What is climate change?

Learn about the causes of climate change and how you can reduce its threat.

Climate change, also called global warming, refers to the rise in average surface temperatures on Earth. An overwhelming scientific consensus maintains that climate change is due primarily to the human use of fossil fuels, which releases carbon dioxide and other greenhouse gases into the air. The gases trap heat within the atmosphere, which can have a range of effects on ecosystems, including rising sea levels, severe weather events, and droughts that render landscapes more susceptible to wildfires.

Is climate change real?

There is broad-based agreement within the scientific community that climate change is real. The U.S. Environmental Protection Agency, the National Aeronautics and Space Administration, and the National Oceanic and Atmospheric Administration concur that climate change is indeed occurring and is almost certainly due to human activity.

What are the causes of climate change?

The primary cause of climate change is the burning of fossil fuels, such as oil and coal, which emits greenhouse gases into the atmosphere—primarily carbon dioxide. Other human activities, such as agriculture and deforestation, also contribute to the proliferation of greenhouse gases that cause climate change.

While some quantities of these gases are a naturally occurring and critical part of Earth’s temperature control system, the atmospheric concentration of CO2 did not rise above 300 parts per million between the advent of human civilization roughly 10,000 years ago and 1900. Today it is at about 400 ppm, a level not reached in more than 400,000 years.

What is Climate Change? What Causes Global Warming?

Increased burning of fossil fuels contributes to climate change.

(Photo: Chris Conway/Getty Images)

What are the effects of climate change?

Even small increases in Earth’s temperature caused by climate change can have severe effects. The earth’s average temperature has gone up 1.4° F over the past century and is expected to rise as much as 11.5° F over the next. That might not seem like a lot, but the average temperature during the last Ice Age was about 4º F lower than it is today.

Rising sea levels due to the melting of the polar ice caps (again, caused by climate change) contribute to greater storm damage; warming ocean temperatures are associated with stronger and more frequent storms; additional rainfall, particularly during severe weather events, leads to flooding and other damage; an increase in the incidence and severity of wildfires threatens habitats, homes, and lives; and heat waves contribute to human deaths and other consequences.

Climate change: the debate

While consensus among nearly all scientists, scientific organizations, and governments is that climate change is happening and is caused by human activity, a small minority of voices questions the validity of such assertions and prefers to cast doubt on the preponderance of evidence. Climate change deniers often claim that recent changes attributed to human activity can be seen as part of the natural variations in Earth’s climate and temperature, and that it is difficult or impossible to establish a direct connection between climate change and any single weather event, such as a hurricane. While the latter is generally true, decades of data and analysis support the reality of climate change—and the human factor in this process. In any case, economists agree that acting to reduce fossil fuel emissions would be far less expensive than dealing with the consequences of not doing so.

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