For example, there is already evidence of:

• Rising temperatures
• Shrinking glaciers and ice sheets
• Increasingly violent storms
• Changes in weather patterns

Rising Temperatures

As greenhouse gas concentrations have increased, the greenhouse effect has led to a dramatic warming of the planet. Of the 21 warmest years on measure, 20 have occurred within the last 25 years. Moreover, 2005 was the hottest year of them all.

For example:

• In Reno, Nevada, daily temperatures exceeded 100 degrees Fahrenheit for 10 days straight, a new record.
• On July 19 (2005), the temperature in Las Vegas, Nevada reached 117 degrees Fahrenheit, an all time high.
• Tucson, Arizona, reached 100 degrees Fahrenheit for 39 consecutive days.

Taken together, over 200 cities and towns in the western United States set all-time temperature-related records.

Shrinking glaciers and ice sheets

Glaciers and ice sheets form an important part of the climate system, as they reflect a lot of the sun’s energy back into the atmosphere and outer space. Additionally, because the polar ice sheets store a great deal of frozen water, their melting and freezing strongly influence the level and composition of the oceans. Thus, the continued melting of the polar ice sheets will in turn lead to a rise in sea levels.

Increasingly violent storms

As climate change warms the surface of the Earth, water temperatures in the oceans rise as well. Warmer water in the top layer of the ocean can in turn fuel more powerful hurricanes. The number of category 4 and category 5 hurricanes has doubled in the last 30 years.

For example:

• In 2006 Australia was hit by several unusually powerful Category 5 cyclones, including the strongest cyclone ever measured (Cyclone Monica).
• The 2005 hurricane season in the Atlantic Ocean included, for the first time in history, four category 5 hurricanes.
• In 2004 Florida was struck by four unusually powerful hurricanes and Japan struck by a record ten typhoons.

As reported by the IPCC, “There is observational evidence for an increase of intense tropical cyclone activity in the North Atlantic since about 1970, correlated with increases of tropical sea surface temperatures. There are also suggestions of increased intense tropical cyclone activity in some other regions where concerns over data quality are greater.”

Changing weather patterns

In many parts of the world, global warming has increased the percentage of annual precipitation that falls as rain instead of snow. This in turn has led to an increase in flooding in the spring and early summer.

In the spring and summer of 2005, for example:

• Europe experienced a disastrous and unprecedented number of floods, causing the Associated Press to report “Nature is going crazy in Europe.”
• Mumbai, India, recorded 37 inches of rain in only 24 hours, causing waters to rapidly rise seven feet; the death toll in western India reached 1,000.

However, in other regions of the world, precipitation has decreased dramatically. Areas in Africa at the edge of the Sahara and on the western coast of South America, for example, have experienced precipitation declines of 40 to 50% over the last century. This decrease in rainfall, coupled with a warmer atmosphere’s ability to draw more moisture out of the soil, has led to a global increase in drought, desertification and water shortages.