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101-555: In April 2007, the MAB issued its first report entitled "National Security and the Threat of Climate Change." The report projects that climate change will pose a serious threat to America's national security, especially by creating instability in already volatile regions. In May 2009 the MAB issued a report that explores the impact of America's energy choices on our national security policies. This report, titled "Powering America’s Defense: Energy and

202-464: A rise in sea levels due to the expansion of water as it warms and the melting ice sheets on land. Other effects on oceans include sea ice decline , reducing pH values and oxygen levels , as well as increased ocean stratification . All this can lead to changes of ocean currents , for example a weakening of the Atlantic meridional overturning circulation (AMOC). The main cause of these changes are

303-482: A bigger impact. The impacts of climate change on nature are likely to become bigger in the next few decades. The stresses caused by climate change, combine with other stresses on ecological systems such as land conversion, land degradation , harvesting, and pollution. They threaten substantial damage to unique ecosystems. They can even result in their complete loss and the extinction of species. This can disrupt key interactions between species within ecosystems. This

404-517: A cascade of effects. This remains a possibility even well below 2 °C (3.6 °F) of warming. A 2018 study states that 45% of environmental problems, including those caused by climate change, are interconnected. This increases the risk of a domino effect . Further impacts may be irreversible, at least over the timescale of many human generations. This includes warming of the deep ocean and acidification. These are set to continue even when global temperatures stop rising. In biological systems,

505-570: A decade or so, and nitrous oxides last about 100 years. The graph gives some indication of which regions have contributed most to human-induced climate change. When these numbers are calculated per capita cumulative emissions based on then-current population the situation is shown even more clearly. The ratio in per capita emissions between industrialized countries and developing countries was estimated at more than 10 to 1. Non- OECD countries accounted for 42% of cumulative energy-related CO 2 emissions between 1890 and 2007. Over this time period,

606-480: A fire starts in an area with very dry vegetation, it can spread rapidly. Higher temperatures can also lengthen the fire season. This is the time of year in which severe wildfires are most likely, particularly in regions where snow is disappearing. Weather conditions are raising the risks of wildfires. But the total area burnt by wildfires has decreased. This is mostly because savanna has been converted to cropland , so there are fewer trees to burn. Prescribed burning

707-870: A high risk at 2.5 °C (4.5 °F). It is possible that some tipping points are close or have already been crossed. Examples are the West Antarctic and Greenland ice sheets, the Amazon rainforest, and warm-water coral reefs. Tipping points are perhaps the most dangerous aspect of future climate change, potentially leading to irreversible impacts on society. A collapse of the Atlantic meridional overturning circulation would likely halve rainfall in India and lead to severe drops in temperature in Northern Europe. Many tipping points are interlinked such that triggering one may lead to

808-517: A lack of comparability, which is problematic when monitoring progress towards targets. There are arguments for the adoption of a common measurement tool, or at least the development of communication between different tools. Emissions may be tracked over long time periods, known as historical or cumulative emissions measurements. Cumulative emissions provide some indicators of what is responsible for greenhouse gas atmospheric concentration build-up. The national accounts balance tracks emissions based on

909-525: A lot year by year. This makes it difficult to determine a trend, and record highs and record lows have been observed between 2013 and 2023. The general trend since 1979, the start of the satellite measurements , has been roughly flat. Between 2015 and 2023, there has been a decline in sea ice, but due to the high variability, this does not correspond to a significant trend. Globally, permafrost warmed by about 0.3 °C between 2007 and 2016. The extent of permafrost has been falling for decades. More decline

1010-856: A particular base year. Choosing between base years of 1750, 1900, 1950, and 1990 has a significant effect for most countries. Within the G8 group of countries, it is most significant for the UK, France and Germany. These countries have a long history of CO 2 emissions (see the section on Cumulative and historical emissions ). The Global Carbon Project continuously releases data about CO 2 emissions, budget and concentration. and industry (excluding cement carbonation) Gt C change Gt C Gt C Gt CO 2 (projection) Distribution of global greenhouse gas emissions based on type of greenhouse gas, without land-use change, using 100 year global warming potential (data from 2020). Total: 49.8 GtCO 2 e Carbon dioxide (CO 2 )

1111-581: A range of activities around the world that seek to ameliorate these issues or prevent them from happening. The effects of climate change vary in timing and location. Up until now the Arctic has warmed faster than most other regions due to climate change feedbacks . Surface air temperatures over land have also increased at about twice the rate they do over the ocean, causing intense heat waves . These temperatures would stabilize if greenhouse gas emissions were brought under control . Ice sheets and oceans absorb

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1212-463: A rate of decline of 4.7% per decade. It has declined over 50% since the first satellite records. Ice-free summers are expected to be rare at 1.5 °C (2.7 °F) degrees of warming. They are set to occur at least once every decade with a warming level of 2 °C (3.6 °F). The Arctic will likely become ice-free at the end of some summers before 2050. Sea ice extent in Antarctica varies

1313-475: A significant contributor to warming. Although CFCs are greenhouse gases, they are regulated by the Montreal Protocol which was motivated by CFCs' contribution to ozone depletion rather than by their contribution to global warming. Ozone depletion has only a minor role in greenhouse warming, though the two processes are sometimes confused in the media. In 2016, negotiators from over 170 nations meeting at

1414-457: A significant margin, Asia's and the world's largest emitter: it emits nearly 10 billion tonnes each year, more than one-quarter of global emissions. Other countries with fast growing emissions are South Korea , Iran, and Australia (which apart from the oil rich Persian Gulf states, now has the highest per capita emission rate in the world). On the other hand, annual per capita emissions of the EU-15 and

1515-469: A thousand years, 20% to 30% of human-emitted CO 2 would remain in the atmosphere. The ocean and land would not have taken them. This would commit the climate to a warmer state long after emissions have stopped. With current mitigation policies the temperature will be about 2.7 °C (2.0–3.6 °C) above pre-industrial levels by 2100. It would rise by 2.4 °C (4.3 °F) if governments achieved all their unconditional pledges and targets. If all

1616-481: A wide variety of threats." Principal Findings The CNA Military Advisory Board looked at the conditions climate changes are likely to produce, how those conditions may affect America's national security interests, and what actions the nation should take to address these consequences. Its principal findings included the following: Recommendations Based on these findings, the Board made several recommendations, including

1717-450: Is a framework of methods to measure and track how much greenhouse gas an organization emits. Cumulative anthropogenic (i.e., human-emitted) emissions of CO 2 from fossil fuel use are a major cause of global warming , and give some indication of which countries have contributed most to human-induced climate change. In particular, CO 2 stays in the atmosphere for at least 150 years and up to 1000 years, whilst methane disappears within

1818-452: Is a greenhouse gas, so this process is a self-reinforcing feedback . The excess water vapour also gets caught up in storms. This makes them more intense, larger, and potentially longer-lasting. This in turn causes rain and snow events to become stronger and leads to increased risk of flooding. Extra drying worsens natural dry spells and droughts. This increases risk of heat waves and wildfires. Scientists have identified human activities as

1919-463: Is a mean annual temperature below 29 °C. As of May 2023, 60 million people lived outside this niche. With every additional 0.1 degree of warming, 140 million people will be pushed out of it. Greenhouse gas emissions Greenhouse gas ( GHG ) emissions from human activities intensify the greenhouse effect . This contributes to climate change . Carbon dioxide (CO 2 ), from burning fossil fuels such as coal , oil , and natural gas ,

2020-458: Is a self-reinforcing feedback of climate change. Large-scale measurements of sea ice have only been possible since satellites came into use. Sea ice in the Arctic has declined in recent decades in area and volume due to climate change. It has been melting more in summer than it refreezes in winter. The decline of sea ice in the Arctic has been accelerating during the early twenty-first century. It has

2121-602: Is an indigenous practice in the US and Australia. It can reduce wildfire burning. The carbon released from wildfires adds to carbon dioxide in Earth's atmosphere and therefore contributes to the greenhouse effect . Climate models do not yet fully reflect this climate change feedback . There are many effects of climate change on oceans . One of the most important is an increase in ocean temperatures . More frequent marine heatwaves are linked to this. The rising temperature contributes to

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2222-478: Is and will be a significant threat to our National Security and in a larger sense to life on earth as we know it to be." "Unlike the problems that we are used to dealing with, these will come upon us extremely slowly, but come they will, and they will be grinding and inexorable," Effects of global warming#Migration and conflict Effects of climate change are well documented and growing for Earth's natural environment and human societies. Changes to

2323-483: Is approximately 1600 gigatons. This is twice the atmospheric pool. Recent warming has had a big effect on natural biological systems. Species worldwide are moving poleward to colder areas. On land, species may move to higher elevations. Marine species find colder water at greater depths. Climate change had the third biggest impact on nature out of various factors in the five decades up to 2020. Only change in land use and sea use and direct exploitation of organisms had

2424-776: Is because species from one location do not leave the warming habitat at the same rate. The result is rapid changes in the way the ecosystem functions. Impacts include changes in regional rainfall patterns. Another is earlier leafing of trees and plants over many regions. Movements of species to higher latitudes and altitudes, changes in bird migrations, and shifting of the oceans' plankton and fish from cold- to warm-adapted communities are other impacts. These changes of land and ocean ecosystems have direct effects on human well-being. For instance, ocean ecosystems help with coastal protection and provide food. Freshwater and land ecosystems can provide water for human consumption. Furthermore, these ecosystems can store carbon. This helps to stabilize

2525-413: Is expected in the future. Permafrost thaw makes the ground weaker and unstable. The thaw can seriously damage human infrastructure in permafrost areas such as railways, settlements and pipelines. Thawing soil can also release methane and CO 2 from decomposing microbes. This can generate a strong feedback loop to global warming . Some scientists believe that carbon storage in permafrost globally

2626-497: Is expected to become rarer. This depends on several factors. These include changes in rain and snowmelt, but also soil moisture . Climate change leaves soils drier in some areas, so they may absorb rainfall more quickly. This leads to less flooding. Dry soils can also become harder. In this case heavy rainfall runs off into rivers and lakes. This increases risks of flooding. Climate change affects many factors associated with droughts . These include how much rain falls and how fast

2727-421: Is exported. In comparison, methane has not increased appreciably, and N 2 O by 0.25% y . Using different base years for measuring emissions has an effect on estimates of national contributions to global warming. This can be calculated by dividing a country's highest contribution to global warming starting from a particular base year, by that country's minimum contribution to global warming starting from

2828-460: Is limited evidence 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 for decades and possibly even millennia. The complete loss of the West Antarctic ice sheet would cause over 5 metres (16 ft) of sea level rise. In contrast to the West Antarctic ice sheet, melt of the Greenland ice sheet

2929-551: Is one of the most important factors in causing climate change. The largest emitters are China followed by the United States. The United States has higher emissions per capita . The main producers fueling the emissions globally are large oil and gas companies . Emissions from human activities have increased atmospheric carbon dioxide by about 50% over pre-industrial levels. The growing levels of emissions have varied, but have been consistent among all greenhouse gases . Emissions in

3030-458: Is projected to take place more gradually over millennia. Sustained warming between 1 °C (1.8 °F) (low confidence) and 4 °C (7.2 °F) (medium confidence) would lead to a complete loss of the ice sheet. This would contribute 7 m (23 ft) to sea levels globally. The ice loss could become irreversible due to a further self-enhancing feedback. This is called the elevation-surface mass balance feedback. When ice melts on top of

3131-467: Is related to temperature. It also increases if humidity is higher. The wet-bulb temperature measures both temperature and humidity. Humans cannot adapt to a wet-bulb temperature above 35 °C (95 °F). This heat stress can kill people. If global warming is kept below 1.5 or 2 °C (2.7 or 3.6 °F), it will probably be possible to avoid this deadly heat and humidity in most of the tropics. But there may still be negative health impacts. There

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3232-633: Is responsible for around 73% of emissions. Deforestation and other changes in land use also emit carbon dioxide and methane . The largest source of anthropogenic methane emissions is agriculture , closely followed by gas venting and fugitive emissions from the fossil-fuel industry . The largest agricultural methane source is livestock . Agricultural soils emit nitrous oxide partly due to fertilizers . Similarly, fluorinated gases from refrigerants play an outsized role in total human emissions. The current CO 2 -equivalent emission rates averaging 6.6 tonnes per person per year, are well over twice

3333-478: Is some evidence climate change is leading to a weakening of the polar vortex . This would make the jet stream more wavy. This would lead to outbursts of very cold winter weather across parts of Eurasia and North America and incursions of very warm air into the Arctic. Warming increases global average precipitation . Precipitation is when water vapour condenses out of clouds, such as rain and snow. Higher temperatures increase evaporation and surface drying. As

3434-451: Is the dominant emitted greenhouse gas, while methane ( CH 4 ) emissions almost have the same short-term impact. Nitrous oxide (N 2 O) and fluorinated gases (F-gases) play a lesser role in comparison. Greenhouse gas emissions are measured in CO 2 equivalents determined by their global warming potential (GWP), which depends on their lifetime in the atmosphere. Estimations largely depend on

3535-563: Is the first major source of greenhouse gas emissions from transportation, followed by aircraft and maritime. Waterborne transportation is still the least carbon-intensive mode of transportation on average, and it is an essential link in sustainable multimodal freight supply chains . Buildings, like industry, are directly responsible for around one-fifth of greenhouse gas emissions, primarily from space heating and hot water consumption. When combined with power consumption within buildings, this figure climbs to more than one-third. Within

3636-449: Is the main greenhouse gas resulting from human activities. It accounts for more than half of warming. Methane (CH 4 ) emissions have almost the same short-term impact. Nitrous oxide (N 2 O) and fluorinated gases (F-gases) play a lesser role in comparison. Emissions of carbon dioxide, methane and nitrous oxide in 2023 were all higher than ever before. Electricity generation , heat and transport are major emitters; overall energy

3737-563: 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 temperatures have surpassed anything in the last 2,000 years. By the end of the 21st century, temperatures may increase to a level last seen in the mid-Pliocene . This was around 3 million years ago. At that time, mean global temperatures were about 2–4 °C (3.6–7.2 °F) warmer than pre-industrial temperatures. The global mean sea level

3838-665: Is very complex, and is affected by how carbon sinks are allocated between regions and the dynamics of the climate system . The graphic shows the logarithm of 1850–2019 fossil fuel CO 2 emissions; natural log on left, actual value of Gigatons per year on right. Although emissions increased during the 170-year period by about 3% per year overall, intervals of distinctly different growth rates (broken at 1913, 1945, and 1973) can be detected. The regression lines suggest that emissions can rapidly shift from one growth regime to another and then persist for long periods of time. The most recent drop in emissions growth – by almost 3 percentage points –

3939-786: The Amazon Rainforest . At 2 °C (3.6 °F) of warming, around 10% of species on land would become critically endangered. Humans are vulnerable to climate change in many ways. Sources of food and fresh water can be threatened by environmental changes. Human health can be impacted by weather extremes or by ripple effects like the spread of infectious diseases . Economic impacts include changes to agriculture , fisheries , and forestry . Higher temperatures will increasingly prevent outdoor labor in tropical latitudes due to heat stress . Island nations and coastal cities may be inundated by rising sea levels. Some groups of people may be particularly at risk from climate change, such as

4040-451: 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. This effect is even worse because climate change brings more frequent droughts to the area. The higher frequency of droughts in the first two decades of

4141-418: The climate system include an overall warming trend , changes to precipitation patterns , and more extreme weather . As the climate changes it impacts the natural environment with effects such as more intense forest fires , thawing permafrost , and desertification . These changes impact ecosystems and societies, and can become irreversible once tipping points are crossed. Climate activists are engaged in

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4242-415: The emissions of greenhouse gases from human activities, mainly burning of fossil fuels and deforestation . Carbon dioxide and methane are examples of greenhouse gases. The additional greenhouse effect leads to ocean warming because the ocean takes up most of the additional heat in the climate system . The ocean also absorbs some of the extra carbon dioxide that is in the atmosphere . This causes

4343-415: 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. This makes it possibly vulnerable to the self-enhancing process of marine ice sheet instability . Marine ice cliff instability could also contribute to a partial collapse. But there

4444-415: The pH value of the seawater to drop . Scientists estimate that the ocean absorbs about 25% of all human-caused CO 2 emissions. The various layers of the oceans have different temperatures. For example, the water is colder towards the bottom of the ocean. This temperature stratification will increase as the ocean surface warms due to rising air temperatures. Connected to this is a decline in mixing of

4545-468: The poor , children , and indigenous peoples . Industrialised countries , which have emitted the vast majority of CO 2 , have more resources to adapt to global warming than developing nations do. Cumulative effects and extreme weather events can lead to displacement and migration . Global warming affects all parts of Earth's climate system . Global surface temperatures have risen by 1.1 °C (2.0 °F). Scientists say they will rise further in

4646-473: The 2010s averaged 56 billion tons a year, higher than any decade before. Total cumulative emissions from 1870 to 2022 were 703 GtC (2575 GtCO 2 ), of which 484±20 GtC (1773±73 GtCO 2 ) from fossil fuels and industry, and 219±60 GtC (802±220 GtCO 2 ) from land use change . Land-use change , such as deforestation , caused about 31% of cumulative emissions over 1870–2022, coal 32%, oil 24%, and gas 10%. Carbon dioxide (CO 2 )

4747-520: The 2030 Paris Agreement increase of 1.5 °C (2.7 °F) over pre-industrial levels. While cities are sometimes considered to be disproportionate contributors to emissions, per-capita emissions tend to be lower for cities than the averages in their countries. A 2017 survey of corporations responsible for global emissions found that 100 companies were responsible for 71% of global direct and indirect emissions , and that state-owned companies were responsible for 59% of their emissions. China is, by

4848-410: The 21st century and other data signal that a tipping point from rainforest to savanna might be close. A 2019 study concluded that this ecosystem could begin a 50-year-long collapse to a savanna around 2021. After that it would become increasingly and disproportionally more difficult to prevent or reverse this shift. Marine heatwaves are happening more often. They have widespread impacts on life in

4949-443: The 21st century the hotter the world will be by 2100. For a doubling of greenhouse gas concentrations, the global mean temperature would rise by about 2.5–4 °C (4.5–7.2 °F). If emissions of CO 2 stopped abruptly and there was no use of negative emission technologies , the Earth's climate would not start moving back to its pre-industrial state. Temperatures would stay at the same high level for several centuries. After about

5050-523: The Accelerating Risks of Climate Change" re-examines the impact of climate change on U.S. national security. The most recent MAB report, "National Security and Assured U.S. Electrical Power," was released in November 2015. The 2015 report found that "the current U.S. electrical grid – based on centralized power generation and interconnected and aging distribution architecture – is susceptible to

5151-495: The EU, the agricultural sector presently accounts for roughly 10% of total greenhouse gas emissions, with methane from livestock accounting for slightly more than half of 10%. Estimates of total CO 2 emissions do include biotic carbon emissions, mainly from deforestation. Including biotic emissions brings about the same controversy mentioned earlier regarding carbon sinks and land-use change. The actual calculation of net emissions

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5252-474: The Earth can cool off. The major anthropogenic (human origin) sources of greenhouse gases are carbon dioxide (CO 2 ), nitrous oxide ( N 2 O ), methane and three groups of fluorinated gases ( sulfur hexafluoride ( SF 6 ), hydrofluorocarbons (HFCs) and perfluorocarbons (PFCs, sulphur hexafluoride (SF 6 ), and nitrogen trifluoride (NF 3 )). Though the greenhouse effect is heavily driven by water vapor , human emissions of water vapor are not

5353-579: The Himalayas in Asia, the retreat of glaciers could impact water supply. The melting of those glaciers could also cause landslides or glacial lake outburst floods . 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. Antarctic ice loss is driven by warm ocean water melting

5454-569: The Risks to National Security," considers the security risks inherent in our current energy posture; energy choices the nation can make to enhance our national security; the impact of climate change on our energy choices and our national security; and the role the Department of Defense can play in the nation's approach to energy security and climate change. The MAB also released reports in 2010, 2011, and 2014 The May 2014 report, "National Security and

5555-667: The US accounted for 28% of emissions; the EU, 23%; Japan, 4%; other OECD countries 5%; Russia, 11%; China, 9%; India, 3%; and the rest of the world, 18%. The European Commission adopted a set of legislative proposals targeting a reduction of the CO 2 emissions by 55% by 2030. Overall, developed countries accounted for 83.8% of industrial CO 2 emissions over this time period, and 67.8% of total CO 2 emissions. Developing countries accounted for industrial CO 2 emissions of 16.2% over this time period, and 32.2% of total CO 2 emissions. However, what becomes clear when we look at emissions across

5656-548: The US are gradually decreasing over time. Emissions in Russia and Ukraine have decreased fastest since 1990 due to economic restructuring in these countries. 2015 was the first year to see both total global economic growth and a reduction of carbon emissions. Annual per capita emissions in the industrialized countries are typically as much as ten times the average in developing countries. Due to China's fast economic development, its annual per capita emissions are quickly approaching

5757-419: The ability of oceans and land sinks to absorb these gases. Short-lived climate pollutants (SLCPs) including methane, hydrofluorocarbons (HFCs) , tropospheric ozone and black carbon persist in the atmosphere for a period ranging from days to 15 years; whereas carbon dioxide can remain in the atmosphere for millennia. Reducing SLCP emissions can cut the ongoing rate of global warming by almost half and reduce

5858-451: The air warms it can hold more water. For every degree Celsius it can hold 7% more water vapour . Scientists have observed changes in the amount, intensity, frequency, and type of precipitation. Overall, climate change is causing longer hot dry spells, broken by more intense rainfall. Climate change has increased contrasts in rainfall amounts between wet and dry seasons. Wet seasons are getting wetter and dry seasons are getting drier. In

5959-508: The atmosphere. The ecosystems most immediately threatened by climate change are in the mountains , coral reefs , and the Arctic . Excess heat is causing environmental changes in those locations that exceed the ability of animals to adapt. Species are escaping heat by migrating towards the poles and to higher ground when they can. Sea level rise threatens coastal wetlands with flooding . Decreases in soil moisture in certain locations can cause desertification and damage ecosystems like

6060-509: The case of Jupiter , or from its host star as in the case of the Earth . In the case of Earth, the Sun emits shortwave radiation ( sunlight ) that passes through greenhouse gases to heat the Earth's surface. In response, the Earth's surface emits longwave radiation that is mostly absorbed by greenhouse gases. The absorption of longwave radiation prevents it from reaching space, reducing the rate at which

6161-456: The cause of recent climate trends. They are now able to estimate the impact of climate change on extreme weather events using a process called extreme event attribution . For instance such research can look at historical data for a region and conclude that a specific heat wave was more intense due to climate change. In addition , the time shifts of the season onsets, changes in the length of the season durations have been reported in many regions of

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6262-601: The climate system. Climate change is a major driver of biodiversity loss in different land types. These include 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 2050, climate change may be the major cause of biodiversity loss globally. Climate change interacts with other pressures. These include habitat modification, pollution and invasive species . Through this interaction, climate change increases

6363-667: The concentration of carbon dioxide and other greenhouse gases. Emissions have grown rapidly since about 1950 with ongoing expansions in global population and economic activity following World War II. As of 2021, measured atmospheric concentrations of carbon dioxide were almost 50% higher than pre-industrial levels. The main sources of greenhouse gases due to human activity (also called carbon sources ) are: Global greenhouse gas emissions are about 50 Gt per year and for 2019 have been estimated at 57 Gt CO 2 eq including 5 Gt due to land use change. In 2019, approximately 34% [20 GtCO 2 -eq] of total net anthropogenic GHG emissions came from

6464-465: The countries that have set or are considering net-zero targets achieve them, the temperature will rise by around 1.8 °C (3.2 °F). There is a big gap between national plans and commitments and the actions that governments have taken around the world. The lower and middle atmosphere, where nearly all weather occurs, are heating due to the greenhouse effect . Evaporation and atmospheric moisture content increase as temperatures rise. Water vapour

6565-413: The difference between a country's exports and imports. For many richer nations, the balance is negative because more goods are imported than they are exported. This result is mostly due to the fact that it is cheaper to produce goods outside of developed countries, leading developed countries to become increasingly dependent on services and not goods. A positive account balance would mean that more production

6666-440: The energy supply sector, 24% [14 GtCO 2 -eq] from industry, 22% [13 GtCO 2 -eq]from agriculture, forestry and other land use (AFOLU), 15% [8.7 GtCO 2 -eq] from transport and 6% [3.3 GtCO 2 -eq] from buildings. Global carbon dioxide emissions by country in 2023: The current CO 2 -equivalent emission rates averaging 6.6 tonnes per person per year, are well over twice the estimated rate 2.3 tons required to stay within

6767-489: The entire life cycle from the production of a good or service along the supply chain to its final consumption. Carbon accounting (or greenhouse gas accounting) is a framework of methods to measure and track how much greenhouse gas an organization emits. The greenhouse effect occurs when greenhouse gases in a planet's atmosphere insulate the planet from losing heat to space, raising its surface temperature. Surface heating can happen from an internal heat source as in

6868-414: The estimated rate 2.3 tons required to stay within the 2030 Paris Agreement increase of 1.5 °C (2.7 °F) over pre-industrial levels. Annual per capita emissions in the industrialized countries are typically as much as ten times the average in developing countries. The carbon footprint (or greenhouse gas footprint ) serves as an indicator to compare the amount of greenhouse gases emitted over

6969-415: The extinction of species would be an irreversible impact. In social systems, unique cultures may be lost. Climate change could make it more likely that endangered languages disappear. Humans have a climate niche. This is a certain range of temperatures in which they flourish. Outside that niche, conditions are less favourable. This leads to negative effects on health, food security and more. This niche

7070-555: The far western Sahel. Storms become wetter under climate change. These include tropical cyclones and extratropical cyclones . Both the maximum and mean rainfall rates increase. This more extreme rainfall is also true for thunderstorms in some regions. Furthermore, tropical cyclones and storm tracks are moving towards the poles. This means some regions will see large changes in maximum wind speeds. Scientists expect there will be fewer tropical cyclones. But they expect their strength to increase. There has probably been an increase in

7171-487: The following: Eleven highly respected retired admirals and generals, headed by former Army Chief of Staff General Gordon R. Sullivan, comprised the CNA Military Advisory Board in 2007. The 2015 MAB members are: Morrow Cater , founding principal of Cater Communications, has served as a strategic communication advisor to the MAB, including managing the media release of several of their influential reports on

7272-442: The future. The changes in climate are not uniform across the Earth. In particular, most land areas have warmed faster than most ocean areas. The Arctic is warming faster than most other regions. Night-time temperatures have increased faster than daytime temperatures. The impact on nature and people depends on how much more the Earth warms. Scientists use several methods to predict the effects of human-caused climate change. One

7373-429: The ice sheet, the elevation drops. Air temperature is higher at lower altitudes, so this promotes further melting. Sea ice reflects 50% to 70% of the incoming solar radiation back into space. Only 6% of incoming solar energy is reflected by the ocean. As the climate warms, the area covered by snow or sea ice decreases. After sea ice melts, more energy is absorbed by the ocean, so it warms up. This ice-albedo feedback

7474-731: The impact of acidification. Warm-water coral reefs are very sensitive to global warming and ocean acidification. Coral reefs provide a habitat for thousands of species. They provide ecosystem services such as coastal protection and food. But 70–90% of today's warm-water coral reefs will disappear even if warming is kept to 1.5 °C (2.7 °F). Coral reefs are framework organisms. They build physical structures that form habitats for other sea creatures. Other framework organisms are also at risk from climate change. Mangroves and seagrass are considered to be at moderate risk from lower levels of global warming. The climate system exhibits "threshold behavior" or tipping points when parts of

7575-824: The importing country, rather than the exporting, country. A substantial proportion of CO 2 emissions is traded internationally. The net effect of trade was to export emissions from China and other emerging markets to consumers in the US, Japan, and Western Europe. Emission intensity is a ratio between greenhouse gas emissions and another metric, e.g., gross domestic product (GDP) or energy use. The terms "carbon intensity" and " emissions intensity " are also sometimes used. Emission intensities may be calculated using market exchange rates (MER) or purchasing power parity (PPP). Calculations based on MER show large differences in intensities between developed and developing countries, whereas calculations based on PPP show smaller differences. Carbon accounting (or greenhouse gas accounting)

7676-472: The intensity of individual heat waves to global warming. Some extreme events would have been nearly impossible without human influence on the climate system. A heatwave that would occur once every ten years before global warming started now occurs 2.8 times as often. Under further warming, heatwaves are set to become more frequent. An event that would occur every ten years would occur every other year if global warming reaches 2 °C (3.6 °F). Heat stress

7777-468: The lapse of formerly declining trends in carbon intensity of both developing and developed nations. China was responsible for most of global growth in emissions during this period. Localised plummeting emissions associated with the collapse of the Soviet Union have been followed by slow emissions growth in this region due to more efficient energy use , made necessary by the increasing proportion of it that

7878-519: The largest declines have been observed in the spring. During the 21st century, snow cover is projected to continue its retreat in almost all regions. Since the beginning of the twentieth century, there has been a widespread retreat of glaciers . Those glaciers that are not associated with the polar ice sheets lost around 8% of their mass between 1971 and 2019. In the Andes in South America and in

7979-707: The levels of those in the Annex I group of the Kyoto Protocol (i.e., the developed countries excluding the US). Africa and South America are both fairly small emitters, accounting for 3-4% of global emissions each. Both have emissions almost equal to international aviation and shipping. There are several ways of measuring greenhouse gas emissions. Some variables that have been reported include: These measures are sometimes used by countries to assert various policy/ethical positions on climate change. The use of different measures leads to

8080-421: The link between climate change, energy, and national security. Her company has also helped organize dozens of state visits featuring MAB members who discuss national security and climate change issues with policymakers, business and community leaders, and the media. "After listening to leaders of the scientific, business, and governmental communities both I and my colleagues came to agree that Global Climate Change

8181-496: The main international treaty on climate change (the UNFCCC ), countries report on emissions produced within their borders, e.g., the emissions produced from burning fossil fuels. Under a production-based accounting of emissions, embedded emissions on imported goods are attributed to the exporting, rather than the importing, country. Under a consumption-based accounting of emissions, embedded emissions on imported goods are attributed to

8282-456: The major source of greenhouse gas emissions in the EU . Greenhouse gas emissions from the transportation sector continue to rise, in contrast to power generation and nearly all other sectors. Since 1990, transportation emissions have increased by 30%. The transportation sector accounts for around 70% of these emissions. The majority of these emissions are caused by passenger vehicles and vans. Road travel

8383-494: The natural environment enter into a new state. Examples are the runaway loss of ice sheets or the dieback of forests. Tipping behavior is found in all parts of the climate system. These include ecosystems, ice sheets, and the circulation of the ocean and atmosphere. Tipping points are studied using data from Earth's distant past and by physical modeling. There is already moderate risk of global tipping points at 1 °C (1.8 °F) above pre-industrial temperatures. That becomes

8484-468: The northern high latitudes , warming has also caused an increase in the amount of snow and rain. In the Southern Hemisphere, the rain associated with the storm tracks has shifted south. Changes in monsoons vary a lot. More monsoon systems are becoming wetter than drier. In Asia summer monsoons are getting wetter. The West African monsoon is getting wetter over the central Sahel , and drier in

8585-649: The number of tropical cyclones that intensify rapidly. Meteorological and seismological data indicate a widespread increase in wind-driven global ocean wave energy in recent decades that has been attributed to an increase in storm intensity over the oceans due to climate change. Atmospheric turbulence dangerous for aviation (hard to predict or that cannot be avoided by flying higher) probably increases due to climate change. Due to an increase in heavy rainfall events, floods are likely to become more severe when they do occur. The interactions between rainfall and flooding are complex. There are some regions in which flooding

8686-423: The ocean layers, so that warm water stabilises near the surface. A reduction of cold, deep water circulation follows. The reduced vertical mixing makes it harder for the ocean to absorb heat. So a larger share of future warming goes into the atmosphere and land. One result is an increase in the amount of energy available for tropical cyclones and other storms. Another result is a decrease in nutrients for fish in

8787-615: The oceans. These include mass dying events and coral bleaching . Harmful algae blooms have increased. This is in response to warming waters, loss of oxygen and eutrophication . Melting sea ice destroys habitat, including for algae that grows on its underside. Ocean acidification can harm marine organisms in various ways. Shell-forming organisms like oysters are particularly vulnerable. Some phytoplankton and seagrass species may benefit. However, some of these are toxic to fish phytoplankton species. Their spread poses risks to fisheries and aquaculture . Fighting pollution can reduce

8888-521: The past 3,000 years. The rate accelerated to 4.62 mm (0.182 in)/yr for the decade 2013–2022. Climate change due to human activities is the main cause. Between 1993 and 2018, melting ice sheets and glaciers accounted for 44% of sea level rise , with another 42% resulting from thermal expansion of water . The cryosphere , the area of the Earth covered by snow or ice, is extremely sensitive to changes in global climate. There has been an extensive loss of snow on land since 1981. Some of

8989-580: The past. Several impacts make their impacts worse. These are increased water demand, population growth and urban expansion in many areas. Land restoration can help reduce the impact of droughts. One example of this is agroforestry . 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. Evidence from Earth's past also shows more fire in warmer periods. Climate change increases evapotranspiration . This can cause vegetation and soils to dry out. When

9090-589: The rain evaporates again. Warming over land increases the severity and frequency of droughts around much of the world. In some tropical and subtropical regions of the world, there will probably be less rain due to global warming. This will make them more prone to drought. Droughts are set to worsen in many regions of the world. These include Central America, the Amazon and south-western South America. They also include West and Southern Africa. The Mediterranean and south-western Australia are also some of these regions. Higher temperatures increase evaporation. This dries

9191-406: The risk of extinction for many terrestrial and freshwater species. At 1.2 °C (2.2 °F) of warming (around 2023 ) some ecosystems are threatened by mass die-offs of trees and from heatwaves. At 2 °C (3.6 °F) of warming, around 10% of species on land would become critically endangered. This differs by group. For instance insects and salamanders are more vulnerable. Rainfall on

9292-445: The soil and increases plant stress . Agriculture suffers as a result. This means even regions where overall rainfall is expected to remain relatively stable will experience these impacts. These regions include central and northern Europe. Without climate change mitigation, around one third of land areas are likely to experience moderate or more severe drought by 2100. Due to global warming droughts are more frequent and intense than in

9393-607: The summit of the United Nations Environment Programme reached a legally binding accord to phase out hydrofluorocarbons (HFCs) in the Kigali Amendment to the Montreal Protocol . The use of CFC-12 (except some essential uses) has been phased out due to its ozone depleting properties. The phasing-out of less active HCFC-compounds will be completed in 2030. Starting about 1750, industrial activity powered by fossil fuels began to significantly increase

9494-440: The upper ocean layers. These changes also reduce the ocean's capacity to store carbon . At the same time, contrasts in salinity are increasing. Salty areas are becoming saltier and fresher areas less salty. Between 1901 and 2018, the average sea level rose by 15–25 cm (6–10 in), with an increase of 2.3 mm (0.091 in) per year since the 1970s. This was faster than the sea level had ever risen over at least

9595-430: The vast majority of excess heat in the atmosphere, delaying effects there but causing them to accelerate and then continue after surface temperatures stabilize. Sea level rise is a particular long term concern as a result. The effects of ocean warming also include marine heatwaves , ocean stratification , deoxygenation , and changes to ocean currents .  The ocean is also acidifying as it absorbs carbon dioxide from

9696-452: The world today is that the countries with the highest emissions over history are not always the biggest emitters today. For example, in 2017, the UK accounted for just 1% of global emissions. In comparison, humans have emitted more greenhouse gases than the Chicxulub meteorite impact event which caused the extinction of the dinosaurs . Transport, together with electricity generation , is

9797-584: The world. As a result, the timing of extreme weather events, such as heavy precipitation and heat waves, is changing to coincide more closely with changes in seasonal patterns. Heatwaves over land have become more frequent and more intense in almost all world regions since the 1950s, due to climate change . Heat waves are more likely to occur simultaneously with droughts. Marine heatwaves are twice as likely as they were in 1980. Climate change will lead to more very hot days and fewer very cold days. There are fewer cold waves . Experts can often attribute

9898-582: The year 1995). A country's emissions may also be reported as a proportion of global emissions for a particular year. Another measurement is of per capita emissions. This divides a country's total annual emissions by its mid-year population. Per capita emissions may be based on historical or annual emissions. One way of attributing greenhouse gas emissions is to measure the embedded emissions (also referred to as "embodied emissions") of goods that are being consumed. Emissions are usually measured according to production, rather than consumption. For example, in

9999-406: Was at about the time of the 1970s energy crisis . Percent changes per year were estimated by piecewise linear regression on the log data and are shown on the plot; the data are from The Integrated Carbon Observation system. The sharp acceleration in CO 2 emissions since 2000 to more than a 3% increase per year (more than 2 ppm per year) from 1.1% per year during the 1990s is attributable to

10100-569: Was occurring within a country, so more operational factories would increase carbon emission levels. Emissions may also be measured across shorter time periods. Emissions changes may, for example, be measured against the base year of 1990. 1990 was used in the United Nations Framework Convention on Climate Change (UNFCCC) as the base year for emissions, and is also used in the Kyoto Protocol (some gases are also measured from

10201-404: Was up to 25 metres (82 ft) higher than it is today. The modern observed rise in temperature and CO 2 concentrations has been rapid. Even abrupt geophysical events in Earth's history do not approach current rates. How much the world warms depends on human greenhouse gas emissions and on how sensitive the climate is to greenhouse gases . The more carbon dioxide (CO 2 ) is emitted in

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