Most widely used climate computer model exaggerates global warming by 67%

A paper published today in the Journal of Climate announces a new version of the computer climate model most widely used by climate scientists and the IPCC, called the Community Climate System Model (CCSM) version 4. The creators claim their program is

 "a fully-coupled, global climate model that provides state-of-the-art computer simulations of the Earth’s past, present, and future climate states."

The abstract, however, contains a remarkable admission that the model exaggerates the global warming from 1850 to 2005 by 0.4°C more than observations. The observed global warming from 1850 to 2005 was only 0.6°C, thus the computer model predicted ~ 67% more global warming than actually occurred. This exaggeration alone could account for all of the claimed "heat trapping" from the increase in man-made carbon dioxide over that same 155 year period. IPCC projections for future global warming based upon this model may be similarly greatly exaggerated.



The Community Climate System Model Version 4



Abstract: The fourth version of the Community Climate System Model (CCSM4) was recently completed and released to the climate community. This paper describes developments to all CCSM components, and documents fully coupled pre-industrial control runs compared to the previous version, CCSM3. Using the standard atmosphere and land resolution of 1° results in the sea surface temperature biases in the major upwelling regions being comparable to the 1.4° resolution CCSM3. Two changes to the deep convection scheme in the atmosphere component result in CCSM4 producing El Nino/Southern Oscillation variability with a much more realistic frequency distribution than CCSM3, although the amplitude is too large compared to observations. They also improve the Madden-Julian Oscillation, and the frequency distribution of tropical precipitation. A new overflow parameterization in the ocean component leads to an improved simulation of the Gulf Stream path and the North Atlantic Ocean meridional overturning circulation. Changes to CCSM4 land component lead to a much improved annual cycle of water storage, especially in the tropics. The CCSM4 sea ice component uses much more realistic albedos than CCSM3, and for several reasons the Arctic sea ice concentration is improved in CCSM4. An ensemble of 20th century simulations produces a pretty good match to the observed September Arctic sea ice extent from 1979 to 2005. The CCSM4 ensemble mean increase in globally-averaged surface temperature between 1850 and 2005 is larger than the observed increase by about 0.4°C. This is consistent with the fact that CCSM4 does not include a representation of the indirect effects of aerosols, although other factors may come into play. The CCSM4 still has significant biases, such as the mean precipitation distribution in the tropical Pacific Ocean, too much low cloud in the Arctic, and the latitudinal distributions of short-wave and long-wave cloud forcings.