Changes

[[Image:Rogerrevelle.jpg|thumb|right|200px|[[Roger Revelle]]]]

[[Image:Rogerrevelle.jpg|thumb|right|200px|[[Roger Revelle]]]]

'''Global warming''' comes and goes in natural cycles of approximately 1,500 years. During these natural periodic increases in the average temperature of the Earth's atmosphere, crops grow better in northern latitudes and deaths from extreme weather decrease. The large arctic island of [[Greenland]] was colonized during the [[Medieval Warm Period]], but the colonies there had to be abandoned during the [[Little Ice Age]] which followed.  

'''Global warming''' is the term ascribed to an increase in global average surface temperature associated with increases in atmospheric concentrations of [[greenhouse gases]].

During the recorded history of mankind, these cycles of warming and cooling have occurred every 1,500 years.<ref>''Unstoppable Global Warming'' by [[Fred Singer]] </ref>

Global warming should not be confused with natural variability of the climate system, such as ice ages. The Earth has experienced numerous [[ice age]]s over the past two million years, during which global temperatures were approximately 6 degrees Celsius cooler than the present. The frigid temperatures allowed ice sheets to expand southward, covering much of [[Asia]], [[Europe]], and [[North America]]. The cooling associated with ice ages is gradual, while the terminations are relatively rapid. However, even the rapid terminations of ice ages take centuries to millennia, which contrasts with the effects predicted for anthropogenic global warming. Projections of future climate predict global surface temperature to rise by 2 degrees Celsius (give or take about 1.5 C) between about the year 2000 and 2100. This predicted rapid warming is attributed to increases in atmospheric carbon dioxide, which through a complex set of climatic feedbacks (e.g., water vapor, lapse rate, albedo, vegetative, and cloud feedbacks) leads to the warming. Ultimately this is the same physical mechanism as the [[greenhouse effect]], in which outgoing infrared radiation is retained by the Earth system, raising the global temperature.

There is a close correlation between the average temperature of the Earth's surface and the amount of [[carbon dioxide]] in the atmosphere. During warm periods, there are high concentrations of atmospheric carbon dioxide, and lower levels during cool periods.

 

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.

==Politics of global warming==

==Politics of global warming==

The Earth has warmed half a degree over the past few decades, and to some the warming appears to be related to increases in carbon dioxide and other greenhouse gases. The possibility of adverse consequences has become a major concern for some environmentalists.

The global average surface temperature warmed about 0.5 C over the second half of the 20th Century, and to some the warming appears to be related to increases in carbon dioxide and other greenhouse gases. The possibility of adverse consequences has become a major concern for environmentalists.

 

Upon the dissolution of the [[USSR]], and when the [[Berlin Wall]] was torn down, leftists sought a new cause. They joined with [[environmentalist]]s to publicize various [[climate change]] issues such as [[ozone depletion]] and the [[runaway greenhouse effect]].

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

Assessments of climate science by the United Nations (see [[IPCC]] - ''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 should be expected over at lease the next century. Associated with such warming are changes in land and sea ice, large-scale weather patterns, and rising sea levels over the next century.

Several prominent scientists have pointed out the [[politicized science]] of the UN's assessment methods. The scientific reports are submitted to a panel of representatives appointed by each country in the IPCC. The panel picks and chooses what they want to put in the [[Summary for Policymakers]], over the objections of scientists whose actual evaluations are disregarded when the do not fit the preordained conclusions of the panel.

Several prominent scientists have pointed out the [[politicized science]] of the UN's assessment methods. The scientific reports are submitted to a panel of representatives appointed by each country in the IPCC.  

==Notes==

==Notes==