Climate change — A Video Map Guide

Before the 1980s, it was unclear whether the warming effect of increased greenhouse gases was stronger than the cooling effect of airborne particulates in air pollution. Scientists used the term inadvertent climate modification to refer to human impacts on the climate at this time. In the 1980s, the terms global warming and climate change became more common, often being used interchangeably. Scientifically, global warming refers only to increased global average surface temperature, while climate change describes both global warming and its effects on Earth's climate system, such as precipitation changes. Climate change can also be used more broadly to include changes to the climate that have happened throughout Earth's history as result of natural processes. The term anthropogenic climate change is sometimes used to describe climate change resulting from human activities. Global warming—used as early as 1975—became the more popular term after NASA climate scientist James Hansen used it in his 1988 testimony in the U.S. Senate. Since the 2000s, usage of climate change has increased. Various scientists, politicians and media may use the terms climate crisis or climate emergency to talk about climate change, and may use the term global heating instead of global warming.

Global surface temperature Temperatures prior to present-day global warming Main articles: Climate variability and change; Temperature record of the last 2,000 years; and Paleoclimatology Global surface temperature reconstruction over the past 2000 years using proxy data from tree rings, corals, and ice cores in blue. Directly observed data is in red. Over the last few million years the climate cycled through ice ages. One of the hotter periods was the Last Interglacial, around 125,000 years ago, where temperatures were between 0.5 °C and 1.5 °C warmer than before the start of global warming. This period saw sea levels 5 to 10 metres higher than today. The most recent glacial maximum 20,000 years ago was some 5–7 °C colder. This period has sea levels that were over 125 metres (410 ft) lower than today. Temperatures stabilized in the current interglacial period beginning 11,700 years ago. This period also saw the start of agriculture. Historical patterns of warming and cooling, like the Medieval Warm Period and the Little Ice Age, did not occur at the same time across different regions. Temperatures may have reached as high as those of the late 20th century in a limited set of regions. Climate information for that period comes from climate proxies, such as trees and ice cores. Warming since the Industrial Revolution In recent decades, new high temperature records have substantially outpaced new low temperature records on a growing portion of Earth's surface. There has been an increase in ocean heat content during recent decades as the oceans absorb over 90% of the heat from global warming. Around 1850 thermometer records began to provide global coverage. Between the 18th century and 1970 there was little

Causes of climate change Physical 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. The climate system experiences various cycles on its own which can last for years, decades or even centuries. For example, El Niño events cause short-term spikes in surface temperature while La Niña events cause short term cooling. Their relative frequency can affect global temperature trends on a decadal timescale. Other changes are caused by an imbalance of energy from external forcings. Examples of these include changes in the concentrations of greenhouse gases, solar luminosity, volcanic eruptions, and variations in the Earth's orbit around the Sun. To determine the human contribution to climate change, unique "fingerprints" for all potential causes are developed and compared with both observed patterns and known internal climate variability. For example, solar forcing—whose fingerprint involves warming the entire atmosphere—is ruled out because only the lower atmosphere has warmed. Atmospheric aerosols produce a smaller, cooling effect. Other drivers, such as changes in albedo, are less impactful. Greenhouse gases Main articles: Greenhouse gas, Greenhouse gas emissions, Greenhouse effect, and Carbon dioxide in Earth's atmosphereCO2 concentrations over the last 800,000 years as measured from ice cores (blue/green) and directly (black) Greenhouse gases are transparent to sunlight, and thus allow it to pass through the atmosphere to heat the Earth's surface. The Earth radiates it as heat, and greenhouse gases absorb a portion of it. This absorption slows the rate at which heat escapes into space, trapping heat near the Earth's

Climate model and Climate change scenario Energy flows between space, the atmosphere, and Earth's surface. Most sunlight passes through the atmosphere to heat the Earth's surface, then greenhouse gases absorb most of the heat the Earth radiates in response. Adding to greenhouse gases increases this insulating effect, causing an energy imbalance that heats the planet up. A climate model is a representation of the physical, chemical and biological processes that affect the climate system. Models include natural processes like changes in the Earth's orbit, historical changes in the Sun's activity, and volcanic forcing. Models are used to estimate the degree of warming future emissions will cause when accounting for the strength of climate feedbacks. Models also predict the circulation of the oceans, the annual cycle of the seasons, and the flows of carbon between the land surface and the atmosphere. The physical realism of models is tested by examining their ability to simulate current or past climates. Past models have underestimated the rate of Arctic shrinkage and underestimated the rate of precipitation increase. Sea level rise since 1990 was underestimated in older models, but more recent models agree well with observations. The 2017 United States-published National Climate Assessment notes that "climate models may still be underestimating or missing relevant feedback processes". Additionally, climate models may be unable to adequately predict short-term regional climatic shifts. A subset of climate models add societal factors to a physical climate model. These models simulate how population, economic growth, and energy use affect—and interact with—the physical climate. With this information, these models can produce scenarios of future greenhouse gas emissions. This is th

Effects of climate change In virtually all countries and territories around the world, scientists in the field of extreme event attribution have concluded that human-caused global warming has increased the number of days of extreme heat events over long-term norms. Environmental effects Effects of climate change on oceans and Effects of climate change on the water cycle The environmental effects of climate change are broad and far-reaching, affecting oceans, ice, and weather. Changes may occur gradually or rapidly. Evidence for these effects comes from studying climate change in the past, from modelling, and from modern observations. Since the 1950s, droughts and heat waves have appeared simultaneously with increasing frequency. Extremely wet or dry events within the monsoon period have increased in India and East Asia. Monsoonal precipitation over the Northern Hemisphere has increased since 1980. The rainfall rate and intensity of hurricanes and typhoons is likely increasing, and the geographic range likely expanding poleward in response to climate warming. The frequency of tropical cyclones has not increased as a result of climate change. Historical sea level reconstruction and projections up to 2100 published in 2017 by the U.S. Global Change Research Program Global sea level is rising as a consequence of thermal expansion and the melting of glaciers and ice sheets. Sea level rise has increased over time, reaching 4.8 cm per decade between 2014 and 2023. Over the 21st century, the IPCC projects 32–62 cm of sea level rise under a low emission scenario, 44–76 cm under an intermediate one and 65–101 cm under a very high emission scenario. Marine ice sheet instability processes in Antarctica may add substantially to these values,[201&#9

Climate change mitigation Global greenhouse gas emission scenarios, based on policies and pledges as of November 2021 Climate change can be mitigated by reducing the rate at which greenhouse gases are emitted into the atmosphere, and by increasing the rate at which carbon dioxide is removed from the atmosphere. To limit global warming to less than 2 °C global greenhouse gas emissions need to be net-zero by 2070. This requires far-reaching, systemic changes on an unprecedented scale in energy, land, cities, transport, buildings, and industry. The United Nations Environment Programme estimates that countries need to triple their pledges under the Paris Agreement within the next decade to limit global warming to 2 °C. With pledges made under the Paris Agreement as of 2024, there would be a 66% chance that global warming is kept under 2.8 °C by the end of the century (range: 1.9–3.7 °C, depending on exact implementation and technological progress). When only considering current policies, this raises to 3.1 °C. Globally, limiting warming to 2 °C may result in higher economic benefits than economic costs. Although there is no single pathway to limit global warming to 2 °C, most scenarios and strategies see a major increase in the use of renewable energy in combination with increased energy efficiency measures to generate the needed greenhouse gas reductions. To reduce pressures on ecosystems and enhance their carbon sequestration capabilities, changes would also be necessary in agriculture and forestry, such as preventing deforestation and restoring natural ecosystems by reforestation. Other approaches to mitigating climate change have a higher level of risk. Scenarios that limit global warming to 1.5 °C

Climate change adaptation Adaptation is "the process of adjustment to current or expected changes in climate and its effects".: 5 Without additional mitigation, adaptation cannot avert the risk of "severe, widespread and irreversible" impacts. More severe climate change requires more transformative adaptation, which can be prohibitively expensive. The capacity and potential for humans to adapt is unevenly distributed across different regions and populations, and developing countries generally have less. The first two decades of the 21st century saw an increase in adaptive capacity in most low- and middle-income countries with improved access to basic sanitation and electricity, but progress is slow. Many countries have implemented adaptation policies. However, there is a considerable gap between necessary and available finance. Adaptation to sea level rise consists of avoiding at-risk areas, learning to live with increased flooding, and building flood controls. If that fails, managed retreat may be needed. There are economic barriers for tackling dangerous heat impact. Avoiding strenuous work or having air conditioning is not possible for everybody. In agriculture, adaptation options include a switch to more sustainable diets, diversification, erosion control, and genetic improvements for increased tolerance to a changing climate. Insurance allows for risk-sharing, but is often difficult to get for people on lower incomes. Education, migration and early warning systems can reduce climate vulnerability. Planting mangroves or encouraging other coastal vegetation can buffer storms. Ecosystems adapt to climate change, a process that can be supported by human intervention. By increasing connectivity between ecosystems, species can migrate to more favourab

Politics of climate change and Climate change mitigation § Policies The Climate Change Performance Index ranks countries by greenhouse gas emissions (40% of score), renewable energy (20%), energy use (20%), and climate policy (20%). .legend.legend-color.legend-text{} High Medium Low Very low No data Countries that are most vulnerable to climate change have typically been responsible for a small share of global emissions. This raises questions about justice and fairness. Limiting global warming makes it much easier to achieve the UN's Sustainable Development Goals, such as eradicating poverty and reducing inequalities. The connection is recognized in Sustainable Development Goal 13 which is to "take urgent action to combat climate change and its impacts". The goals on food, clean water and ecosystem protection have synergies with climate mitigation. The geopolitics of climate change is complex. It has often been framed as a free-rider problem, in which all countries benefit from mitigation done by other countries, but individual countries would lose from switching to a low-carbon economy themselves. Sometimes mitigation also has localized benefits though. For instance, the benefits of a coal phase-out to public health and local environments exceed the costs in almost all regions. Furthermore, net importers of fossil fuels win economically from switching to clean energy, causing net exporters to face stranded assets: fossil fuels they cannot sell. Policy options Climate policy A wide ra

Denial and misinformation Climate change denial and Fossil fuels lobby Data has been cherry picked from short periods to falsely assert that global temperatures are not rising. Blue trendlines show short periods that mask longer-term warming trends (red trendlines). Blue rectangle with blue dots shows the so-called global warming hiatus. Public debate about climate change has been strongly affected by climate change denial and misinformation, which first emerged in the United States and has since spread to other countries, particularly Canada and Australia. It originated from fossil fuel companies, industry groups, conservative think tanks, and contrarian scientists. Like the tobacco industry, the main strategy of these groups has been to manufacture doubt about climate-change related scientific data and results. People who hold unwarranted doubt about climate change are sometimes called climate change "skeptics", although "contrarians" or "deniers" are more appropriate terms. There are different variants of climate denial: some deny that warming takes place at all, some acknowledge warming but attribute it to natural influences, and some minimize the negative impacts of climate change. Manufacturing uncertainty about the science later developed into a manufactured controversy: creating the belief that there is significant uncertainty about climate change within the scientific community to delay policy changes. Strategies to promote these ideas include criticism of scientific institutions, and questioning the motives of individual scientists. An echo chamber of climate-denying blogs and media has further fomented misunderstanding of climate change. Public awareness and opinion Climate communication, Media coverage of climate change, and Public opin

For broader coverage of this topic, see History of climate change science. Early discoveries Eunice Newton Foote showed carbon dioxide's heat-capturing effect in 1856, foreseeing its implications for the planet. (Carbon dioxide was called "carbonic acid gas".) Scientists in the 19th century such as Alexander von Humboldt began to foresee the effects of climate change. In the 1820s, Joseph Fourier proposed the greenhouse effect to explain why Earth's temperature was higher than the Sun's energy alone could explain. Earth's atmosphere is transparent to sunlight, so sunlight reaches the surface where it is converted to heat. However, the atmosphere is not transparent to heat radiating from the surface, and captures some of that heat, which in turn warms the planet. In 1856 Eunice Newton Foote demonstrated that the warming effect of the Sun is greater for air with water vapour than for dry air, and that the effect is even greater with carbon dioxide (CO2). In "Circumstances Affecting the Heat of the Sun's Rays" she concluded that "[a]n atmosphere of that gas would give to our earth a high temperature". This 1912 article succinctly describes the greenhouse effect, how burning coal creates carbon dioxide to cause global warming and climate change. Starting in 1859, John Tyndall established that nitrogen and oxygen—together totalling 99% of dry air—are transparent to radiated heat. However, water vapour and gases such as methane and carbon dioxide absorb radiated heat and re-radiate that heat into the atmosphere. Tyndall proposed that changes in the concentrations of these gases may have caused climatic changes in the past, including ice ages. Svante Arrhenius noted that water vapour in air continuously varied, but the CO2 concentration in air was influenced by long-term geological processes. Warming