Present-day climate change includes both global warming—the ongoing increase in global average temperature—and its wider effects on Earth's climate system. In a broader sense, climate change also includes previous long-term changes to Earth's climate. The modern-day rise in global temperatures is driven by human activities, especially fossil fuel (coal, oil and natural gas) burning since the Industrial Revolution.: "For the 2016–2025 decade average, observed warming relative to 1850–1900 was 1.26 [1.13 to 1.36] °C, of which 1.24 [1.0 to 1.5] °C was human-induced." 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. Earth's atmosphere now has roughly 50% more carbon dioxide, the main gas driving global warming, than it did at the end of the pre-industrial era, reaching levels not seen for millions of years.: "Concentrations of , methane (), and nitrous oxide () have increased to levels unprecedented in at least 800,000 years, and there is high confidence that current concentrations have not been experienced for at least 2 million years."
Climate change has an increasingly large impact on the environment. Heat waves and wildfires are becoming more common.*: "Observed increases in areas burned by wildfires have been attributed to human-induced climate change in some regions (medium to high confidence)" Amplified warming in the Arctic has contributed to thawing permafrost, retreat of glaciers and sea ice decline.: "Over the last decades, global warming has led to widespread shrinking of the cryosphere, with mass loss from ice sheets and glaciers (very high confidence), reductions in snow cover (high confidence) and Arctic sea ice extent and thickness (very high confidence), and increased permafrost temperature (very high confidence)." 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.: "Sustained net zero anthropogenic emissions of and declining net anthropogenic non- radiative forcing over a multi-decade period would halt anthropogenic global warming over that period, although it would not halt sea level rise or many other aspects of climate system adjustment."
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.
: "Effectiveness15 of adaptation in reducing climate risks16 is documented for specific contexts, sectors and regions (high confidence) ... Soft limits to adaptation are currently being experienced by small-scale farmers and households along some low-lying coastal areas (medium confidence) resulting from financial, governance, institutional and policy constraints (high confidence). Some tropical, coastal, polar and mountain ecosystems have reached hard adaptation limits (high confidence). Adaptation does not prevent all losses and damages, even with effective adaptation and before reaching soft and hard limits (high confidence)." 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 + 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 by the end of the century.: "The full implementation and continuation of the level of mitigation effort implied by unconditional or conditional NDC scenarios lower these projections to 2.8 °C (range: 1.9–3.7) and 2.6 °C (range: 1.9–3.6), respectively. All with at least a 66 per cent chance."
There is widespread support for climate action worldwide, and most countries aim to stop emitting carbon dioxide.: "As at 1 June 2024, 101 parties representing 107 countries and covering approximately 82 per cent of global GHG emissions had adopted net-zero pledges either in law (28 parties), in a policy document such as an NDC or a long-term strategy (56 parties), or in an announcement by a high-level government official (17 parties)." Fossil fuels can be phased out by ending their subsidies, 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.: "Stringent emissions reductions at the level required for 2°C or 1.5°C are achieved through the increased electrification of buildings, transport, and industry, consequently all pathways entail increased electricity generation (high confidence)." Carbon can also be removed from the atmosphere, for instance by increasing forest cover and farming with methods that store carbon in soil.
Terminology
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.: "'Climate change' and 'global warming' are often used interchangeably but have distinct meanings. ... Global warming refers to the upward temperature trend across the entire Earth since the early 20th century ... Climate change refers to a broad range of global phenomena ...[which] include the increased temperature trends described by global warming.": "The terms global warming and climate change can be used interchangeably. Climate change is more accurate scientifically to describe the various effects of greenhouse gases on the world because it includes extreme weather, storms and changes in rainfall patterns, ocean acidification and sea level". 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.: "Climate change refers to a change in the state of the climate that can be identified (e.g., by using statistical tests) by changes in the mean and/or the variability of its properties and that persists for an extended period, typically decades or longer. Climate change may be due to natural internal processes or external forcings such as modulations of the solar cycles, volcanic eruptions and persistent anthropogenic changes in the composition of the atmosphere or in land use." 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., "News reporters gave only a little attention ...". 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 temperature rise
Temperatures prior to present-day global warming
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 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.: "This report adopts the 51-year reference period, 1850–1900 inclusive, assessed as an approximation of pre-industrial levels in AR5 ... Temperatures rose by 0.0 °C–0.2 °C from 1720–1800 to 1850–1900"
Warming since the Industrial Revolution
Around 1850 thermometer records began to provide global coverage.: "Global-scale observations from the instrumental era began in the mid-19th century for temperature and other variables ... the period 1880 to 2012 ... multiple independently produced datasets exist." Between the 18th century and 1970 there was little net warming, as the warming impact of greenhouse gas emissions was offset by cooling from sulfur dioxide emissions. Sulfur dioxide causes acid rain, but it also produces sulfate aerosols in the atmosphere, which reflect sunlight and cause global dimming. After 1970, the increasing accumulation of greenhouse gases and controls on sulfur pollution led to a marked increase in temperature.
Ongoing changes in climate have had no precedent for several thousand years. Multiple datasets all show worldwide increases in surface temperature, at a rate of around 0.2 °C per decade.. The 2016–2025 decade warmed to an average 1.26 °C [1.13–1.36 °C] compared to the pre-industrial baseline (1850–1900). Not every single year was warmer than the last: internal climate variability processes can make any year 0.2 °C warmer or colder than the average. From 1998 to 2013, negative phases of two such processes, Pacific decadal oscillation (PDO) and Atlantic multidecadal oscillation (AMO) caused a short slower period of warming called the "global warming hiatus". After the "hiatus", the opposite occurred, with 2024 well above the recent average at more than +1.5 °C. This is why the temperature change is defined in terms of a 20-year average, which reduces the noise of hot and cold years and decadal climate patterns, and detects the long-term signal.
A wide range of other observations reinforce the evidence of warming.. Figure 2.5. The upper atmosphere is cooling, because greenhouse gases are trapping heat near the Earth's surface, and so less heat is radiating into space. Warming reduces average snow cover and forces the retreat of glaciers. At the same time, warming also causes greater evaporation from the oceans, leading to more atmospheric humidity, and more and heavier precipitation. Plants are flowering earlier in spring, and thousands of animal species have been permanently moving to cooler areas.
Differences by region