How can we talk about climate change over the next 100 years when we can’t be sure of tomorrow’s weather?

Answer:

Weather and climate are different. The methods used to forecast changes in weather and climate differ as well.

Climate can be thought of as average weather, including weather’s variability over long time periods. Natural changes in climate happen over the course of decades, centuries and many millennia. Global Circulation Models (GCM) are able to account for the many factors that influence climate over long periods, such as changes in the sun’s energy and the level of greenhouse gases (GHG) in the atmosphere. These models tell us what the average weather is likely to be but are not able to identify specific weather events.

Watch this 2-minute video explaining trend & variation:

Basic physics tells us that greenhouse gases (GHG) trap the Earth’s heat and cause warming. But the Earth’s climate is very complex, involving interactions between the air, land and oceans.

Scientists use computer models, Global Circulation Models (GCM), to project climate changes associated with the increased concentration of GHGs. Present models are able to simulate our current climate and reproduce variations in past climate. This information gives us confidence in their ability to predict future climates. With improvements in computing power, these models continue to improve – becoming more refined and accurate.