The first thing to be aware of is that the warming effect of carbon dioxide is strongly logarithmic. Of the 3°C that carbon dioxide contributes to the greenhouse effect, the first 20 ppm has a greater effect than the following 300 ppm. By the time we get to the current level of 388 ppm, each 100 ppm increment will produce only about 0.1° of warming. With the atmospheric carbon dioxide content currently rising at about 2 ppm per annum, temperature will rise at 0.1° of warming every 50 years. ,
If that is true, you will ask, how does the Intergovernmental Panel on Climate Change (IPCC) get its icecap-melting figure of 6°C for doubling of the pre-industrial level 280 ppm to 560 ppm? It is widely accepted that, in the absence of feedbacks, doubling would produce a rise of 1°C. The IPCC climate modelling assumes that the feedback from this rise will be positive; that is, that the extra heat will result in more water vapour in the atmosphere, which in turn will cause more heat to be trapped, and the system compounds away until 1°C gets turned into 6°C. As described, the Earth’s climate would be tremendously unstable, prone to thermal runaway at the slightest disturbance.
The real world evidence says the opposite. In late 2007, Dr. Roy Spencer of the University of Alabama published a paper analysing data from the Aqua satellite. Based on the response of tropical clouds. Dr. Spencer demonstrated that the feedback is negative. He calculates a 0.5°C warming for a doubling of the pre-industrial carbon dioxide level. Global warming, as caused by carbon dioxide, is real but it is also minuscule, and will be lost in the noise of the climate system.