Understanding Climate Change

To understand climate change, we need to know the difference between climate and weather. Weather is the state of the atmosphere at any given time, including temperature, precipitation or winds. Climate is the “average weather” over a period ranging from months to thousands or millions of years.^.

Climate change refers to changes in the climate that occur over a long period of time. It's a change in predicted weather patterns. Climate change shows itself in many ways, including changes in rainfall, droughts, increasing floods and heat waves. It also makes the ocean become more acidic, causes the ice caps to melt, and raises sea levels. Learn more about our changing climate from the 2014 U.S. National Climate Assessment.

Causes of Climate Change

A rapidly growing body of research has strengthened and added local detail to previous knowledge about the causes and consequences of climate change.

Human activities have increased atmospheric levels of greenhouse gases (carbon dioxide, methane, and nitrous oxide) to levels unprecedented in at least the past 800,000 years. The Earth's climate system is warming, global sea level is rising, snow and ice are declining, and ocean chemistry and climate extremes are changing.

From a global scale to the scale here at home, many of these changes can be attributed to human causes. Learn what you can do.

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