Kininmonth on the Stern Report

 

November 2, 2006

The Age


THE Stern report claims there is only a narrow window of opportunity within which the world must act to prevent dangerous climate change. A primary finding is that research since the 2001 report of the Intergovernmental Panel on Climate Change shows the climate to be more sensitive to carbon dioxide emissions than thought, thus requiring immediate and drastic action.


Quite properly, Stern recognises that the scientific evidence of human influence on climate is an essential starting point for the economics. It is the science that establishes whether there is a problem, its risk and scale.


However, it is in the science discussion that Stern is ignorant of the complexity of climate. The claim that there is no plausible explanation, other than human activities, for the observed warming of the past 30 years is wrong. The report gives no credence to internal variability of the climate system as the ocean and atmosphere fluids interact to transport heat from the tropics to the poles. Nor does it recognise the cyclic centennial to millennial oscillations in the climate record for which there are as yet no agreed explanations. The emergence of Earth from Ice Age conditions 20,000 years ago, when vast ice sheets covering North America and Northern Europe receded, sea level rose 130 metres, and the biosphere expanded and flourished in the warmer, wetter world, is ignored.



Unlike the IPCC, the Stern report does recognise the fading influence of carbon dioxide as concentration increases. Most of the greenhouse effect of carbon dioxide is in the first 50 parts per million (ppm). Beyond this the rate of increase of the greenhouse effect rapidly decreases with increasing concentration. There is no argument with Stern's basic finding that the direct increase in the greenhouse effect from a doubling of carbon dioxide is to increase the Earth's surface temperature by about 1 degree.


The argument is with Stern's further claim that there are positive feedbacks in the climate system that act to amplify the direct warming. The latter is at the heart of the alarmist predictions. Stern's simple explanation is that a warmer atmosphere holds more water vapour, also a greenhouse gas, and it is the extra water vapour that amplifies the direct warming effect.


Thus, the direct warming of about 1 degree is projected to become between 1.4 and 5.8 degrees for a doubling of carbon dioxide concentration. The range of projected global warming arises because the amplification can only be estimated using computer models. Stern says that the climate models use the laws of nature and are thus vastly different from those used in economic analyses, "which rely predominantly on curve fitting". The statement that the "accuracy of climate predictions is limited by computer power" is stunning in its ignorance as even the IPCC highlights a range of scientific uncertainties.


Stern fails to identify the important role of evaporation in cooling Earth's surface. As surface temperature rises, evaporation increases at a near exponential rate. This extraction of heat is a strong damping factor to further temperature rise.


There will be no runaway greenhouse effect because the fading influence of carbon dioxide and rapid increase of evaporation combine to restrict temperature rise.


Warming from carbon dioxide increase is relatively small in the context of natural climate variability. It follows that a cut in human-caused carbon dioxide emissions will have little impact on the future climate.


William Kininmonth was head of the National Climate Centre and is author of Climate Change: A Natural Hazard.