Just for the hell of it (especially for you guys sweltering in triple digit heat) http://snowballearth.org/ "Planet Earth covered by ice from pole to pole for long periods in the geological past." "Snowball earth describes the coldest global climate imaginable - a planet covered by glacial ice from pole to pole. The global mean temperature would be about -50°C (-74°F) because most of the Sun's (Solar) radiation would be reflected back to space by the icy surface. [The fraction of radiation reflected is termed albedo (a) and it ranges widely from ~0.1 for liquid water, ~0.3 for bare land, ~0.45-0.65 for bare ice depending on the bubble content, to ~0.9 for fresh snow.] The average equatorial temperature would be about -20°C (-10°F), roughly similar to present Antarctica. Without the moderating effect of the oceans, temperature fluctuations associated with the day-night and seasonal cycles would be greatly enhanced. Because of its solid surface, the climate on a snowball earth would have much in common with present Mars. Despite the cold and dry climate, the atmosphere would still transport some water vapor from areas of sublimation (direct change from solid to vapor) to areas of condensation. Given sufficient time, glacial ice would thicken and flow in the opposite direction. Glacial flowage results in sedimentary deposits (glacial erratics, tills, moraines, eskers, ice-rafted debris, etc.) that fingerprint the glacial activity long after the ice has disappeared."
Warm periods on earth like the one we have been living in the last several thousand years have been just brief periods in earth's geological history. Most of the past history of earth has been spent in an ice age.
Saves planet from ice age... see the last sentence. http://www.elitetrader.com/vb/threa...read&forumid=27 Jan Esper of Johannes Gutenberg University in Mainz, Germany, thinks that at least some of those tree rings actually show something else: a long-term cooling trend that lasted right up until the Industrial Revolution. The trend came about because of reduced solar heating caused by changes to the Earth's orbit known as Milankovitch wobbles, says Esper. His results suggest the Roman world was 0.6 °C warmer than previously thought â enough to make grape vines in northern England a possibility. Esper and his colleagues say that warmer summers do not necessarily make tree rings wider â but they often make them denser. He studied the density of tree rings in hundreds of northern Scandinavian trees and found that they showed evidence of a gradual cooling trend that began around 2000 years ago. The finding fits with other proxies for temperature â such as the chemical make-up of air trapped in glaciers and the organic remains in ancient lake sediments â which have also suggested a cooling trend. Esper's study is the latest to indicate that temperatures were less stable than originally thought. In 2009, Darrell Kaufman of Northern Arizona University at Flagstaff published evidence, using a range of proxies, that indicated a cooling in the Arctic for most of the past 2000 years (Science, DOI: 10.1126/science.1173983). Esper's findings suggest that the cooling trend was even stronger than Kaufman concluded. The finding does not change our understanding of the warming power of carbon dioxide. In fact, it shows that human CO2 emissions have interrupted a long cooling period that would ultimately have delivered the next ice age.
The sun will have the final say as to when the next ice age arrives. GW scientists have been trying to put the cart before the horse for nearly 20 years.
"Background The U.N.-based IPCC (Intergovernmental Panel on Climate Change) produced its latest report in 2007 (AR4). Its position on global warming (based on the outputs of computerized climate models) indicates that the models only depend on anthropogenic CO2 after 1970 â prior to that, warming and cooling is explained by natural factors. So even though industrial civilizations have been producing increased amounts of CO2 since the late 1800s, it only becomes a factor in the models after 1970." http://www.appinsys.com/globalwarming/GW_History.htm