Climate change is a long-term shift in Earth’s average temperatures and weather patterns, including changes in rainfall, storms, and seasons. While climate has always varied naturally, today’s climate change refers mainly to the rapid warming observed since the late 1800s. This modern shift is primarily driven by human activities that increase heat-trapping gases in the atmosphere.
It is closely related to, but not identical with, “global warming.” Global warming describes the rise in average surface temperature, while climate change includes the broader consequences of that warming. These consequences can differ by region, producing both wetter floods and drier droughts.
Earth is warmed by sunlight, and the planet releases some of that energy back into space as infrared heat. Certain gases in the atmosphere absorb and re-emit part of this heat, keeping the lower atmosphere warmer than it would otherwise be. This natural “greenhouse effect” makes Earth habitable.
Problems arise when human activities strengthen that effect by adding more greenhouse gases. The biggest contributor is carbon dioxide (CO2), largely from burning coal, oil, and natural gas. Methane (CH4) from fossil fuel production, agriculture, and waste is also important because it is very effective at trapping heat, especially over shorter timescales.
Warming triggers feedbacks that can amplify change. For example, melting snow and ice exposes darker land and water that absorb more sunlight, increasing warming. Warmer air holds more water vapor, which is itself a greenhouse gas, further strengthening heat retention.
Oceans play a central role by absorbing most of the excess heat and a large share of added CO2. This moderates short-term warming but leads to ocean heatwaves, changes in currents, and rising sea levels. When seawater warms it expands, and melting glaciers and ice sheets add additional water, raising coastal flood risks.
Heat extremes have become more frequent and intense in many regions. Heatwaves can push temperatures beyond what people, crops, and infrastructure are designed to handle. This raises the risk of heat illness, stresses power grids, and increases water demand.
Heavy rainfall events have intensified in many places because warmer air can carry more moisture. When conditions trigger storms, that extra moisture can fall quickly, increasing the chance of flash floods. Some regions, however, experience longer dry spells between storms, raising drought risk.
Wildfire conditions are worsening in parts of the world as hotter temperatures dry soils and vegetation. Longer fire seasons and more extreme fire weather can turn ignitions into large, fast-moving fires. Smoke can spread far beyond the burn area and cause major health impacts.
Climate change matters because it affects the basic systems societies rely on: food, water, health, housing, and economic stability. Even small changes in averages can translate into large changes in extremes, and extremes are what often cause disasters. Impacts are uneven, with the greatest risks often falling on communities with fewer resources to adapt.
Public health is directly affected through heat stress, wildfire smoke, and changes in disease patterns. Infrastructure is also vulnerable: roads can buckle in extreme heat, stormwater systems can be overwhelmed by intense rainfall, and coastal assets face higher flood and erosion risks. These pressures can increase costs for maintenance, insurance, and emergency response.
Ecosystems and biodiversity are at risk as habitats shift faster than many species can adapt. Changes to oceans, including warming and ocean acidification, can disrupt food webs and fisheries. Because nature supports pollination, water filtration, and carbon storage, ecological damage can feed back into economic and social impacts.
Addressing climate change involves two complementary strategies. Climate mitigation reduces the amount of warming by cutting greenhouse gas emissions and enhancing carbon sinks, while climate adaptation reduces harm by preparing for impacts that are already occurring. The more warming is limited, the easier and less expensive adaptation becomes.
The scientific foundations of climate change go back nearly two centuries. In the 1820s, Joseph Fourier described how the atmosphere could trap heat, and in the 1850s–1860s, Eunice Foote and John Tyndall showed that gases like water vapor and CO2 absorb infrared radiation. In 1896, Svante Arrhenius estimated that doubling CO2 could warm the planet.
In 1958, Charles David Keeling began precise measurements of atmospheric CO2, producing the “Keeling Curve,” which shows a steady rise alongside seasonal cycles. Over time, additional evidence from temperature records, melting ice, rising seas, and shifting ecosystems strengthened the link between greenhouse gases and warming. Modern climate science combines observations with physics-based models to test explanations and project future outcomes.
International attention grew as impacts and evidence mounted. Agreements and national policies have aimed to curb emissions, though progress has varied by country and sector. Today, the field integrates atmospheric science, oceanography, ecology, economics, and risk management.
“Climate change is the same as weather.” Weather is day-to-day, while climate is the long-term pattern of conditions over decades. A cold day does not contradict climate change, just as a hot day does not prove it by itself. What matters are long-term trends and changes in the frequency of extremes.
“Scientists can’t agree.” The core finding that human activities are warming the planet is supported by extensive evidence and broad agreement across relevant scientific fields. Debate continues about details like regional impacts and the pace of specific changes, which is normal in active research. Those uncertainties do not erase the main conclusion.
“CO2 is too small a fraction of the atmosphere to matter.” Small concentrations can have large effects when they interact strongly with infrared radiation. Many influential substances are effective at low concentrations, and CO2’s heat-trapping properties are well measured in laboratories and observed in the real atmosphere.
“If the climate changed naturally before, today’s change must be natural too.” Natural drivers like volcanic eruptions and solar variations do affect climate, and they are accounted for in attribution studies. The rapid warming trend since the industrial era aligns with rising greenhouse gases from human activity, while natural factors alone cannot explain the observed pattern.
“We can just adapt, so mitigation isn’t necessary.” Adaptation helps, but it has limits and can become extremely costly at higher levels of warming. Some impacts, like the loss of certain ecosystems or the long-term commitment to sea level rise, can be hard or impossible to fully reverse. Mitigation reduces the scale of future risks.
Some aspects can be slowed or stabilized by rapidly reducing greenhouse gas emissions, but not everything snaps back quickly. CO2 can remain in the atmosphere for a long time, and oceans respond slowly, so sea level rise and some warming effects can persist. The sooner emissions fall, the more avoidable impacts remain within reach.
Global warming is the rise in Earth’s average surface temperature, mainly due to increased greenhouse gases. Climate change includes global warming plus the wider set of changes that follow, such as shifting rainfall patterns, stronger heat extremes, and sea level rise. In practice, people often use the terms interchangeably, but climate change is broader.
Scientists combine multiple lines of evidence: rising greenhouse gas levels from fossil fuels, measured heat-trapping effects, and warming patterns consistent with greenhouse forcing. Models that include human emissions match observed trends far better than those using natural factors alone. Additional “fingerprints,” like cooling in the upper atmosphere alongside warming near the surface, also point to greenhouse gases.
CO2 is the largest contributor to long-term warming because of the volume emitted and its persistence. Methane is more potent in the short term and contributes strongly despite lower concentrations. Other important gases include nitrous oxide and certain industrial gases, alongside indirect effects from pollutants that influence clouds and atmospheric chemistry.
High-impact actions often involve energy and transport choices, reducing waste, and supporting low-carbon policies. Examples include improving home efficiency, choosing lower-carbon travel when possible, and shifting some consumption toward less carbon-intensive options. Collective action—voting, workplace decisions, and community projects—can multiply individual efforts by changing systems and incentives.