Effects of climate change
The effects of climate change span the impacts on physical environment, ecosystems and human societies due to ongoing human-caused climate change. The future impact of climate change depends on how much nations reduce greenhouse gas emissions and adapt to climate change. Effects that scientists predicted in the past—loss of sea ice, accelerated sea level rise and longer, more intense heat waves—are now occurring. The changes in climate are not expected to be uniform across the Earth. In particular, land areas change more quickly than oceans, and northern high latitudes change more quickly than  the tropics. There are three major ways in which global warming will make changes to regional climate: melting ice, changing the hydrological cycle (of evaporation and precipitation) and changing currents in the oceans. Physical changes include extreme weather, glacier retreat, sea level rise, declines in Arctic sea ice, and changes in the timing of seasonal events (such as earlier spring flowering). Since 1970, the ocean has absorbed more than 90% of the excess heat in the climate system. Even if global surface temperature is stabilized, sea levels will continue to rise and the ocean will continue to absorb excess heat  from the atmosphere for many centuries. The uptake of carbon dioxide from the atmosphere is leading to ocean acidification. Climate change has degraded land by raising temperatures, drying soils and increasing wildfire risk. Recent warming has strongly affected natural biological systems. Species worldwide are migrating poleward to colder areas. On land, species move to higher elevations, whereas marine species find colder water at greater depths. Between 1% and 50% of species on land were assessed to be at substantially higher risk of extinction due to climate change. Coral reefs and shellfish are vulnerable to the combined threat of ocean warming  and acidification. Food security and access to fresh water are at risk due to rising temperatures. Climate change has profound impacts on human health, directly via heat stress and indirectly via the spread of infectious diseases. The vulnerability and exposure of humans to climate change varies from one economic sector to another and will have different impacts in different countries. Wealthy industrialised countries, which have emitted the most CO, have more resources and so are the least vulnerable to global warming. Economic sectors that are likely to be affected include agriculture, fisheries, forestry, energy, insurance, financial services, tourism, and recreation . Some groups may be particularly at risk from climate change, such as the poor, women, children and indigenous peoples. These groups have much higher levels of vulnerability to environmental determinants of health, wealth and other factors. They also have much lower levels of capacity available for coping with environmental change. This can result in environmental migration, especially in developing countries where people are directly dependent on land for food, feed, fibre, timber and energy. Observed and future changes in temperature. Global warming affects all elements of Earth's climate system. Global surface temperatures have risen by 1 °C and  are expected to rise further in the future. Night-time temperatures have increased faster than daytime temperatures. The impact on the environment, wildlife, society and humanity depends on how much more the Earth warms. One of the methods scientists use to predict the effects of human-caused climate change, is to investigate past natural changes in climate. To assess changes in Earth's past climate scientists have studied tree rings, ice cores, corals, and ocean and lake sediments. These show that recent warming has surpassed anything in the last 2,000 years. By the end of the 21st century, temperatures may  increase to a level not experienced since the mid-Pliocene, around 3 million years ago. At that time, mean global temperatures were about 2–4 °C warmer than pre-industrial temperatures, and the global mean sea level was up to 25 meters higher than it is today. Greenhouse gas emissions scenarios. How much the world warms depends on what humans do or not to limit GHG emissions, and how sensitive the climate is to greenhouse gases. Scientists are pretty sure that with double the amount of GHG in the atmosphere the world would warm by 2.5 °C to 4  °C; but how much more humans will emit is less certain. The projected magnitude of warming by 2100 is closely related to the level of cumulative emissions over the 21st century (total emissions between 2000 and 2100). The higher the cumulative emissions over this time period, the greater the level of warming is projected to occur. If emissions of were to be abruptly stopped and no negative emission technologies deployed, the Earth's climate would not start moving back to its pre-industrial state. Instead, temperatures would stay elevated at the same level for several centuries. After about a  thousand years, 20% to 30% of human-emitted will remain in the atmosphere, not taken up by the ocean or the land, committing the climate to a warmer state long after emissions have stopped. Mitigation policies currently in place will result in about 2.7 °C (2.0–3.6 °C, depending on how sensitive the climate is to greenhouse gas emissions) warming above pre-industrial levels. If all unconditional pledges and targets made by governments are achieved the temperature will rise by around 2.4 °C. If additionally all the countries that adopted or are considering to adopt net-zero targets  will achieve it the temperature will rise by a median of 1.8 °C. There is a substantial gap between national plans and commitments and actions so far taken by governments around the world. Weather-related changes. The lower and middle atmosphere, where nearly all of the weather occurs, are heating due to the enhanced greenhouse effect. Increased greenhouse gases cause the higher parts of the atmosphere, the stratosphere to cool. The heated atmosphere contains more water vapour, which is itselfs also a greenhouse gas and acts as an self-reinforcing feedback. Global warming leads to an increase in extreme  weather events such as heat waves, droughts, cyclones, blizzards and rainstorms. Such events will continue to occur more often and with greater intensity. Some individual extreme weather events are caused by climate change. Precipitation (rainfall). Warming by greenhouse gas forcing has increased contrasts in rainfall amounts between wet and dry seasons. This means colloquially: "wet seasons are getting wetter, dry seasons are getting drier". Warming has also resulted in a detectable increase in the precipitation of northern high latitudes. Higher temperatures lead to increased evaporation and surface drying. As the air warms, its water-holding capacity also increases, particularly over  the oceans. Air holds 7% more water vapour for every degree Celsius it is warmed. Changes have already been observed in the amount, intensity, frequency, and type of precipitation. Widespread increases in heavy precipitation have occurred even in places where total rain amounts have decreased. Global warming is expected to be accompanied by a reduction in rainfall in the subtropics and an increase in precipitation in subpolar latitudes and some equatorial regions. In other words, regions which are dry at present will generally become even drier, while regions that are currently wet will generally become even wetter. This projection does  not apply to every locale, and in some cases can be modified by local conditions. Drying is projected to be strongest near the poleward margins of the subtropics (for example, South Africa, southern Australia, the Mediterranean, and the south-western U.S.), a pattern that can be described as a poleward expansion of these semi-arid zones. In the case of precipitation, the rising temperatures will intensify the Earth's water cycle, increasing evaporation. Increased evaporation will result in more frequent and intense downpours and cause extended droughts in certain regions. As a result, storm-affected areas are likely to experience  increases in precipitation and an increased risk of flooding. In contrast, areas far away from storm tracks are likely to experience less precipitation and an increased risk of drought. Changes in regional climate are expected to include greater warming over land, with most warming at high northern latitudes, and least warming over the Southern Ocean and parts of the North Atlantic Ocean. Future changes in precipitation are expected to follow existing trends, with reduced precipitation over subtropical land areas, and increased precipitation at subpolar latitudes and some equatorial regions. Heat waves and temperature extremes. Global warming boosts the probability of  extreme weather events such as heat waves where the daily maximum temperature exceeds the average maximum temperature by 5 °C (9 °F) for more than five consecutive days. In the last 30–40 years, heat waves with high humidity have become more frequent and severe. Extremely hot nights have doubled in frequency. The area in which extremely hot summers are observed has increased 50–100 fold. Heat waves with high humidity pose a big risk to human health while heat waves with low humidity lead to dry conditions that increase wildfires. The mortality from extreme heat is larger than the  mortality from hurricanes, lightning, tornadoes, floods, and earthquakes together. It was estimated in 2013 that global warming had increased the probability of local record-breaking monthly temperatures worldwide by a factor of 5. This was compared to a baseline climate in which no global warming had occurred. Using a medium global warming scenario, they project that by 2040, the number of monthly heat records globally could be more than 12 times greater than that of a scenario with no long-term warming. Future climate change will include more very hot days and fewer very cold days. The frequency, length and  intensity of heat waves will very likely increase over most land areas. Higher growth in anthropogenic GHG emissions would cause more frequent and severe temperature extremes. Globally, cold waves have decreased in frequency. There is some evidence climate change leads to a weakening of the polar vortex, which would make the jet stream more wavy. This would lead to outbursts of very cold winter weather across parts of Eurasia and North America. Tropical cyclones and storms. Global warming not only causes changes in tropical cyclones, it may also make some impacts from them worse via sea level rise. The intensity  of tropical cyclones (hurricanes, typhoons, etc.) is projected to increase globally, with the proportion of Category 4 and 5 tropical cyclones increasing. Furthermore, the rate of rainfall is projected to increase, but trends in the future frequency on a global scale are not yet clear. Changes in tropical cyclones vary by region. Increases in temperature are expected to produce more intense convection over land and a higher frequency of the most severe storms. Weather-related impacts. Floods. Increased rainfall intensity due to climate change can worsen flooding. Sea level rise further increases risks of flooding: if sea levels rise by  a further 0.15 m, 20% more people will be exposed to a 1 in a 100 year coastal flood, assuming no population growth and no further adaptation. With an extra 0.75 m, this rises to a doubling of people exposed. It has been determined that climate change and variability have the potential to drastically impact human exposure to flood hazards, but this comes with a lot of uncertainty due to multiple climate models. Similar to droughts, climate change has also been shown to have the potential to increase the frequency of bigger storm events. This increase in the frequency of  large storm events would alter existing Intensity-Duration-Frequency curves (IDF curves) due to the change in frequency, but also by lifting and steepening the curves in the future. Between 1994 and 2006, satellite observations shows an 18% increase in the flow of freshwater into the world's oceans, partly from melting ice and partly from increased precipitation driven by an increase in global ocean evaporation. Much of the increase is in areas which already experience high rainfall. One effect, as perhaps experienced in the 2010 Pakistan floods, is to overwhelm flood control infrastructure. Droughts. Climate change affects multiple factors  associated with droughts, such as how much rain falls and how fast the rain evaporates again. Warming over land drives an increase in atmospheric evaporative demand which will increase the severity and frequency of droughts around much of the world. Due to limitations on how much data is available about drought in the past, it is often impossible to confidently attribute droughts to human-induced climate change. Some areas however, such as the Mediterranean and California, already show a clear human signature. Their impacts are aggravated because of increased water demand, population growth, urban expansion, and environmental protection efforts in  many areas. In 2019 the Intergovernmental Panel on Climate Change issued a Special Report on Climate Change and Land. The main statements of the report include: In the years 1960 – 2013 the area of drylands in drought, increased by 1% per year. In the year 2015 around 500 million people lived in areas that was impacted by desertification in the years 1980s – 2000s. People who live in the areas affected by land degradation and desertification are "increasingly negatively affected by climate change". Wildfires. Globally, climate change promotes the type of weather that makes wildfires more likely. In some areas, an  increase of wildfires has been attributed directly to climate change. That warmer climate conditions pose more risks of wildfire is consistent with evidence from Earth's past: there was more fire in warmer periods, and less in colder climatic periods. Climate change increases evaporation, which can cause vegetation to dry out. When a fire starts in an area with very dry vegetation, it can spread rapidly. Higher temperatures can also make the fire season longer, the time period in which severe wildfires are most likely. In regions where snow is disappearing, the fire season may get particularly more extended. Even  though weather conditions are raising the risks of wildfires, the total area burnt by wildfires has decreased globally. This is mostly the result of the conversion of savanna into croplands, after which there is less forest area that can burn. Prescribed burning, an indigenous practice in the US and Australia, can reduce the area burnt too, and may form an adaptation to increased risk. The carbon released from wildfires can further increase greenhouse gas concentrations. This feedback is not yet fully integrated into climate models. Changes for oceans. The main physical effects of global warming on the world ocean are  sea level rise, ocean warming, ocean acidification, loss of oxygen, an increase in marine heatwaves, and changes to ocean currents including a possible slowdown or shutdown of thermohaline circulation. These physical changes disturb marine ecosystems, which can cause both extinctions and population explosions, change the distribution of species, and impact coastal fishing and tourism. Warming of the ocean surface due to higher air temperatures leads to increased water temperature stratification. The decline in mixing of the ocean layers piles up warm water near the surface while reducing cold, deep water circulation. The reduced up and down mixing reduces the ability  of the ocean to absorb heat, directing a larger fraction of future warming toward the atmosphere and land. Energy available for tropical cyclones and other storms is expected to increase, nutrients for fish in the upper ocean layers are set to decrease, as well as the capacity of the oceans to store carbon. Warmer water cannot contain as much oxygen as cold water, changing the gas exchange equilibrium to reduce ocean oxygen levels and increase oxygen in the atmosphere. Increased thermal stratification may lead to increases in respiration rates of organic matter, further decreasing water oxygen content. The ocean  has already lost oxygen, throughout the entire water column and oxygen minimum zones are expanding worldwide. This has adverse consequences for ocean life. Atlantic Meridional Overturning Circulation (AMOC). The Atlantic Meridional Overturning Circulation (AMOC), an important component of the Earth's climate system, is a northward flow of warm, salty water in the upper layers of the Atlantic and a southward flow of colder water in the deep Atlantic. Potential impacts associated with AMOC changes include reduced warming or (in the case of abrupt change) absolute cooling of northern high-latitude areas near Greenland and north-western Europe, an increased  warming of Southern Hemisphere high-latitudes, tropical drying, as well as changes to marine ecosystems, terrestrial vegetation, oceanic uptake, oceanic oxygen concentrations, and shifts in fisheries. According to a 2019 assessment in the IPCC's Special Report on the Ocean and Cryosphere in a Changing Climate it is very likely (greater than 90% probability, based on expert judgement) that the strength of the AMOC will decrease further over the course of the 21st century. Warming is still expected to occur over most of the European region downstream of the North Atlantic Current in response to increasing GHGs, as well as  over North America. With medium confidence, the IPCC report stated that it is very unlikely (less than 10% probability) that the AMOC will collapse in the 21st century. The potential consequences of such a collapse could be severe. Ice and snow changes. The cryosphere, the area of the Earth covered by snow or ice, is extremely sensitive to changes in global climate. Northern Hemisphere average annual snow cover has declined in recent decades. This pattern is consistent with warmer global temperatures. Some of the largest declines have been observed in the spring and summer months. During the 21st century, snow  cover is projected to continue its retreat in almost all regions. Glaciers and ice sheets decline. Since the beginning of the twentieth century, there has been a widespread retreat of glaciers. The melting of the Greenland and West Antarctic ice sheets will continue to contribute to sea level rise over long time-scales. The Greenland ice sheet loss is mainly driven by melt from the top, whereas Antarctic ice loss is driven by warm ocean water melting the outlet glaciers. Future melt of the West Antarctic ice sheet is potentially abrupt under a high emission scenario, as a consequence of  a partial collapse. Part of the ice sheet is grounded on bedrock below sea level, making it possibly vulnerable to the self-enhancing process of marine ice sheet instability. A further hypothesis is that "marine ice cliff instability" would also contribute to a partial collapse, but limited evidence is available for its importance. A partial collapse of the ice sheet would lead to rapid sea level rise and a local decrease in ocean salinity. It would be irreversible on a timescale between decades and millennia. In contrast to the West Antarctic ice sheet, melt of the Greenland ice sheet is  projected to be taking place more gradually over millennia. Sustained warming between 1 °C (low confidence) and 4 °C (medium confidence) would lead to a complete loss of the ice sheet, contributing 7 m to sea levels globally. The ice loss could become irreversible due to a further self-enhancing feedback: the elevation-surface mass balance feedback. When ice melts on top of the ice sheet, the elevation drops. As air temperature is higher at lower altitude, this promotes further melt. Sea ice decline. Sea ice reflects 50% to 70% of the incoming solar radiation, while 6% of  the incoming solar energy is reflected by the ocean. With less solar energy, the sea ice absorbs and holds the surface colder, which can be a positive feedback toward climate change. As the climate warms, snow cover and sea ice extent decrease. Large-scale measurements of sea-ice have only been possible since the satellite era. The age of the sea ice is an important feature of the state of the sea ice cover. Sea ice in the Antarctic has hardly changed since those measurements began. Though extending the Antarctic sea-ice record back in time is more difficult due  to the lack of direct observations in this part of the world. Arctic sea ice began to decline at the beginning of the twentieth century but the rate is accelerating. Since 1979, satellite records indicate the decline in summer sea ice coverage has been about 13% per decade. The thickness of sea ice has also decreased by 66% or 2.0 m over the last six decades with a shift from permanent ice to largely seasonal ice cover. While ice-free summers are expected to be rare at 1.5 °C degrees of warming, they are set to occur at least  once every decade at a warming level of 2.0 °C. The Arctic will likely become ice-free at the end of some summers before 2050. Permafrost thawing. The southern part of the Arctic region (home to 4 million people) has experienced a temperature rise of 1 °C to 3 °C (1.8 °F to 5.4 °F) over the last 50 years. Canada, Alaska and Russia are experiencing initial melting of permafrost. This may disrupt ecosystems and by increasing bacterial activity in the soil lead to these areas becoming carbon sources instead of carbon sinks. Eastern Siberia 's permafrost is gradually disappearing in the southern regions, leading to the loss of nearly 11% of Siberia's nearly 11,000 lakes since 1971. At the same time, western Siberia is at the initial stage where melting permafrost is creating new lakes, which will eventually start disappearing as in the east. Furthermore, permafrost melting will eventually cause methane release from melting permafrost peat bogs. Wildlife and nature impacts. Recent warming has strongly affected natural biological systems. Species worldwide are moving poleward to colder areas. On land, species move to higher elevations, whereas marine species find colder water at greater depths . Of the drivers with the biggest global impact on nature, climate change ranks third over the five decades before 2020, with only change in land use and sea use, and direct exploitation of organisms having a greater impact. The impacts of climate change in nature and nature's contributions to humans are projected to become more pronounced in the next few decades. Examples of climatic disruptions include fire, drought, pest infestation, invasion of species, storms, and coral bleaching events. The stresses caused by climate change, added to other stresses on ecological systems (e.g. land conversion, land degradation, harvesting, and pollution ), threaten substantial damage to or complete loss of some unique ecosystems, and extinction of some critically endangered species. Key interactions between species within ecosystems are often disrupted because species from one location do not move to colder habitats at the same rate, giving rise to rapid changes in the functioning of the ecosystem. Impacts include changes in regional rainfall patterns, earlier leafing of trees and plants over many regions; movements of species to higher latitudes and altitudes in the Northern Hemisphere; changes in bird migrations in Europe, North America and Australia; and shifting of the oceans' plankton and fish from  cold- to warm-adapted communities. Ecosystems on land. Climate change has been estimated to be a major driver of biodiversity loss in cool conifer forests, savannas, mediterranean-climate systems, tropical forests, and the Arctic tundra. In other ecosystems, land-use change may be a stronger driver of biodiversity loss, at least in the near-term. Beyond the year 2050, climate change may be the major driver for biodiversity loss globally. Climate change interacts with other pressures such as habitat modification, pollution and invasive species. Interacting with these pressures, climate change increases extinction risk for a large fraction of terrestrial and  freshwater species. Between 1% and 50% of species in different groups were assessed to be at substantially higher risk of extinction due to climate change. Amazon rainforest. Rainfall that falls on the Amazon rainforest is recycled when it evaporates back into the atmosphere instead of running off away from the rainforest. This water is essential for sustaining the rainforest. Due to deforestation the rainforest is losing this ability, exacerbated by climate change which brings more frequent droughts to the area. The higher frequency of droughts seen in the first two decades of the 21st century, as well as other data , signal that a tipping point from rainforest to savanna might be close. One study concluded that this ecosystem could enter a mode of a 50-years-long collapse to a savanna around 2021, after which it would become increasingly and disproportionally more difficult to prevent or reverse this shift.<ref name="10.1038/s41467-020-15029-x"></ref> Marine ecosystems. Marine heatwaves have seen an increased frequency and have widespread impacts on life in the oceans, such as mass dying events and coral bleaching. Harmful algae blooms have increased in response to warming waters, loss of oxygen and eutrophication. Between one-quarter and  one-third of our fossil fuel emissions are consumed by the earth's oceans, which are now 30 percent more acidic than they were in pre-industrial times. This acidification poses a serious threat to aquatic life, particularly creatures such as oysters, clams, and coral with calcified shells or skeletons. Melting sea ice destroys habitat, including for algae that grows on its underside. It is likely that the oceans warmed faster between 1993 and 2017 compared to the period starting in 1969. Warm water coral reefs are very sensitive to global warming and ocean acidification. Coral reefs provide a habitat  for thousands of species and ecosystem services such as coastal protection and food. The resilience of reefs can be improved by curbing local pollution and overfishing, but 70–90% of today's warm water coral reefs will disappear even if warming is kept to 1.5 °C. Coral reefs are not the only framework organisms, organisms that build physical structures that form habitats for other sea creatures, affected by climate change: mangroves and seagrass are considered to be at moderate risk for lower levels of global warming according to the Special Report on the Ocean and Cryosphere in a Changing Climate . Abrupt changes and irreversible impacts. Tipping points. Self-reinforcing feedbacks amplify climate change. The climate system exhibits "threshold behaviour" or tipping points when these feedbacks lead parts of the Earth system into a new state, such as the runaway loss of ice sheets or the destruction of too many forests. Tipping points are studied using data from Earth's distant past and by physical modelling. There is already moderate risk of global tipping points at 1 °C above pre-industrial temperatures, and that risk becomes high at 2.5 °C. Tipping points are "perhaps the most 'dangerous' aspect of  future climate changes", leading to irreversible impacts on society. Many tipping points are interlinked, so that triggering one may lead to a cascade of effects, even well below 2 °C of warming. A 2018 study states that 45% of environmental problems, including those caused by climate change are interconnected and make the risk of a domino effect bigger. Irreversible impacts. There are a number of climate change impacts on the environment that may be irreversible, at least over the timescale of many human generations. These include the large-scale singularities such as the melting of the Greenland and West  Antarctic ice sheets, and changes to the Atlantic Meridional Overturning Circulation. In biological systems, the extinction of species would be an irreversible impact. In social systems, unique cultures may be lost or the survival of endangered languages may be exacerbated due to climate change. For example, humans living on atoll islands face risks due to sea level rise, sea surface warming, and increased frequency and intensity of extreme weather events. Impacts on health, food security and water security. Food security, agriculture and marine food production. Climate change will impact agriculture and food production around the world due to the effects  of elevated CO in the atmosphere; higher temperatures; altered precipitation and transpiration regimes; increased frequency of extreme events; and modified weed, pest, and pathogen pressure. Droughts result in crop failures and the loss of pasture for livestock. The rate of soil erosion is 10–20 times higher than the rate of soil accumulation in agricultural areas that use no-till farming. In areas with tilling it is 100 times higher. Climate change makes this type of land degradation and desertification worse. Climate change is projected to negatively affect all four pillars of food security: not only how much food is available , but also how easy food is to access (prices), food quality and how stable the food system is. In many areas, fisheries have already seen their catch decrease because of global warming and changes in biochemical cycles. In combination with overfishing, warming waters decrease the maximum catch potential. Global catch potential is projected to reduce further in 2050 by less than 4% if emissions are reduced strongly, and by about 8% for very high future emissions, with growth in the Arctic Ocean. Water security. Between 1.5 and 2.5 billion people live in areas with regular water security issues. If global  warming would reach , water insecurity would affect about twice as many people. Water resources are projected to decrease in most dry subtropical regions and mid-latitudes, but increase in high latitudes. However, as streamflow becomes more variable, even regions with increased water resources can experience additional short-term shortages. The arid regions of India, China, the US and Africa are already seeing dry spells and drought impact water availability. Water resources can be affected by climate change in various ways. The total amount of freshwater available can change, for instance due to dry spells or droughts. Heavy rainfall and flooding  can have an impact on water quality: pollutants can be transported into water bodies by the increased surface runoff. In coastal regions, more salt may find its way into water resources due to higher sea levels and more intense storms. Higher temperatures also directly degrade water quality: warm water contains less oxygen. Socio-economic impacts. The effects of climate change on humans are far reaching. Climate change impacts health, the availability of drinking water and food, inequality and economic growth. The effects of climate change are often interlinked and can exacerbate each other as well as existing vulnerabilities. The impacts  are often exacerbated by related environmental disruptions and pressures such as pollution and biodiversity loss. Some areas may become too hot for humans to live in while people in some areas may experience internal or long-distance displacement (and thus become climate refugees) triggered by climate change related changes or disasters. The effects of climate change, in combination with the sustained increases in greenhouse gas emissions, have led scientists to characterize it as a "climate emergency" or "climate crisis". Some climate researchers and activists have called it an "existential threat to civilization". Economic impacts. Overall economy and inequality. Economic forecasts  of the impact of global warming vary considerably. Researchers have warned that current economic modelling may seriously underestimate the impact of potentially catastrophic climate change, and point to the need for new models that give a more accurate picture of potential damages. Nevertheless, one 2018 study found that potential global economic gains if countries implement mitigation strategies to comply with the 2 °C target set at the Paris Agreement are in the vicinity of US$17 trillion per year up to 2100 compared to a very high emission scenario. Global losses reveal rapidly rising costs due to extreme weather  events since the 1970s. Socio-economic factors have contributed to the observed trend of global losses, such as population growth and increased wealth. Part of the growth is also related to regional climatic factors, e.g., changes in precipitation and flooding events. It is difficult to quantify the relative impact of socio-economic factors and climate change on the observed trend. The trend does, however, suggest increasing vulnerability of social systems to climate change. Climate change has contributed towards global economic inequality. Wealthy countries in colder regions have either felt little overall economic impact from climate change, or possibly benefited, whereas  poor hotter countries very likely grew less than if global warming had not occurred. The total economic impacts from climate change are difficult to estimate, but increase for higher temperature changes. For instance, total damages are estimated to be 90% less if global warming is limited to 1.5 °C compared to 3.66 °C, a warming level chosen to represent no mitigation. One study found a 3.5% reduction in global GDP by the end of the century if warming is limited to 3 °C, excluding the potential effect of tipping points. Another study noted that global economic impact  is underestimated by a factor of two to eight when tipping points are excluded from consideration. In the Oxford Economics high emission scenario, a temperature rise of 2 degrees by 2050 would reduce global GDP by 2.5% – 7.5%. By the year 2100 in this case, the temperature would rise by 4 degrees, which could reduce the global GDP by 30% in the worst case. Most affected sectors apart from agriculture and fisheries. Thermal power stations (fossil fuel plants and nuclear power plants) depend on water to cool them. Not only is there increased demand for fresh water, but climate change  can increase the likelihood of drought and fresh water shortages. Another impact for thermal power plants, is that increasing the temperatures in which they operate reduces their efficiency and hence their output. Changes in the amount of river flow correlate with the amount of energy produced by a dam. The result of diminished river flow can be a power shortage in areas that depend heavily on hydroelectric power. Brazil in particular, is vulnerable due to its having reliance on hydroelectricity as increasing temperatures, lower water flow, and alterations in the rainfall regime, could reduce total energy production by 7% annually  by the end of the century. Oil and natural gas infrastructure is affected by the effects of climate change and the increased risk of disasters such as storm, cyclones, flooding and rising sea levels. Insurance is an important tool to manage risks, but often unavailable to poorer households. Due to climate change, premiums are going up for certain types of insurance, such as flood insurance. Poor adaptation to climate change further widens the gap between what people can afford and the costs of insurance, as risks increase. In 2019, Munich Re noted that climate change could cause home insurance to  become unaffordable for households at or below average incomes. Roads, airport runways, railway lines and pipelines, (including oil pipelines, sewers, water mains etc.) may require increased maintenance and renewal as they become subject to greater temperature variation. Regions already adversely affected include areas of permafrost, which are subject to high levels of subsidence, resulting in buckling roads, sunken foundations, and severely cracked runways. Displacement and migration. Climate change affects displacement of people in several ways. Firstly, involuntary displacement may increase through the increased number and severity of weather-related disasters which destroy homes and habitats. Effects of climate change such  as desertification and rising sea levels gradually erode livelihood and force communities to abandon traditional homelands for more accommodating environments. On the other hand, some households may fall (further) into poverty due to climate change, limiting their ability to move to areas less affected. According to the Internal Displacement Monitoring Centre in 2020 approximately 30 million people were displaced by extreme weather events while approximately 10 million by violence and wars and climate change significantly contributed to this. The United Nations says there are already 64 million migrants in the world fleeing wars, hunger, persecution and the effects of global  warming. In 2018, the World Bank estimated that climate change will cause internal migration of between 31 and 143 million people as they escape crop failures, water scarcity, and sea level rise. The study only included Sub-Saharan Africa, South Asia, and Latin America.Asia and the Pacific is the global area most prone to natural disasters, both in terms of the absolute number of disasters and of populations affected. It is highly exposed to climate impacts, and is home to highly vulnerable population groups, who are disproportionately poor and marginalized. A 2015 Asian Development Bank report highlights "environmental hot  spots" that are particular risk of flooding, cyclones, typhoons, and water stress. Gradual but pervasive environmental change and sudden natural disasters both influence the nature and extent of human migration but in different ways. United Nations High Commissioner for Refugees stated that climate change increases mass displacement, in many regions, including Sahel, East Africa, South Asia, the "drought corridor" in Latin America. 90% of refugees comes from "climate vulnerable hotspots". Some Pacific Ocean island nations, such as Tuvalu, Kiribati, and the Maldives, are considering the eventual possibility of evacuation, as flood defense may become economically unrealistic. Governments have considered various  approaches to reduce migration compelled by environmental conditions in at-risk communities, including programs of social protection, livelihoods development, basic urban infrastructure development, and disaster risk management. Some experts support migration as an appropriate way for people to cope with environmental changes. However, this is controversial because migrants – particularly low-skilled ones – are among the most vulnerable people in society and are often denied basic protections and access to services. Slow-onset disasters and gradual environmental erosion such as desertification, reduction of soil fertility, coastal erosion and sea-level rise are likely to induce long-term migration. Migration related to  desertification and reduced soil fertility is likely to be predominantly from rural areas in developing countries to towns and cities. Conflict. Climate change can worsen conflicts by exacerbating tensions over limited resources like drinking water (in the case of water conflicts). Climate change also has the potential to cause large population dislocations and migration, which can also lead to increased tensions. However, factors other than climate change are judged to be substantially more important in affecting conflict. These factors include intergroup inequality and low socio-economic development. In some cases, climate change can even lead to more peaceful relationships between  groups, as environmental problems requires common policy to be developed. Global warming has been described as a "threat multiplier". Certain conditions make it more likely that climate change impacts conflict: ethnic exclusion, an economy dependent on agriculture, insufficient infrastructure, poor local governance, and low levels of development. A spike in wheat prices following crop losses from a period of drought may have contributed to the onset of the "Arab Spring" protests and revolutions in 2010. Social impacts on vulnerable groups. The impacts of climate change on humans are not distributed uniformly within communities. Individual and social factors such as gender , age, education, ethnicity, geography and language lead to differential vulnerability and capacity to adapt to the effects of climate change. The following more vulnerable groups have been identified: Human settlements. A major challenge for human settlements is sea level rise, indicated by ongoing observation and research of rapid declines in ice-mass balance from both Greenland and Antarctica. Estimates for 2100 are at least twice as large as previously estimated by IPCC AR4, with an upper limit of about two meters. Depending on regional changes, increased precipitation patterns can cause more flooding or extended drought stresses water resources. A 2020  study projects that regions inhabited by a third of the human population could become as hot as the hottest parts of the Sahara within 50 years without a change in patterns of population growth and without migration, unless greenhouse gas emissions are reduced. The projected annual average temperature of above 29 °C for these regions would be outside the "human temperature niche" – a suggested range for climate biologically suitable for humans based on historical data of mean annual temperatures (MAT) – and the most affected regions have little adaptive capacity as of 2020. In small islands and megadeltas, inundation as  a result of sea level rise is expected to threaten vital infrastructure and human settlements. This could lead to issues of statelessness for populations in countries such as the Maldives and Tuvalu and homelessness in countries with low-lying areas such as Bangladesh. Projections for cities in 2050. In 2019 the Crowther Lab from ETH Zürich paired the climatic conditions of 520 major cities worldwide with the predicted climatic conditions of cities in 2050. 22% of the major cities are predicted to have climatic conditions that do not exist in any city today. 2050 London will have a climate similar  to 2019 Melbourne, Athens and Madrid like Fez, Morocco, Nairobi like Maputo. The Indian city Pune will be like Bamako in Mali, Bamako will be like Niamey in Niger. Brasilia will be like Goiania. Increased extreme heat exposure from both climate change and the urban heat island effect threatens urban settlements. Impacts on people in especially affected regions. The Arctic, Africa, small islands, Asian megadeltas and the Middle East are regions that are likely to be especially affected by climate change. Low-latitude, less-developed regions are at most risk of experiencing negative impacts due to climate change. The ten  countries of the Association of Southeast Asian Nations (ASEAN) are among the most vulnerable in the world to the negative effects of climate change, however, ASEAN's climate mitigation efforts are not commensurate with the climate change threats the region faces. Africa is one of the most vulnerable continents to climate variability and change because of multiple existing stresses and low adaptive capacity. Climate change is projected to decrease freshwater availability in central, south, east and southeast Asia, particularly in large river basins. With population growth and increasing demand from higher standards of living, this decrease could adversely affect more  than a billion people by the 2050s. Small islands, whether located in the tropics or higher latitudes, are already exposed to extreme weather events and changes in sea level. This existing exposure will likely make these areas sensitive to the effects of climate change. Developed countries are also vulnerable to climate change, and have already been negatively affected by increases in the severity and frequency of some extreme weather events, such as heat waves, floods, wildfires, and tropical cyclones. Low-lying coastal regions. For historical reasons to do with trade, many of the world's largest and most prosperous cities  are on the coast. In developing countries, the poorest often live on floodplains, because it is the only available space, or fertile agricultural land. These settlements often lack infrastructure such as dykes and early warning systems. Poorer communities also tend to lack the insurance, savings, or access to credit needed to recover from disasters. Socioeconomic impacts of climate change in coastal and low-lying areas will be overwhelmingly adverse. The following impacts were projected in 2007 with very high confidence: Given high coastal population density, estimates of the number of people at risk of coastal flooding from climate-driven sea -level rise varies from 190 million, to 300 million or even 640 million in a worst-case scenario related to the instability of the Antarctic ice sheet. The most people affected are in the densely-populated and low-lying megadeltas of Asia and Africa. The Greenland ice sheet is estimated to have reached a point of no return, continuing to melt even if warming stopped. Over time that would submerge many of the world's coastal cities including low-lying islands, especially combined with storm surges and high tides. Small islands. Small islands developing states are especially vulnerable to the  effects of climate change, especially sea level rise. They are expected to experience more intense storm surges, salt water intrusion, and coastal destruction. Low-lying small islands in the Pacific, Indian, and Caribbean regions are at risk of permanent inundation and population displacement. On the islands of Fiji, Tonga and western Samoa, concentrations of migrants from outer islands inhabit low and unsafe areas along the coasts. Atoll nations, which include countries that are composed entirely of the smallest form of islands, called motus, are at risk of entire population displacement. These nations include Kiribati, Maldives, the Marshall Islands, Tokelau, and  Tuvalu. Vulnerability is increased by small size, isolation from other land, low financial resources, and lack of protective infrastructure. A study that engaged the experiences of residents in atoll communities found that the cultural identities of these populations are strongly tied to these lands. Human rights activists argue that the potential loss of entire atoll countries, and consequently the loss of national sovereignty, self-determination, cultures, and indigenous lifestyles cannot be compensated for financially. Some researchers suggest that the focus of international dialogues on these issues should shift from ways to relocate entire communities to strategies that instead allow  for these communities to remain on their lands.