We often hear the claim that the science of climate change is settled, that there is general agreement that humans have been causing most of the recent warming trend, and that it will all end in global disaster unless we do something about it. Let me state at the outset that I am not sure any of these blanket claims are accurate.
Yes, there has been great progress in our understanding of climate dynamics in recent years. Yes, most climatologists are convinced that global warming is mainly due to humans. And yes, anthropogenic greenhouse gas emissions undoubtedly have an effect on the global mean temperature. What we dont know, however, is how much of an effect. More importantly, most researchers who support the theory of anthropogenic global warming are by no means agreed that it will result in large-scale calamity even if CO2 emissions were to double.
Benny Peiser is responding to the openDemocracy article of David King, the British governments chief scientific advisor:
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Significant gaps in our understanding of terrestrial climate remain. Only last week, new research revealed that we dont know very much about the amount of the suns energy that is absorbed by the Earth and the amount reflected back into space (see here). We know even less about how this process effects temperatures.
Neither do we genuinely understand the causes and effects of solar variability and how it alters the climate. Nevertheless, the idea that the sun, more so perhaps than humans, is the principal driver of terrestrial climate has been gaining ground in recent years. In March 2005, Jan Veizer, one of Canadas top Earth scientists, published a comprehensive review of recent findings and concluded that empirical observations on all time scales point to celestial phenomena as the principal driver of climate, with greenhouse gases acting only as potential amplifiers. (see Celestial Climate Driver: A Perspective From Four Billion Years Of The Carbon Cycle). I dont know whether Veizer is right, but I believe his findings should be carefully assessed instead of being ignored or disparaged because they go against the grain.
As David King points out in his contribution to the openDemocracy debate, the majority of scientists and science organisations endorse the view that humans are to blame for recent climate change. Nevertheless, this support is not universal. A number of distinguished scientific organisations such as the Russian Academy of Sciences (RAS)or the American Association of State Climatologists (AASC) remain sceptical.
Indeed, the American Association of Petroleum Geologists (AAPG), an international organisation of more than 30,000 Earth scientists, has formally rejected the view that anthropogenic factors are the main drivers of global warming, stressing: The earths climate is constantly changing owing to natural variability in earth processes. Natural climate variability over recent geological time is greater than reasonable estimates of potential human-induced greenhouse gas changes. Because no tool is available to test the supposition of human-induced climate change and the range of natural variability is so great, there is no discernible human influence on global climate at this time.
A recent survey among some 500 international climate researchers found that a quarter of respondents still question whether human activity is responsible for the most recent climatic changes. How decision-makers and the interested public deal with these scientific doubts and uncertainties is another matter. But it is vital for the health and integrity of science that critical evaluation and scepticism are not scorned or curbed for political reasons.
This article appears as part of openDemocracys online debate on the politics of climate change. The debate was developed in partnership with the British Council as part of their ZeroCarbonCity initiative a two year global campaign to raise awareness and stimulate debate around the challenges of climate change.