Changes

According to geologists, the Earth has experience numerous [[ice age]]s during which the temperature dropped so far that [[glacier]]s could cover [[North America]] and [[Europe]].  

According to geologists, the Earth has experience numerous [[ice age]]s during which the temperature dropped so far that [[glacier]]s could cover [[North America]] and [[Europe]].  

There is a close correlation between the average temperature of the Earth's atmosphere and the amount of [[carbon dioxide]] in the atmosphere. During warm periods, the carbon dioxide level increases, and during cool periods it decreases.<ref>[http://www.nature.com/nature/journal/v399/n6735/abs/399429a0.html Climate and Atmospheric History of the Past 420,000 years from the Vostok Ice Core]</ref> Today the carbon dioxid concentration is 380 ppm. The pre-industrial level was 280 ppm. The current carbon dioxide concentration ist the highest since at least 650,000 years.<ref>[http://www.sciencemag.org/cgi/content/short/310/5752/1313/ Stable Carbon Cycle–Climate Relationship During the Late Pleistocene]</ref>

There is a close correlation between the average temperature of the Earth's atmosphere and the amount of [[carbon dioxide]] in the atmosphere. During warm periods, the carbon dioxide level increases, and during cool periods it decreases.<ref>[http://www.nature.com/nature/journal/v399/n6735/abs/399429a0.html Climate and Atmospheric History of the Past 420,000 years from the Vostok Ice Core]</ref> Today the carbon dioxid concentration is 380 ppm. The pre-industrial level was 280 ppm. The current carbon dioxide concentration ist the highest since at least 650,000 years.

==Politics of global warming==

==Politics of global warming==

Assessments of climate science by the United Nations (see [[IPCC]] - ''Intergovernmental Panel on Climate Change'')

Assessments of climate science by the [[United Nation]]s (see [[Intergovernmental Panel on Climate Change]])

have claimed that there is a scientific consensus on the subject. According to their latest report, scientists are 90% sure that over 50% of the observed global warming in recent decades is human-caused, and that continued global warming could be expected to raise sea levels by one foot over the next century.

have claimed that there is a scientific consensus on the subject. According to their latest report, scientists are 90% sure that over 50% of the observed global warming in recent decades is human-caused, and that continued global warming could be expected to raise sea levels by one foot over the next century.