In my letter published in Saturday's Australian I referred to the more than 30,000 scientists in the US who have signed a petition denying that increased human activity is the principal cause of higher temperatures (it appears 32,000 scientists are now expected to sign). I also referred to two articles published in pro-global warming science journals predicting up to a decade of cooling, which would imply no increase in average global temperature for about 20 years ie since 1998.

Global Temperature – 1975 -2007

Annual average global temperature anomaly (departures from the 1961-1990 mean) based on published data from the UK Hadley Centre.

I have received a number of enquiries for further information about the petition and the two articles. Attached is an article by Lawrence Solomon giving a brief history of the development of the petition by the Oregon Institute of Science and Medicine. At the end of the article I have included the initial section of the web page of that Institute outlining the petition.

The other two articles, which were drawn to my attention by a paleoclimatologist, Mr Bob Foster, are as follows:

"Advancing decadal-scale climate prediction in the North Atlantic sector",

N.S. Keenleyside et al 2008, Nature v 453,1May pp 84-88.

"Mother Nature Cools the Greenhouse, But Hotter Times Still Lie Ahead",

Richard A. Kerr, Science "News of the Week", 2 May 2008 .

Both of these articles are accessible (at a small charge) on the websites of Science and Nature but I have a copy of the Kerr article that I can send to anyone interested. It seems clear they were orchestrated to appear at the same time with the same message. In Nature there are actually 3 pieces on the cooling thesis preceded by the following summary :

“The fluctuating climate of the North Atlantic has profound consequences , including changes in hurricane activity, surface temperatures and rainfall from North America to Europe and Africa. In principle, these changes could be predicted if the current state of the ocean were known, but the necessary subsurface observations are lacking. Keenlyside et al now show that detailed knowledge of the ocean state is not strictly necessary for producing useful predictions on decadal timescales. Their approach, which has proved its worth in ‘retrospective‘ forecasts, uses existing sea surface temperature observations to improve the forecasting power of climate models. The new model predicts that over the next decade, natural climate variations in the North Atlantic and tropical Pacific oceans will temporarily offset the projected anthropogenic warming; surface temperatures in Europe and North America may even cool a little during the period.”

Note that Kerr's article includes the following comments:

“As climate-change skeptics like to point out, worldwide temperatures haven’t risen much in the past decade. If global warming is such hot stuff, they ask, why hasn’t it soared beyond the El Niño-driven warmth of 1998? Mainstream climate researchers reply that greenhouse warming isn’t the only factor at work. And in a new paper, they put some numbers on that rebuttal.

The study ‘shows how natural climate variability can mask the global warming effect of greenhouse gases … but only for a few years.”...“Looking into the future, the model forecasts a slowing of heat-carrying Atlantic currents and thus a cooling over the North Atlantic, North America, and western Europe in the next decade. It even predicts a slight cooling of the globe. But by 2030, forecast global temperatures bounce back up to the warming predicted with greenhouse gases alone.”

The summary of the article by Keenleyside et al is as follows:

"The climate of the North Atlantic region exhibits fluctuations on decadal timescales that have large societal consequences. Prominent examples include hurricane activity in the Atlantic and surface-temperature and rainfall variations over North America, Europe and northern Africa. Although these multidecadal variations are potentially predictable if the current state of the ocean is known, the lack of subsurface ocean observations that constrain this state has been a limiting factor for realizing the full skill potential of such predictions. Here we apply a simple approach - that uses only sea surface temperature (SST) observations - to partly overcome this difficulty and perform retrospective decadal predictions with a climate model. Skill is improved significantly relative to predictions made with incomplete knowledge of the ocean state, particularly in the North Atlantic and tropical Pacific oceans. Thus these results point towards the possibility of routine decadal climate predictions. Using this method, and by considering both internal and natural variations and projected future anthropogenic forcing, we make the following forecast: over the next decade, the current Atlantic meridional overturning circulation will weaken to its long-term mean; moreover, North Atlantic SST and European and North American surface temperatures will cool slightly, whereas tropical Pacific SST will remain almost unchanged. Our results suggest that global surface temperatures may not increase over the next decade, as natural climate variations in the North Atlantic and tropical Pacific temporarily offset the projected anthropogenic warming."

COMMENT: It is difficult to avoid the conclusion even from these summaries that such analyses of climate changes and its causes - which come after the last IPCC report - indicate that the whole analytical exercise is very much work in progress. They also raise the question of whether their acceptance of a cooling period, followed by a later period of resumed warming, is an insurance policy designed to provide a period of protection for scientists (including the IPCC, whose next report won't be until 2014) who have gone out on a limb on the causes of higher temperature - "Yes, temperatures have been falling a little but ...".

However, if there is now likely to be a cool period it behaves the Government to let us know and to (at the very least) postpone the early introduction of action to reduce CO2 emissions..

Finally, it may also be worth noting that yesterday's Age quotes the Melbourne weather bureau as now predicting the coldest winter for a decade, with an excellent snow season. Perhaps our very own weather bureau has accepted the cool period predictions ?