Water Vapor's Role in Climate Change

Water covers nearly three-quarters of Earth. It is continuously moving above, on and below Earth's surface, cycling among ice, liquid water and vapor. This cycling of water shapes the climate by delivering rain and snow, and it supports life on Earth. Water and climate are deeply interconnected, and as the climate changes so does the distribution and cycling of Earth's water.

 

Discover how water and climate affect each other by watching the video in the graphic above.

With climate change, Earth is getting warmer as greenhouse gases build up and trap more heat in the atmosphere. These warmer temperatures cause increased evaporation of water from places like oceans, lakes, streams and soil. This leads to higher levels of water vapor in the atmosphere, which means that precipitation events tend to be heavier. Whether the water falls as rain or snow depends on temperature. Therefore, if winter temperatures remain below freezing in areas like the northeastern United States, the increased moisture in the air could mean heavier snow storms.

Increased water vapor in the air can also further increase warming. Water vapor is actually a greenhouse gas, which traps heat in the atmosphere and causes temperatures to rise. But unlike other greenhouse gases that can linger in the atmosphere for years, water vapor usually stays in the air for a few days before falling back to Earth as precipitation.

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So, as warm temperatures lead to more water vapor in the air, more water vapor in the air leads to warmer temperatures, which creates a positive feedback loop. A positive feedback loop is called "positive" not because it's a good thing, but rather because the effects of one process enhance the effects of another, which in turn positively reinforce the effects of the original.

Discussion Questions

  • Why is water vapor considered a "greenhouse gas?"
  • How does water vapor differ from other greenhouse gases?
  • Using water vapor as an example, describe what is meant by a "positive feedback loop."
  • How can heavier snow events be explained in terms of climate change?

This video explainer is part of our Clue into Climate collection of resources.


An interactive version of this explainer is featured in our Clue into Climate e-book series. Click on the tabs below to download our free e-books and subscribe to our iTunes U course. You can also visit our e-books page to view our other offerings.

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Look into the causes of climate change, and discover how scientists develop and use climate models.

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Learn about how climate change influences precipitation patterns and how it impacts our frozen landscape.

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Investigate shifts in the distribution of plant and animal species due to climate change, and the effects of increased carbon dioxide emissions on the ocean.

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See how communities are preparing for sea level rise and other impacts of climate change, and ways we can help minimize future climate change.

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