Why is it said that Amazon creates 20% of the oxygen production of the world, when it accounts with less than 14-12.8% of the forest area? Many times we see in articles that the Amazon rainforest creates 20% of the oxygen of the world . Even french president Macron stated this in a tweet Macron tweet

According to this Amazonas size Amazon size is 5.5 millions km². But according to this List of countries by forest area

World forest area is between 39 millions to 43 millions km2, depending if you believe the world forest area they give, or the added forest area of each country (which surpasses 43 millions km2) . I suppose other data is taking into account to say Amazonas create 20% of the oxygen.

Why is it said that Amazon creates 20% of the oxygen production of the world, when it accounts with less than 14-12.8% of the forest area?

I cannot find any language in peer-reviewed literature (as far as publicly accessible) that makes the 20% claim reported in the question. I therefore consider this claim to be of obscure and dubious origin.

About 50% to 55% of the oxygen produced via photosynthesis is estimated to come from the world's oceans, as reported in the following two papers:

Curtis A. Suttle, "Marine viruses -- Major players in the global ecosystem." Nature Reviews Microbiology 5 (10): 801-12 (2007)

  The oceans cover more than 70% of the Earth’s surface. They control the climate, provide a significant amount of the protein that is consumed globally and produce approximately half of the Earth's oxygen.

A. Yu. Borisov, L. O. Björn, "On oxygen production by photosynthesis: A viewpoint", Photosynthetica (2018) 56: 44

  We also find that the ocean produces 22% more oxygen than the land surface.

According to an expert quoted by the BBC, about 16% of the land-based oxygen production from photosynthesis occurs in the Amazon basin:

  A large proportion of the world's oxygen is produced by plankton, explains Professor Malhi. He says of the oxygen produced by land-based plants, about 16% comes from the Amazon.

Is this claim plausible? Based on the reported size of Amazonian forests at 6-8 million km2 and the world's total forested area of about 40 million km2, I am inclined to answer in the affirmative, although not all of the land-based oxygen production occurs in forested areas.

Yale's Global Forest Atlas:

  Amazon basin is the largest tropical rainforest in the world, covering a size approximately equal to the lower 48 United States. 6-8 million square kilometers of forest house approximately 10% of the world’s biodiversity and 15% of its freshwater.

Based on data from the FAO suborganization of the UN

  Forests cover 31 percent of the world’s land surface, just over 4 billion hectares.

The area of a forest and its oxygen production are unlikely to be in strict linear proportion to one another, as the rate of photosynthesis should depend on such factors as solar irradiation (which varies with latitude and cloud cover) and temperature (in boreal forests) or the seasons (for deciduous forest in moderate climates). The density of a forest will likewise be influenced by the availability of water and nutrients.

How do scientists estimate the amount of oxygen produced via photosynthesis? Best I can tell from a perusal of the literature this is done indirectly by estimating total biomass, which itself is determined by a combination of satellite data and on-the ground measurements. Such estimates carry a non-trivial amount of uncertainty.

Nowak, David J., Robert Hoehn, and Daniel E. Crane. "Oxygen production by urban trees in the United States."
Arboriculture & Urban Forestry. 33 (3): 220-226. (2007)

  The net amount of oxygen produced by a tree during a year is directly related to the amount of carbon sequestered by the tree, which is tied to the accumulation of tree biomass.

S.S. Saatchi, R.A. Houghton, R.C. Dos Santos Alvala, J.V. Soares and Y. Yu,
"Distribution of aboveground live biomass in the Amazon basin",
Global Change Biology (2007) 13, 816-837

  To determine the spatial distribution of forest biomass of the Amazon basin, we report a method based on remote sensing metrics representing various forest structural parameters and environmental variables, and more than 500 plot measurements of forest biomass distributed over the basin. [...] We estimate that the total carbon in forest biomass of the Amazon basin, including the dead and belowground biomass, is 86 PgC with ± 20% uncertainty.

The reason is: human nature. People like to exaggerate to make a point, and quite often they are such excellent liars that they believe their own exaggerations. Clearly the Amazon does not create 20 percent of the worlds oxygen. Most of the oxygen in the atmosphere is fossil oxygen, produced by photosynthetic organisms long before there were any rainforests, and as Universal Learner says, most of the CO2 disposal and oxygen production takes place in the oceans.

By saying this, I don't mean to downplay the importance of the Amazon rainforest (some of it is rainforest and some is the more inflammable monsoon forest). It is full of desirable wild life, some of it rare and endangered. It is tragic to see so much of it disappearing. Nevertheless, naturalists, ecologists and environmentalists should try to be more objective and stick to the facts. Although the Amazon tropical forest doesn't provide as much oxygen or dispose of as much CO2 as is sometimes claimed, it still makes a valuable contribution.


What could possibly be a rational basis for rejecting climate science? Here is my logic (thus not opinion) if the anthropogenic global heating AGH deniers actually do not have any rational climate science basis for rejecting anthropogenic global heating then everyone should understand that their position is baseless.

It would seem that consistent failure by global heating deniers to provide a rational basis for their rejection of climate science would form sufficient evidence that no such rational basis exists.

I am diligently striving to use logical analysis to cut to the heart of the truth about global heating in such a way that all true skeptics (not those hired to lie) will immediately see the light of the truth.

I make this post so that all global heating deniers will be provided an opportunity to present their side.

If such a rational basis exists, then it can be provided. If it cannot be provided then no such rational basis exists. If no such rational basis for rejecting climate science exists then the matter of: anthropogenic global heating (AGH) is concluded in closure.

3C ± 1.5C for every doubling of CO2 plus the following 100 PPM spike in global CO2 since 1950 really seem to explain the temperature increase.

If we apply climate sensitivity analysis to the current level of atmospheric CO2 we find that this increase of CO2 predicts a temperature equilibrium of +1.65C: 3 * log2(410 / 280) = 1.65C.

https://en.wikipedia.org/wiki/Climate_sensitivity#Intergovernmental_Panel_on_Climate_Change

If the issue is assessed on other grounds than science ones there can be rational reasons to reject climate science. e.g. if it is being assessed with respect to how addressing versus not addressing AGW impacts costs, competitiveness and profitability of specific business enterprises then rejecting climate science and encouraging other business operators as well as governments, courts and regulators to reject it, to avoid compliance costs of addressing it appears rational. The advice given by lawyers to people and companies facing lawsuits to admit no responsibility and seek to undermine the plaintiff's arguments, including questioning the veracity of expert witnesses is not irrational. Unethical perhaps, but it is not irrational.

Just because someone says that man made CO2 emissions are not the sole cause of climate warming does not mean they are rejecting climate science. On the contrary, it is those who claim it is the sole cause who are rejecting science. Prof.Malte Janson of the University of Chicago, quoted in the journal Nature Geoscience, is among those who say man made CO2 is not the sole cause of climate warming, but his academic status will probable deter the climate fanatics from labelling him an heretic and climate change denier.

Jensen's team have found that increase or decrease of sea ice in the Southern Ocean around Antarctica plays an important part in the CO2 content of the atmosphere. When there is an increase in sea ice, the ocean beneath the ice can no longer release CO2 into the atmosphere, and that, in addition to the ice reflecting solar radiation back into space, causes cooling. When the sea ice retreats, the opposite effect occurs: CO2 is released and there is also less reflectivity, so the world warms up. This helps explain why the Milankovitch cycles are not an infallible guide as to when ice ages will occur.

Between 1979 and 2014, ice cover in the Southern Ocean increased, and had this trend continued, then according to Prof.Jansen it might have eventually led to the start of a mini ice age or worse, but from 2014 to the present time the ice has been retreating. No one is sure what will happen next, whether the ice will continue to retreat or resume its advance. According to the researchers, the Younger Dryas climate event of  about 12,800 years ago may have been caused by a sea ice advance of this sort. It is also a possible cause of the 400 year Little Ice Age from roughly AD 1400 to AD 1800. The point I am making is that many so-called climate change deniers are in fact nothing of the sort, they are just less fanatical than those who have made climate change their religion.


Are weather forecast models more accurate for either high or low temperatures? The other day our low temperature for the day was ~10 degrees F below our forecast low.  I've noticed this before in the winter, especially when temperatures start to go below 0 degrees F (-18 degrees C).  This made me wonder if the models used to forecast high and low temperature are different, and if so is one indeed more accurate?  Conversely, if the same model is used, is it as accurate for both high and low temperatures?

I was able to find one student project from Dartmouth College in which a statistical analysis of forecast high and low temperatures were compared from three five years sets (1970-4, 1980-4, and 1990-4) of data from 15 different United States cities representing different influences such as latitude, water, and land influences.  One of the findings of this dataset of 5,269 records was that the forecasts where more accurate in the summer than in the fall and winter.  This seems to hint that warmer temperatures are forecasted more accurately than colder temperatures, at least on a seasonal basis.  I'm hoping there's more information out there that can either confirm or deny this conclusion without the seasonal bias.

There are two ways to answer your question: the first would be by verifying historical forecast data (calculating the difference to observed temperatures) and looking into a temperature dependency of these errors. This would certainly be doable - but in this context on Stackexchange not.
So I suppose you refer to a general, more physically interpretable explanation what the difference in forecasting higher or lower temperatures is.
Even though it makes a difference for physical processes like radiation and evaporation if temperatures are high or low, the characteristics stay the same - more explicitly said:
Temperature differences matter more than absolute temperatures!
For example:

The net radiation (budget) is proportional to the difference of soil and atmospheric temperature (each to the fourth power).

Deeper layers of soil keep the surface warm by transporting heat (also proportional to the temperature difference).

and so on...

But there is a significant difference in the active physical processes:
At daytime (Tmax), the near surface air is (mostly) coupled to the temperature of higher layers of air by turbulence. On a sunny summerday, the surface air can not get significantly warmer than the air above because if it gets warmer, the air rises and cooler air from above cools the surface layer. In this way, the surface air temperature is 'tied down' so that it can not reach extrordinary temperatures without also heating up a say 1500 m boundary layer of air.
If the surface air is cooler than the air above it gets decoupled from the temperatures above - turbulence is reduced, and theoretically the temperatures could drop a looong way down, until the incoming (longwave) radiation from the atmosphere (say hi to greenhouse gases) stops this temperature drop. The equilibrium temperature depends mostly on the amount of water vapor above our heads -> warmer in the tropics, cooler nights in polar regions. But the equilibrium is practically never reached. In most cases it is a dynamic thing with  ground heat flux and sporadic wind gusts - which are of very local effect.
Conclusion
Comparing these two cases one can see that the Tmax is more homogenously distributed in space because it mostly depends on the airmass. Minimum temperatures can be very different even for close locations because it really depends on your surrounding: trees, buildings, ridges. You can see the lowest Tmin at high altitude locations which are not exposed to wind gusts (sinkholes) which are covered by snow (isolated from soil heat).
So by analyzing a forecast error dataset, you would most likely see that Tmax are more accurately forecast.

The problem you may be seeing is due to how the weather industry calculates the low temperature for the day.  They use the period from 7pm of the current day to 7am of the following day.  Sounds completely ridiculous?  Me too, you can easily observe this for yourself.  Go to a site like intellicast and where it shows the 10-day weather forecast, it will also show the temperature as a graph line.  You can see that the forecast lows of the day are often wrong - it is the low for the next day.


What kind of tooth is this? Please help me identify this tooth and the era its from. I found it in Panama City Beach Florida. Its cold and hard when i bite it. It looks very old. Possibly a shark tooth?

It looks very much like a shark tooth, but it looks like it’s weathered and worn. It may have spent a good deal of time buried below the sand, being slowly ground by the sand and tide action. Eventually it became dislodged and after a while of being worn smoother it washed up and you found it.


Chicxulub Asteroid Remains? Do scientists know if the Chicxulub asteroid disintegrated completely upon impact or if any (large or small) chunks of the asteroid remained intact? If it is possible that a significant fragment of the asteroid survived could it have been preserved until today somehow (i.e. can it be found)?

There are micro-tectites galore, strewn over thousands of square kilometres. But remains of the actual bolide? Hard to say, because the impact crater is now buried under 600 metres of sediment. Earlier this year the joint IODP-ICDP drilling program drilled to a depth of 1300 metres. As far as I know, their findings are not published yet.

https://products.kitsapsun.com/archive/1998/11-19/0016_extinction__piece_of_dinosaur-kil.html
Here you go. Its amazing to see what happened to Earth, at the end of the Mesazoic.


Is non-randomly-sampled historical data representative? I'm a global warming skeptic, and one of my concerns is the accuracy of historical global temperatures. Since these temperatures weren't sampled at random locations or gridded points, can they be considered an accurate representation of "global temperature"?

Thoughts/etc:

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3982162/ talks about this in a temporal sense, since using the average of the minimum and maximum daily temperatures at a given location isn't really a great way of determining average temperature. However, it doesn't discuss geographical random sampling/gridding.
http://onlinelibrary.wiley.com/doi/10.1002/joc.4580/full notes this problem exists, and takes uniformly gridded measurements, but it's limited to a specific region and time period (1979-2012).
I know climate scientists slice the Earth up into grids to avoid clustering bias, but that's not the same thing, and isn't useful if the original readings don't accurately represent the slice/region.
I also realize that climate scientists have other measures of global warming, but linear regression of actual temperature measurements seems to be the most used to convince the public, so their accuracy seems important.
As a skeptic, I'd also like to know if, in general, most of the arguments for global warming are statistical in nature (ie, linear regression on measured variables), or the statistical ones are just the most "photogenic" for public consumption? In other words, is the whole non-randomly-sampled/gridded temperature argument a red herring?

EDIT (to clarify question):

To determine the Earth's mean surface temperature, we can employ one of these methods:

Measure the Earth's temperature at every point and average. Of course, this is physically impossible, since a point is a 0-dimensional mathematical abstraction, but we can do something close with satellites.
Select a large number of random points on the Earth's surface (this random distribution is uniform in longitude, but not in latitude-- in latitude, it would look like a cosine curve), measure the temperature, and average. In addition to giving us a mean, it would give us a standard deviation so we can say "we are 95% confident that the Earth's true mean temperature is X plus or minus Y".
Take a uniformly spaced grid (non trivial, since the distance between longitudes vary by latitude), measure the temperature at those points and average. This is similar to the first approach, but with fewer points. Unless we believe our grid points introduce a bias, this should be as accurate as random sampling.

My problem: temperature measurements in the past were made using NONE of these methods. The points where temperature was measured were not chosen randomly or in a gridded fashion. Therefore, how can they be an accurate measurement of historical temperature, even if we only consider temperature changes?

NOTE: I realize surface temperature isn't the best measure of global warming, since water has a much higher specific heat than land (among other things), but that's my focus for this question.

Samples don't need to be random to be valid, it helps but it is not essential especially if exhaustive, consistent, and has a large sample size, especially when dealing with observational studies. Representative sample is different than random sample. Remember we are not trying to attain the global temperature to the highest degree of accuracy in one instant, we are trying to measure the change in temperature over a long span of time. Thus consistency in location is more important than randomizing location.

The fact that the sampling points do not move is essential, we know temperature is affected by regional conditions if the samples were re-randomized(moved) with every measurement it would make it less accurate not more. Remember what is being measured, the change, because the sampling points are not moved the the change will be accurate because it essentially becomes a stratified sample. If I am measuring changes in engine temperature for instance I don not want to measure at a different point each time, as long as the points(locations) are consistent the sample will retain high accuracy. A random sampling would be LESS accurate because it would invite confounding because we know the distribution of temperature across the engine (or globe) is not random. Any shift in location between measurements would invite confounding data. Almost no science uses a truly random samples, it's just not possible. Consider things like exhaustive sampling, cluster sampling, stratified sampling, and systematic sampling all are used more often than true random sampling and each is more accurate than random in the right circumstances.

Consider an example, say you are trying to measure the temperature change in an engine over time. Where on the engine I attach my sensors does not matter as long as I do not move them, especially if I put many sensors on it. I could put thirty sensors all on the left side engine, and it would measure the change in temperature very accurately, compared to moving the sensors between every measurement. Don't fall for the perfect solution fallacy. Also remember this is an observational/descriptive study by its very nature.

Each point on the map is more like a repetition, the real independent is the time at which they are sampled, which is either stratified or clustered depending on which study you refer too. Note that multiple sets of data points are also compared. NOAA, BEST, etc. are each independent data sets that can be compared, and show the same pattern.

High and low are used for measurements because that is all that was recorded in the oldest measurements, so changing the format would require throwing out all that data, drastically shortening the sample size (loosing more than half the time span). In this case the accuracy gained by the much larger number of samples is more than would be gained by a random or grid location. Random is rarely possible with historic data which is why the size and consistency of the data set is so important. The nice thing is these are also compared to other sampling methods on other time scales to test to see if they show the same pattern. Historic scientists are aware of the limitations of their data which is why independent verification is so important.

Now consider ice core data, I was surprised when you said surface temperature was the most used, I see ice core data far more often, because it records a much longer span of time, and records other things (like $CO_{2}$ content) as well. Again each core is a repetition and the core can be sampled in a random or stratified way, stratified is the most common because it is more exhaustive in a core sample. Ice cores are also compared to ice cores for m other locations.

Another consideration is cross-comparison, that is the use of multiple independent forms of measure, ice core compared to satellite, compared to surface, etc. Dozens of different forms of measurements/experiments are compared and show the same pattern.

This is probably one of the best overviews of the science I have seen. It is a little old (2013) so if anyone has seen a more recent version I would love to use it instead.

No, they are not representative. Scientifically not ideal. You wouldn't start from there if you had today's plan BUT it is all you have got. When you have imperfect data you have to be honest and point out it's imperfections and, if possible, calculate or estimate the effect of those imperfections on your results/conclusions. Whether or not the clever climatologists have done so to the necessary degree is beyond me (maybe it's not beyond you ?). Early IPCC reports seemed to have plenty of "not sure" "inconclusive" "insufficient data" comments but these have, of course, somewhat reduced in number.The reason is not better historical data, you still have the same old data you had before, but clearly better "treatment". Whether the data has been tortured by humans or integrated circuits is again beyond me. Perhaps it has not been tortured at all. If we wanted to examine a prisoner who claimed he had been tortured when the guards said they "didn't touch him, gov !" We would have a look beneath his clothes at his skin. So get the climatoligist to show you how exactly they treated their data, get the outer layer of clothes stripped off, and ask them to explain those bruise marks. Be suspicious of anyone who says it was an accident while playing hockey.


Has Antarctica's coastline been completely mapped? (map discrepancies) Looking at different world maps, I noticed that there is considerable variety in how the coastline of Antarctica is depicted (even when taking the different map projections into consideration).
Are these discrepancies caused by the fact that the coastline of Antarctica has not been precisely mapped because the ice sheet obscures it in satellite and aerial photography? Do we have the technology to look through the ice sheet and locate the bedrock and has it been used on every part of Antarctica's coastline, or does map data still contain some guess work and interpolation?
Or are there perhaps competing ideas about how a coastline covered in ice should be outlined on a map? I noticed e.g. that Google Maps displays Berkner Island while Wikipedia claims that the island's bedrock is completely below sea-level.

Examples: Google Maps has a very different outline for the islands under the Filchner-Ronne ice shelf than other sources:

example 1: from Google Maps

example 2: from an example using the D3-Geo-Projection code library (not sure where the dataset is from)

example 3: from Wikipedia's Antarctica article (similar to example 2, but using a very different projection)

The key sentence here is

(not sure where the dataset is from)

Every cartographer has to decide what level of detail to use. Mathematicians discovered the Coastline paradox for themselves in the 1960's, but it has always been a fundamental part of cartography.
Different sources of data will come out of different methods of data collection, digitization, and storage.
Regardless of the method used, somewhere there has to be a cutoff. You can't represent a detail smaller than the pen you (or computers) draw it with. The cutoff may be a concsious decision of the cartographer based on the purpose of the map, or an effect of the software used. Or just carelessness.
But this means that different datasets and choices of representation will result in a radically different appearance of the map.

What you are seeing is mostly different projections. Look at the last two images. The penultimate image has latitude lines that are straight and parallel to one another, longitude lines that are straight and parallel to one another, and the latitude and longitude are orthogonal to one another. The latitude lines are curved in the last image. The longitude lines, which aren't shown in the latter image, would not be parallel in this protection.


How was Nastapoka arc formed? As wikipedia says, the Nastapoka arc is a geological feature located on the southeastern shore of Hudson Bay, Canada.
(Other description with picture at the Royal Astronomical Society of Canada)

No signatures of an impact event was found. However, 'A hole was drilled on Neilson Island, within the arc, in 1962. The core lacked any evidence of shock metamorphism, but one hole was not regarded as sufficient to settle the question of possible meteoric origin. '

Is that possible that the impact material was buried deep in the past hundreds of thousands of years?

There is other believable mechanism that can form that shape?

Gravity anomalies surveys are used to understand the nature of the crustal material. Positive anomalies, or higher gravity than surroundings suggests higher density (heavier) material, (iron, metallic composition) where lower some lighter alternatives.

A good example of this is the Chicxulub impact. The map of gravity anomalies show the crater quite clearly, even if it is buried under thick layers of sea sediments or surface (Yucatan, MX).

On the other hand, Nastapoka arc is harder to define using similar methods. This recent paper (PDF) (now published here) discusses that it may have more to do with crustal dynamics than an impact. Nevertheless they present an  interesting gravity map of the site (See figure), where any links to an impact in this area would not be obvious.

It is true that major glacial activity occurred repeatedly during the Pleistocene east of the Hudson Bay (eg: Laurentidian Ice Sheet sweeping again and again), but yet the Chicxulub impact was subject to many factors of erosion as well since its formation near the K-T boundary.

Still these kind of surveys indicate the nature of the material in the crust - so even if several glaciations impacted the Nastapoka arc area, there would be some kind of patterns still present indicating heavy metals (Chondrite or anything typical of an impact, iron or circular metamorphism).

To conclude, unless other surveys suggests an alternative interpretation path in the future, few evidences strongly support the theory of an ancient impact at Nastapoka.

Perhaps a Comet miles across broke up as it entered the Earth's atmosphere traveling from South to North about 12900 years ago and various large portions would explain all the anomalies including the "new crater" in Greenland, North Carolina Bays and Nebraska impacts and destruction with fire of Megalithic sites in Peru...slamming into the huge Laurentide Ice Sheets absorbed most but not all of the impact from the many large pieces of such a monstrous set of impacts something like that from a shotgun that would have been 100x to 1000x (or more) more powerful than Tunguska or the 1815 Tambora Volcanic event (where there was "no summer") except that the effect lasted 1200-1300 years (10900 BC to 9600 BC). An increase of Platinum 100 fold circa 12890 BP +- 5 years in Greenland Ice Cores hint that such a hypothesis generally known as the Younger Dryas Impact Hypothesis may well have happened but there are many criticisms such as the fact that the amount and volume of fires was not especially high during that 1200-1300 year time period and that the 10890 BC or 12800-12900 BP time period is not agreed upon for some of the phenomena. So it remains a HYPOTHESIS and not enough evidence yet to make it a proper CONJECTURE.


In terms of the greenhouse effect, what is the Earth's heat capacity? (Question moved from physics to earth science)

Has the earth’s atmosphere reached an equilibrium at which the input radiation energy roughly equals its output, or is the output significantly lower than the input because the energy is being used to heat up stuff? In other words – if the atmosphere’s composition remains exactly the same as it is now, will the atmosphere continue getting warmer, or will the temperature remain as it is now?

If Chuck Norris removed all man- and cow-made greenhouse gases from the atmosphere in an instant – would the atmospheric temperature return to "normal" in a few years, or would there be a significant lag due to the high heat capacity of atmosphere, oceans, and land?

Edits to make my question more precise are appreciated.

For the greenhouse effect, the problem is not a matter of heat capacity. For example, Carbon Dioxide has a specific heat capacity of 0.843 J g$^{-1}$ K$^{-1}$ while $\ce{N_2}$, which is the largest component of the atmosphere, has a specific heat capacity of 1.039 J g$^{-1}$ K$^{-1}$ and water vapor, the most common greenhouse gas on earth, has a specific heat capacity of 1.865 J g$^{-1}$ K$^{-1}$. Thus, the warming isn't necessarily a thermodynamic problem, with regards to heat capacity (though it is, in a ways, a problem of entropy).

The reason that some gases are greenhouse gases is more of a radiative transfer problem than a thermodynamic problem, but the two overlay with regards to molecular structure. Water vapor's absorption spectrum shows that it absorbs most infrared radiation. This graphic demonstrates how much radiation of each wavelength is absorbed by different gases.

You may ask "well, that's dandy, but why do some gases absorb only some parts of the spectra?" Well, that is a bit more complicated, and is dependent on the molecular structure, quantum mechanics, and spectroscopy.

To answer your hypothetical questions directly:

  Has the earth’s atmosphere reached an equilibrium at which the input radiation energy roughly equals its output, or is the output significantly lower than the input because the energy is being used to heat up stuff?

In a ways, yes, that is a fundamental assumption, per Kirchoff's law.

  if the atmosphere’s composition remains exactly the same as it is now, will the atmosphere continue getting warmer, or will the temperature remain as it is now?

There would be a lag before major changes are seen, per Fourier's law. But since water vapor is a greenhouse gas, we would do best not to deus ex machina all greenhouse gases away. Additionally, we need greenhouse gases for survival- too little and we all freeze.

  Has the earth’s atmosphere reached an equilibrium at which the input
  radiation energy roughly equals its output, or is the output
  significantly lower than the input because the energy is being used to
  heat up stuff?

Well, we are almost always at some sort of radiative equalibrium, per Kirchoff's law. For example, the hotter an object becomes, the faster it will cool, per Stefan-Boltzmann Law.


Where did the atmosphere's nitrogen come from? According to Wikipedia's article Atmosphere of Earth:

  Outgassing from volcanism, supplemented by gases produced during the late heavy bombardment of Earth by huge asteroids, produced [Earth's second] atmosphere, consisting largely of nitrogen plus carbon dioxide and inert gases.

However, it doesn't explain any further than that. Where exactly did the nitrogen come from? Was it already gaseous or was it in the form of compounds that broke down releasing N2 gas?

There was some free nitrogen in the secondary atmosphere, and also some ammonia (NH3). Ammonia is present today in the atmospheres of Jupiter, Saturn and other gas giants in the outer solar system. The main constituent of the Earth's primeval atmosphere was carbon dioxide, which also makes up the bulk of the atmospheres of Venus and Mars. The ammonia eventually decomposed into nitrogen and hydrogen.

When we look at the atmospheres of Mars and Venus, we see that they contain only 3 percent nitrogen, while our atmosphere contains 78 percent. The main reason for this is that Mars and Venus still retain most of their primeval CO2, while Earth's has largely disappeared because of biological processes (coal,limestone etc). The atmosphere of Titan also contains a massive percentage of nitrogen because competing gases, apart from methane, have mostly disappeared, frozen out by the intense cold

We also need to consider outgassing from volcanoes. These emissions consist mainly of CO2 and water vapour, but there are small amounts of nitrogen and ammonia, and other gases as well.


What determines how fast clouds move? Do cirrus clouds in the upper troposphere move faster than cumulus and stratus clouds in the lower atmosphere?

What about clouds associated with extratropical systems, compared with clouds in the tropics?

Cloud particles are suspended in air, and their movement is governed by:

Wind; whichever way the wind blows, the clouds go (with some exceptions such as lenticular clouds; thanks jamesqf comment).  The wind is often strongest in the upper troposphere (there are no clouds in the upper atmosphere), so upper tropospheric clouds will move faster than near-surface clouds.
Convection: strong updrafts will force particles upward, as will forced convection by wind reaching obstacles
Particle size: larger particles are more likely to fall down.  Note that "fall down" may be used either relative to the surrounding air, or relative to the ground (i.e. precipitation that may or may not reach the ground).

So the type of cloud is indirectly relevant: different cloud types are associated with different particle sizes, are to a larger or smaller degree the consequence of convection, and are more or less likely to contain precipitation-sized particles.

Upper atmospheric pressure is lower than surface pressure which entails higher elevation clouds will indeed move faster than lower elevation clouds which will move at slower speeds.


How can we accurately quantify the degree of scientific certainty that global heating is caused by humans? How can we accurately quantify the degree of scientific certainty that global heating is caused by humans?

It seem virtually certain that the huge 100 ppm spike in $\small\mathsf{CO_2}$ since 1950 can only be caused by humans. Can we be as sure that this huge spike in $\small\mathsf{CO_2}$ caused the 1 $\small\mathsf{^o}$C increase in global temperatures as we are that tobacco causes cancer?

Do validated alternative explanations exist?

What kinds of objective measures are typically used to determine the specific degree of scientific certainty?

There is a trend showing an increasing slope in the following graph data
1910 to 1960---0.41---50 years / 0.41 = 122 years per degree
1960 to 2018---1.03---58 years / 0.87 =  67 years per degree

https://data.giss.nasa.gov/gistemp/graphs/graph_data/Global_Mean_Estimates_based_on_Land_and_Ocean_Data/graph.txt

I am trying to point out exactly how implausible global heating NOT CAUSED BY BY HUMANS really is to skeptical minds that are not very good with science.

There are a few ways

Basically the best way is to see how many experts in the field are convinced, as great as it would be to assess the evidence individually, one person can't be an expert in everything and unless you and your audience are a climate scientists most papers are going to be beyond a lay assessment. So the best thing you can do for the lay public is look to the experts, people who have spent decades researching the subject and have the best ability to assess the data, and see what their assessment is.

NASA has a wonderful site dedicated to collecting assessments. They fall into three rough categories.

Meta analysis

A meta analysis of published works shows the number of scientific papers rejecting anthropomorphic climate change is vanishingly small (0.7%) and shrinking. those uncertain was even smaller (0.3%)

Professional survey

the same analysis also surveyed 29,000 published climatologists and showed a 97% support for anthropomorphic climate change and the rest being largely no-position. this is even skewed by expertise, when accounting for the number of published papers (a rough way of measuring expertise) it shows even stronger support among more published authors with most of the opposition being from authors that only publish a small number of papers.

Public statements by relevant scientific societies.

The American Meteorological Society and Geological Society of America as well as many others have made public statements in favor of anthropomorphic climate change. And of course you have the statements by the Intergovernmental Panel on Climate Change.

No, it is not possible to establish a human cause with the degree of certainty you are asking for. There have been similar episodes in the distant past when either there were no humans at all, or the total emissions of all the worlds cooking fires were comparable with the emissions of one solitary and unremarkable volcano  If global heating with humans as the sole cause were as certain as the existence of gravity, there would be no controversy or debate about it.

What can be established with certainty is that since the industrial revolution got well under way there has been a fairly substantial ppm rise in atmospheric CO2, and this has coincided with a small but measurable rise in global temperature. Whether this is entirely coincidence or whether it is cause and effect is hotly debated, and there is not unanimous agreement even among professional meteorologists and climatologists. There was already some global warming (called an interglacial) long before the industrial revolution added some extra CO2 to the atmosphere, but most scientists think this additional CO2 has accelerated global warming.

There are natural mechanisms which extract CO2 from the atmosphere, and these natural mechanisms are very slightly more effective when CO2 content increases. However, if the increase is too rapid it can be more than these natural mechanisms can deal with. Climate change is a natural phenomenon which has been under way for the past 4.5 billion years and is likely to continue for as long as the world exists.


Projecting rectangular stereography centred on 42°N, 10°E I am reposting from GIS Stack Exchange as here might also be someone who might help:

I have a precipitation GRIB2 file obtained at EUMETSAT H-SAF I am able to decode it to ascii but the software I am using (gdal, ArcMap,...) does not recognize the projection (in the title) so I am not able to properly project to Web Mercator for example.
So can anyone please suggest software that preferably works on Ubuntu and projects either grib2 files to other projections or is able to recognise the projection from decoded ascii.

The product (H-SAF 05) manual stated the datasets are in the projection mentioned in the title. EUMETSAT user support answered me the datasets use a polar stereographic projection with 25-75°N lat, 25°W- 45°E long.


Can we reduce the scale of volcanic eruptions by drilling some canals or bombing some holes in the crater? As we know, when large scale volcanic eruptions occurs, large amounts of ashes and lava rushed out at short time, is it possible to drill some canels or bomb some holes in the crater so that the gas or lava can leak out slower in stead of rushing out quickly and hence reduce the scale of volcanic eruption?

I will be using for an example in this answer the collapse of the lava dome at Mount St Helens in 1980. The lava dome on top of the mountain grew between March 20 and May 18, and then a landslide caused by the angle of the top of the dome exceeding the angle of repose of the country rock caused the pressure on the magma chamber underneath to be released, causing it to instantly boil and explode. Your suggestion to relieve pressure by either drilling or bombing would have had the same effect. Drilling or bombing a hole in this dome would have caused the pressure to greatly reduce, making all of the dissolved gases in the chamber to exsolve out, causing the pressure to instantly greatly increase, over what the surrounding rock was capable of containing.

So by bombing or drilling a magma chamber that might be about to explode, you run the very real risk of guaranteeing that it will explode. The precursors earthquakes to the Mount St Helens eruption would have been the signal that something was wrong you would use to justify this intervention, and as a result you would have simply advanced the timetable of eruption.

A good analogy is that of a radiator cap on a hot car engine. The coolant inside the radiator might be sitting at 20 or 30°C over its boiling temperature, but because it is under higher pressure due to the heat and being pumped around, it has not boiled. Once that pressure is relieved, it will instantly boil out of the radiator because of the reduction in pressure.

Layman speaking!  I don't believe any of the above answers are correct.  If answer one is correct that the amount of lava on top is causing increasing pressure on the gas underneath then releasing the lava on top by creating a flow should theoretically reduce the pressure on the gases resulting in a smaller explosion.  Maybe drilling is not the answer due to type of magma filling the hole but certainly bunker bombs or some type of explosive could be used to control the flow and to relieve pressure?  Most of these volcanos seem to be isolated from populations and therefore are open to any type of intervention.  Why not blow the side of a volcano apart on the preferred side and see what happens?


Is the color of the sky the same everywhere on earth? Is the color of the sky at noon (local time) in, say, NY, Buenos Aires, London, Nairobi, Sydney, New Delhi and Tokyo the same? I choose the specific time of noon to exclude the twilight colors of the sky and I choose cities that aren't above the northern or southern pole to make it easier.

Also can the color of the sky be the same or not depending of the season? For instance, the color of the sky of Buenos Aires on January 1st would be the color of the sky in NY on June 1st.

Also, is the color of the sky of one region on earth the same all year round and all day long, once again, without taking in account twilight?

Absolutely not. While the answers by casey and farrenthorpe correctly state that the blue color is due to Rayleigh scattering, the composition of the atmosphere varies considerably from place to place - and with different composition come different degrees of scattering, and different color / intensity. Typically regions of greater industrial activity will carry larger densities of particles which, in the presence of moisture in the air, will become scatterers. The wavelength dependence is a function of the size of the particles - so as the size changes, so will the color.

See my answer to the question Why is the sun brighter in Australia compared to parts of Asia. The same mechanism that makes the sun "brighter" also makes the sky "darker" (namely, less scatter).

This is true even on a nominally "clear" day - because there is always some particulate matter in the atmosphere. And the concentration of particulates really does vary with location on earth - see this image  as an example (from NASA).

The other point worth keeping in mind is altitude: the sky looks darker when you are at the top of a mountain, even if the composition of the atmosphere is the same. That is because there is "less atmosphere" to scatter. And of course, some places on Earth are (always) at a different altitude...

The color of the sky in Norway was greenish.
In the Netherlands it was just blue.
I saw this on my vacation to Norway around 1990.
I supposed the sky in Norway was more greenish because of the large woods.
So I suppose the color of the sky is also due to the reflection in it of what is on the ground.
Presumably the sky in a large desert will cary the color reflection of the sand.
Also the draining (partly) of the IJselmeer, a large Sea in the Netherlands caused the light in the sky supposedly to have become different.
As I remember, less bright.


Conditions of Thunderstorms Why do some heavy rainstorms and hailstorms not produce any lightning or thunder at all when I thought that these conditions of heavy rain and hail are right to bring lightning and thunder but don’t and why some tornadoes don’t produced lightning or thunder when the conditions are right for lightning and thunder to form?

For lightning to form there has to be a rising current of air within the cloud, carrying ice crystals and water droplets upwards. The droplets become hail, and start to fall as the air becomes thinner, rubbing some electrons off the minute ice crystals, which continue to rise, now positively charged. The soft hail falls to lower levels and is now negatively charged. Positive and negative charges have a great attraction for each other, as the electromagnetic force is almost unbelievably powerful.

Air is a bad conductor, so although the separated charges gradually build up they won't recombine until the build-up of charge is sufficiently strong to overcome the resistance of the air. Leaders from the oppositely charged regions are constantly probing for a viable passage where a lightning flash can get through to recombine their positive and negative charges.

Sometimes a way is found where the build-up of charge is sufficiently strong to overcome air resistance and a lightning stroke occurs, but if the charge build up is not sufficiently strong no spectacular flash will occur. Instead, the separated charges gradually leak away until charge equilibrium is established. So although it may seem to you that conditions are right for lightning to occur, that may not actually be the case.

More unusually, separation of charge can also happen in dry conditions like dust storms and forest fires, where rising dust particles take the place of water. A vaguely similar process of charge separation takes place in a Van der Graaf generator, which can produce artificial miniature lightning discharges.

Perhaps, a coincidence of a lack of cosmic rays stimulating lightning in that moment could be the variable here that is lacking to kickstart lightning in those two situations mentioned by the question/problem. A Russian physcist named Gurevich proposed that after many years of failed measurements to explain the spark inside a cloud. Gurevich suggested that even cosmic rays coming from halfway across the galaxy could be enough to provide 'a conductive path that initiates lightning'. https://www.scientificamerican.com/article/experts-do-cosmic-rays-cause-lightning/


How to design an experiment to quantify back radiation from atmospheric carbon dioxide? Based on our current knowledge of CO$_2$ and current instrumental techniques, how big would a laboratory sample of air with 400ppm of CO$_2$ need to be in order to quantify the back radiation from CO$_2$?

I am envisioning a large container with many cubic metres of gas, probably thermally isolated longitudinally and with a radiative IR input at one end (A) plus measuring apparatus at the other end (B) and some distributed thermistors throughout. We know the thermal input at A, measure the thermal output at the B and measure the trapped thermal energy via the thermistors.

I would like to get a result with something like +/- 1% accuracy. Would this be possible? Assume I have a budget of at least $10,000,000.

The thing is, we don´t have any instruments(to my knowledge) to measure the intensity of that radiation. But, we measure the intensity of atmospheric emission from space with satellites, which is seen as the "effective temperature". Logically this is the same as the net radiation downwards. And heat transfer then confirms that no net radiation arrives at the surface. Which is equal to "no radiation at all". Because "net" radiation is the only radiation that can heat anything.

There are lots of people claiming that measurements done with IR sensors and pyrgeometers confirm backradiation. This is not true and it is based on a misunderstanding of the function of the device, as well as misapplication of the stefan-boltzmann equation. Both IR-thermometers and pyrgeometers use the s-b equation  in combination with a thermocouple or thermopile(pyrgeometer). They are both a kind of more advanced and more sensitive thermometers. The thermopile consist of a sensor measuring a gradient across itself indirectly by changes in resistance acting on a current through the thermopile. So, by determining the gradient in the thermopile, it can sense the amount of heat transferred to the surroundings using the s-b equation. When someone claims measurements show "back-radiation", they refer to measurements done with these devices. As most interested people understand, a measurement of heat transfer away from the device, cannot show incoming radiation from a colder atmosphere. If you measure something hotter than the temperature of the thermopile, sure, then you have high accuracy. But a measurement of "back-radiation" from the atmosphere is per definition a measurement of something colder than the device. Because the atmosphere is almost always colder(exception is inversion, but that is not relevant). So any measurement of backradiation made from the surface, is a measurement of nothing. It is simply what the device doesn´t measure coming from the atmosphere. This is what I mean with "misapplication" of the s-b equation. It can not, and should not, be used that way. That is, to add flux densities that are not calculated as "net" transfer.

In regards to your suggested experiment. Unless the gas is hotter than the instruments(if using IR-instruments), you will measure a heat sink, not any backradiation. And, yes, that is what greenhouse gases really are. Heat sinks. The earth emit its heat to the ultimate bottomless heat sink in space, the only observed infinity, and greenhouse gases are added heat sinks along the highway for heat, that leads to 3 Kelvin space.

"Logically this is the same as the net radiation downwards".

No, this is not the case. The atmosphere is almost black and opaque at certain wavelengths such as 15um (CO2). Then only the external layers radiate, mostly. The rest of the atmosphere transport heat by convection.

The atmosphere is black because an absorbed IR photon energy will excite a CO2 molecule, for example, for a time which is 1000 x bigger than mean time between collisions in the case of low altitude. The molecule will deexcite through collision first.

Due to the gravity gradient, the top of the atmosohere is low pressure and mean time between collisions is much longer. We can see CO2 radiation from a thicker layer, this is the little glitch in the middle of the 15um band dip.

But at low altitude, only 10m of atmosphere will backradiate and the energy density is low because the temperature difference with earth is small.

The backradiation diagram from Nasa in ipcc AR4 is simply wrong. This happens (remember Mann hockeystick scandal).


Movement of the Prime/Greenwich Meridian The line on the ground at the Greenwich Observatory is itself on a tectonic plate that is moving, so is the prime meridian still 0 degrees, 0 minutes, 0 seconds?

If not - what are the implications (if any)? For example, if my GPS says I am 100 km west of Greenwich Observatory, am I 100 km west of 0 0 0 or 100 km west of the line on the ground? Who (and what) decides this kind of thing?

Curious punter, not a scientist....

Remember it is just an imaginary line on the Earth's surface used for georeferencing purposes, so movement of the reference line has no implications so long as we can still reference to it (hence the International Reference Meridian).

In fact, the position of the Greenwich  meridian has changed throughout history, mainly due to the Airy Transit Observatory (the original location of the Greenwich meridian) being built next door to the previous one (to maintain the service to shipping). Such changes had no significant practical effect. Historically, the average error in the determination of longitude was much larger than the change in position. The adoption of WGS84 ("World Geodetic System 84") as the positioning system has moved the geodetic prime meridian 102.478 metres east of its last astronomic position (measured at Greenwich). The position of the current geodetic prime meridian is not identified at all by any kind of sign or marking (as the older astronomic position was) in Greenwich, but can be located using a GPS receiver.
Due to the movement of Earth's tectonic plates, the line of 0° longitude along the surface of the Earth has slowly moved toward the west from this shifted position by a few centimetres; that is, towards the Airy Transit Observatory  (or the Airy Transit Observatory  has moved toward the east, depending on your point of view) since 1984 (or the 1960s). With the introduction of satellite technology, it became possible to create a more accurate and detailed global map. With these advances there also arose the necessity to define a reference meridian that, whilst being derived from the Airy Transit Circle, would also take into account the effects of plate movement and variations in the way that the Earth was spinning - the International Reference Meridian.

See:

Malys, S., Seago, J.H., Pavlis, N.K. et al.  (2015) "Why the Greenwich meridian moved" Journal of Geodesy. 89 (12) pp 1263–1272

Dolan, G (2013). "WGS84 and the Greenwich Meridian". The Greenwich Meridian.

The answer to your question: '...if my GPS says I am 100 km west of Greenwich Observatory, am I 100 km west of 0 0 0 or 100 km west of the line on the ground?'
is
You are 100km west of the reference meridian (0 deg 0 min 0 arc sec). The line on the ground is slowly moving with its tectonic plate by about 3cm/year to the northeast (that 3cm/yr is with respect to the best terrestrial reference frame, the ITRF, now ITRF2014).. Any line on the ground would have to be redrawn/reinstalled periodically if it were intended to remain an accurate depiction of the reference meridian's location on the ground.


How to tell if a single day of weather is an anomaly or due to climate change? I am interested in understanding how to tell if a single day of 'abnormal' weather is due to climate change or not.

From my understanding, you would compare this day's weather to historical weather. However, is a day-to-day comparison accurate? Or would you have to take a large sample, like week, month, or season?

It seems to me like it would be hard to compare one day to another historical weather average, because the day could just be an outlier not due to climate change...

In other words, how do you tell if a seasonal storm or really hot summer day is due to climate change?

I am interested in understanding how to tell if a single day of 'abnormal' weather is due to climate change or not.

You can't. The day-to-day, locale-to-locale variations in weather are huge compared to the changes that occur from year-to-year and decade-to-decade, averaged over the surface of the Earth. Most of those climatological variations are periodic in nature (e.g., El Niño Southern Oscillation, North Atlantic Oscillation; note the "oscillation" in the names). Climate change is the small but steady secular change in climate.

Another way to look at it: Even the most pessimistic of projections is for a 4°C increase over the course of a hundred years. That corresponds to 0.04°C change per year. Weather can bring about a 4°C change over the course of a few minutes. Any one weather event can be attributed to the noisy, flukey nature of weather. Climate change begins to become apparent when one looks at weather events that occur all over the face of the Earth, and over the course of several decades.

Edited answer...

Individual days weather variations can only be considered anomalies, since the theory of global climate change/global warming/anthropogenic CO2 related greenhouse effect acceleration only is theorized and described as affecting the planet over the course of decades and/or centuries and globally, not individual days or individual locations.

With that said

The weather variations in history have been far greater than any that have occurred during man's brief history of recording the weather, and far greater than any that have occurred during mans use of fossil fuels:

Answer:  Weather is weather.  Climate change is a "theory", not a "premise".  Therefor with the question depends on the factual existence of climate change, which I believe is incorrect since the foundation knowledge doesn't support the extrapolation of measurement and observation to the extent some people have taken it.

Please consider that between quantum theory and the standard model, there is a reconciliation that has not been found.  The balance point between that which is miniscule, and that which is massive has NOT been found.  Our knowledge of physics is incomplete.

Example:  Quantum theory vs Standard model (which dictates an origin where the entire universe existed momentarily in a singluarity smaller than a grain of sand that then expanded to create the universe)...  No Big Bang? Quantum equation predicts universe has no beginning

So where we have observed and believe we understand what we perceive as "matter", we actually only understand the nature of 5% of what exists.  The remainder, dark matter and dark energy fill the void between electrons and nuclei. Similarly between stars and planets.  This is NASA's web site where the approximate quantification of Dark Matter and Dark Energy is published material:

NASA Quantification of Dark Energ - Dark Matter

  By fitting a theoretical model of the composition of the Universe to the combined set of cosmological observations, scientists have come up with the composition that we described above, ~68% dark energy, ~27% dark matter, ~5% normal matter.

Without an understanding of the nature of the balancing act that lies in the middle between tiny and huge, believing we understand energy retention, energy dissipation, and the triggers involved to the point that we can properly determine the way the planetary energy system works is ludicrous.  Physics in it's current state of development does NOT support our belief in CO2 based global warming.

With the researchers at CERN currently considering and looking for a FIFTH fundamental force, HOW can we believe we know how our planet actually works.CERN Looking for FIFTH fundamental Force

  Engineers have spent more than a year upgrading the LHC's systems. The hope is that this will allow a new realm of physics to be opened up!!

And when it comes to choosing the mathematical model that best fits our observations, we are still waffling between String Theory 11D, String Theory 12D.  And we are attempting to determine if said strings even exist?!?!  Discussion of the number of dimensions that exist

  which posits that there are 10 or 11 dimensions in our universe.

So with our very OBVIOUS failure to understand physics, 95% of it being a dark mystery, and waffling over the number of fundamental forces, whether the origin of the universe was a big bang, how many dimensions there are, etc....HOW is it, we can ask ourselves questions like, is daily weather indicative of climate change, when we should be asking, is it viable to believe we have mastered knowledge of the physics of our existence, to the point necessary to be sure that climate change exists.

We cannot.


What is the origin of oil? Most people may believe that oil comes from dead plants and animals, but there are alternative theories that are known as Abiogenic Petroleum Origin. If oil in generated in this manner it could mean we could find oil on other planets or moons as well.

As far as we can tell, almost all crude oil (petroleum) is biogenic, and specifically comes from marine organisms. That's the only theory that is supported by the geological record, by the thermodynamics, and by what we know of the biology and the chemistry.

That's not to exclude the possibility of abiogenic petroleum: indeed, we know that abiogenic liquid hydrocarbons are possible, because we can synthesise them ourselves. So finding hydrocarbons that cannot be biogenic does not show that most fossil fuels are abiogenic: it merely shows that some abiogenic hydrocarbons exist.

However, the quack theory, popular in Soviet Russia and with other fringe pseudo-scientists, is that almost all oil discovered in the ground comes from abiogenic sources. Geoff Glasby looked at how the pseudo-science came about, in his article Abiogenic Origin of Hydrocarbons: An Historical Overview (Resource Geology, vol. 56, no. 1, 85–98, 2006) DOI:10.1111/j.1751-3928.2006.tb00271.x

Actual environmental scientist here. Crude oil and other similar "fossil fuels" are the result of organic materials held at intense pressures for millions of years. That is the only theory accepted by modern scientists outside of the Ukraine. There is no other theory, because no other hypothesis has been supported with the kind of evidence necessary to even consider mentioning it in conversation. Anything that says otherwise is pseudo-science.

Oil = organic materials


Is continental drift caused by lava pushing the seabed apart? My daughter has a writing assignment based on a handout about plate tectonics. One paragraph says:

  Molten rock from the earth's mantle pushes up through the surface at the mid-Atlanic ridge. The rock cools and forms new sections of crust on the ocean floor. The ocean floor has to make room for the new crust. To make enough room, the ocean floor must spread out. As a result, the earth's plates shift.

It's been a long time since I was in school and this is far from my field, but this doesn't sound right to me. Isn't the main cause convection currents in the earth's mantle? Is cooling lava pushing the plates apart a cause? I thought it was basically an effect — where the plates diverge, molten rock pushes up and fills in. (Or, is this just two ways of looking at the same thing?)

No, lava does not push the plates apart.

The mid-ocean ridge basalt is passively filling the space left by the plates moving apart. Plate motion is driven by gravity (image by Vic DiVenere at Columbia; see note below):

There are thought to be two main effects at play: ridge push, and slab pull. We don't know much about their relative importance, but it probably varies spatially (e.g. Ribeiro, 2012, Soft Plate and Impact Tectonics, Springer).

Ridge push happens not because the new lava is pushing, but because the ridge is high up. It's so high that in some places it sticks out of the water (e.g. Iceland). It's high because it's hot — but not from deep convection. A geophysical technique called seismic tomography suggests that the hot zone is relatively shallow. As the new plate cools, it thickens and sinks 'downhill', pushing the older plate ahead.

Slab pull is easier to imagine: a subducting plate, sinking into the asthenosphere (uppermost mantle), pulls the younger plate behind it. Not all margins are destructive, however, so slab pull does not operate everywhere. Indeed, the relative important of push and pull is debated.

You will sometimes see figures like this one, strongly implying that convection and plate motion are strongly coupled. The earth is a complex system so the processes are certainly related, but we don't understand the frictional forces (drag) at the lithosphere–asthenosphere boundary well (e.g. read this primer by DiVenere). These images, while prevalent, are an unhelpful over-simplification.

Note: I'm using DiVenere's copyrighted image under 'fair use' terms. Please replace it with an open version if you find one! (But not one with convection cells :)

Lava pushes the plates apart at midocean ridges with 5000 bars. This is how mountains are built. Slab pull and gravity ridge push cannot build the observed mountains. In addition, they cannot drive tectonics, externally energy is required.


Why is there so much oil in Saudi Arabia, Venezuela and Canada, but almost none in Europe? Why do some countries have a lot of oil reserves, while some others don't?

I wouldn't say there's 'almost none' in Europe, but the global distribution of petroleum is uneven. The reason is that petroleum systems need a convergence of conditions that is relatively rare.

For a start, the comment about the inappropriateness of a political map for this purpose is spot on. This USGS map of global petroleum systems, and non-petroleum-rich basins, is much better — apart from the fact that it perversely omits the USA's substantial endowment:

These 'petroleum systems' are essentially modern or ancient sedimentary basins with a particular combination of features. I'll refer to a previous answer about a specific region: Why would there be no hydrocarbons in the Sveconorwegian belt? Paraphrasing, and self-plagiarizing, here's what you need for a hydrocarbon (oil or gas) accumulation:

  A kerogen-rich source rock that has been 'cooked' to thermal maturity. So you need lots of organic matter, burial, and time.
  A migration pathway from the source to a trapping configuration, and time for this to have happened.
  A structural or stratigraphic trap, such as an anticline, and the geological conditions that have preserved it since filling.
  A reservoir rock — a porous and permeable rock. Usually this is a sedimentary rock (like sandstone, which there's lots of in Saudi!).

  Only 'conventional' hydrocarbon deposits, such as you might find in
  the North Sea, Saudi Arabia, or the Gulf of Mexico, need all these
  conditions. 'Shale gas' is basically just a mature source rock — we
  can extract hydrocarbons from it by fracking, for example.

So the map of global petroleum resources is a map of places where these criteria converge. Certain deltas are prolific (Mississippi, Niger), because you have rapid burial of sand and organic material. In other places, one or more of the conditions has not been met. Much of Canada, for example, is exposed basement granite: none of the components are there.

The unevenness is exacerbated by the Pareto distribution of system productivity — as with most natural things, we have a few giants, and a long tail. So the WCSB and Saudi stick out as anomalous, making the distribution even more 'lumpy'.

The amount of oil in the ground is an indicator of how much life used to be there. So, we can conclude that those areas that have a large amount of oil were those that had more vegetation millions of years ago.


Can Ozone (O$_3$) form in a vacuum and if so can it deflect solar radiation I am working on a geoengineering/space infrastructure project and part of that includes the possibility of using oxygen mined from the moon (specifically lunar regolith) to cause ballistic objects to spin spreading particles in a loose shield to reflect sunlight. The material would all be collected back on the moon which would intercept the orbit of the material. However, as ozone is just 3 oxygen atoms that connect together in the presence of sunlight, would releasing clouds of oxygen in a way that pushes the clouds together allow the formation of O$_3$, even temporarily?

If this would work, would O$_3$ free-floating in very loose clouds in space help deflect solar radiation at all?

This is part of a larger project to create targeted shading effects to produce a limited risk effect on the earth like regrowing ice sheets. There are a lot of reasons for people to find this project silly but all the research I have done continues to support it in new and interesting ways and any concerns people have raised so far have theoretical solutions. So please don't take time to simply criticize without providing meaningful feedback.

If this would work, would $O_3$ free-floating in very loose clouds in space help deflect solar radiation at all?

No, for many reasons:

Your cloud will disperse. That's what gases do in vacuum.
And then the dispersed cloud will get swept away by radiation pressure and the solar wind.
So you'll have to be constantly replenishing your loose cloud.
There are 3 billion metric tons of ozone in the Earth's atmosphere.
Compare that huge quantity with the 380.95 kilograms of lunar rock brought back by the six Apollo missions that landed on the Moon, or the 0.401 kilograms retrieved by Russia's unmanned Luna missions.

The engineering feat you are proposing is more than six orders of magnitude larger than anything humankind has done with regard to space. The Apollo program peak cost was a bit less than 5% of the total US federal budget. A factor of ten (one order of magnitude) larger scope would be far beyond the capabilities of the US government. Even with the entire world pitching in, a two order of magnitude increase would be nearly impossible. A six order of magnitude increase is economically impossible.

The worst part: Even if successful, your cloud won't do much. Oxygen in all its forms (atomic oxygen, molecular oxygen, and ozone) is nicely transparent in the frequency range where sunlight is at its peak. Evidence: You can see the stars on a clear night.

I think mining oxygen from the moon in vast quantities would be a very expensive project and would deplete the ice believed to be present in some lunar craters at the poles. This would be better used to provide drinking water for astronauts. Obtaining oxygen by other methods would be even more expensive and difficult.

Ballistic objects will spin without the aid of oxygen. A shell is made to spin by the rifling in the barrel of the cannon which fires it, and this would also happen if the cannon was fired on the moon.

If you could release vast clouds of O2 on the moon, solar radiation would ionise it to O3 just as happens in the upper atmosphere of Earth, but to form a protective barrier which could intercept ultraviolet radiation would require unrealistically large quantities of O2 which could never be obtained. Whether you mean a protective barrier for the moon or an additional protective barrier for the Earth, it is not feasible that enough oxygen could be obtained to give a useful result.


When will the Final Ice Age happen? As the Sun's luminosity slowly rises, the Earth's surface temperature will climb. Will Earth ever be too warm to have any more glacial periods? If so, when will that be?

Edit: The existing answer misunderstood the question. I'd like some boundary conditions, e.g. "when the sun's luminosity is 10% higher and the Earth becomes a 'moist greenhouse'" and "when the Sun turns Earth into a cinder". Those conditions would imply that the last Ice Age will happen 1-4 billion years from now. A better estimate would be awesome. Unless there's something I'm missing, with Stefan-Boltzmann and some reasonable assumptions (e.g. linear increase in luminosity) it should be possible to get a back-of-the-envelope calculation for this.

At the moment, nobody knows for sure whether or not changes in the Sun's luminosity can cause long-term climate changes. There have been various studies done, most since the advent of global warming, that have tried to address this. The conclusions have been interesting:

The Sun is not responsible for the recent warming of the Earth.
It's not yet known whether or not the Sun has influenced climate in the past.

Here are some studies (one supporting each side of the long-term debate):

A report by the National Research Council (available here) found that sunspot activity could be a major contributor to small changes in the Sun's brightness. There is a periodic trend in sunspot activity that lasts 11 years, and studies have considered this when looking at long-term trends. One target of inquiry is the Maunder Minimum, a period of low sunspot activity:

The Maunder Minimum coincided with the Little Ice Age, a short period of low temperatures. In fact, the Sun may be entering a similar period within the next few decades. Observations could show whether or not there is a link between the two events.

However, the NRC concluded that it is hard, if not impossible, to find any data supporting theories that there is a long-term patter. Hal Maring summarized it best:

  Hal Maring, a climate scientist at NASA headquarters who has studied the report, notes that “lots of interesting possibilities were suggested by the panelists.  However, few, if any, have been quantified to the point that we can definitively assess their impact on climate.”

In the paper Possible solar origin of the 1,470-year glacial climate cycle demonstrated in a coupled model by Holger et al., periods called Dansgaard–
Oeschger events were studied. These are climate oscillations lasting 1,470 years. Holger et al. analyzed ice cores from Greenland and attempted to model solar forcing, the amount of energy absorbed by Earth or radiated into space. They also used the ocean and atmosphere to account for changes (the NRC report, too, concluded that solar effects can trickle down through the atmosphere and other parts of Earth). Their conclusion was that, despite the fact that no records of 1,470-year solar cycle exist, the analysis supported a connection between solar variability and changes in Earth's climate.

Before anyone gets too excited, I'll add this: 1) I haven't been able to find any comments from other scientists on the paper, so I'm not sure how well-received it was, and 2) The 1,470-year cycle can not account for long-term glacial periods, or the recent rise in global temperatures.

Another potentially interesting (and paywalled) paper can be found here. An informative website is here, but I'm not sure if it's entirely neutral. It does seem to present both sides, though.

I'll end on this: Whether or not the Sun severely impacts the Earth's climate, Milankovitch cycles are the biggest influence on ice ages.

It will take some pretty drastic changes in the Sun's luminosity to change the glacial periods . . . which the Sun will be undergoing in about billion years or so. It will still be on the main sequence, and will stay there for 4.4 billion years more, but it will have brightened by about 10%.

Once of the consequences of this will be that the Earth will lose its oceans. Through a process called the "moist greenhouse" effect, water heats up and reaches the atmosphere, where the hydrogen atoms are freed from the oxygen atoms and escape to space. This occurs at a tiny, tiny rate at present, but in about one billion years, the Sun will be bright enough that this will occur at a catastrophic rate.

That places the last glacial period somewhere between now and one billion years in the future. To figure this out, we have to look at long term patterns, such as Milankovitch Cycles. This graph illustrates them best:

From the present day to the far right, though, is only 800,000 years. That's unhelpful. This graph, while a bit clearer, shows only the variations without accounting for any changes in the Sun's luminosity (though that will not affect us during the next 800,000 years!).

Here's the actual answer to your question: We don't know. That's because some parts of the Earth will be affected more by the Sun's brightening that others. For example, the NRC found that the Pacific Ocean experienced a strong relationship with solar activity. So as the Sun gets brighter, some areas could still be strongly affected by Milankovitch cycles, while others might find themselves getting hotter than they would normally be.

We can be sure of one thing, though: It will certainly be before one billion years from now!

I believe the final ice age will happen around 100 to 150 million years from now and the sun gets 1% hotter every 100 millions years and after about 100 million years or so it will be too hot for any ice ages to happen after that point in time.


How were the sea levels around western Europe during the Medieval Warm Period? The Medieval Warm Period (MWP) or Medieval Climatic Anomaly was a time from about 950 to 1250 when climate was warmer than in the timespans immediately before and after.

My question is if this warming lead to significant changes in sea level and how these looked like around western Europe, how the sea levels developed during this time.

Since the change in temperature was not globally uniform, it is of course possible that the sea level changes didn't amount to much.

In the global sense the sea level data are not entirely consistent, but then, there are always going to be apparent variations when you are comparing proxy data from different sources. As far as Europe is concerned sea level rose between 1.0 and 1.6 metres throughout the Medieval Warm Period - or maybe as much as 2.0 metres by some of the more extreme estimates. Following this was the 'little ice age' (actually not an ice age at all), when sea level fell by almost as much. See for example the graphs of Behre 2004, and Puls, 2008, (German North Sea coast),both of which are reproduced in Kwaad's paper, which is a good overview.

http://www.kwaad.net/SeaLevel-MiddleAges-LittleIceAge.html

Whatever sea level change you regard as definitive, the important point is that these were just minor variations superimposed upon a major sea level trend. Overall the post-glacial sea level, from about 8000 years ago, was a rapid rise from -50 metres (or so), flattening off during the last two millennia, and now massively accelerating again, primarily due to human-induced climate change.

The Tower of London was built during this period on the banks of the Thames  River level is the same today as it was then.
People seem to forget that the Anasazi in SW America disappeared during this same period due to prolonged drought so there was no food to eat.
The Chinese also have three hundred years of weather records recording changes in their weather as well. Particularly, an increase in rainfall during the peak of the European temperature increases.
Tree rings in North American West show a slow down in growth.
So when “warmers” try to say that the weather changes during this period of time was a local occurrence they, as usual, don’t know what the hell they are talking about.