Global warming is the term ascribed to an increase in global average surface temperature. Average Earth surface air temperature has risen just over one degree since 1850. 
Assessments by the United Nations promote the view that the warming since around 1850 is mostly human-caused. In February, 2007, the Intergovernmental Panel on Climate Change, a body of climate change scientists established by the United Nations, released their fourth assessment report on climate change. That report concluded that recent global climate change was "very likely" caused by human activity, .
Politicians who support the Kyoto Protocol have made the claim that there is a cause and effect relationship between increases in atmospheric concentrations of greenhouse gases and air temperature.[Citation Needed]
Natural variability of the climate system
Secular scientists think that the Earth has experienced numerous ice ages over two million years, during which global temperatures dropped approximately 6 degrees Celsius and then returned to normal. 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.
Warming of other Planets
And it's not just the earth that has variations. Since the Viking spacecraft reached Mars in the 1970's until recent readings were taken, the average temperature on Mars has risen 1.1 degrees Fahrenheit just as the average temperature on the earth has risen. Since human industrialization is probably not to blame for the change on Mars, other causes are being considered. The scenario most postulated by those who believe this is due to local changes on Mars and is not is dust storms, although solar conditions are certainly a possibility. Recently, it has also been found that similar to the earth and Mars, that Neptune is undergoing global warming as well. Measurements taken at the Lowell observatory in Arizona have shown an increase in Neptune's brightness and temperature since 1980 following the same pattern found on the earth, and Mars. As with Mars, it is assumed this is not due to human influence. 
Politics of global warming
The global average surface temperature warmed about 0.5 °C (0.9 °F) over the second half of the 20th Century,Template:Fact-science 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.
Assessments of climate science by the United Nations (see IPCC - Intergovernmental Panel on Climate Change) have claimed that 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. Science published a literature search by Naomi Oreskes concluding that "scientific consensus" overwhelmingly supports the IPCC reports. 
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. Several scientists have complained about their work being misrepresented by the U.N.[Citation Needed]
There is wide agreement among the American public that Global Warming is a reality. A poll conducted March 11-14 of 2007 found that the majority of the American public (59%) believes we are already seeing the effects of Global Warming, an additional 3% and 8% respectively believe they will see the effects with in a few years or within their lifetime, and 19% believe that Global Warming will be seen, not in their lifetime, but in future generations—only a small minority 8% believe that Global Warming will never happen. .
- Does a global temperature exist?, Journal of Non-Equilibrium Thermodynamics, June 2007.
- Fighting the Hoax
- The appliance of science by Mike Hulme.
- An Inconvenient Truth, Film by Al Gore
- Climate Sensitivity and Observed Negative Feedbacks, lecture by Richard Lindzen and Roberto Rondanelli.
- Nature of Arguments for Anthropogenic Global Warming, by Richard Lindzen
- Global Warming: The Origin and Nature of the Alleged Scientific Consensus - Richard S. Lindzen, Alfred P. Sloan Professor of Meteorology at the Massachusetts Institute of Technology
- Global warming smear targets
- The physical evidence of earth's unstoppable 1,500-year climate cycle
- Survey Shows Climatologists Are Split on Global Warming
- The Great Global Warming Swindle - Documentary Film
- Hansen's group at the Goddard Institute wrote, "Global warming is now 0.6 °C [1.0 °F] in the past three decades and 0.8 °C [1.4 °F]in the past century." http://data.giss.nasa.gov/gistemp/2005/
- Poling report on Gallup poll for March 11-14, 2007