Portal:Climate change

The Climate Change Portal

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Present-day climate change includes both global warming—the ongoing increase in global average temperature—and its wider effects on Earth's climate system. Climate change in a broader sense also includes previous long-term changes to Earth's climate. The current rise in global temperatures is driven by human activities, especially fossil fuel (coal, oil and natural gas) burning since the Industrial Revolution. Fossil fuel use, deforestation, and some agricultural and industrial practices release greenhouse gases. These gases absorb some of the heat that the Earth radiates after it warms from sunlight, warming the lower atmosphere. Carbon dioxide, the primary gas driving global warming, has increased in concentration by about 50% since the pre-industrial era to levels not seen for millions of years.

Climate change has an increasingly large impact on the environment. Deserts are expanding, while heat waves and wildfires are becoming more common. Amplified warming in the Arctic has contributed to thawing permafrost, retreat of glaciers and sea ice decline. Higher temperatures are also causing more intense storms, droughts, and other weather extremes. Rapid environmental change in mountains, coral reefs, and the Arctic is forcing many species to relocate or become extinct. Even if efforts to minimize future warming are successful, some effects will continue for centuries. These include ocean heating, ocean acidification and sea level rise.

Climate change threatens people with increased flooding, extreme heat, increased food and water scarcity, more disease, and economic loss. Human migration and conflict can also be a result. The World Health Organization calls climate change one of the biggest threats to global health in the 21st century. Societies and ecosystems will experience more severe risks without action to limit warming. Adapting to climate change through efforts like flood control measures or drought-resistant crops partially reduces climate change risks, although some limits to adaptation have already been reached. Poorer communities are responsible for a small share of global emissions, yet have the least ability to adapt and are most vulnerable to climate change.

Many climate change impacts have been observed in the first decades of the 21st century, with 2024 the warmest on record at +1.60 °C (2.88 °F) since regular tracking began in 1850. Additional warming will increase these impacts and can trigger tipping points, such as melting all of the Greenland ice sheet. Under the 2015 Paris Agreement, nations collectively agreed to keep warming "well under 2 °C". However, with pledges made under the Agreement, global warming would still reach about 2.8 °C (5.0 °F) by the end of the century.

There is widespread support for climate action worldwide, and most countries aim to stop emitting carbon dioxide. Fossil fuels can be phased out by stopping subsidising them, conserving energy and switching to energy sources that do not produce significant carbon pollution. These energy sources include wind, solar, hydro, and nuclear power. Cleanly generated electricity can replace fossil fuels for powering transportation, heating buildings, and running industrial processes. Carbon can also be removed from the atmosphere, for instance by increasing forest cover and farming with methods that store carbon in soil. (Full article...)

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The atmosphere of Earth consists of a layer of mixed gas (commonly referred to as air) that is retained by gravity, surrounding the Earth's surface. It contains variable quantities of suspended aerosols and particulates that create weather features such as clouds and hazes. The atmosphere serves as a protective buffer between the Earth's surface and outer space. It shields the surface from most meteoroids and ultraviolet solar radiation, reduces diurnal temperature variation – the temperature extremes between day and night, and keeps it warm through heat retention via the greenhouse effect. The atmosphere redistributes heat and moisture among different regions via air currents, and provides the chemical and climate conditions that allow life to exist and evolve on Earth.

By mole fraction (i.e., by quantity of molecules), dry air contains 78.08% nitrogen, 20.95% oxygen, 0.93% argon, 0.04% carbon dioxide, and small amounts of other trace gases (see Composition below for more detail). Air also contains a variable amount of water vapor, on average around 1% at sea level, and 0.4% over the entire atmosphere.

Earth's primordial atmosphere consisted of gases accreted from the solar nebula, but the composition changed significantly over time, affected by many factors such as volcanism, outgassing, impact events, weathering and the evolution of life (particularly the photoautotrophs). In the present day, human activity has contributed to atmospheric changes, such as climate change (mainly through deforestation and fossil-fuel–related global warming), ozone depletion and acid deposition. (Full article...)

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Larsen Ice Shelf

Credit: NASA

The collapse of Larsen B Ice Shelf, showing the diminishing extent of the shelf from 1998 to 2002

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WikiProjects


WikiProject Climate change	WikiProject Environment	WikiProject Globalization

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In the news

From the Wikinews Climate change category

Additional News

Monsoons in India become more erratic.^[2]
Climate modellers Syukuro Manabe and Klaus Hasselmann win Nobel Prize.^[3]

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Official portrait, 2022

Regina McCarthy (born May 3, 1954) is an American air quality expert who served as the first White House national climate advisor from 2021 to 2022. She previously served as the thirteenth Administrator of the Environmental Protection Agency from 2013 to 2017.

A Massachusetts native, McCarthy holds degrees from the University of Massachusetts Boston and Tufts University. She was a civil servant in the Massachusetts state government, holding various environmental roles and serving as an environmental advisor to the Governor of Massachusetts. She served as commissioner of the Connecticut Department of Environmental Protection from 2004 to 2009 before joining the EPA in 2009.

On March 4, 2013, President Barack Obama nominated McCarthy to replace Lisa Jackson as EPA administrator. Confirmation hearings started on April 11, 2013. On July 18, 2013, she was confirmed after a record 136-day confirmation process, becoming the face of Obama's global warming and climate change initiative. (Full article...)

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General images

The following are images from various climate-related articles on Wikipedia.

Image 1Exterior of a Stevenson screen used for temperature measurements on land stations. (from History of climate change science)
Image 2Earth's energy budget (in W/m²) determines the climate. It is the balance of incoming and outgoing radiation and can be measured by satellites. The Earth's energy imbalance is the "net absorbed" energy amount (from Earth's energy budget)
Image 3Energy flows between space, the atmosphere, and Earth's surface. Rising greenhouse gas levels are contributing to an energy imbalance. (from Causes of climate change)
Image 4CO₂ concentrations over the last 500 million years (from Carbon dioxide in the atmosphere of Earth)
Image 5Earth's energy balance and imbalance, showing where the excess energy goes: Outgoing radiation is decreasing owing to increasing greenhouse gases in the atmosphere, leading to Earth's energy imbalance of about 460 TW. The percentage going into each domain of the climate system is also indicated. (from Earth's energy budget)
Image 6Solar irradiance (yellow) plotted with temperature (red) since 1880. (from History of climate change science)
Image 7CO₂ sources and sinks since 1880. While there is little debate that excess carbon dioxide in the industrial era has mostly come from burning fossil fuels, the future strength of land and ocean carbon sinks is an area of study. (from Causes of climate change)
Image 8Over 400,000 years of ice core data: Graph of CO₂ (green), reconstructed temperature (blue) and dust (red) from the Vostok ice core (from Carbon dioxide in the atmosphere of Earth)
Image 9Greenhouse gases allow sunlight to pass through the atmosphere, heating the planet, but then absorb and redirect the infrared radiation (heat) the planet emits. (from Carbon dioxide in the atmosphere of Earth)
Image 10Air pollution has substantially increased the presence of aerosols in the atmosphere when compared to the preindustrial background levels. Different types of particles have different effects, but overall, cooling from aerosols formed by sulfur dioxide emissions has the overwhelming impact. However, the complexity of aerosol interactions in atmospheric layers makes the exact strength of cooling very difficult to estimate. (from Causes of climate change)
Image 11Terms like "climate emergency" and climate crisis" have often been used by activists, and are increasingly found in academic papers. (from History of climate change science)
Image 12Modeled simulation of the effect of various factors (including GHGs, Solar irradiance) singly and in combination, showing in particular that solar activity produces a small and nearly uniform warming, unlike what is observed. (from History of climate change science)
Image 13Brown bars indicate drivers that increase global warming, and blue bars indicate those that decrease global warming. Future global warming potential for long lived drivers like carbon dioxide emissions is not represented. (from Causes of climate change)
Image 14James Croll (from History of climate change science)
Image 15Erratics, boulders deposited by glaciers far from any existing glaciers, led geologists to the conclusion that climate had changed in the past. (from History of climate change science)
Image 16A diagram which shows where the extra heat retained on Earth due to the energy imbalance is going.
Image 17The concentration of atmospheric carbon dioxide has been increasing in progressively greater amounts. (from Carbon dioxide in the atmosphere of Earth)
Image 18The rate of global tree cover loss has approximately doubled since 2001, to an annual loss approaching an area the size of Italy. (from Causes of climate change)
Image 19The growth in Earth's energy imbalance from satellite and in situ measurements (2005–2019). A rate of +1.0 W/m² summed over the planet's surface equates to a continuous heat uptake of about 500 terawatts (~0.3% of the incident solar radiation). (from Earth's energy budget)
Image 20Joseph Fourier (from History of climate change science)
Image 21The Global Carbon Project shows how additions to CO₂ since 1880 have been caused by different sources ramping up one after another. (from Causes of climate change)
Image 22John Tyndall's ratio spectrophotometer (drawing from 1861) measured how much infrared radiation was absorbed and emitted by various gases filling its central tube. Such measurements furthered understanding of the greenhouse effect that underlies global warming and climate change. (from History of climate change science)
Image 23Schematic drawing of Earth's excess heat inventory and energy imbalance for two recent time periods. (from Earth's energy budget)
Image 24Eunice Newton Foote recognized carbon dioxide's heat-capturing effect in 1856, appreciating its implications for the planet. (from History of climate change science)
Image 25A Sankey diagram illustrating a balanced example of Earth's energy budget. Line thickness is linearly proportional to relative amount of energy. (from Earth's energy budget)
Image 26Extreme event attribution methods generally involve applying climate change models to scenarios in both the "real" world that is experiencing global warming, and a simulated world that does not suffer the drivers of global warming. Differences between the results of the two processes—especially the frequency, intensity and impacts of extreme weather events—are then analyzed to arrive at the attribution result. (from History of climate change science)
Image 27Warming influence of atmospheric greenhouse gases has nearly doubled since 1979, with carbon dioxide and methane being the dominant drivers. (from Causes of climate change)
Image 28Charles Keeling, receiving the National Medal of Science from George W. Bush, in 2001 (from History of climate change science)
Image 29Since the 1980s, global average surface temperatures during a given decade have almost always been higher than the average temperature in the preceding decade. (from History of climate change science)
Image 30Global average temperatures show that the Medieval Warm Period was not a planet-wide phenomenon, and that the Little Ice Age was not a distinct planet-wide time period but rather the end of a long temperature decline that preceded recent global warming. (from Temperature record of the last 2,000 years)
Image 31Atmospheric CO₂ concentration measured at Mauna Loa Observatory in Hawaii from 1958 to 2023 (also called the Keeling Curve). The rise in CO₂ over that time period is clearly visible. The concentration is expressed as μmole per mole, or ppm. (from Carbon dioxide in the atmosphere of Earth)
Image 32Observed temperature from NASA vs the 1850–1900 average used by the IPCC as a pre-industrial baseline. The primary driver for increased global temperatures in the industrial era is human activity, with natural forces adding variability. (from Causes of climate change)
Image 33Annual CO₂ flows from anthropogenic sources (left) into Earth's atmosphere, land, and ocean sinks (right) since year 1960. Units in equivalent gigatonnes carbon per year. (from Carbon dioxide in the atmosphere of Earth)
Image 34Between 1850 and 2019 the Global Carbon Project estimates that about 2/3rds of excess carbon dioxide emissions have been caused by burning fossil fuels, and a little less than half of that has stayed in the atmosphere. (from Carbon dioxide in the atmosphere of Earth)
Image 35CO₂ reduces the flux of thermal radiation emitted to space (causing the large dip near 667 cm⁻¹), thereby contributing to the greenhouse effect. (from Carbon dioxide in the atmosphere of Earth)
Image 36CO₂ concentrations over the last 800,000 years as measured from ice cores (blue/green) and directly (black) (from Causes of climate change)
Image 37Physical drivers of global warming that has happened so far. Future global warming potential for long lived drivers like carbon dioxide emissions is not represented. Whiskers on each bar show the possible error range. (from Carbon dioxide in the atmosphere of Earth)
Image 38Human fingerprints for global warming (summary of observational evidence that human carbon dioxide emissions are causing the climate to warm). (from Causes of climate change)
Image 39Increase in the Earth's non-cloud greenhouse effect (2000–2022) based on satellite data. (from Earth's energy budget)
Image 40Earth's energy imbalance has increased in the 21st century, reaching values twice that of prior estimates from the IPCC. The ability to observe this imbalance is deteriorating because satellites are being decommissioned. (from Earth's energy budget)
Image 41Main sources of global methane emissions (2008–2017) according to the Global Carbon Project (from Causes of climate change)
Image 42The impact of the greenhouse effect on climate was presented to the public early in the 20th century, as succinctly described in this 1912 Popular Mechanics article. (from History of climate change science)
Image 43Carbon dioxide observations from 2008 to 2017 showing the seasonal variations and the difference between northern and southern hemispheres (from Carbon dioxide in the atmosphere of Earth)
Image 44The US, China and Russia have cumulatively contributed the greatest amounts of CO₂ since 1850. (from Carbon dioxide in the atmosphere of Earth)
Image 45Concentration of atmospheric CO₂ over the last 40,000 years, from the Last Glacial Maximum to the present day. The current rate of increase is much higher than at any point during the last deglaciation. (from Carbon dioxide in the atmosphere of Earth)
Image 46Cumulative land-use change contributions to CO₂ emissions, by region. (from Causes of climate change)
Image 47Top panel: Observed global average temperature change (1870— ).Bottom panel: Data from the Fourth National Climate Assessment is merged for display on the same scale to emphasize relative strengths of forces affecting temperature change. Human-caused forces have increasingly dominated.
(from Causes of climate change)
Image 48Air-sea exchange of CO₂ (from Carbon dioxide in the atmosphere of Earth)
Image 49James Hansen during his 1988 testimony to Congress, which alerted the public to the dangers of global warming (from History of climate change science)
Image 50Earth heating estimates from a combination of space altimetry and space gravimetry. (from Earth's energy budget)
Image 51The Keeling Curve shows the long-term increase of atmospheric carbon dioxide (CO₂) concentrations since 1958. (from Causes of climate change)
Image 52Milutin Milanković (from History of climate change science)
Image 53Correspondence between temperature and atmospheric CO₂ during the last 800,000 years (from Carbon dioxide in the atmosphere of Earth)
Image 54Sea ice reflects 50% to 70% of incoming sunlight, while the ocean, being darker, reflects only 6%. As an area of sea ice melts and exposes more ocean, more heat is absorbed by the ocean, raising temperatures that melt still more ice. This is a positive feedback process. (from Causes of climate change)
Image 55Mean temperature anomalies during the period 1965 to 1975 with respect to the average temperatures from 1937 to 1946. This dataset was not available at the time. (from History of climate change science)
Image 56Scientific consensus on causation: Academic studies of scientific agreement on human-caused global warming among climate experts (2010–2015) reflect that the level of consensus correlates with expertise in climate science.
A 2019 study found scientific consensus to be at 100%, and a 2021 study concluded that consensus exceeded 99%. Another 2021 study found that 98.7% of climate experts indicated that the Earth is getting warmer mostly because of human activity. (from History of climate change science)
Image 57The rising accumulation of energy in the oceanic, land, ice, and atmospheric components of Earth's climate system since 1960. (from Earth's energy budget)
Image 58Meat from cattle and sheep have the highest emissions intensity of any agricultural commodity. (from Causes of climate change)
Image 59This diagram of the carbon cycle shows the movement of carbon between land, atmosphere, and oceans in billions of metric tons of carbon per year. Yellow numbers are natural fluxes, red are human contributions, white are stored carbon. (from Carbon dioxide in the atmosphere of Earth)
Image 60The Fourth National Climate Assessment ("NCA4", USGCRP, 2017) includes charts illustrating that neither solar nor volcanic activity can explain the observed warming. (from Causes of climate change)
Image 61Longwave-infrared absorption coefficients of water vapor and carbon dioxide. For wavelengths near 15-microns, CO₂ is a much stronger absorber than water vapor. (from Carbon dioxide in the atmosphere of Earth)

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... that Mars' south polar ice cap may be melting due to global warming?

(Pictured left: Photo of Mars' south polar ice taken by Mars Global Surveyor.)

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Climate change in the Arctic

Credit: NASA

the Arctic temperature trend between August 1981 and July 2009. Due to global warming, which is exacerbated at the Arctic, there's a significant warming over this 28 year period.