What Causes Climate Change?

Climate change is a natural process that has been sped up by human activities. The problem today is that we are experiencing an unnatural acceleration of climate change caused by the interplay of several factors, including:

  1. Changes in the amount of solar radiation entering the Earth’s atmosphere (due to shifts in the Earth’s axis, for example);
  2. Changes in the amount of solar radiation that is then reflected back out into space. This is called albedo, and can be affected by the amount of reflective cloud cover or ice cover on the planet; and
  3. Changes in the amount of energy that is allowed to escape from the planet, back out into space. This is different from albedo, and is affected by the amount of greenhouse gases, such as carbon dioxide and methane, in the atmosphere.

Natural Climate Change

The Earth’s climate is always changing. Natural cycles — occurring over very long time spans — have warmed and cooled the planet over eons. These cycles are driven by slight changes in the Earth’s orbit and/or the amount of solar energy. As a result of these cycles, the Earth has changed dramatically over the eons — the planet’s climate has been both much warmer and much cooler than it is today.

Natural or geologic climate change is driven primarily by shifts in the Earth’s axis around the sun. These changes — known as Milankovitch cycles — affect the angle of the Earth in relation to the sun, and thus affect the amount of solar energy that reaches the planet.

Learn more about natural climate change and how it differs from human-caused climate change. Visit NOAA’s Ocean Service Education website.

Modern Climate Change

Natural or geologic climate change should not be confused with modern climate change. Today, when most people talk about climate change, they are really talking about modern climate change, also known as anthropogenic — human-caused — climate change. The climate change we are experiencing today differs dramatically from geologic climate change because:

  1. Modern climate change is caused by humans.
  2. Greenhouse gas emissions from human activities are the primary driver for modern climate change. This is in contrast to geologic climate change, which is primarily caused by changes in the Earth’s rotation or axis, or changes in the amount of solar energy.
  3. Modern climate change is occurring at a much more rapid rate than geologic climate change.