1. The earth is a natural greenhouse and is kept warm by water vapors, carbon dioxide (CO2), and other gases in the atmosphere, which absorb the sun’s energy and radiate it back toward the earth. This type of warming is called “natural greenhouse effect.” “Enhanced greenhouse effect,” on the other hand, causes global climate change due to excessive levels of CO2 in the atmosphere.

2. Without the atmosphere to create a greenhouse-type effect, the average temperature on Earth would be just 5° Fahrenheit (F).

3. Natural levels of CO2 in the atmosphere have varied throughout history between 180 and 300 parts per million (ppm). Today’s CO2 levels hover around 380 ppm, representing a 25% increase over the highest recorded natural levels.

4. In the year 1997 alone, the concentration of CO2 in the atmosphere increased by 2.87 ppm; this increase is more than any other year on record.

5. The year 2005 was the warmest on record, and the years 1998 and 2007 are tied for the second warmest. The eight warmest years on record have all occurred since 1998.

6. Scientists expect a 3.5° F increase in average global temperatures by the year 2100, resulting in the warmest temperatures in the past million years. During the Pliocene epoch 1.8 million years ago, when the earth’s temperatures were roughly equivalent to today, sea levels were 12-18 feet higher.

7. Geologists believe sea levels could rise between seven and 23 inches by the end of the century if current warming trends continue.

8. Worldwide, one hundred million people live within three feet of sea level, and much of the world’s population is clustered in coastal areas.

9. The polar bear, while surviving in drastically reduced numbers, is already effectively extinct in its natural habitat—and no amount of change can save it. Scientists estimate that just 20,000 to 25,000 polar bears still survive in the wild.

10. The first forced relocation due to the effects of climate change occurred in 2007 when 100 residents of Tegua Island in the Pacific Ocean were evacuated due to rising sea levels and subsequent flooding.

11. For the past million years, cool climate conditions have primarily prevailed throughout the world. It was under these conditions that the human species evolved.

12. The earth has always experienced cyclical bouts of climate change. Recorded temperatures throughout history display graphs of peaks and valleys with occasional extreme periods, such as the Little Ice Age of the seventeenth and eighteenth century and the Medieval Warm Period of the eleventh century.

13. According to NASA studies, average temperatures around the world have increased 1.4° F since 1880, with most of the change occurring in recent decades.

14. During the twentieth century, the earth experienced two warming trends. The first was a burst in temperature from 1900-1930, and the second is a continuing increase in temperature beginning in the 1970s.

15. The last two decades of the twentieth century were the hottest decades in more than 400 years and may have been the hottest decades for several thousand years.