Earth is warming. Heat waves have become longer and more extreme. Cold snaps have become shorter and milder. Northern Hemisphere snow cover has decreased. Rivers and lakes are freezing later and thawing earlier. Arctic sea ice has declined. Glaciers and ice caps are melting in many parts of the world.
Why is this happening? What impacts will it have? What can we do about it?
Global warming is closely associated with a broad spectrum of other changes, such as increases in the frequency of intense rainfall, decreases in Northern Hemisphere snow cover and Arctic sea ice, warmer and more frequent hot days and nights, rising sea levels, and widespread ocean acidification. Learn more about these changes.
To compare today’s climate with that of the distant past, scientists use proxy data, which provide indirect evidence of how temperature and other climate properties varied before instrumental measurements became available. Learn more about proxy data.
Human-generated emissions of carbon dioxide and other greenhouse gases impact the balance of several global climate processes. Understanding the greenhouse effect, carbon cycle, climate forcing, and climate feedbacks helps to explain how and why climate is changing. Learn more about these processes.
Human activity is causing climate change by increasing the concentration of greenhouse gases in the atmosphere. Natural processes cannot account for the recent change in temperature. Learn more about the causes of climate change.
As the global average temperature continues to rise, impacts of climate change are expected to increase. These impacts will affect ecosystems, food, the ocean, coasts, society, weather, and humans. Learn about the impacts of climate change and how society and ecosystems might adapt.
Climate scientists have developed sophisticated computer models to estimate future climate change. Learn about how climate models work, how they are tested, and how will our decisions affect climate.
The environmental, economic, and humanitarian risks of climate change indicate a pressing need for substantial action to limit the magnitude of climate change and to prepare for adapting to its impacts. Learn more about mitigating climate change and adapting to its impacts.