What is Global Climate Change?
 

The objectives of this section are to describe global climate processes and to explain how climate projections are made. Global climate change refers to a change in the average weather conditions on Earth, including changes in temperature, precipitation, and wind patterns. The natural greenhouse effect helps to maintain a livable temperature on Earth. Nevertheless, over long time periods there has been significant natural variability in mean temperature which was manifested as glacial and interglacial periods. Climate change over the last century is associated with an enhanced greenhouse effect caused by increased emissions of carbon dioxide (CO₂) and other greenhouse gases that have been released into the atmosphere through human activity, including the burning of fossil fuels and deforestation. Climate change in the coming decades is likely to be experienced as increasing climate extremes, both in temperatures and in rainfall. This section examines the differences between weather and climate, climate variability and climate change, and past and present climate, and explains how climate projections are made.

All of the Issue Briefs are also available as printable 'factsheets'; feel free to download and print them as needed using the button in the upper right corner of each page.
 

1. What causes global climate change?
    
2. How does climate change today compare with climate change in the past?
    
3. What is the evidence that the climate is changing?
    
4. What is a global climate model?
    
5. How do scientists make projections about future climate change and climate impacts?