When scientists talk about the issue of climate change, their concern is about changes in global climate patterns due to global warming as a result of human activities.

A natural layer of heat-trapping gases including water vapor, carbon dioxide (CO2) and methane (CH4) surrounds the earth and produces a greenhouse effect. These gases keep the earth warm enough to support life. Burning large amounts of fossil fuels is dramatically increasing the concentration of these gases. Like the glass in a greenhouse, these gases collect in the atmosphere and prevent the earth's excess heat from escaping. As the gases thicken, the earth's temperature increases.

Since the beginning of the 20th century, the mean surface temperature of the earth has increased by about 0.6oCelsius (1.1o F).

Strong evidence attributes most of the warming over the last 50 years to human activities that have altered the chemical composition of the atmosphere through the buildup of greenhouse gases. The biggest change is the additional release of CO2 by human activities.

As the earth continues to warm experts predict that we will have to prepare for more heat waves and droughts, more extreme weather events bringing floods and destruction, higher instances of heat related illnesses and deaths, and increased insect and rodent spread infectious disease. Over 15,000 deaths were blamed on extreme heat in Europe in the summer of 2003.