“

The current global food situation is likely to increase protectionism and prioritize local foodsecurity. Agriculture is already highly protectionist in the developed world.”

Downward Pressures(i.e., factors that would reduce food prices in this timeframe)
Technological development: Adaptation and mitigation will be crucial to keep foodprices from soaring in the face of increasing climate change e ects, including lesspredictable growing seasons. Electric or hydrogen-powered vehicles would also help
by reducing the cost of transport.

“

I generally expect prices to decline after the current spike and revert to long-term trends. In
the long term, prices are a function of growing demand (including both population growth andgrowing meat consumption), improvements in technology (a countervailing e ect to the one
before), and cost of supply (which climate change will generally increase). For my forecast I am
also assuming that many projections underestimate future technological innovation andbehavioral change, which are inherently poorly represented in economic models (aka computable
general equilibrium). Factors that probably bias these upward include potential growth in labgrown meat and a behavioral shift toward less meat-intensive diets.”“

Transportation costs may decrease by 2050 if the land component is optimized throughelectric and/or hydrogen-powered vehicles.”Population growth: While increased global population would mean increased demand
for food, it could also mean gains in productivity.

“

A few people mention population growth as a driver for increased food demand and higher
prices. The counterpoint to this is that more people makes for a more productive civilization
through progress in technology, infrastructure, etc.”

Cyclical nature of agriculture: The Superforecasters also point out the cyclical natureof agriculture and the e ect of outlier events on single-year outcomes as a source of
uncertainty.

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In the long term, factors that would push index higher, like climate change, more mouths tofeed, water shortages, potential political, economic, and cultural stresses, will be o set by
improvements in technology and development; therefore, status quo seems most probable.
However, agriculture, if treated as part of the economy where various kinds of food are justcommodities, is cyclical, so it is hard to predict in which point of the cycle 2050 will fall. Options
A, D, and E seem as outliers for me which can happen due to extraordinary circumstances in thatparticular year but would not be representative or typical for, say, the 2045-2055 period.”ff

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Q8: ASSUMING THAT THE EARTH’S GLOBAL AVERAGE SURFACETEMPERATURE INCREASES BY 7°C IN 2100 AS COMPARED TO 1880,
WHAT WILL BE THE FAO FOOD PRICE INDEX VALUE FOR 2100?

Resolution Criteria: The outcome will be determined using data as reported by the FAO.
For 2021, the real Food Price Index was 125.1.
In a scenario envisioning a global average surface temperature increase of 7°C in 2100
above the 1880 levels, the Superforecasters expect the FAO Food Price Index to be
above 120.0 (64% probability in total).

“

For a 7°C increase to have happened, unless it was caused by a one-time event, adaptations
would have been underway for decades. Food scarcity would exist, but global population may
have already su ered signi icant culling. Moving north does not necessarily mean inding fertile
land. Tundra is fragile. Technology may have solved some of the problems, and if energy isabundant and cheap, much food may be grown indoors, but not likely on a scale to feed theworld. The time scale is long enough and the temperature shift radical enough that I forecast thiswith a low degree of con idence.”“

This is worse than the worst-case RCP 8.5 scenario. Even if yields for grains don’t fall muchbecause the planted land moves to Canada and Siberia, total food production will probably belower. There’s no way to overcome warmed oceans. Hardest-hit areas will be in the tropics andtheir ability to adapt is not great without support. Changes in trade policy, diet, and land use willlag behind. Population growth will probably have stopped under those conditions. If the foodproduction system is under extreme stress, chances are prices will be higher.”“It’s important to keep in mind that climate science generally omits complex interactions
between risks, so numbers cited are likely to be underestimates considering climate change
will exert negative e ect through multiple pathways. Also, scaling these non-linearly for 7°C andfactoring in inelasticity of food demand suggests very high prices.”

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On the other hand, the pace, and timing, of the temperature change will play a majorrole here: If the bulk of temperature increase happened prior to 2100 and unfolded
somewhat gradually, humanity would have started adaptations in earnest and global
population would have decreased by 2100.

“

While humans would adapt to a 7-degree Celsius rise, the transitional period, when thetemperature was still rising rapidly, would be rocky. Such a fast-changing landscape, pairedwith the increasingly global nature of the food supply chain, would likely lead to signi icant
periods of disruption.”

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I am not saying it is going to be a bed of roses, but perhaps it will also not be an apocalypse.”CLIMATE CHANGE

HEAT
Q9: HOW MANY HEAT-RELATED DEATHS WILL THERE BE IN THE
WORLD IN 2023?

Resolution Criteria: The outcome will be determined using data reported by Global
Burden of Disease. There were 307,846 heat-related deaths in 2019.

Base Rate
The trend in heat-related deaths worldwide has been up since 1990, and shows signsof acceleration, according to the Superforecasters. Annual heat-related death igure
hasn’t been below 350,000 (upper boundary of Bin C) since 2011.

“

It is clear that humanity can be successful in adapting to climate change in some ways. For
example, nations should have the tools in the coming years to reduce the death toll resulting
from stronger and more frequent storms and looding, and perhaps from the spread of zoonotic
diseases. Humanity will have a lot more trouble dealing with other climate impacts. Heat is one
such impact. The upward trend of heat deaths since 1990 has been inexorable. This is likely tocontinue. We haven’t seen deaths drop to less than 250,000 since 2011. Bin A is very unlikely.
Outlier years on the low side have happened before (2008 and 2011), though.”

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The data since 1990 strongly suggests a combination of two things: The trend is accelerating,and the variance in the data is increasing.”

CLIMATE CHANGE

Upward Pressures(i.e., factors that would lead to more heat-related deaths)
Increased global temperatures: The Superforecasters expect global temperatures tocontinue to rise; even though this e ect will be more pronounced in the year anddecades to come, rising temperatures already create stress for many global systems.

“

The average world temperature and absolute world population have both increased since 2019(the last year for which data was available) and I expect both to continue to increase until 2023
and beyond.”

Population growth: Global population continues to not only grow but also age. Health,age, and poverty are pre-existing conditions increasing one’s risk of death from heat.

“

The growing and ageing population combined with rising temperatures suggest that the
upward rate would continue.”

Improvements in data collection: Better data collection in lower-income countries,
which bear the brunt of heat- and climate-related risks, could lead to a higher numberof reported deaths in this category.

“

There is a chance that data collection improves in the hardest hit places, in which case thenumbers will show an increase, beyond what the linear (or quadratic) trends would predict.”

Outlier events: Because this forecast focuses on a single year, a signi icant heat wave,
grid failure, or unrest could lead to an elevated number of heat-related deaths next
year.

“

The rather obvious fact is that older, poorer adults with health issues bear the brunt of thisdangerous trend. A catastrophic failure of a major electrical grid in the midst of a summer heatwave could result in a drastic number of deaths in the US—one of the countries not expected tohave a major impact on the global numbers.”

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Downward Pressures(i.e., factors that would lead to fewer heat-related deaths)
Adaptation and mitigation: There is already some evidence of successful adaptationand mitigation measures limiting the number of climate-related deaths in many partsof the world. Some Superforecasters argue, for instance, that the number of heatrelated deaths in 2022 has so far been lower than could be expected.

“

Heat waves this year have not seen as many deaths as expected. A main reason seems to bebetter adaptation, including public agencies becoming better at warnings and messaging,
though there is more to be desired in terms of disaster preparedness.”“

There is a general upward trend in temperature as well as variation in temperature. On theother hand, more heat waves and greater awareness of heat waves will accelerate e orts tomitigate deaths.”

Year-to-year variation in the global trend: While an outlier event (as described above)
could increase the number of heat-related deaths next year, cooler temperatures,
below the trend, could have an opposite e ect.

“

Climate shows a lot of variation from year to year. 2022 looks like a hot year, but 2023 could be
relatively cooler, without negating any of the current long-term e ects of climate warming.”

Poor reporting in high-risk countries: Business-as-usual scenario in data collection
and reporting may lead to a lower reported number of deaths, particularly in poorer
countries that also tend to be at greater risk from heat waves.

“

While I don’t doubt that plenty of people are dying because of high temperatures, and that the
number of people dying from high temperatures is increasing, as temperatures andpopulations increase faster than mitigating measure are, when heat waves hit megacities inunderdeveloped countries, it’s at best a very rough guesstimate as to how many people are dying
as a result of the heat.”“

Other than following the trend line and maximum yearly variance, my forecast accounts for thefollowing uncertainties: 1. Inaccuracy of reporting, particularly in developing countries in SE
Asia and Africa, where the majority of deaths occur. 2. Unrest leading to more vulnerable people,
but also possibly less reporting of actual heat-related deaths .”

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Q10: HOW MANY HEAT-RELATED DEATHS WILL THERE BE IN THE
WORLD IN 2050?

Resolution Criteria: The outcome will be determined using data reported by Global
Burden of Disease. There were 307,846 heat-related deaths in 2019.

Base Rate
By taking the historical data and projecting the trendline out to 2050, theSuperforecasters arrive at an outcome on the border between answer options B and C
as a starting point in their forecast. They assign a 33% probability the decadal averageof annual heat-related deaths in the world from 2041 to 2050 will be more than
400,000 but fewer than 500,000 (answer option C) and a 20% probability it will be
300,000-400,00 (answer option B).

“

Base rates here may be of limited value for obvious reasons. Heat deaths will be higher in 2050
than in 2020. The pattern is clear. The big question is the rate of increase. Linear progression
suggests we’ll be right on the line between B and C. Is that justi ied? With an indication thathumanity is learning to adapt, a range of 300,000 to 400,000 is still possible. On the other hand,once we reach critical tipping points (e.g., wet bulb temperatures), deaths from heat will begin torise exponentially. When regions of the Earth that used to support civilization become too hot tolive in, we will have reached the limit of adaptation.”“

The trend has been upwards since 1990, and it looks quite linear, with a potential tendency togrow faster. When looking at the resolution site, it’s up from 200,000 to 300,000 in 30 years,
and it’s a fair bet to assume that this will continue. 20-30 more years out from now into to2040-2050, something around 400,000 is the absolute minimum to expect.”“On the one hand, increasing temperatures strongly suggest increasing heat-related deaths.
Runaway climate change e ects could worsen this. On the other hand, mitigations may help
reduce the number of deaths even if temperatures continue to rise. Some math: Extrapolating alinear trend from 1990 onwards suggests an estimate in the 370,000 range. Extrapolating a linear

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trend from the 2010-2019 data suggests an estimate in the 440,000 range. Extrapolating aquadratic trend from 1990 onwards gives an estimate above 500,000 (but below 600,000). Thissuggests that, on balance, our estimates should be concentrated in the B-D range with someallowance for answer option E due to possible runaway e ects, and answer option A due topossible mitigations and precautions.”

Upward Pressures(i.e., factors that would lead to more heat-related deaths)
Rising global temperatures: While the world can adapt to rising temperatures overtime, this increase creates a risk, and sudden spikes in the temperature are particularly
dangerous.

“

Consistently hot weather is probably less dangerous than a sudden hot spell in an area that’s
not used to it. So, if climate change causes an area to gradually get hotter over a few decades,with no sudden spikes, humans adapt well. Climate change is much more dangerous if it leads tomore sudden spikes of heat in areas that don’t expect them. Needless to say, less a luent areas
likely will su er more.”“

Increased heat waves, in number and severity, are here to stay during this time frame, andlikely beyond. Increased temperatures and growing urbanization are two big factors in thisdecade’s numbers growing over past decades.”Population growth and urbanization: The Superforecasters expect 2041-2050 to be a
decade that still has a growing population with relatively high poverty rates. Rapid
urbanization is a risk factor here.

“

Urbanization (urban heat island [UHI] e ect) is an issue as cities are hotter than the countrysideand less likely to have the informal ’checking on a neighbor’ system. Urbanization is projected
to increase from ~55% now to ~68% by 2050.”“

It strikes me that global population increase through 2050 and a continuing shift tourbanization are all but guaranteed to o set any improvements in functionalities, so I would
conclude that climate impacts will not be decreasing. All of this leads me to thinking that the key
to annual heat-related deaths will come down to e ective urban adaptations and the increasing
implementation of heat mitigation strategies. Moving entire populations out of regions or
subcontinents simply is not a viable solution and a failure to adapt is not really an option.”

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Global inequalities: More a luent countries are likely to fare much better in 2041-2050
thanks to technological development and adaptations; the same may still be
una ordable to lower-income countries (LIC) for economic or governance reasons.

“

The solutions to preventing heat deaths aren’t new, we already have them: shelter, airconditioning, and easily accessible water. None of these solutions are likely to be any morea ordable than they are now for the poorest countries.”“

Status quo per capita is 372,000. However, migration to cities and the urban heat island e ectwill increase this. Adaptation is possible in this time period. For instance, after the 2003 EU
heatwave, simple measures were taken that reduced future mortality. Even though 2022 washotter than 2003, there were a lot fewer deaths. However, adaptation is unlikely to happen in LIC
in this time frame due to governance issues.”

Interaction among climate risks: The Superforecasters do not expect heat-related
deaths to grow exponentially in 2041-2050, but reserve a 17% probability this number
will exceed 600,000 due to the possibility the currently understudied interaction
among climate change e ects will lead to a tipping point.

“

Some models suggest annual deaths’ increase by a factor of 3 without adaptation, and 1.4 witha very hypothetical adaptation. However, these numbers are probably underestimates, as themodels include no interactions among the climate change e ects and the data doesn’t cover all
countries (notably excluding Southwest Asia, Central America, and Africa). In general, theinteraction between hazards is a ’missing link’ in the climate literature because most studies focus
on one hazard or risk factor at a time. Possible interactions include: 1. Heat and humidity. 2. Heatand timing. 3. Heatwaves and heat. 4. Heat and drought. 5. Heat and other weather hazards. 6.
Heat and societal preparedness.”“

Whatever the deaths are now, I’m forecasting things will be marginally worse, in terms ofdeaths as a percentage of the population, in 2041-2050, but not exponentially worse. There’sde initely a chance, though, that if temperatures rise more and faster than predicted and atipping point is reached in some countries, overloading health systems and the limits of thehuman body, that it could get exponentially—or at least signi icantly—worse.”

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Downward Pressures(i.e., factors that would lead to fewer heat-related deaths)
Adaptation and mitigation: The Superforecasters expect adaptation and mitigatione orts to continue in the coming decades, which should help prevent a sharp increasein average heat-related deaths.

“

I think that climate change will kill many people, but I’m just not very convinced that there will
be a meaningful increase to the heat-related death rate speci ically. It’s a pretty tractable casefor adaptation (e.g., depopulating super-hot regions, changing norms/regulations regarding
outdoor physical labor, better buildings and cooling), whereas I think a lot of the second- andthird-order impacts of climate change (e.g., war, famine, zoonotic spillover pandemics) will be themajor killers, and potentially much less tractable.”“

My conclusion is that as the world population begins to appreciate that the climate is going tocontinue to heat, adaptation to those to those changes will accelerate, and while heat deaths
while continue to rise, the rate at which they rise will be lower.”

Poverty reduction: Reduction of poverty due to either international cooperation or
growing wealth in some parts of the world would also help contain heat-related deathsin this period.

“

A decline in mortality risk per a unit of temperature is to be expected as societies becomericher and some adaptation to climate change begins to take place.”

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Q11: ASSUMING THAT THE EARTH’S GLOBAL AVERAGE SURFACETEMPERATURE INCREASES BY 7°C IN 2100 AS COMPARED TO 1880,
WHAT WILL BE THE DECADAL AVERAGE OF ANNUAL HEAT-RELATED
DEATHS IN THE WORLD FROM 2091 TO 2100?

Resolution Criteria: The outcome will be determined using data reported by Global
Burden of Disease. There were 307,846 heat-related deaths in 2019.
Unlike in the case of deaths caused by loods and drought in this scenario (see therelevant sections below), the Superforecasters see a 7°C increase in global averagesurface temperature in 2100 above the 1880 level as a major risk for heat-related
annual deaths. Adaptation in this scenario will be at its limit, the number of con licts
will rise, and there is little reason to feel optimistic about the quality of governance andinternational cooperation in a world that is 7°C warmer on average. The
Superforecasters see a 58% probability more than 1.2 million heat-related deaths willon average be recorded annually in the last decade of the century.

“““

Adaption obviously works well, to a certain degree. But for an increase of 7 degrees Celsius,I
would consider the ability to adapt becoming overstretched.”
This scenario would certainly involve revolutions, wars (especially over water and food or
possible farmland), and migration on an unprecedented level.”

Going to 7C, considering the non-linearities of the climate system, could mean large increases
in mortality. Numbers lower than Bin E would require very substantial adaptation measures(and for the world to get lucky and be on the lower end of some of these estimates), which arepossible, but decision-makers have yet to start walking the walk. While capacity to handle heat
will rise, it will be unevenly distributed. Given that societies are on track to continued economic
and political inequality, adaptation is likely to be limited.”“

If we’re talking a rise of 7 degrees Celsius, that suggests a collective global failure of epic
proportions. Nothing about that scenario would give me faith that, having failed to curb
emissions, the better part of the world would somehow succeed in aiding the least fortunate to

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adapt. The speed with which such a rise would occur would also make adaptation exceptionallydi icult.”

On the other hand, if this rapid increase in surface temperatures led to a drastic
decrease of global population, and if the bulk of it happened before 2091, the decadal
average of annual heat-related deaths could come in at a lower number.

“

The increase would be too fast (1 degree every 15 years) for the global economy to adapt andfor humans to migrate to safer areas. On the other hand, it could reduce heat deaths because
the population is so much smaller.”“

The only chance I see of B-C-D bin resolution in this scenario would be if the timing of thewarming was such that the bulk of the temperature rise and its e ects were experienced prior
to the last decade of the century—so that when 2091-2100 came, most of those who were able toadapt had already adapted and those that couldn’t had already perished.”

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FLOODS
Q12: HOW MANY DEATHS WILL BE CAUSED BY FLOODS IN THE
WORLD IN 2023, ACCORDING TO OUR WORLD IN DATA (OWID)?

Resolution Criteria: The outcome will be determined using data as reported by the
OWiD. For 2020, there were 6,179 deaths caused by loods.

Base Rate
Annual deaths attributed to loods in the past 20 years have been relatively low. The
closest it came to breaching 10,000 (upper boundary of answer option B) was in 2013
with 9,819 deaths. The trend in 2010-2020 has been down (i.e., fewer recorded deaths
caused by loods), and the average deaths per year caused by loods over the last ive
years of data (i.e., 2016-2020) were about 4,400, based on the Superforecasters’
calculations.

“

Annual deaths caused by loods during the past 20 years (2001-2020) have been low and morestable than ever. There were no years with more than 10,000 deaths in this period. Annual
deaths during the previous two 20-year periods (1961-1980 and 1981-2000) veered from very low
deaths (fewer than 3,000) to high deaths (10,000-30,000). Years of catastrophic deaths(30,000-100,000) also occurred three times during this 40-year period. Modern society is better
equipped to handle lood disasters than before. That accounts for the low and stable numbers
during the period 2001-2020.”“

Trend was actually down in 2010-2020. Even though climate change will likely continue toresult in an increase of the frequency and severity of looding worldwide, I don’t see it as a risk
like I do heat waves.”

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Upward Pressures(i.e., factors that would lead to more deaths caused by loods)
Increased number of catastrophic events: In 2021, a total of 432 catastrophic eventswere recorded, which is above the average of 357 annual catastrophic events for
2001-2020. Floods dominated these events, with 223 occurrences, up from an averageof 163 annual lood occurrences recorded across the 2001-2020 period. Increased
number of events can exert an upward pressure on the outcome, particularly in thecase of lash loods, which are sudden and harder to predict.

““Flash loods often catch residents by surprise, which causes the most deaths when it comes tolooding.”
Flash looding is the main killer here. The predicted increase in hurricanes in 2023 could
increase the deaths associated with looding.”

Population growth: Although the timeframe of this question is very short, population
growth, particularly in lood zones, may lead to a higher number of deaths—but this is
more likely to play out in the medium to long term and will have only a limited e ect
for 2023.

“

The more frequent low numbers (bin A) for previous 20-year periods can be attributed to thelower global population then. Perhaps, too, there were fewer people who lived in lood zones.
Evidently, there has been a 24% increase in people living in lood zones, to 80 million since 2000.”Single-year volatility: The outcome can be skewed by a single, high-impact event.

“All it takes is for a single massive event, like the Vargas tragedy in Venezuela in 1999 that
resulted in 10,000-30,000 deaths, to skew the result for the year.”

Downward Pressures(i.e., factors that would lead to fewer deaths caused by loods)
Better forecasting and early warning systems: Although the world already has more
looding—and greater population—than 20 years ago, the number of deaths caused by

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loods did not rise accordingly in this period. The Superforecasters attribute thisoutcome to better weather forecasting and dissemination of early warning systems, afactor which is going to play a role in 2023 outcomes as well.

“

While looding has increased over the years, deaths aren’t going up at the same rate. Improved
early warning systems is the big reason this number isn’t likely to explode in 2023, even if theincrease in hurricanes comes true.”“

Despite climate-change-induced increasing rainfall and severe weather, the number of people
killed by looding annually around the world is unlikely to reach the very high numbers ofearlier years. The reasons are better weather prediction, better governmental planning, andrescue capability, and better mass communication and warning.”

Stringency of the resolution criteria: Because the resolution source counts only
deaths caused directly by loods, and does not include those caused in the aftermath,the Superforecasters see only an 18% probability the 2023 outcome will be above thebase rate.

“

Given the low numbers, the Our World in Data source seems to be just counting deaths thatwere directly related to looding, rather than the peripheral deaths that loods leave in theirwake, namely due to poor sanitation, crop failure, and displacement. If the resolution criteria
included those other deaths, I’d feel much di erently about this question.”““

Downstream events such as starvation and disease are not included.”Lack of signi icant climate change e ects in this timeframe.
Changes are unlikely to be signi icant in 2023.”

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Q13: HOW MANY DEATHS WILL BE CAUSED BY FLOODS IN THE
WORLD IN 2050, ACCORDING TO OUR WORLD IN DATA (OWID)?

Resolution Criteria: The outcome will be determined using data as reported by the
OWiD. For 2020, there were 6,179 deaths caused by loods.

Base Rate
The decadal average deaths attributed to loods in the past 20 years have been
relatively low and the trend since a high in 2000 has been down (i.e., fewer recorded
deaths caused by loods).

“

Focusing on the decadal annual averages since 1969 (re lecting data starting in 1960), thehighest decadal annual average was for the ten years ending in 2000 (with 9,925 deaths),
following some higher values in 1998-1999. Since then, the averages have dropped steadily,
despite (presumably) tracking and attribution only getting better.”“Yes, climate change is accelerating, and the decade in question will likely see more frequentand extreme loods than that during 1960-2019. Meanwhile, the type of event(s) that would kickus up into Bin C or higher have not occurred since 1959. Clearly, it would be naive to say that they
won’t happen anymore, but after 60 years without one, I’m fairly comfortable assigning a pretty
low probability (11%) to that type of event (or multiple events summing to that level) occurring in
the decade in question here.”

Upward Pressures(i.e., factors that would lead to more deaths caused by loods)
Climate change e ects: The Superforecasters expect climate change e ects tobecome more pronounced in this period, leading to greater volatility.

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CLIMATE CHANGE“

I’m predicting more extreme weather in this timeframe. I also expect more international
cooperation and improved detection systems. But even these two things could beoverwhelmed by the unexpected events (mudslides), human fallibility (failed dams), and apossible deluge of extreme weather.”““

The speed at which lash loods happen makes it di icult to get warnings out in time. Some
85% of lood deaths are lash lood deaths.”
The extreme weather has already hit us, and will likely hit us harder, and in unforeseen ways, inthe future.”

Population growth: Population pressures and increasing urbanization mean more
people are likely to move into lood zones, which in turn increases the risk of higher
deaths from catastrophic events. Human factor can play a role too if people in danger
zones choose to ignore early warnings.

“

More people are moving into lood zones worldwide, which should increase the risk of truly
catastrophic death tolls. Globally, there has been a 24% increase in people living in lood zones,
to 80 million since 2000. That trend of people moving into lood zones is not likely to reverse
given the growing populations in urban centers, and the likely need to house millions of climate
refugees in the coming decades.”“In short-term and immediate lood risk situations, it’s very hard for individuals to evaluate theirrisks, and this is one reason you see so many clips of governors pleading with their people toget on the road early and so few do.”“Increasing population is likely to lead to more people living in lood zone areas in poorer
countries, although attribution of these deaths may still be to other causes, e.g., famine,storms, etc.”

Global Inequality: This has been the most cited factor among those limiting global
ability to adapt to climate risks. Limited technological development is another such
risk.

“

In less developed countries, many people lack the short-term transportation options or the
long-term economic lexibility to get out of the way.”

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“

The decadal average hasn’t been lower than 5,000 since the 1960s, when there were fewer
loods and fewer people; I don’t think our warning or transportation systems will be so muchbetter by the 2040s that I’d expect us to fall below that level on that account.”

Downward Pressures(i.e., factors that would lead to fewer deaths caused by loods)
Adaptation: Historically, humanity’s adaptation to climate risks has been remarkable. It
is unlikely to stop in this period.

“

Let’s not downplay the possibility of successful adaptation to new climate conditions. After all,
we’re seeing greater climate impacts now, yet deaths from looding are both low and stablecompared to previous decades.”“Technology is making it easier to make better lood assessments and this should result in evenmore e ective global mitigation e orts by 2050. Continuing to improve forecasting anddisaster response should keep deaths from lood events in check even as the world’s population
increases.”“

Increased looding should be more than outweighed by the increase in warning systems. Thishas been the historical trend.”

Stringency of the resolution criteria: Only deaths caused directly by looding are
included in the resolution criteria. This has led the Superforecasters as a group to
assign a 75% probability in total that the decadal average of deaths caused by loods in
2041-2050 will remain within the historical base rate.

“

The bulk of the dire problems caused by looding are problems once-removed from the looditself, and therefore not counted in this resolution criteria. If a family starved to death twomonths after the lood, because their crops were ruined, or 10 percent of a village died of cholera
because of unsanitary water related to the lood, I don’t think this would show up in the data. Do I
think loods in some regions of the world will get worse because of climate change? Absolutely.
But I’m not convinced that will show up that much in this data.”“

All in all, I see looding more as a threat multiplier and driver of migration and other risks(starvation, disease, con lict, food availability).”

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Q14: ASSUMING THAT THE EARTH’S GLOBAL AVERAGE SURFACETEMPERATURE INCREASES BY 7°C IN 2100 AS COMPARED TO 1880,
WHAT WILL BE THE DECADAL AVERAGE OF ANNUAL DEATHS
CAUSED BY FLOODS IN THE WORLD FROM 2091 TO 2100,
ACCORDING TO OUR WORLD IN DATA (OWID)?

Resolution Criteria: The outcome will be determined using data as reported by the
OWiD. For 2020, there were 6,179 deaths caused by loods.
In a scenario envisioning a 7°C increase in the Earth’s global average surface
temperature in 2100 above the 1880 levels, the Superforecasters have a wide
distribution across the outcomes, with 61% in total for 10,000 to about 125,000
deaths recorded as a decadal average at the end of the century.

“

The increase would be too fast (1 degree every 15 years) for the global economy to adapt andfor humans to migrate to safer areas, leading to starvation, failure of governance and healthcare systems, etc. It could reduce lood deaths because the population is so much smaller. Or it
could increase lood deaths due to inability to migrate, failures of warning systems, mitigation
measures, etc.”“

While I think loods in some regions of the world will get worse because of climate change, I’m
not convinced that the dire impacts of said looding (famine, disease, displacement, increased
poverty) will show up that much in the resolution-source data. Even with the 7°C rise, I still think
this will be the case to some degree. Especially with better meteorological forecasting, theaftermath of looding is often—though, to be sure, not always—more lethal than the lood itself,
particularly in developing nations. That said, the pace of change matters; the more rapid the risein temperature, the greater the likelihood that meteorologists and the general public will becaught by surprise by unprecedented storms and storm surges that bring looding with it. People
can and will adapt to higher temperatures, but not overnight. And a 7°C rise over the next 78
years implies enormous change in a short period of time.”

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On the other hand, if this increase in temperatures is anticipated, technologicaldevelopment will help mitigate the toll brought by loods to an extent.

““

By the time we get to the year 2090, humans have igured out how to prevent massive
amounts of deaths by lood (as de ined by OWiD).”

I’ve got to factor in innovation and natural progression. The massive looding won’t startsuddenly in the year 2100—there will be an increase in the trend. And, presumably, humans
would start to sort away from those zones where possible. Although, as has been mentioned, it’s
not always possible or easy to do that because of being locked into an area economically, etc.”“

To what extent might technology play a role in slowing sea-level rise caused by global
warming? Flooding infrastructure is already being implemented in places like New Orleans,
Venice, and The Netherlands. Barriers or dams around Greenland’s ice sheets and glaciers could
also be cost e ective and helpful to low-lying developing countries.”

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STORMS
Q15: HOW MANY DEATHS WILL BE CAUSED BY STORMS IN THE
WORLD IN 2023, ACCORDING TO OUR WORLD IN DATA (OWID)?

Resolution Criteria: The outcome will be determined using data as reported by the
OWiD. For 2020, there were 1,723 deaths caused by storms.

Base Rate
Because the forecast of storm deaths in 2023 focuses on a single year, it is highly
susceptible to the impact of outlier events—major storms that can cause a signi icant
number of casualties. According to the Superforecasters, such events typically occur
every 20 years, resulting in a spike in deaths. Recent data shows a fairly consistentpattern of deaths between 1,000 and 4,000. Furthermore, over the past 50 years, therate of deaths over 4,000 has been declining. The Superforecasters expect 2023 to bemainly in line with the overall trend (60% probability for OWiD reporting 1,000-4,000
deaths caused by storms next year), but keep a 25% probability for “more than 4,000
but less than 20,000” deaths in case of an outlier event. Climate change is not likely to
be a major driver in 2023.

Upward Pressures(i.e., factors that would lead to more deaths caused by storms)
One Superforecaster points out years with catastrophic numbers of deaths (>100,000
in 1900-2020), although not a base-case scenario, are not becoming increasinglyf47

rare. One reason for the above is that the most vulnerable populations to storm surges
are still vulnerable.

“

It is no coincidence that these are also some of the poorest countries who are least able toadapt to the increasing ferocity of storms. Topping the list are Myanmar, Bangladesh,
Philippines, Vietnam, Haiti, Honduras, and Nicaragua. I would also add the islands of Oceania andAfrica.”Compounding this, the populations of those vulnerable areas tend to have lower trustin authorities and institutions, which limits the e ectiveness of early warning andmitigation. Furthermore, the information used to calculate the base rate may belawed: It is possible that some of the countries with greater vulnerability to storms
weren’t collecting or reporting data e ectively during earlier years. With improved
data collection and reporting methods, the number of known deaths may be higher.

Downward Pressures(i.e., factors that would lead to fewer deaths caused by storms)
Better forecasting and early warning systems: The following factors tend to bene itricher countries irst, but poorer areas have seen some improvement as well throughinternational cooperation and relief e orts: a.Better weather forecasting; b. Early
warning systems; and c. Dissemination of communication technologies.

“

Weather prediction has improved a lot in the last 50 years. At the time of cyclone Bhola in
Bangladesh [in 1970], the forecast was missing. Pakistan didn’t have their own weather
forecasting satellite. Some limited data was shared by the US. Now such weather information iscommercially available. Also, warning broadcasting to a ected areas has improved manifold due
to television and mobile phones.”“

Most years from 1960 onward fall within 1,000-4,000 range. There are a few outlier years, 1970
being the most signi icant. Earlier detection than in past years and more international
cooperation in relief e orts are two reasons why I’m not dipping too far into the higher ranges,
even though it’s predicted to be a heavy looding season in the most at-risk populations of thesubcontinent, plus Myanmar.”

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Stringency of the resolution criteria: The Superforecasters also note that there aresome limitations to the data OWiD reports for this metric: It counts only those deaths
that were directly related to storms, rather than the peripheral deaths that storms andstorm-related looding leave in their wake, namely due to poor sanitation, crop failure,and displacement. As such, we may be underestimating the impact of storms if weonly rely on this metric.

“

Modern technology has given regions in the path of storms more hours/days to prepare than intimes past—which could lessen the immediate impact of the storm in terms of human deaths,
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Q16: WHAT WILL BE THE DECADAL AVERAGE OF ANNUAL DEATHS
CAUSED BY STORMS IN THE WORLD FROM 2041 TO 2050,
ACCORDING TO OUR WORLD IN DATA (OWID)?

Resolution Criteria: The outcome will be determined using data as reported by the
OWiD. For 2020, there were 1,723 deaths caused by storms.

Base Rate
The Superforecasters see a 57% probability the average annual number of deaths
caused by storms in this period will be 5,000-20,000, and a 25% probability it will be
below 5,000.

“

While I do expect ’fewer than 5,000’ will become the norm in the irst half of this century
because nations are dealing better with the threat of storm surges, and that is where the trend
is headed, a single catastrophic 100,000+ event can bring up the decadal average from, say,
2,000 to 12,000. The countries most at risk are Myanmar, Bangladesh, Philippines, Vietnam, Haiti,
Honduras, Nicaragua, and Mozambique.”Upward Pressures(i.e., factors that would lead to more deaths caused by storms)
Historical base rates may play less of a role here as climate change a ects weather
patterns and multiple risks start to interact. This may lead to storms moving to new
regions that may not have appropriate warning systems.

“

Although climate change is going make storms and deadly storm surges stronger, more
frequent, and more destructive, rich and developing nations can learn to adapt so as to ensure
mortality rates remain low. Humans can learn to adapt very e ectively to this kind of natural
disaster. On the other hand, the poorest nations will remain as vulnerable as they were in the

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1970s-2000s unless they receive assistance from rich countries to build up climate resilience. The
actions and rhetoric of rich countries do not inspire con idence that this will happen.”“

Better forecasting and warning systems are e ective if there is enough time, viable routes tosafe places, the means to get there, and a population willing to follow orders. Projections for2050 place most of southern Vietnam under water at high tide, most of Alexandria, Bangkok, andBasra. These are not wealthy areas where people will just move to their summer homes.”“

A key factor is how communities respond, in terms of preparedness and resilience.
Preparedness requires both prediction capability (which is improving) as well as
communication and level of institutional trust, the latter of which is likely to be severely lacking inmany parts of the world.”

Downward Pressures(i.e., factors that would lead to fewer deaths caused by storms)
The focus on the decadal average for 2041-2050 makes the second forecast in thisgroup less susceptible to single-year outlier events.

“

There will probably be outlier years between now and 2040 (and between now and 2050), but I
don’t think there will be enough outlier years that they pull the average up over 20,000.”

Better forecasting and early warning systems: The Superforecasters see a very low
probability (3% in total) that deaths caused by storms in the period under investigation
will reach catastrophic level of 80,000 or higher. However, here, too, second-ordere ects, such as the increase in disease, famine, and poverty that might follow in themonths and years after a storm, likely won’t be captured in the available metrics.

“

The factors driving this include better forecasting, early warning, better infrastructure,
improving search and rescue technology, etc. All of these factors are going to continue getting
better over the coming decades, even in the face of mounting climate change.”

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CLIMATE CHANGEDROUGHT
Q17: WHAT WILL BE THE DECADAL AVERAGE OF ANNUAL DEATHS
CAUSED BY DROUGHT IN THE WORLD FROM 2041 TO 2050,
ACCORDING TO OUR WORLD IN DATA (OWID)?

Resolution Criteria: The outcome will be determined using data as reported by the
OWiD. For 2020, there were 45 deaths caused by drought.
The Superforecasters see a 52% probability that be the decadal average of annual
deaths caused by drought in the world from 2041 to 2050 will remain below 5,000.
Such deaths in the recent years have been relatively low, in part due toimprovements in technology and logistics enabling international aid, and in part due
to the di iculty of attributing deaths directly to drought in the data.

“

Similar to loods, droughts are dangerous as multipliers for other mortality risks, which are notmeasured here, particularly through migration, food insecurity, and broader ecosystem
impacts (e.g., forest ire risks). Mortality associated with drought is highly dependent on preexisting vulnerabilities, such as poverty, age, and socio-economic disadvantages more generally.”“

It will be easier for the developed world to episodically provide emergency food and water tothe developing world than to accommodate refugees leeing drought-stricken areas. As aresult, I expect the recent reported trend, in which deaths from drought have been minimal, tocontinue. Over the past decade (2011-2020), seven of the 10 years recorded no drought deaths,
and only double digits on the others for a decadal average of 17 per year. So, unless the reporting
standard changes, I don’t see any of the upper bins as probable.”“

To experience events which would fall in 5,000-20,000 range or greater, you would have to go
back to the early 1980s. I feel the ability of the international community to respond tohumanitarian crises will prevent us from seeing such events again.”

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Some Superforecasters argue, however, that historical base rates may be of limited
value given the timeframe and the increasing impacts of climate change. They see
therefore a potential for some increase in deaths caused by drought (26% probability
the average deaths will reach 5,000-40,000 per year).

“Droughts have killed 650,000 since 1970. The 50-year average comes out to 13,000 per year.
Though the trend has been downwards over time, we’ve seen the decadal average shift backup this decade. Like with storm surges and loods, we should see deaths for most years remain
low but punctuated by years of extremely high deaths, thus bringing the decadal average up. The
climate conditions for the 2040s will be vastly di erent. Single-year catastrophes are likely toreturn.”“

The world has gotten better at providing basic necessities to a ected populations. However,climate change is straining the marginal areas of the planet. With ’dry areas getting drier,’ somemarginal lands will no longer be productive. Therefore, the pressure on regional populations will
intensify. The average number of deaths since 1990 has been less than 800/year. Global
population is expected to increase through 2050, but at an ever-decreasing rate. Africa will be
the fastest growing region but also one a ected by climate change, putting more people inharm’s way.”

A more extreme scenario:“

Clearly, the world has learned to reduce the impact of drought using communications, airtransport, and ample stock of basic food stu s. Rolling forward 20 years, will this trend
continue? Obviously, most forecasters believe it will. But what if we have crop failures across awide swath of the planet? Who comes to the rescue if Russia fails, or if the US heartland has a’dust bowl’ year?”Yet, most Superforecasters believe the impact of climate change will be moderate inthis timeframe, with greater e ects expected after 2050.

“

The e ects of climate change will undoubtedly be more apparent (and potentially devastating)by the end of this period. Wealthy countries will remain well-positioned to mitigate the mostextreme impacts, albeit in potentially less-comfortable circumstances than at present. However,poorer and less developed countries have potential to experience catastrophic loss of life,
depending on the location, severity, and duration of a drought. That said, I think the potential forcatastrophic impacts is higher during the latter half of this century.”

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The most extreme climate impacts are out longer than 20-30 years, so I would expect a slightincrease with global warming over this time period, but not a dramatic one.”

Wealthier countries will be able to adapt faster, including through international tradeand relocation away from vulnerable areas. Climate change will exacerbate thealready existing vulnerabilities, especially in poorer regions of the world. Areas prone
to con lict may be hit particularly hard .

“Developed countries and regions such as the US and Europe will have droughts but shouldhave almost no deaths from it unless the political and economic situation severely deteriorates.
Wealthy countries can shift resources from one region to another and buy food on theinternational market. Embargoes and con lict zones can upend this calculation, however. Even inpoor countries, basic food supplies can often be distributed if there are no military con licts
where food becomes a tool of power.”“

In areas where the worst droughts are likely to happen, those e ects are already being felt, andin the next 5-10 years, populations will shift to wetter areas from those regions where possible.
Of course, there are the poor who will not be able to migrate, but I’m not sure they will havesurvived another 20 years without inding some way to mitigate their situation. Besides, wealthy
countries may decide it is easier to truck in water or build desalinators than to take in hordes ofrefugees.”“

Nowadays, drought as a weather condition is not enough to cause large-scale deaths, as basic
humanitarian aid will be delivered if images of dying people start to emerge on the internet,
and it will happen quite fast. The problem is if drought happens in con lict zone or in failed state
as it happened in Somalia in 2010.”

Furthermore, there are projections that population growth, which could place greater
strain on scarce resources, is slowing, which may also mitigate the impacts of drought
and resulting food shortages. Therefore, even though droughts can be expected to
become longer and more severe, due to adaptation, but also due to the stringency ofdata (that such deaths must be directly caused by drought, discounting any secondorder e ects in the metric), the Superforecasters expect an increase in the averagedeaths caused by drought, but say it will not be an exponential one in this period.

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Q18: ASSUMING THAT THE EARTH’S GLOBAL AVERAGE SURFACETEMPERATURE INCREASES BY 7°C IN 2100 AS COMPARED TO 1880,
WHAT WILL BE THE DECADAL AVERAGE OF ANNUAL DEATHS
CAUSED BY DROUGHT IN THE WORLD FROM 2091 TO 2100,
ACCORDING TO OUR WORLD IN DATA (OWID)?

Resolution Criteria: The outcome will be determined using data as reported by the
OWiD. For 2020, there were 45 deaths caused by drought.
This question is predicated on a failure to limit surface temperature increases. If the
Earth’s global average surface temperature increases by 4°C/7°F in 2100 as compared
to 1880, the Superforecasters expect this rise to be gradual, giving the world
population time to adapt.

“

As drought increases over time, there will be several mitigation processes. Rich cities will move
to desalination, which will become increasing cheap. Poor cities will move to migration, which
will decrease the population. Drought in poor areas is likely to occur far before 2091 in any
reasonable climate scenario.”

Even this increase in global temperatures would suggest, as one Superforecaster
writes, that “global governance over the course of the century had been poor,
suggesting, in turn, that e orts to mitigate the impacts of climate change indeveloping nations had also been poor.”“

While 7 degrees F will certainly a ect quality of life and livability of the planet, I think that will
have started happening at 4 and 5 degrees, which gives time for mass relocation andadvanced developments. Clearly, things will have to change, whether we start treating water as avaluable commodity like oil and have pipelines and tankers carrying to more deserti ied areas, ordesalination plants are all the rage. People won’t remain in a crisis situation for decade after
decade.”

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The adaptations to climate change will be well embedded by 2091. Unfortunately, that is likely
to mean many lives claimed by drought, but it’s likely to occur before the end of the century.”

If the Earth’s global average surface temperature increases by 7°C in 2100 ascompared to 1880, the Superforecasters see a 32% probability the decadal average ofannual deaths caused by drought will be fewer than 10,000, a 25% probability it will be
10,000-50,000, and a 43% probability in total it will exceed 50,000.

“

Do I think a 7°C rise in temperature is likely to lead to millions of deaths from drought,
particularly in the developed world, whether or not someone is standing there with a clipboard
to record them? Given all that I’ve read about the likely impacts of a 7°C rise, absolutely. And I
also still think that many of those deaths wouldn’t be re lected in the OWiD numbers. As withloods, many of the impacts of drought in the developed world will be once or twice removed
from the inciting incident.”“

I think about 5-6°C is the tipping point for the human civilization. Migration, droughts, storms,
etc., will greatly impact the way we live. The rate of change is important here because if the
major portion of the temperature change is before, say, 2070, most of the adapting to it will bedone before 2091. World population will greatly reduce even before 2090. If the change is backloaded—say, most temperature change happens between 2070 to 2100—then adapting will be
still ongoing in decade 2091-2100, and deaths could be much higher during that period.
Assuming the likely scenario is linear increase in temperature, the major portion of the droughts,
migration, depopulation will probably happen during 2060-2090, then continued at the slower
rate in 2090s.”“

Necessity is the mother of invention: To survive past 2050 and the predicted peak of global
population and widespread drought conditions, adaptations will have to have been made wellprior to 2091-2100.”

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FUTURE OF THE AMAZON BIOME
Q19: WHAT PERCENTAGE OF THE CURRENT AMAZON BIOME WILL
TRANSITION TO SAVANNAH OR GRASSLAND AS OF 2100?

Resolution Criteria: There are concerns that the Amazon rainforest biome will see
dramatic changes in the 21st century.

Current Modeling
The status quo trend would lead to 30-40% (answer option D). The Superforecasters
point out that in a worst-case scenario in which carbon emissions aren’t curtailed andtemperatures rise by about 4.7 degrees Celsius by 2100, modelers predict that only
about 36% South American forest will be considered stable. The likely rise in thetemperature and the rate of intentional deforestation will play a role, however, inwhether this outcome would occur.

“

How likely is that kind of warming? The latest IPCC report says 2.4-3.5C. Other modelers
estimate 1.5-3.5C. Climate Action Tracker’s ’Policies and action’ scenario is 2.5-2.9C (represents
current policies). On balance, I would put my central guesstimate at 2.5C, but my full uncertainty
range would be quite large. My current thinking is that the 99% distribution could be something
like 1.4-5.5C. This uncertainty distribution is very dependent on the climate sensitivity (which is far
from settled) for a given amount of GHG concentrations, and tipping points in, e.g., permafrost
melting, Atlantic circulation, and the carbon cycle (including forest carbon) and associatedfeedbacks.”

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Upward Pressures(i.e., factors that would lead to greater transition of the Amazon biome to savannah or
grassland by 2100)
Human factors: Political climate, population growth and urbanization, as well as
lifestyle and dietary choices of local and global consumers will determine the rate of
deforestation.

“

While the impact might be global, the decisions will be made locally. The anti-environmental
movement in Brazil has long roots going to the 1980s. This movement is partly a development
perspective and partly a backlash against the international community. Thus, the ability tomoderate is severely limited.”“

I don’t think the two main threats to the Amazon biome, man and warming, are equal, but afeedback loop makes that more complex. Man is more likely to make a more permanent
clearing of the Amazon. Once land is claimed from the biome, by roads and farms, it’s less likely
to revert to the biome. A bimodal distribution of forecasts may be sensible if you don’t know
where the politics of Brazil will go in the next few decades. I’m shading toward this: forces lessfavorable to maintaining the biome will at least be competitive in the next few decades. For atipping point caused by man, there doesn’t have to be another 78 years of such rule. In only ive
years of such rule, there has been about 17% of the Amazon destroyed. How many more ive-year
periods of such rule can the Amazon bear before there is a tipping point?”“

The most common reason for deforestation is to create grazeable land for livestock. Brazil uses
80% of its deforested land in the Amazon for raising cattle. Worldwide, we destroy over 6
million acres of land to raise cattle. Deforestation also makes space for people to live. In manycases, people cut forests down for urban development. With these areas free, cities can expand
housing, highways, and commercial space, contributing to strong local economies. As of April
2020, there are 7.8 billion people on Earth. Because of our booming population, usable land isbecoming more and more scarce. Deforestation, furthermore, creates jobs and tax revenues:
logging jobs and potential mining jobs created by clearing forest, and new farming jobs in thearea. These new jobs and commercial ventures also lead to increased tax revenues to fund social
services and other government ventures.”“

Experience to-date on the transition to plant-based foods or away from beef is a very di icult
journey. Food is politics, security, and the agribusiness is very powerful. Add in consumer
behavior, the right to choose what I want to eat, and there are more negative feedback forces and

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loops than positive. Governments would lead on this topic, but government transitioning farmers
and farms is very di icult.”

Environmental tipping points: Climate change-related e ects are another source ofconcern, and here potential tipping points create a high degree of uncertainty.

“

The loss of resilience will only increase as time goes by, so that the ’tipping point’ will
eventually be reached and the rainforest will begin to convert to savannah. Since it is 75+ years
to 2100, the amount converted will probably be in the upper answer options.”“

There are human factors that enhance the transitioning process. Increased land use leads tofragmentation of the forests. That leads to reduced resilience and reduced rainfall in thecenters of the remaining patches. These local climate changes can ’cascade’ and possiblytransform the landscape in a very short time. Forests could convert into grasslands and/or an
open-canopy, degraded state and that likelihood increases when fragmentation and humansettlement in the region is high.”“

As far as I can tell, all the answer options are possible for the reasons forecasters have provided
throughout: We don’t know exactly how much of the rainforest humans are going to cut down,
we don’t know what the impact of climate change will be, and we don’t know where the tipping
points are for a much larger collapse. The loss between 1970 and now was about 20%. Just
projecting that rate would get us 30.19% by 2100. But it’s hard to know if we should instead
expect a higher rate of deforestation than over the past 52 years, because of climate change andthe possibility of hitting tipping points where a large-scale transition to savannah occurs even inregions which humans haven’t cleared, or instead a lower rate, because as Brazil gets richer, it will
be more willing to forego the economic bene its of cutting down trees.”

Downward Pressures(i.e., factors that would lead to lower transition of the current Amazon biome to savannahor grassland by 2100)
Mitigation e orts: The Superforecasters would expect less of the Amazon biome totransition to savannah or grassland by 2100 if we start seeing evidence of a shift in thepolitical climate away from deforestation or greater international cooperation in thisarea. That said, the Superforecasters largely expect mitigation e orts to remain
limited.

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Political factors (i.e., who is in o ice in Brazil and their policies) can have a signi icant impact
up to a point. However, this is mitigated by two factors: 1) Slash-and-burn farming rapidly uses
up the soil and the farmers move on. These areas then tend to recover; and 2) political parties goin cycles, so over the next 80 years, we can expect policies to swing between protection anddestruction.”“International pressure has, at times, been successful in reducing deforestation. Starting in
2009, deforestation was reduced but the trend has reversed. 2022 is starting out as the worst
six months of deforestation for the Brazilian Amazon since 2008. Better governance will help, butthere is no easy path forward.”“

Brazil’s initial pledge in Paris included some forest restoration (actually 120,000 sq.km). Thiswas eventually changed in Brazil’s later Paris Agreement plan (i.e., NDC), but nevertheless thisshows that restoration is within the Overton window and remains a possibility, should we seepolitical change in Brazil.”“International support for avoided deforestation or reforestation is another mechanism. There’s
been a long-running e ort to establish a system of ecosystem payments that incentivize forest
communities to keep forests intact (e.g., the so-called REDD). More recently, the climateagreement in the aviation sector (known as CORSIA) is generally reliant on o sets to achieve its
targets and could hypothetically constitute demand for forest credits. There was also a long
period in which Norway engaged with Brazil to help it— inancially—with reducing deforestation.
I’d say it’s likely that, should a more cooperative government be elected in Brazil, similar
partnerships will emerge.”

Future trends in meat and soy consumption: Lower demand for Brazil’s meat and soy
exports would take away one incentive for converting the Amazon to farmland.

“

The major cause of Amazon destruction is growing soy, feed, and grazing of beef for export. I
agree that climate change could a ect the composition of the Amazon. For me, this question
also hinges on major meat-eating regions such as China and Europe changing their consumer
eating habits. The growth of meat substitutes is still a single-digit share of market. An increased
awareness, however, could shift the demand needle just enough to reduce the land destruction
and facilitate regrowth. But getting farmers to re-wild their land needs government interventions.”

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COST OF SOLAR ENERGY
Q20: WHAT WILL BE THE MIDPOINT FOR UNSUBSIDIZED SOLAR
PHOTOVOLTAIC LEVELIZED COST OF ENERGY (LCOE) IN 2023,
ACCORDING TO LAZARD?

Resolution Criteria: In its 2021 analysis (Version 15.0), Lazard reported a range of $30/
MWh to $41/MWh, with a midpoint of $35.50.

Base Rate
The historical trend has been toward cost declines associated with cumulative
deployment.

““

If the current trend of LCOE continues, the mean LCOE value in 2023 should be between $34
to $34.5.”

The trajectory is likely to either latten ($35.50 for 2022 and 2023) or continue to decline at thesame pace as 2020/2021 ($34.50 for 2022 and $33.50 for 2023). A steeper decline, to as low
as $28.50, is much more likely than an increase to over $37.00.”

Upward Pressures(i.e., factors that would lead to higher LCOE)
Higher associated costs: Increased component/material costs, cost of labor, and costof capital of capital due to higher interest rates are some of the factors that, especiallyin combination with supply chain issues, could drive LCOE higher.

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Upward cost dynamics are: Supply chain shortages and disruptions, general in lationarypressures, increased cost of capital investment related to interest rates, increased demand
exceeding supply driving up prices.”“

In the time between 2021 and 2023, I anticipate only incremental change in technology andcosts. In lation is likely to impact installation costs harder than material costs, which are basedon long-term material contracts. Assuming installation and transport are more than 3/4 theproject cost in some regions, prices could increase with the cost of labor at 5-10% in the time ofthis question.”“

The resolution source provided sensitivity analysis where we can see midpoint if cost of debt
has increased to 9% or 10%, resulting in 39 USD and 43 USD respectively. I am pretty sure thatcost of debt due to rate hikes has increased at least by 2%, which is in answer option E territory.”“

The days of dramatic declines in cost of solar energy may be over, at least for now. Polysilicon
and component costs and supply chain issues are ongoing and not expected to fully resolve
until mid- to late 2023. Labor costs for installation, sales, marketing, and overhead are also
increasing. Given the above, I’m assuming lat to slightly higher pricing in 2023 in comparison to
the 2021 igures. I see more indicators of escalation than reduction. However, a potential
recession could soften demand enough to a ect prices next year.”Supply chain issues and trade barriers: Supply chain issues, tari s, and trade barriers
are other examples of upward pressures on LCOE. A particular risk would also be a
China/Taiwan con lict, although the likelihood of this happening in 2023 is low,according to the Superforecasters.

““

Due to global turmoil (both economic and political), I expect higher LCOE.”
Risk factors include instability between China, Taiwan, and Japan. If this leads to war or even
China capturing small islands and shoals, it could interrupt global supply.”

Increased demand for photovoltaics (PV): Increased demand, particularly in the factof supply constraints, could also lead to higher costs in the short term.

“First, electric car sales have risen sharply. This may increase the demand for PVs because of theneed to charge the cars and the desire to do it ecologically. California accounts for nearly halfof all new electric car sales and has a climate (political and natural) that favors solar energy. Those
who buy electric cars are also making a major foray into green energy. This could drive up

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demand and thus cost, especially while there are supply chain issues. Second, fuel prices are
currently declining, but the winter is likely to be very di icult for Europe due to issues related to
Russian supplies of oil and gas. This could lead to accelerating the move to photovoltaics, thus
driving up the global cost due to increased demand.”

Downward Pressures(i.e., factors that would lead to lower LCOE)
Technological advancement: Many Superforecasters expect technological progress(learning by doing) and increased deployment, with current higher costs of materials
in fact accelerating the pace of development.

““

The future will hold a wide variety of innovative sustainability methods. I predict the techniquesthat will sustain humanity into future will become widely available.”

There is a tension between rising costs due to cost of capital and decreasing costs due toimprovements in technology. High costs have salience at present, but development marches
on, and in some cases, the cost of materials is leading to accelerated development work, which I
think might most bene it the utility-scale part of the market in 2023.”

Economies of scale and production capacity in China: China’s production capacity,
coupled with the economies of scale, is another key factor that will exert a downward
pressure on LCOE.

““

Project size is growing increasingly large over time, which should bring down deployment
costs due to economies of scale.”

China’s in lation rate in June was 2.5% compared to 9.1% in the US. This will help keep the costof installation and maintenance low. The US In lation Reduction Act will lead to a massive
increase of utility-scale PV projects, but 16 months is a short time to go from concept to inancing
approvals and completion. For this reason, I don’t see it as a signi icant factor in 2023, but it will
be in future years. Germany and other European countries are likely to boost PV utility-scale
projects in an e ort to decouple from Russian energy dependence. Like the US, these e orts will
have a signi icant long-term impact, but 2023 is very near term.”

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The midpoint has fallen every year and my instinct is that will continue, however slowly.
Growing economies of scale will continue to grow this year and next and the technology willcontinue year-on-year improvements.”

Increase in investment: Finally, green transition is expected to bring more investment
in solar energy in the West, while China continues to prioritize this sector domestically,
which may have some impact in 2023 and greater impact beyond.

“Due to the Russian invasion of Ukraine, the EU will be investing in alternative energy sources
and they would be wise to include the low cost of solar energy as a main new energy supply
source.”“Share of deployment in China means that in lation may not be as much of a concern as it is inmany Western countries. Beijing has also shown solar to be an industry of interest, and will
likely continue to prioritize deployment.”“

Increased tensions between China/Taiwan/US, global supply chain issues, general in lation,and the gas crisis in Europe driven by the war in Ukraine will force e orts to shift to green
energy. If the agreement between Schumer and Manchin is enacted basically in its current form,
it will increase investment in solar energy, which should drive down LCOE in the long run.”

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EXTINCTION
Q21: WILL CLIMATE CHANGE BE A CAUSE OF HUMAN EXTINCTION
BY 2100?

Q22: WILL CLIMATE CHANGE BE A CAUSE OF HUMAN EXTINCTION
BY 2300?

The Superforecasters see a very low risk that climate change be a cause of humanextinction by either 2100 or 2300. The Superforecasters assign a 1% probability on
aggregate that climate change will be a necessary, but not necessarily su icient, causeof human extinction by 2100. Forecasts on this question ranged primarily between 0
and 1%, with just one Superforecaster entering a higher forecast of 10%. The median
decimal forecast for those forecasting between 0-1% is 0.00055%. The aggregate
forecast for 2300 is 3%. Of 26 Superforecasters active on this question, 21 madeforecasts between 0-1% and median decimal forecast for those is 0.05%. Of the ive
Superforecasters who forecast above 1%, four gave forecasts between 2-5% and one
gave a forecast of 55%.

Key Drivers behind the Consensus Forecast
The Superforecasters see total extinction as a high bar, as each of the relevant risks
carries only a very small probability.

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Although climate change will exacerbate almost any crisis, and although climate change could
increase the likelihood of extinction-level events, extinction is a Boolean event, and I think it isunlikely that climate change will be a necessary precondition. Extinction is a very high bar.”“

If one were to try to get a handle on the total risk resulting from climate’s many indirect
impacts, it could go something like this. If the probabilities of extinction by nuclear war,
engineered pandemics, AI, nanotech, natural risks (volcanoes, asteroids), and unknown unknowns
for 2100 are respectively 1/1,000, 1/1,000, 1/100, 1/1,000, 1/10,000 and 1/1,000, and if climatechange is a necessary condition in 10%, 10%, 1%, 10%, 30%, 5% of all such scenarios respectively,
assuming independence, that would suggest a total risk of 0.048% (~1/2000).”“

Will there be wars fought over, or that can be said to be a direct result of, climate change? A
nuclear war? A war that leads to the weaponization of Arti icial General Intelligence?
Depending on how such a war developed, it might su ice to resolve the question. Or will theravages of climate change become so bad that a non-anthropogenic risk (asteroid, supervolcano,etc.) that wouldn’t otherwise lead to our extinction does so—in a way that su ices to resolve thisquestion? These are the issues the team should consider. But even considering them, the risk inthis time frame is close to zero. Don’t get me wrong, I do believe that we’re going through aparticularly dangerous period in human existence. But even if we’ve vastly underestimated therisks of climate change, and ind that the models were wrong, and the most dire predictions, atthe very tail end of the probability curve, come to pass, I struggle to envision a scenario where
the entire human race is rendered extinct by these dates.”

The Superforecasters cite adaptability of humans as a species. Humans live in a wide
range of climates, each with their respective challenges. Even if a major catastrophe
drastically reduces global population, some people will ind a way to survive andadapt. Furthermore, by 2100, we will likely be a multi-planet species, someSuperforecasters argue.

“

Maybe I’m too optimistic, but I do see the human race addressing climate change via (a)transition to clean energy, (b) innovation, and possibly (c) geo-engineering and/or carbon
capture. We aren’t addressing it as fast as we should, but we will get there, su ering more thannecessary on the way. Complete extinction, as in every last human is dead, is exceedingly
unlikely. Even in the most dire circumstances, I envision 50-100,000 people surviving via
extraordinary measures for at least a considerable period of time.”“

I think any scenario causing human extinction is very unlikely; climate change may haveprofound e ects on how we live, but there is very low probability it causes human extinction.
Engineered pathogen? Massive nuclear war as climate change causes a scarcity of food? Are

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there major feedback/feed-forward loops in the climate that we don’t yet know about/understandthat would make the planet uninhabitable? Even then, human ingenuity would probably manage
some sort of existence.”“

Climate change has a good chance to make us miserable, and cause deaths, for the reasons I
mentioned above. But it will not cause extinction to a species that’s resilient and clever enoughto ind solutions.”“

I can easily see that many of the disasters described by my colleagues could lead to thecollapse of civilization. But not to total human extinction. By 2100 we will likely be a multiplanet species.”

Variability of climate conditions across the globe also means humanity will have, atleast temporarily, more hospitable areas to lock to, which will give humans time toadapt. Furthermore, current climate modeling o ers some cause for optimism withregard to extinction.

“

Change is not the same everywhere. Therefore, risks are not spread evenly. Rate of change andduration count. This varies by location. Yes, there will be dead zones in the oceans where there
is not enough oxygen for marine life and plants. But there are a number of mitigation things
humans can do to survive. Rich nations and people will be able to a ord those. Could the rich live
in a dystopia where they never go outside, grow food inside, have enough energy and live theirlives in some metaverse headset or even 3D cave simulations? Maybe.”“

In climate model simulations, it requires substantial warming (more than 6 degrees Celsius) tocreate zones deadly to endothermic mammals and birds over substantial areas. That is not
likely to happen even by the year 2300 in the most likely carbon emissions scenarios. With 3
degrees Celsius of global warming, which current research indicates is the most likely future,most of the world’s terrestrial biosphere will avoid crossing the 35 degrees Celsius wet-bulb limit
for signi icant periods of time.”

Risks to the Consensus Forecast(i.e., factors that would make the Superforecasters change their forecast)
The risk is not zero, however, according to many Superforecasters. Among the
scenarios they considered, con lict in its various forms represents a prominent risk,
including nuclear risk, risks from AI or biological weapons, or a Götterdämmerung

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scenario where a faction on the losing side in a con lict decides to take humanity downwith them through malevolent use of the abovementioned weapons.

“

Leading contenders are genetically engineered pathogens and AI risk. Nuclear war is unlikely
to lead to extinction, even with the possibility of nuclear winter. While neither AI or engineered
pathogens would be directly caused by climate change, the rapid warming of the planet will
increase resource scarcity and fuel con lict. This is likely to lead to more malevolent uses oftechnology.”“

As humanity becomes equipped with ever more dangerous means of destroying itself (e.g.,
biological and AI weapons, including DIY variants), the risks that climate-induced disasters will
precipitate extinction-level con lict increase.”“

I assume climate will be a necessary condition in a relatively large share of extinction scenarios(5-30%). I tend to agree with William MacAskill that most of the existential risk comes fromcon lict (he says 90%). Climate change is a threat multiplier, so we’d expect a non-negligible rolein con lict.”“Tipping cascade,” or a cascade of adverse climate e ects, is another scenario theSuperforecasters are concerned about.

“

Just because what life that existed on earth some 55 million years ago was able to adapt overthousands or hundreds of thousands or millions of years doesn’t mean we’ll be able to in thenext few hundred without decimating our species. IPCC models deal with probabilities, notcertainties. They could be wrong, or it could just be that the temperature in 2300 falls on the far
upper tail of the probability curve.”“

Humans are able to survive in a wide range of climates, and there are a lot of us spread acrossthe globe. The only two possible scenarios I am aware of where climate change can cause
human extinction are: (1) An ecological collapse cascade: Due to climate change someecosystems collapse, and this causes a cascade that causes basically all/most ecosystems that
we are dependent on for our survival to collapse. Due to the speed of the change, life is not able
to evolve fast enough to adapt to the new conditions. (2) Hothouse Earth/Venus e ect: During
global warming, we hit a series of positive feedback e ects (like methane released by the meltingof Siberian permafrost), and this outweighs the negative feedback e ects like increased
vegetation growth, leading to a runaway warming scenario where Earth becomes uninhabitable(like Venus) to humans (and probably all life except maybe very simple forms).”

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Climate projections don’t generally account for reinforcing feedbacks such as the melting ofArctic permafrost and, perhaps more signi icantly, the thawing of methane clathrates in theocean. Both of these could release very large amounts of greenhouse gases into the atmosphere,
theoretically causing a runaway greenhouse e ect leading to much higher temperatures andperhaps pushing Earth beyond habitability. Note that the science is very murky on such
feedbacks.”“

All life is interconnected. Humans depend upon biodiversity for food, medicine, clean air andwater, pest control and so much more. Technological advancement should be able to keep
pace with incremental changes, but perhaps less so with too many large overlapping
catastrophes.”“

The combined impact of direct and secondary e ects of climate change, including resource
wars, zoonotic diseases, wet bulb temperatures, aridi ication, food loss, water scarcity,
infertility, etc., could wipe us out. All of these factors would come into play in a 4C-5C warmer
world. A 5C warmer world is quite plausible even under a ’moderate’ emissions scenario (RCP 4.5)
thanks to positive feedbacks such as ice-albedo, carbon sinks becoming carbon emitters,
methane release, and global dimming, although the timing is unclear. Ill-conceived
geoengineering (e.g., stratospheric sulfate aerosol injection) done out of desperation would makethe problem worse. Passing 5C by 2100 or so means we’ll pass the threshold for entering a mass
extinction event comparable to the Big Five extinction events. In the past, few animal species
larger than a rabbit survived these events. While extinction in this scenario is likely to play out
over the course of many centuries, can we be con ident that it won’t happen within two?”

Reduced resilience followed by the above, AI, or non-anthropogenic catastrophe isanother way through which climate change could be a necessary, but not necessarily
su icient, cause of human extinction. Climate change could reduce our capacity torespond to the event.

“

Using Toby Ord’s ’anatomy of extinction risk’ framework, climate change could: (1) be precondition for the origin, (2) amplify the catastrophe, (3) diminish our resilience. The mostobvious e ect to me is (1), but (3) could be more important as climate change will a ect ouraccess to water, food, and energy, cause mass migration, erode institutions, and conceivably
trigger social chaos on a global scale. Total climate risk is a lot higher from considering resiliencein addition to the more common arguments around climate as a pre-condition. It also shows thatclimate change could be a part of risks that are otherwise non-anthropogenic (like volcanic
eruptions or asteroid impacts).”

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In sum, the Superforecasters see climate change as a cause of extinction very
unlikely. Societal collapse, however, is another matter, and is the chief reason theycite to be mindful of such tail risks as described in section above.

““

Though this forecast is very low, I believe climate change is one of the greatest challenges, or
the greatest, of the next 80 years, and if not solved, it will radically decrease our quality of life.”

I do think we should be investing enormous amounts of time and money into preventing theworst-case climate-change scenarios from occurring. And I think we should be extraordinarily
mindful of the tail ends of the probability curve when it comes to potential consequences ofpumping unprecedented levels of greenhouse gasses into the atmosphere.”70

CLIMATE CHANGE

From groundbreaking theory to powerhouse practiceIn 2011, IARPA—the US intelligence community’s equivalent to DARPA—launched amassive competition to identify cutting-edge methods to forecast geopolitical events. Four
years, 500 questions, and over a million forecasts later, the Good Judgment Project (GJP)—led by Philip Tetlock and Barbara Mellers at the University of Pennsylvania—emerged as
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Good Judgment Inc is now making this winning approach to harnessing the wisdom of thecrowd available for commercial use. Our clients benefit from the externally validated
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