This article documents notable events, research findings,

effects Effect may refer to: * A result or change of something ** List of effects ** Cause and effect, an idiom describing causality Pharmacy and pharmacology * Drug effect, a change resulting from the administration of a drug ** Therapeutic effect, a ...

, and responses related to

global warming and climate change In common usage, climate change describes global warming—the ongoing increase in global average temperature—and its effects on Earth's climate system. Climate change in a broader sense also includes previous long-term changes to E ...

during the year 2021.

Summaries

* 26 February: The United Nations Synthesis Report on '' Nationally Determined Contributions under the Paris Agreement'' stated that "estimated reductions referred to in paragraphs (on greenhouse gas emissions) fall far short of what is required, demonstrating the need for Parties to further strengthen their mitigation commitments under the Paris Agreement". * 21 June: the

World Meteorological Organization The World Meteorological Organization (WMO) is a specialized agency of the United Nations responsible for promoting international cooperation on atmospheric science, climatology, hydrology and geophysics. The WMO originated from the Intern ...

wrote that "2021 is a make-or-break year for climate action, with the window to prevent the worst impacts of climate change—which include ever more frequent more intense droughts, floods and storms—closing rapidly." * 28 July: a follow-on to the 2019 ''World Scientists' Warning of a Climate Emergency'' noted "an unprecedented surge in climate-related disasters since 2019" and stated there is "mounting evidence that we are nearing or have already crossed tipping points associated with critical parts of the Earth system". * 6 September: editors from over 200 health journals published a joint editorial stating "The science is unequivocal; a global increase of 1.5 °C above the pre-industrial average and the continued loss of biodiversity risk catastrophic harm to health that will be impossible to reverse.... The greatest threat to global public health is the continued failure of world leaders to keep the global temperature rise below 1.5 °C and to restore nature." * 30 September: UN Secretary-General António Guterres stated that "time is running out. Irreversible climate tipping points lie alarmingly close." He called for more ambition as current NDCs will lead to a rise of 2.7 °C, saying that "all leaders must recognize that we are in the middle of a climate emergency".

Measurements and statistics

20211231 Vital signs of the planet - NASA - climate change

* 25 January: a review article published in ''

The Cryosphere ''The Cryosphere'' is a peer-reviewed scientific journal focusing on all aspects of frozen water and ground (especially glaciers) on Earth and on other planetary bodies. It was established in 2007 and is published by Copernicus Publications on beha ...

'' reported that Earth lost 28 trillion tonnes of ice between 1994 and 2017, 68% being from atmospheric melting and 32% by oceanic melting. The ''rate'' of ice loss rose 57% since the 1990s–from 0.8 to 1.2 trillion tonnes per year–raising global sea level 34.6 ±3.1 mm in that time period. * 9 February: a study published in ''

Environmental Research Environmental science is an interdisciplinary academic field that integrates physics, biology, and geography (including ecology, chemistry, plant science, zoology, mineralogy, oceanography, limnology, soil science, geology and physical geogra ...

'' concluded that airborne fine particulate matter (PM_2.5) caused by burning fossil fuels causes 8.7 million premature deaths annually, including China (2.4 million), India (2.5 million) and parts of eastern US, Europe and Southeast Asia. * 16 February: study results published in the '' PNAS'' (study's time period: 1990–2018) reported widespread advances and lengthening of pollen seasons (up to 20 days) and increases in pollen concentrations (up to 21%) across North America, with human forcing of the climate system contributing about 50% of the trend in pollen seasons and about 8% of the trend in pollen concentrations. *

Atlantic meridional overturning circulation The Atlantic meridional overturning circulation (AMOC) is part of a global thermohaline circulation in the oceans and is the zonally integrated component of surface and deep currents in the Atlantic Ocean. It is characterized by a northward fl ...

(AMOC): ::* 25 February: a ''Nature Geoscience'' article reported an "unprecedented" (since AD 400) decline in the twentieth century of the

(AMOC), which is now in its weakest state in more than 1,000 years. The AMOC redistributes heat on the planet and has a major impact on climate. In particular, weakness in the AMOC, which includes the

Florida Current The Florida Current is a thermal ocean current that flows from the Straits of Florida around the Florida Peninsula and along the southeastern coast of the United States before joining the Gulf Stream Current near Cape Hatteras. Its contributing ...

and the Gulf Stream, counteracts its moderating effect on the climate in Europe. ::* 5 August: a study published in ''

Nature Climate Change ''Nature Climate Change'' is a monthly peer-reviewed scientific journal published by Nature Publishing Group covering all aspects of research on global warming, the current climate change, especially its effects. It was established in 2011 as the ...

'' presented "spatially consistent empirical evidence that, in the course of the last century, the AMOC may have evolved from relatively stable conditions to a point close to a

critical transition Critical transitions are abrupt shifts in the state of ecosystems, the climate, financial systems or other complex dynamical systems that may occur when changing conditions pass a critical or bifurcation point. As such, they are a particular type ...

". * February: measurements from

Mauna Loa Observatory The Mauna Loa Observatory (MLO) is an atmospheric baseline station on Mauna Loa, on the island of Hawaii, located in the U.S. state of Hawaii. The observatory Since 1958, initially under the direction of Charles Keeling, followed by his s ...

showed that, for the first time, atmospheric levels reached 417 parts per million (ppm), a concentration 50% higher than the 278ppm pre-industrial level. * 8 March: a study published in ''

''—studying the combined effects of average global

sea level rise Globally, sea levels are rising due to human-caused climate change. Between 1901 and 2018, the globally averaged sea level rose by , or 1–2 mm per year on average.IPCC, 2019Summary for Policymakers InIPCC Special Report on the Ocean and Cry ...

and natural and human-induced subsidence—estimated that subsiding coastal locations may locally experience up to four times more ''relative'' sea level rise than could be attributed to global sea level rise alone. * 17 March: a study by the International Federation of Red Cross and Red Crescent Societies estimated that, globally between September 2020 and February 2021, 12.5 million people were displaced by adverse impacts of climate change, the annual average exceeding 20 million. * 17 March: a study published in ''

Nature Nature, in the broadest sense, is the physical world or universe. "Nature" can refer to the phenomena of the physical world, and also to life in general. The study of nature is a large, if not the only, part of science. Although humans are ...

'' estimated that

trawling Trawling is a method of fishing that involves pulling a fishing net through the water behind one or more boats. The net used for trawling is called a trawl. This principle requires netting bags which are towed through water to catch different spec ...

's disturbance of carbon stored in sea beds can re-mineralize sedimentary carbon into amounts equivalent to 15–20% of the atmospheric absorbed by the ocean each year, and comparable to that of terrestrial farming. * 18 March: a study accepted for publication in ''

Environmental Research Letters ''Environmental Research Letters'' is a quarterly, peer-reviewed, open-access, scientific journal covering research on all aspects of environmental science. It is published by IOP Publishing. The editor-in-chief is Daniel Kammen (University of ...

'' estimated that the severity of heatwave and drought impacts on crop production in Europe roughly tripled over the preceding 50 years, from –2.2 (1964–1990) to -7.3% (1991–2015). * 1 April: a study published in ''

'' estimated that anthropogenic climate change has reduced global agricultural

total factor productivity In economics, total-factor productivity (TFP), also called multi-factor productivity, is usually measured as the ratio of aggregate output (e.g., GDP) to aggregate inputs. Under some simplifying assumptions about the production technology, growt ...

by about 21% since 1961, and 26–34% in warmer regions such as Africa, Latin America and the Caribbean. * 7 April: NOAA reported carbon dioxide levels were higher than at anytime in the past 3.6 million years, in the Mid-Pliocene Warm Period when sea level was about 24 mm (78 ft) higher than today and the average temperature was about 4 °C (7 °F) higher than in pre-industrial times. * '' NOAA's redefinition of "average" and "normal":'' ::* April: NOAA's Climate Prediction Center (CPC) states it will use 1991–2020 as the new 30-year period of record, with "average" numbers of named Atlantic storms rising from 12 to 14, hurricanes from 6 to 7, and major hurricanes remaining at 3; Eastern Pacific and Central Pacific numbers remain unchanged over 1981–2010. ::* May: NOAA's

NCEI The National Centers for Environmental Information (NCEI), an agency of the United States government The federal government of the United States (U.S. federal government or U.S. government) is the national government of the United St ...

supersedes weather and climate data from 1981–2010 with data from 1991–2020 to change its designation of "

Climate Normal Climatological normal or climate normal (CN) is a 30-year average of a weather variable for a given time of year. * 28 April: a study published in ''

'' attributed 21±3% of the observed sea-level rise from 2000–2019 to melting glaciers (267±16 gigatonnes per year), and identified a mass loss acceleration of 48±16 gigatonnes per year per decade. * 11 May: a study published in ''

Nature Communications ''Nature Communications'' is a peer-reviewed, open access, scientific journal published by Nature Portfolio since 2010. It is a multidisciplinary journal and it covers the natural sciences, including physics, chemistry, earth sciences, medici ...

'' estimated that land use change affected 32% of the global land area from 1960 to 2019, about four times greater than previously estimated. * 20 May: The Arctic Monitoring and Assessment Programme reported that, from 1971 to 2019, the annually averaged Arctic near-surface air temperature increased by 3.1 °C, three times faster than the global average. * 21 May: a study published in ''

Geophysical Research Letters ''Geophysical Research Letters'' is a biweekly peer-reviewed scientific journal of geoscience published by the American Geophysical Union that was established in 1974. The editor-in-chief is Harihar Rajaram. Aims and scope The journal aims for rap ...

'' reported that, despite greater raw warming in high latitudes, the tropics have greater normalized warming and actually experienced more record-breaking heat events from 1960 to 2019. * 24 May: a study published in ''

Nature Geoscience ''Nature Geoscience'' is a monthly peer-reviewed scientific journal published by the Nature Publishing Group. The Chief Editor is Tamara Goldin, who took over from Heike Langenberg in February 2020. It was established in January 2008. Scope The ...

'' reported mercury in Greenland ice sheet meltwater being two orders of magnitude higher than from Arctic rivers, and, accounting for about 10% of the estimated global riverine flux, estimated it to be globally significant. * 31 May: a study published in ''

'' concluded that 37% of warm-season heat-related deaths from 1991 to 2018 can be attributed to anthropogenic climate change and that increased mortality is evident on every continent. * 4 June: a study published in ''

Science Advances ''Science Advances'' is a peer-reviewed multidisciplinary open-access scientific journal established in early 2015 and published by the American Association for the Advancement of Science. The journal's scope includes all areas of science, inclu ...

'' concluded that previous estimates of emissions caused by human cultivation of peatlands from 1750 to 2018 should be increased by 18% to account for emissions from cultivated northern peatlands in calculating the carbon budget. * 15 June: a study accepted for publication in ''

'' reported that satellite and ''in situ'' observations independently show an approximate doubling of

Earth's Energy Imbalance Earth's energy budget accounts for the balance between the energy that Earth receives from the Sun and the energy the Earth loses back into outer space. Smaller energy sources, such as Earth's internal heat, are taken into consideration, but m ...

(EEI) from mid-2005 to mid-2019. * 28 July: a study published in ''

'' revealed a significant positive global energy imbalance based on satellite observations from 2001 to 2020, and concluded that there is less than 1% probability that this imbalance can be explained by natural internal variability of the

climate system Earth's climate system is a complex system having five interacting components: the atmosphere (air), the hydrosphere (water), the cryosphere (ice and permafrost), the lithosphere (earth's upper rocky layer) and the biosphere (living things). '' ...

. * 31 August: the

WMO The World Meteorological Organization (WMO) is a specialized agency of the United Nations responsible for promoting international cooperation on atmospheric science, climatology, hydrology and geophysics. The WMO originated from the Internat ...

published an ''Atlas of Mortality and Economic Losses from Weather, Climate and Water Extremes (1970–2019),'' indicating that the number of disasters has increased by a factor of five, driven by climate change, more extreme weather and improved reporting; but because of improved early warnings and disaster management the number of deaths decreased almost three-fold. * 1 September: a study published in ''

'' found that since 2001, fires in the Amazon rainforest had potentially impacted ranges of 77.3–85.2% of threatened species in the region, reducing the biodiversity that contributes to the ecological and climatic stability of the Amazon Basin. * 12 October: a study published in the Proceedings of the NAS estimated a nearly 200% increase in urban heat extremes among 13,115 urban areas from 1983 to 2016. * October: The Global Coral Reef Monitoring Network's ''Status of Coral Reefs of the World'' reported that "between 2009 and 2018, there was a progressive loss amounting to 14% of the coral from the world's coral reefs, which is more than all the coral currently living on Australia's coral reefs". * 30 March 2022: Ember's ''Global Electricity Review'' reported that in 2021,

wind Wind is the natural movement of air or other gases relative to a planet's surface. Winds occur on a range of scales, from thunderstorm flows lasting tens of minutes, to local breezes generated by heating of land surfaces and lasting a few ho ...

and solar power reached a record 10% of global electricity, with clean power being 38% of supply, more than coal's 36%. However, demand growth rebounded, leading to a record rise in coal power and emissions. * 7 April 2022: NOAA reported an annual increase in global atmospheric methane of 17 parts per billion (ppb) in 2021—averaging 1,895.7 ppb in that year—the largest annual increase recorded since systematic measurements began in 1983. The increase during 2020 was 15.3 ppb, itself a record increase.

Natural events and phenomena

* 7 February: a rock-ice avalanche in the

Chamoli district Chamoli district is a district of the Uttarakhand state of India. It is bounded by the Tibet region to the north, and by the Uttarakhand districts of Pithoragarh and Bageshwar to the east, Almora to the south, Pauri Garhwal to the southwest, ...

in the Indian Himalayan Mountains killed dozens and left hundreds missing. The death count grew to 204, with 27 million cubic meters of rock and ice collapsing. * March: a ''Science Brief'' review of >90 peer-reviewed scientific articles reported consensus that ocean warming from human-induced climate change is likely fueling more powerful tropical cyclones with increased precipitation rates (through enhanced atmospheric moisture), the increased power and rising sea levels amplifying flooding. Models project that some regions will experience increases in rapid intensification, a poleward migration of the latitude of maximum intensity or a slowing of the forward motion of the storms. Most climate model studies project the annual ''number'' of tropical cyclones to decrease or remain approximately the same. * 5 March: an article published in ''

Science Science is a systematic endeavor that Scientific method, builds and organizes knowledge in the form of Testability, testable explanations and predictions about the universe. Science may be as old as the human species, and some of the earli ...

'' concluded that the Atlantic Multidecadal Oscillation is not an internal multidecadal (40- to 60-year) oscillation distinct from climate noise, but is instead a manifestation of competing time-varying effects of anthropogenic greenhouse gases and sulfate aerosols. * 11 March: a review article published in '' Frontiers in Forests and Global Change'' concluded that warming from non- agents (especially and ) in the Amazon basin largely offsets—and most likely exceeds—the climate change mitigating effect of the region's uptake. * 22 March: a study published in ''

'' concluded that accelerated decline in terrestrial water storage (TWS) caused by glacial ice melting was the main driver of a rapid eastward drift of the

geographic north pole The North Pole, also known as the Geographic North Pole or Terrestrial North Pole, is the point in the Northern Hemisphere where the Earth's axis of rotation meets its surface. It is called the True North Pole to distinguish from the Mag ...

after the 1990s. * 26 March: the full bloom date of cherry blossoms in

Kyoto Kyoto (; Japanese language, Japanese: , ''Kyōto'' ), officially , is the capital city of Kyoto Prefecture in Japan. Located in the Kansai region on the island of Honshu, Kyoto forms a part of the Keihanshin, Keihanshin metropolitan area along wi ...

, Japan—when the majority of buds are open to the skies—occurred earlier than any time since records began in the year 812 CE; historically, the bloom date occurs about 17 April. * 9 April: a study published in ''

'' citing multiple complementary lines of evidence, reported methane-oxidising bacteria (MOB) dwelling in the bark of ''

Melaleuca quinquenervia ''Melaleuca quinquenervia'', commonly known as the broad-leaved paperbark, paper bark tea tree, punk tree or niaouli, is a small- to medium-sized tree of the myrtle family, Myrtaceae. It grows as a spreading tree up to tall, with its trunk co ...

'' (a paper bark tree common in Australia) reduced methane emissions by 36±5%. * 13 April: a study of fruitflies published in ''

'' found that the temperature at which male fertility is lost is much lower than critical thermal limits (CTLs) for survival, suggesting that species, especially tropical species, are more vulnerable to extinction than previously presumed, and that evolution and plasticity are unlikely to rescue populations from extinction. * 16 April: ''

'' published results of a study of

boreal forests Taiga (; rus, тайга́, p=tɐjˈɡa; relates to Mongolic and Turkic languages), generally referred to in North America as a boreal forest or snow forest, is a biome characterized by coniferous forests consisting mostly of pines, spruces, ...

, concluding that

forest fires A wildfire, forest fire, bushfire, wildland fire or rural fire is an unplanned, uncontrolled and unpredictable fire in an area of combustible vegetation. Depending on the type of vegetation present, a wildfire may be more specifically identif ...

shifted tree dominance from slow-growing black spruce to fast-growing

deciduous In the fields of horticulture and Botany, the term ''deciduous'' () means "falling off at maturity" and "tending to fall off", in reference to trees and shrubs that seasonally shed leaves, usually in the autumn; to the shedding of petals, ...

broadleaf trees, resulting in a net ''increase'' in carbon storage and suggesting potential mitigation of the feedback effect of boreal forest fires to global warming. * 17 April: winds of

Typhoon Surigae Typhoon Surigae, known in the Philippines as Super Typhoon Bising, was the strongest Northern Hemisphere tropical cyclone to form before the month of May, one of the most intense tropical cyclones on record and the strongest tropical cyclone wor ...

rapidly intensified In meteorology, rapid intensification is a situation where a tropical cyclone intensifies dramatically in a short period of time. The United States National Hurricane Center defines rapid intensification as an increase in the maximum sustained wi ...

by 170 km/hr (105 mph) in 36 hours to reach 306 km/hr (190 mph), becoming the strongest typhoon, cyclone or hurricane ever observed in February, March, April or May. * 14 June: a study published in the

Proceedings of the National Academy of Sciences ''Proceedings of the National Academy of Sciences of the United States of America'' (often abbreviated ''PNAS'' or ''PNAS USA'') is a peer-reviewed multidisciplinary scientific journal. It is the official journal of the National Academy of Sci ...

concluded that

Rocky Mountain The Rocky Mountains, also known as the Rockies, are a major mountain range and the largest mountain system in North America. The Rocky Mountains stretch in straight-line distance from the northernmost part of western Canada, to New Mexico in ...

subalpine forest Montane ecosystems are found on the slopes of mountains. The alpine climate in these regions strongly affects the ecosystem because temperatures fall as elevation increases, causing the ecosystem to stratify. This stratification is a crucial f ...

s are burning more than at any point in the past 2,000 years, with contemporary rates of burning being 22% higher than the maximum rate reconstructed over the past two millennia. * 18 June: a study published in ''

''—accounting for

, storm surge, and wave runup at exposed open coasts—estimated that globally aggregated annual overtopping hours had increased by almost 50% over the preceding two decades. * Late June: the

2021 Western North America heat wave The 2021 Western North America heat wave was an extreme heat wave that affected much of Western North America from late June through mid-July 2021. Rapid attribution analysis found this was a 1000-year weather event, made 150 times more likely ...

set a new all-time Canadian temperature record of 49.6 °C (121.28 °F), World Weather Attribution concluding that heat waves of such intensity would be at least 150 times rarer without human-induced climate change. * 14 July: a study published in ''Nature'' found that the intensification of the dry season and an increase in deforestation seem to promote higher carbon emissions in the eastern Amazon, in line with studies that indicate an increase in tree mortality as a result of climatic changes across Amazonia. * 10 August: studying the 2020 heat wave in Siberia, a study published in the '' PNAS'' suggested that

gas hydrates Clathrate hydrates, or gas hydrates, clathrates, hydrates, etc., are crystalline water-based solids physically resembling ice, in which small non-polar molecules (typically gases) or polar molecules with large hydrophobic moieties are trapped i ...

trapped in carbonate rock formations became unstable, possibly "add(ing) unknown quantities of methane to the atmosphere in the near future"—in addition to that long known to be produced from microbial decay of organic matter. * 14 August: the >3000 m peak of the Greenland ice sheet experienced rain for the first known time in recorded history, in one of nine instances in the past 2,000 years in which the temperature exceeded the freezing point. * 2 March 2023: a study published in ''

'' said that boreal fires, typically accounting for 10% of global fire emissions, contributed 23% in 2021, by far the highest fraction since 2000. 2021 was an abnormal year because North American and Eurasian boreal forests synchronously experienced their greatest water deficit.

Actions, and goal statements

Science and technology

* 8 February: XPrize announced a competition to bestow its largest-ever prize, $100 million donated by

Elon Musk Elon Reeve Musk ( ; born June 28, 1971) is a business magnate and investor. He is the founder, CEO and chief engineer of SpaceX; angel investor, CEO and product architect of Tesla, Inc.; owner and CEO of Twitter, Inc.; founder of The ...

to be awarded in 2025, for technology to remove carbon from air or water. Winning entries must show an ability to scale up to removing billions of metric tons of carbon. * February: Porsche announced trials to start in 2022 to develop

synthetic fuel Synthetic fuel or synfuel is a liquid fuel, or sometimes gaseous fuel, obtained from syngas, a mixture of carbon monoxide and hydrogen, in which the syngas was derived from gasification of solid feedstocks such as coal or biomass or by refo ...

that it claims will have the same " well to wheel impact"— produced throughout manufacture and sale—as electric vehicles. * February and earlier:

Aptera Motors Aptera Motors (formerly Accelerated Composites) is an American startup high-efficiency car company based in Carlsbad, California. The original company, Aptera Motors, Inc., was founded in 2005 and liquidated in 2011. In 2019, Aptera Motors w ...

indicated it would produce in 2021 a three-wheel, highly aerodynamic electric vehicle powered by 34 square feet of solar cells, also having rechargeable batteries. * Late February: a Cambridge University study estimated that bitcoin

mining Mining is the extraction of valuable minerals or other geological materials from the Earth, usually from an ore body, lode, vein, seam, reef, or placer deposit. The exploitation of these deposits for raw material is based on the economic ...

energy consumption—at that time on the order of 100

terawatt-hours A kilowatt-hour (unit symbol: kW⋅h or kW h; commonly written as kWh) is a unit of energy: one kilowatt of power for one hour. In terms of SI derived units with special names, it equals 3.6 megajoules (MJ). Kilowatt-hours are a common bil ...

annually—possessed a carbon footprint equivalent to Argentina's, a figure likely increased by interest in bitcoin in early 2021 from major Wall Street institutions. * March: ''The Guardian'' reported on the design of " Vortex Bladeless", a curved-top cylindrical turbine whose main body oscillates resonantly with the wind to generate electricity, the design occupying a much smaller footprint than blade-driven

wind turbine A wind turbine is a device that converts the kinetic energy of wind into electrical energy. Hundreds of thousands of large turbines, in installations known as wind farms, now generate over 650 gigawatts of power, with 60 GW added each yea ...

s. * 18 March: a feasibility study published in ''

Nature Sustainability ''Nature Sustainability'' is a monthly peer-reviewed scientific journal published by Nature Portfolio. It was established in 2018. The editor-in-chief is Monica Contestabile. Abstracting and indexing The journal is abstracted and indexed in: ...

'' described how suspending solar panels above water canals not only reduces evaporation and mitigates land use, but increases the efficiency of the panels due to the water's cooling effect. * Reported 30 March: taking advantage of generally stronger winds further from shore, the world's first ''floating'' windfarm, a 30 megawatt facility 15 mi (24 km) off Aberdeenshire, Scotland, broke records for energy output. * 31 March: a study published in the '' PNAS'' concluded that if food waste is diverted from landfills to avoid methane emissions, food-waste-derived n-paraffin

volatile fatty acid Short-chain fatty acids (SCFAs) are fatty acids with fewer than six carbon atoms. Derived from intestinal microbial fermentation of indigestible foods, SCFAs are the main energy source of colonocytes, making them crucial to gastrointestinal health ...

-based sustainable aviation fuels could enable up to a 165% reduction in greenhouse gas emissions relative to fossil-derived aviation fuels. * 9 April: the

World Economic Forum The World Economic Forum (WEF) is an international non-governmental and lobbying organisation based in Cologny, canton of Geneva, Switzerland. It was founded on 24 January 1971 by German engineer and economist Klaus Schwab. The foundation, ...

described how companies can use microorganisms to convert into a protein powder for use in animal feed. * 14 May: a study published in ''

'' described a distributed temperature sensing (DTS) system achieving a vertical resolution of ~0.65 m (~25 in.) along a

fiber-optic cable A fiber-optic cable, also known as an optical-fiber cable, is an assembly similar to an electrical cable, but containing one or more optical fibers that are used to carry light. The optical fiber elements are typically individually coated with ...

, a two-order-of-magnitude improvement over discretely-spaced sensor arrangements. In the Greenland ice sheet, the

optical fiber An optical fiber, or optical fibre in Commonwealth English, is a flexible, transparent fiber made by drawing glass ( silica) or plastic to a diameter slightly thicker than that of a human hair. Optical fibers are used most often as a mea ...

system discovered strong spatial heterogeneity in deformation between and within different ice sections. * 8 June: a study published in ''

'' concluded that artificial ocean alkalinisation (AOA), if carried out with sufficient magnitude and duration, can use current technology to reverse the impact of global

ocean acidification Ocean acidification is the reduction in the pH value of the Earth’s ocean. Between 1751 and 2021, the average pH value of the ocean surface has decreased from approximately 8.25 to 8.14. The root cause of ocean acidification is carbon dioxid ...

on the

Great Barrier Reef The Great Barrier Reef is the world's largest coral reef system composed of over 2,900 individual reefs and 900 islands stretching for over over an area of approximately . The reef is located in the Coral Sea, off the coast of Queensland, ...

until atmospheric concentrations return to today's values—possibly centuries in the future. * August reports: in the first customer delivery of its type in history, Swedish company Hybrit said it was delivering "green steel" to truck-maker

Volvo AB The Volvo Group ( sv, Volvokoncernen; legally Aktiebolaget Volvo, shortened to AB Volvo, stylized as VOLVO) is a Swedish multinational manufacturing corporation headquartered in Gothenburg. While its core activity is the production, distributio ...

for prototype vehicles, the steel made using renewable electricity and hydrogen rather than

coking coal Metallurgical coal or coking coal is a grade of coal that can be used to produce good-quality coke. Coke is an essential fuel and reactant in the blast furnace process for primary steelmaking. The demand for metallurgical coal is highly coupled ...

. * 8 September: the largest

direct air capture Direct air capture (DAC) is a process of capturing carbon dioxide () directly from the ambient air (as opposed to capturing from point sources, such as a cement factory or biomass power plant) and generating a concentrated stream of for seque ...

plant, collecting about 4,000 tons of atmospheric } a year to store it underground, began operation in Iceland, selling the most expensive

carbon offset A carbon offset is a reduction or removal of emissions of carbon dioxide or other greenhouse gases made in order to compensate for emissions made elsewhere. Offsets are measured in tonnes of carbon dioxide-equivalent (CO2e). One ton of carb ...

in the world for as much as almost $1,400 per ton. * 5 October: the Nobel Prize in Physics was awarded "for the physical modeling of Earth's climate, quantifying variability and reliably predicting global warming" to atmospheric physicist Syukuro Manabe (modeled a 40 km (25 mi) high vertical column) and

Klaus Hasselmann Klaus Ferdinand Hasselmann (, born 25 October 1931) is a German oceanographer and climate modeller. He is Professor Emeritus at the University of Hamburg and former Director of the Max Planck Institute for Meteorology. He was awarded the 2021 ...

(developed a model incorporating stochastics (chaotic systems) and identifying human "fingerprints" in climatic effects).

Political, economic, legal, and cultural actions

* From 1 March 2019: the United Nations declared 2021 to be the beginning of the

UN Decade on Ecosystem Restoration The United Nations Decade on Ecosystem Restoration runs from 2021 to 2030. Similar to other nature related international decades, its purpose is to promote the United Nation's environmental goals. Specifically, to facilitate global cooperation for ...

, having an "aim of supporting and scaling up efforts to prevent, halt and reverse the degradation of ecosystems worldwide and raise awareness of the importance of successful ecosystem restoration". President Joe Biden at the Leaders Summit on Climate (01)

President Joe Biden at the Leaders Summit on Climate (01)

* 5 January 2021: a Senate run-off election in the U.S. state of

Georgia Georgia most commonly refers to: * Georgia (country), a country in the Caucasus region of Eurasia * Georgia (U.S. state), a state in the Southeast United States Georgia may also refer to: Places Historical states and entities * Related to the ...

placed the

Democratic party Democratic Party most often refers to: *Democratic Party (United States) Democratic Party and similar terms may also refer to: Active parties Africa *Botswana Democratic Party *Democratic Party of Equatorial Guinea *Gabonese Democratic Party *Demo ...

in narrow control of both houses of

Congress A congress is a formal meeting of the representatives of different countries, constituent states, organizations, trade unions, political parties, or other groups. The term originated in Late Middle English to denote an encounter (meeting of ...

, as both U.S. Senate Democratic candidates from the state of Georgia,

Raphael Warnock Raphael Gamaliel Warnock ( ; born July 23, 1969) is an American Baptist pastor and politician serving as the junior United States senator from Georgia since 2021. A member of the Democratic Party, he assumed office on January 20, 2021. Since 2 ...

and

Jon Ossoff Thomas Jonathan Ossoff ( ; born February 16, 1987) is an American politician serving as the senior United States senator from Georgia since 2021. A member of the Democratic Party, Ossoff was previously a documentary filmmaker and investigativ ...

win those elections, improving Democratic President Biden's prospects for implementing climate-related policies. Both Raphael Warnock and Jon Ossoff are supporters and advocates the

Green New Deal Green New Deal (GND) proposals call for public policy to address climate change along with achieving other social aims like job creation and reducing economic inequality. The name refers back to the New Deal, a set of social and economic refo ...

, proposed for the United States. * 15 January: France's Total—among Europe's top energy companies that had accelerated plans to cut emissions and build large renewable energy businesses—became the first major global energy company to quit the

American Petroleum Institute The American Petroleum Institute (API) is the largest U.S. trade association for the oil and natural gas industry. It claims to represent nearly 600 corporations involved in production, refinement, distribution, and many other aspects of the ...

lobby group, whose largest members resisted investor pressure to diversify to renewables. * 20 January: on the afternoon of his inauguration, U.S. President Joe Biden signed a letter re-committing the nation to the 2015 Paris climate accord, reversing

Donald Trump Donald John Trump (born June 14, 1946) is an American politician, media personality, and businessman who served as the 45th president of the United States from 2017 to 2021. Trump graduated from the Wharton School of the University of P ...

's withdrawal that took formal effect on 4 November 2020 (the U.S. had been the only country in the world not signatory to the accord.) The

White House The White House is the official residence and workplace of the president of the United States. It is located at 1600 Pennsylvania Avenue NW in Washington, D.C., and has been the residence of every U.S. president since John Adams in ...

website was promptly changed to recite that Biden "will take swift action to tackle the climate emergency", reversing Trump's removing mention of greenhouse gas emissions on his first day in office in 2017. * 28 January: General Motors said that by 2035 it will end sale of all gasoline and diesel powered passenger cars and light

SUVs A sport utility vehicle (SUV) is a car classification that combines elements of road-going passenger cars with features from off-road vehicles, such as raised ground clearance and four-wheel drive. There is no commonly agreed-upon definitio ...

(excluding medium and heavy duty trucks), and will sell about 30 types of electric vehicles, and planned to halt and review new oil and gas leases on federal lands and waters. * January: newly elected U.S. President Joe Biden promised to make the federal government's fleet of 645,000 vehicles 100% all-electric by 2030. * Late January:

NRG Energy NRG Energy, Inc. is an American energy company, headquartered in Houston, Texas. It was formerly the wholesale arm of Northern States Power Company (NSP), which became Xcel Energy, but became independent in 2000. NRG Energy is involved in ener ...

announced that it would be indefinitely shutting down the U.S.'s only remaining facility for

carbon capture and storage Carbon capture and storage (CCS) or carbon capture and sequestration is the process of capturing carbon dioxide (CO2) before it enters the atmosphere, transporting it, and storing it (carbon sequestration) for centuries or millennia. Usually th ...

(CCS), generally presented by the fossil fuel industry as a " clean coal" technology. * 1 February: ExxonMobil announced it would invest $3 billion through 2025 (about 3% to 4% of its planned annual capital expenditures) on lower-emission energy technologies, primarily

projects—distinguished from BP and

Royal Dutch Shell Shell plc is a British multinational oil and gas company headquartered in London, England. Shell is a public limited company with a primary listing on the London Stock Exchange (LSE) and secondary listings on Euronext Amsterdam and the New Yo ...

who are pursuing renewables. * Reported in February: Mexico's populist president Andrés Manuel López Obrador indicated intentions to pursue fossil fuel projects and curtail clean energy, pursuing energy sovereignty with state-run bodies and relegating private clean energy companies to a secondary role. * 16 February: billionaire philanthropist

Bill Gates William Henry Gates III (born October 28, 1955) is an American business magnate and philanthropist. He is a co-founder of Microsoft, along with his late childhood friend Paul Allen. During his career at Microsoft, Gates held the positions ...

published the book, ''

How to Avoid a Climate Disaster ''How to Avoid a Climate Disaster: The Solutions We Have and the Breakthroughs We Need'' is a 2021 book by Bill Gates. In it, Gates presents what he learned in over a decade of studying climate change and investing in innovations to address glob ...

''. * 17 February:

Ford Ford commonly refers to: * Ford Motor Company, an automobile manufacturer founded by Henry Ford * Ford (crossing), a shallow crossing on a river Ford may also refer to: Ford Motor Company * Henry Ford, founder of the Ford Motor Company * Ford F ...

said that by 2026 its European division, with 5% of that region's passenger car market, will offer only electric and plug-in hybrid models, and by 2030 all its passenger cars will run solely on batteries. * 2 March:

Volvo The Volvo Group ( sv, Volvokoncernen; legally Aktiebolaget Volvo, shortened to AB Volvo, stylized as VOLVO) is a Swedish multinational manufacturing corporation headquartered in Gothenburg. While its core activity is the production, distributio ...

said that it will convert its entire lineup to battery power by 2030 and will sell them exclusively online—no longer selling cars with internal combustion engines, including hybrids. * 25 March: the Supreme Court of Canada ruled constitutional, the ''

Greenhouse Gas Pollution Pricing Act The ''Greenhouse Gas Pollution Pricing Act'' (french: Loi sur la tarification de la pollution causée par les gaz à effet de serre) is a Canadian federal law establishing a set of minimum national standards for carbon pricing in Canada to meet ...

'' (2018), which required provinces and territories to implement carbon gas pricing systems or adopt one imposed by the federal government. * April:

JPMorgan Chase JPMorgan Chase & Co. is an American multinational investment bank and financial services holding company headquartered in New York City and incorporated in Delaware. As of 2022, JPMorgan Chase is the largest bank in the United States, the ...

set a goal to finance $2.5 trillion over the following 10 years to combat climate change and advance sustainable development, and Citigroup said it would back $1 trillion of similar efforts by 2030. These announcement followed a similar one by

Bank of America The Bank of America Corporation (often abbreviated BofA or BoA) is an American multinational investment bank and financial services holding company headquartered at the Bank of America Corporate Center in Charlotte, North Carolina. The bank ...

. * 22–23 April: beginning on Earth Day, U. S. President Joe Biden hosted a virtual Leaders Summit on Climate attended by 40 world leaders, aiming to return the U.S. to being a leader in the global effort to reduce greenhouse gas emissions, which CNN called a "stark departure" from the

Trump administration Donald Trump's tenure as the 45th president of the United States began with his inauguration on January 20, 2017, and ended on January 20, 2021. Trump, a Republican from New York City, took office following his Electoral College victory ...

. * 29 April: Germany's

Federal Constitutional Court The Federal Constitutional Court (german: link=no, Bundesverfassungsgericht ; abbreviated: ) is the supreme constitutional court for the Federal Republic of Germany, established by the constitution or Basic Law () of Germany. Since its in ...

unanimously ruled that the German government must set clear goals for reducing greenhouse gas emissions beyond 2030, stating that existing law placed too much of a burden on future generations to reduce greenhouse gas emissions. * 12 May: The U.S. administration granted final approval to the nation's first large-scale offshore

wind farm A wind farm or wind park, also called a wind power station or wind power plant, is a group of wind turbines in the same location used to produce electricity. Wind farms vary in size from a small number of turbines to several hundred wind turb ...

about 15 miles off the coast of

Martha's Vineyard, Massachusetts Martha's Vineyard, often simply called the Vineyard, is an island in the Northeastern United States, located south of Cape Cod in Dukes County, Massachusetts, known for being a popular, affluent summer colony. Martha's Vineyard includes the ...

, expected to generate 800 megawatts (enough to power about 400,000 homes), with an ultimate goal to deploy enough offshore wind turbines by 2030 to power 10 million homes. A June 7 article in ''The New York Times'' reported that Europe had 5,400 offshore wind turbines, compared to seven (7) in the United States. * 28 May: court and shareholder actions succeeded against Shell Oil (Dutch court ordering Shell to cut emissions by 45% within 10 years),

Exxon-Mobil ExxonMobil Corporation (commonly shortened to Exxon) is an American multinational oil and gas corporation headquartered in Irving, Texas. It is the largest direct descendant of John D. Rockefeller's Standard Oil, and was formed on November 3 ...

(two climate activist hedge fund candidates receiving board positions), and

Chevron Chevron (often relating to V-shaped patterns) may refer to: Science and technology * Chevron (aerospace), sawtooth patterns on some jet engines * Chevron (anatomy), a bone * '' Eulithis testata'', a moth * Chevron (geology), a fold in rock ...

(shareholders imposing emissions targets). * 11–13 June: leaders at the

47th G7 summit The 47th G7 summit was held from 11 to 13 June 2021 in Cornwall, England, during the United Kingdom's tenure of the presidency of the Group of Seven (G7), an inter-governmental political forum of seven advanced nations. The participants includ ...

reaffirmed their goal to limit global heating to 1.5 °C and promised to cut collective emissions in half by 2030, but did not clearly lay out a plan to raise $100 billion a year for poorer countries to adopt clean energy, and did not agree on a timeline to end use of coal for electric power. * 24 June: the European Parliament approved a landmark law to make the EU's greenhouse gas emissions targets legally binding, setting targets to reduce net EU emissions by 55% by 2030 from 1990 levels and eliminate net emissions by 2050. * 15 July: the government of Greenland decided to cease issuing new licenses for oil and gas exploration "based upon economic calculations, but considerations of the impact on climate and the environment also play a central role in the decision". * 18 August: a study published in ''

,'' considering the effect of ultraviolet radiation on the growth of plants serving as a

carbon sink A carbon sink is anything, natural or otherwise, that accumulates and stores some carbon-containing chemical compound for an indefinite period and thereby removes carbon dioxide () from the atmosphere. Globally, the two most important carbon si ...

, estimated that the

Montreal Protocol The Montreal Protocol is an international treaty designed to protect the ozone layer by phasing out the production of numerous substances that are responsible for ozone depletion. It was agreed on 16 September 1987, and entered into force o ...

's late 1980s prohibition of ozone-depleting chemicals may have prevented an additional 115—235 parts per million of atmospheric , which might have led to a 0.50–1.0 °C increase in global average temperature by 2100. * Mid-September: China began enforcing the

Kigali Amendment The Kigali Amendment to the Montreal Protocol is an international agreement to gradually reduce the consumption and production of hydrofluorocarbons (HFCs). It is a legally binding agreement designed to create rights and obligations in internatio ...

(2016) to the

, pledging to immediately stop emitting

HFC-23 Trifluoromethane or fluoroform is the chemical compound with the formula CHF3. It is one of the " haloforms", a class of compounds with the formula CHX3 (X = halogen) with C3v symmetry. Fluoroform is used in diverse applications in organic s ...

, a greenhouse gas 14,600 times more powerful than carbon dioxide. * 21 September: China announced it will stop funding overseas coal projects, estimated to affect 54 gigawatts, the cancellation averting about three months worth of global greenhouse gas emissions. * 1–12 November: 2021 United Nations Climate Change Conference (COP26), postponed for a year because of the

COVID-19 pandemic The COVID-19 pandemic, also known as the coronavirus pandemic, is an ongoing global pandemic of coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The novel virus was first identi ...

, takes place in Glasgow, Scotland, resulting in the

Glasgow Climate Pact The Glasgow Climate Pact is an agreement reached at the 2021 United Nations Climate Change Conference (COP26). The pact is the first climate agreement explicitly planning to reduce unabated coal usage. A pledge to "phase out" coal was change ...

. * 10 November: in a case involving mining in a protected region of the Ecuadorian rainforest, the

Constitutional Court of Ecuador The Constitutional Court of Ecuador (Spanish: ''Corte Constitucional del Ecuador''), previously the Constitutional Tribunal of Ecuador (''Tribunal Constitucional del Ecuador'') is the constitutional court of Ecuador. History The Court was cre ...

issued a landmark decision interpreting the country's constitutional provisions to grant

rights Rights are legal, social, or ethical principles of freedom or entitlement; that is, rights are the fundamental normative rules about what is allowed of people or owed to people according to some legal system, social convention, or ethical theory ...

and confer protections to ecosystems. * 8 April 2022: the

reported that for the first time,

and solar generated more than 10% of electricity globally in 2021, with fifty countries having crossed the 10% threshold. However, power from coal rose 9% to a new record high.

Mitigation goal statements

* 27 January: newly elected U.S. President Joe Biden signed executive orders designed to put the country on a path to 100 percent carbon-free electricity by 2035 and net-zero greenhouse gas emissions by 2050. * February: IBM pledged to have

net-zero emissions Carbon neutrality is a state of net-zero carbon dioxide emissions. This can be achieved by balancing emissions of carbon dioxide with its removal (often through carbon offsetting) or by eliminating emissions from society (the transition to the "p ...

by 2030 (cutting emissions by 65% by 2025 compared to 2010 levels), following similar pledges by

Microsoft Microsoft Corporation is an American multinational technology corporation producing computer software, consumer electronics, personal computers, and related services headquartered at the Microsoft Redmond campus located in Redmond, Washin ...

(to be "carbon negative" by 2030) and

Amazon Amazon most often refers to: * Amazons, a tribe of female warriors in Greek mythology * Amazon rainforest, a rainforest covering most of the Amazon basin * Amazon River, in South America * Amazon (company), an American multinational technolog ...

(net-zero by 2040). * 21 April: co-legislators of the European Climate Law reached a provisional agreement on a key element of the European Green Deal, which the European Commission said "enshrines the EU's commitment to reaching climate neutrality by 2050 and the intermediate target of reducing net greenhouse gas emissions by at least 55% by 2030, compared to 1990 levels". * 22 April: At the 2021 Leaders' Climate Summit on Earth Day, U.S. President Joe Biden announced a new target for the US, aiming to reduce greenhouse gas emissions by 50-52% by 2030 relative to 2005 levels.

Adaptation goal statements

* May: A Carbon Disclosure Project survey found that in 2020, about 43% of 800 surveyed cities (combined population: 400 million) did not have a climate adaptation plan.

Public opinion and scientific consensus

* In January, the

United Nations Development Programme The United Nations Development Programme (UNDP)french: Programme des Nations unies pour le développement, PNUD is a United Nations agency tasked with helping countries eliminate poverty and achieve sustainable economic growth and human dev ...

released results of the Peoples Climate Vote (1.2 million respondents in over 50 countries), which found that 64% said that climate change was an

emergency An emergency is an urgent, unexpected, and usually dangerous situation that poses an immediate risk to health, life, property, or environment and requires immediate action. Most emergencies require urgent intervention to prevent a worsening ...

. * In June, the

Yale Program on Climate Change Communication The Yale Program on Climate Change Communication (YPCCC) is a research center within the Yale School of the Environment that conducts scientific research on public climate change knowledge, attitudes, policy preferences, and behavior at the global, ...

and Facebook Data for Good jointly published ''International Public Opinion on Climate Change'', describing beliefs, attitudes, policy preferences, and behaviors of Facebook users in 31 countries and territories worldwide, including knowledge and beliefs, perceived risks, support for government action, economic concerns, and activism. * 19 October: based on a review of 3,000 peer-reviewed publications randomly chosen from a dataset of 88,125 published since 2012, a study published in ''

'' concluded with high statistical confidence that the scientific consensus on human-caused contemporary climate change exceeds 99% in the peer reviewed scientific literature.

Projections

* 24 January, the

listed top 10 risks by ''likelihood'' (extreme weather as #1, climate action failure as #2, human environmental damage as #3) and by ''severity'' (climate action failure as #2, human environmental damage as #6, extreme weather as #8). * 9 February: a '' Communications Earth & Environment'' article concluded that emissions reductions must increase by 80% beyond nationally determined contributions (NDCs) (from 1% to 1.8% per year) to meet the 2°C target of the 2015 Paris Convention. * 19 February: a study published in ''

'' studied 1952–2011 data on the timing of seasons and projected that, by 2100, summer in the northern mid-latitudes will last nearly half a year and winter will last less than 2 months. * 8 March: a study published in ''

'' concluded that "limiting global warming to 1.5 °C will prevent most of the tropics from reaching a TW of 35 °C (95 °F), the limit of human adaptation". * 16 March: the

International Renewable Energy Agency The International Renewable Energy Agency (IRENA) is an intergovernmental organization mandated to facilitate cooperation, advance knowledge, and promote the adoption and sustainable use of renewable energy. It is the first international organis ...

's ''Outlook'' indicated that energy transition investment would have to increase by 30% over planned investment to a total of US$131 trillion between 2021 and 2050—$4.4 trillion/year—to meet 2050 reduction targets. * 8 April: a study published in ''

'' projected that limiting 21st-century warming to 2 °C will halve the Antarctic ice shelf area susceptible to collapsing and disintegrating, compared to the 34% of all Antarctic ice shelf loss projected for 4 °C warming. * 9 April: a study published in ''

'' used higher resolution climate models that included modeling of ocean eddies, to project that global mean

at the end of this century would be about 25% lower than previous models. * 20 April: a study accepted for publication in ''

'' concluded that immediately pursuing all presently available methane emission reduction measures could avoid 0.25 °C additional global mean warming by mid-century, and set a path to avoid more than 0.5 °C warming by 2100. * 22 April: Swiss re-insurer

Swiss Re Swiss Reinsurance Company Ltd,
Swiss Re. Retrieved on 18 January 2011. "Swiss Reinsurance Company Ltd ("Swiss Re") ...

forecast that, compared to growth levels without climate change, the world will have 11—14% less economic output (as much as $23 trillion less, annually) by 2050. * 30 April: a study published in ''

'' projected that the positive feedback effect of crustal rebound as the

West Antarctic Ice Sheet The Western Antarctic Ice Sheet (WAIS) is the segment of the continental ice sheet that covers West Antarctica, the portion of Antarctica on the side of the Transantarctic Mountains that lies in the Western Hemisphere. The WAIS is classified as ...

melts, could cause an 18% amplification of the 21st century's

global mean sea level Mean sea level (MSL, often shortened to sea level) is an average surface level of one or more among Earth's coastal bodies of water from which heights such as elevation may be measured. The global MSL is a type of vertical datuma standardised ...

(GMSL) rise, and 1 meter additional GMSL rise over the next millennium. * 5 May: a study published in ''

'' projected that limiting global warming to 1.5 °C would reduce the land ice contribution to

by 2100 from 25 cm to 13 cm (from 10 to 6 in.), with glaciers responsible for half the sea level rise contribution. * 5 May: a study published in ''

'' used an observationally calibrated ice sheet–shelf model to project that with 2 °C global warming, Antarctic ice loss will continue at its current pace; but that current policies would allow 3 °C warming and give an abrupt jump around 2060 to an order of magnitude increase in the rate of sea-level rise (to 0.5 cm/yr) by 2100. * 5 May: a study accepted for publication in ''

'' reported that greenhouse gas emissions have heated the

troposphere The troposphere is the first and lowest layer of the atmosphere of the Earth, and contains 75% of the total mass of the planetary atmosphere, 99% of the total mass of water vapour and aerosols, and is where most weather phenomena occur. From ...

and cooled the stratosphere so that stratospheric thickness has shrunk over decades, and projected an additional thinning of 1.3 km by 2080 if Earth follows an RCP 6.0 scenario. * 5 May: The

United Nations Environment Programme The United Nations Environment Programme (UNEP) is responsible for coordinating responses to environmental issues within the United Nations system. It was established by Maurice Strong, its first director, after the United Nations Conference on th ...

's Global Methane Assessment forecast that human-caused methane emissions can be reduced by up to 45 percent this decade and would avoid nearly 0.3 °C of global warming by 2045, and can be consistent with keeping the 1.5˚C goal for the century. * May: Bloomberg NEF projected that by 2027, battery-powered electric vehicle prices would reach price parity with internal combustion engine vehicles in all light vehicle segments in Europe. * 20 May: a study published in ''

'' applied palaeoecological evidence (14,000–3600 years ago) to conclude that

alpine Alpine may refer to any mountainous region. It may also refer to: Places Europe * Alps, a European mountain range ** Alpine states, which overlap with the European range Australia * Alpine, New South Wales, a Northern Village * Alpine National Pa ...

areas actually developed ''less'' plant biodiversity with the upward advance of forest treelines, the researchers' simulation projecting a substantive decrease in plant biodiversity in response to global warming-related treeline rise. * 20 May: the Arctic Monitoring and Assessment Programme reported climate models projecting that the probability of an ice-free Arctic summer is 10 times greater under a 2 °C global warming scenario compared with a 1.5 °C scenario. * 26 May: an article published in the ''Proceedings of the National Academy of Sciences'' projected that under RCP 8.5 ("business as usual" scenario), the temperature experienced by an average human will change more in coming decades than over the past six millennia; the mean ''human-experienced'' temperature rise by 2070 will amount to an estimated 7.5 °C—about 2.3 times the mean global temperature rise; and 3.5 billion people will be exposed to mean annual temperature ≥29.0 °C−presently found in 0.8% of the global land surface (mainly the Sahara) but projected to cover 19% of global land in 2070. * 29 July: a study published in ''

'' estimated that adding 4,434 metric tons of —the lifetime emissions of 3.5 average Americans—will cause one excess death globally between 2020 and 2100. The study included only heat-related mortality impacts, and not indirect impacts such as flooding, storms, and crop failures. * 24 August: a study published in the '' PNAS'' estimated that collectively, climate tipping points increase the

social cost of carbon The social cost of carbon (SCC) is the marginal cost of the impacts caused by emitting one extra tonne of greenhouse gas (carbon dioxide equivalent) at any point in time, inclusive of 'non-market' impacts on the environment and human health. Th ...

(SCC) by about 25%, and that there is about a 10% chance of climate tipping points more than doubling the SCC.

Significant publications

* (Full report: >250MBytes; all 3,949 pages) : Link t
Summary for Policymakers
(41 pages) * * * * * * *
extract
an
archive thereof
* * * *
Executive Summary
* (WMO-No. 1267; 90 pp). * * * * * * *

Notes

References

External links

Organizations

The Intergovernmental Panel on Climate Change (IPCC)

World Meteorological Organization (WMO)

Climate indicators
at the U.S. Environmental Protection Agency

Surveys, summaries and report lists

* * * {{Human impact on the environment 2021 in science Climate change History of climate variability and change Global environmental issues