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What the difference is between climate and weather?

We often hear about the weather. We also hear about climate. The two terms are related. But they are not the same thing. What’s the difference? It’s a question of time. Weather takes place over short periods of time—hours, days, or weeks. Climate describes the weather over decades.

Both weather and climate describe events taking place in our atmosphere. Specifically, events affecting the lowest layer of the atmosphere, or troposphere. That’s the layer we interact with on a daily basis.

Climate and weather deal with temperature and precipitation. That’s a fancy word for water falling as rain, snow, hail, or sleet. Precipitation comes from clouds, so we also use terms like sunny, partly cloudy, or overcast to describe the weather. And the atmosphere is rarely still, making wind another important weather feature.

All aspects of weather ultimately come from sunlight. The sun heats the Earth unevenly. In tropical areas near the equator that receive the most sunlight, the surface warms quickly. That causes warm air to rise. Air from cooler regions rushes in to fill the space left behind, creating wind. Earth’s rotation plays a role in wind and weather patterns, too.

Heat also causes water to evaporate from rivers, lakes, and oceans. As more water enters the atmosphere, clouds form that may later drop precipitation. This often falls as a gentle rain or snow. Clouds over the ocean can eventually form storms. If these continue to build, they can become tropical storms or hurricanes. When they barrel onshore, they bring a deluge of rain and damaging winds. Over land, cold air colliding with warm air can also create strong winds and storms.

Weather can change very quickly, from minute to minute or hour to hour. Sometimes weather patterns last longer—for days, weeks, or even months. But weather patterns don’t last for years. Climate, on the other hand, tells us what weather patterns are like over decades.

Climate tells us what we can expect from the weather. Are winters typically cold and snowy? Are summers hot and humid? Does an area stay above freezing all year long? Does it receive almost no rain on a particular year? Such patterns describe the climate for a particular region. Scientists typically look at weather patterns over a 30-year period to get a sense of what is normal for the climate in a particular area.

When scientists look at weather records before the 1980s, they find that fairly consistent patterns occurred in different parts of the planet. But over the last 30 to 40 years, those patterns have been changing. Temperatures have been getting warmer. That’s especially true at night and in areas near the North and South Poles. Precipitation patterns are changing too. Some areas are getting more rain than they did in the past, often in the form of big storms. Other areas aren’t getting as much as they used to and are experiencing drought. It’s changes in those long-term patterns that tell us the climate is changing.

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A large iceberg has broken away from the Helheim Glacier and floats among slabs of pack ice in Sermilik Fjord along the southeastern coast of Greenland. The glacier, about 3 miles wide at its mouth, has been shrinking rapidly in recent years. WHOI researchers are investigating whether changes in the fjords are contributing to the loss of ice. (Photo by Nick Cobbing © Greenpeace International)

Climate Change

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Krajick, Kevin. James Hansen’s Climate Warning, 30 Years Later. State of the Planet, Columbia University. https://blogs.ei.columbia.edu/2018/06/26/james-hansens-climate-warning-30-years-later/ June 26, 2018.

NASA. What’s the Difference Between Weather and Climate? https://www.nasa.gov/mission_pages/noaa-n/climate/climate_weather.html February 1, 2005.

NOAA. What’s the Difference Between Weather and Climate? https://www.ncei.noaa.gov/news/weather-vs-climate  Accessed on January 7, 2021.

NOAA SciJinks. Why Does Wind Blow? https://scijinks.gov/wind/ Accessed on January 7, 2021.

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