Introduction | The Sun | Energy | The Greenhouse Effect | What Affects Climate? | Climate Change?

Are Climates Changing?

Like many questions in science, the question of how our planet is warming includes some parts that are very well understood and other parts that are not as well understood. Scientists use what we know about how the Earth works to make a special type of computer program called a global climate model. Global climate models help us predict how global warming may affect our planet in dozens to hundreds of years. To get the best predictions, scientists compare the results of many different model experiments and check results with data we have observed. A detailed outlook for the next 100 years is updated every few years by thousands of experts from around the world.

Here are some things that we know:

  • Greenhouse gases (such as water vapor and carbon dioxide) act to warm Earth’s atmosphere by trapping heat and radiating some of it back toward the Earth surface.
  • The amount of greenhouse gases in our atmosphere is increasing. Carbon dioxide has risen more than 30 percent since people started using fossil fuels and levels are now the highest in more than 400,000 years.
  • Earth’s average surface temperature has risen more than 1 degree Fahrenheit (0.6 degrees Celsius) since 1900.
  • The amount of sea ice in the Arctic has decreased severely over the last 50 years as the ice melts.
  • Glaciers are melting.
  • Over 25 percent of the world’s coral reefs have already died due to warming oceans.
  • Earth will continue to warm as people use more fossil fuels and the amount of greenhouse gases increases

Here’s what models have predicted for the next 100 years:

  • Global temperatures may rise 2 to 10 degrees Fahrenheit (about 1 to 6 degrees Celsius).
  • Sea level may rise up to 35 inches (88 centimeters).
  • More moisture from the oceans will evaporate into the air, which means more rain for some areas and more drought for others.
  • Some places will warm more than other places, and some places might even become cooler.
  • There will be less cold days in wintry places and more summer heat waves.
  • Vermont’s maple trees could vanish within a generation as climates change.
  • Places like Glacier National Park in Montana will have no more glaciers; the ice there is expected to melt completely by 2030.

We may know that the Earth will continue to warm as the amount of greenhouse gasses increases. But what we do not know is how this will affect people, plants, and animals. Some regions will become considerably hotter or cooler, or wetter or drier, than others. Some places might have stronger storms or stronger droughts. All these changes can affect the way people live their lives and the way ecosystems exist.