What is Global Warming?

The term Global Warming describes the observed and projected increase in globally averaged temperatures over time. Because the global climate is a dynamic system, global warming has occurred in the past and will occur in the future. Using surface station temperature measurements and satellite-based measurements, researchers have identified an increasing trend in the global average surface air temperatures. The Intergovernmental Panel on Climate Change has determined that this increase can be attributed to a combination of natural climate variations and human factors. One of the leading causes under investigation is the greenhouse effect of gasses in the atmosphere.

What is the Greenhouse Effect?

The Greenhouse Effect obtained its name from the behavior of a greenhouse. A greenhouse's glass allows shortwave radiation to enter but then prohibits outgoing longwave radiation from exiting, thus warming the air in the greenhouse. Although the behavior of the atmosphere is different from that of a greenhouse, the result is similar and thus the warming effect was termed the Greenhouse Effect. If it wasn't for the natural greenhouse effect, almost all radiation would be returned to space and the average surface temperature would be around 0°C. Atmospheric gasses that cause this effect include water vapor (H₂O), carbon dioxide (CO₂) and methane (CH₄). If the amount of these gasses in the atmosphere increases, then the greenhouse effect will be magnified and warmer global temperatures will result.

Some of the impacts of global warming may include stronger storms, migration of agricultural zones, spreading of tropical diseases, melting of glaciers and ice caps and increases in pollution levels.

To learn even more about global warming and climate change, visit one of the following web sites:

• Global Climate Change Indicators
• Global Climate Change, Vital Signs of the Planet
• Global Warming fact page from the Union of Concerned Scientists
• Global Warming Science Education, Climate Change Science Education and Global Warming Solutions
• Global Warming: The Early Warning Signs
• Greenhouse Gas Online: All About Greenhouse Gas Science
• Intergovernmental Panel on Climate Change (IPCC)
• National Academies Climate Change Expert Reports
• RealClimate commentary blog on climate change by working climate scientists
• State of the Climate, monthly summaries recapping climate-related global and national scale occurrences
• The Environmental Protection Agency (EPA) Global Warming Site
• What is Global Warming, National Geographic


• Want more sites? Check out the GCMD global warming links page.