| Global warming is expected to increase the intensity | | | | as it radiates back into the space, causing an increase |
| of forces of nature, such as tornadoes and | | | | in the average temperature of the Earth's surface. |
| hurricanes. It is determined not by individual weather | | | | Since the late 1800's, the global average temperature |
| events, such as heat waves or cold snaps or | | | | has increased about 0.7 to 1.4 degrees F (0.4 to 0.8 |
| hurricanes, but by the global mean surface | | | | degrees C). Global warming is determined not by |
| temperature. It is already increasing the intensity of | | | | individual weather events, but by the global mean |
| hurricanes in the North Atlantic, increasing the risk of | | | | surface temperature. North America experienced a |
| devastating impacts when a storm hits. | | | | fairly normal winter in 2006-2007, and some parts had |
| Global warming is also leading to more dramatic | | | | extremely cold weather this year ? |
| swings in the weather in some areas. It is already | | | | Greenhouse gases are an air pollution problem, and all |
| affecting the world we know, endangering polar | | | | air pollution problems of the past have cost |
| bears, shortening ski seasons and creating more | | | | significantly less to fix than projected, while declining |
| intense storms. Global warming is a huge risk, it is an | | | | faster than expected. This gives cause to hope that |
| increase in the average temperature of the earth's | | | | artificial greenhouse gases can be controlled |
| surface. | | | | reasonably cheaply and without wrenching sacrifices |
| Global warming is bad news for human life, including | | | | to the global economy. Greenhouse gases are |
| changes in agricultural yields, melting of glaciers and | | | | released by activities such as the burning of fossil |
| the extinction of certain species for ever. | | | | fuels, land clearing, and agriculture. Other phenomena |
| Global warming is an increase of average world | | | | such as solar variation and volcanoes have had |
| temperatures as a result of what is known as the | | | | smaller and probably negative effects 1950. |
| greenhouse effect. Certain gases in the atmosphere | | | | Global warming is already under way. The evidence is |
| behave like glass in a greenhouse, permitting sunlight | | | | vast and the urgency of taking action becomes |
| through to heat the earth's surface but trapping heat | | | | clearer with every new scientific study. |