The world's leading climate scientists said global warming has begun, is very likely caused by man, and will be unstoppable for centuries. The phrase very likely translates to a more than 90 percent certainty that global warming is caused by man's burning of fossil fuels. That was the strongest conclusion to date, making it nearly impossible to say natural forces are to blame.
The scientists said global warming's connection varies with storms in different parts of the world, but that the storms that strike the Americas are global warming-influenced.
Later, described qualitatively by Svante Arrhenius.
First man who speculated changes CO 2 in the atmosphere could substantially alter the surface temperature through the greenhouse effect. ["On the Influence of Carbonic Acid in the Air Upon the Temperature of the Ground", Philosophical Magazine 1896(41): 237-76]
Formulated Arrhenius' greenhouse law
if the quantity of carbonic acid increases in geometric progression, the augmentation of the temperature will increase nearly in arithmetic progression.
Intergovernmental Panel on Climate Change Fourth Assessment Report. (Chapter 1: Historical overview of climate change science) said that average earth surface temperature is 15 °C (33 °C warmer without Greenhouse Effects)
Sami Solanki, the director of the Max Planck Institute for Solar System Research in Katlenburg-Lindau, Germany said:
“ The sun has been at its strongest over the past 60 years and may now be affecting global temperatures... the brighter sun and higher levels of so-called "greenhouse gases" both contributed to the change in the Earth's temperature, but it was impossible to say which had the greater impact ”
Solanki agrees with the scientific consensus that the marked upswing in temperatures since about 1980 is attributable to human activity.
" Just how large this role [of solar variation] is, must still be investigated, since, according to our latest knowledge on the variations of the solar magnetic field, the significant increase in the Earth’s temperature since 1980 is indeed to be ascribed to the greenhouse effect caused by carbon dioxide ."
Stott's 2003 work mentioned in the model section above largely revised his assessment, and found a significant solar contribution to recent warming, although still smaller (between 16 and 36%) than that of the greenhouse gases.
According to the clathrate gun hypothesis a runaway greenhouse effect could be caused by liberation of methane gas from hydrates by global warming if there are sufficient hydrates close to unstable conditions.
Melting permafrost peat bogs and methane hydrate.
Methane being 21-times more potent a greenhouse gas than carbon dioxide
Cause loss of carbon from terrestrial ecosystems, leading to an increase of atmospheric CO2 levels.
One model in particular (HadCM3) indicates a secondary carbon cycle feedback due to the loss of much of the Amazon rainforest in response to significantly reduced precipitation over tropical South America.
Researchers suggest any such feedback would accelerate global warming.