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A climate model for every season

By Mark S. Lawson - posted Friday, 25 September 2009

Anyone paying attention to developments in the scientific debate on global warming will have realised that the global warming side has largely admitted that global temperatures have been declining over the past decade.

But having admitted to this point, albeit indirectly and reluctantly, the resulting strenuous efforts to explain away the inconvenient lack of warming has resulted in at least two or possibly three different stories. To make the issue more confusing for global warmers, one of those explanations includes an extraordinary admission by an ardent pro-warming scientist that the decline in temperatures may continue for decades thanks to a major climate cycle going into a cooling phase.

These developments - plus some recent advances - have collectively delivered a major blow to the CO2-based models for forecasting climate conditions which have dominated the debate.


Let us look at the different stories. Readers will recall that Family First Senator Steve Fielding recently returned from a conference in the US to declare that some scientists are saying earth’s climate is driven by “solar flares” (actually he meant solar activity or solar magnetic activity), and convened a debate between sceptical scientists and those who supported the government’s climate legislation.

This is not to rehash that debate but point to a part of the response by the government scientists. See Environment Minister Penny Wong’s response in full.

Here is an extract:

The observational evidence clearly indicates that the climate system has continued to warm since 1998. During this period ocean heat content has risen, ice and snow have continued to melt, and there has been no material trend in global air temperatures.

When changes in surface air temperature are considered, it is important to note that at time scales of around a decade, natural variability can mask the atmospheric warming trend caused by the increasing concentration of greenhouse gases. For example, global average surface temperatures clearly increased between 1975 and 2008 but some shorter periods, such as 1981-1989, showed no warming. Such behaviour is consistent with the outputs of climate models such as those assessed by the IPCC.

So, although we still have global warming the story has changed. Instead of increases in air temperatures and tipping points just around the corner we should be looking at ocean temperatures. Also note that in the decade chosen as an illustration of a temporary lack of warming, 1981-1989, temperatures were in fact increasing. They have been declining since 1998 (the response says “no material trend”).

The response also includes some graphs which supposedly show that the oceans are warming but are unsourced. The sceptics later grumbled they had to guess which paper the graph came from and pointed to three other papers which don’t show warming in the oceans. However, the argument need not detain us, because the government scientists are quite right to point out that natural variations over a decade can mask other forces at work but, if so, what causes those natural variations? When are they likely to end? How do we know that the increase between the mid-70s and the beginning of the century was not also a natural variation? The IPCC, incidentally, declared in its 2007 report (PDF 4.01MB) that all the global temperatures changes up to 1940 are natural.


Another reason not to bother with the details of the argument is that there are other, quite different explanations from the pro-warming side. Judith L. Lean, of the Naval Research Laboratory in Washington and David H. Rind of NASA’s Goddard Institute for Space Studies, a bastion of the IPCC, recently published a paper forecasting temperature increases for the next two decades. The paper suggests that there will be warming at twice the rate forecast by the IPCC, but it also concedes that natural variations will mess up the forecast. The scientists say, “This lack of overall warming (in the forecasts) is analogous to the period from 2002 to 2008 when decreasing solar irradiance also countered much of the anthropogenic warming”. In other words, according to this lot the sun is the problem. They don’t say anything about oceans.

Not happy with that story? Another is given by Mojib Latif of the Leibniz Institute of Marine Sciences at Kiel University, Germany. As noted in the story on the New Scientist website, Latif, a climate modeller and most certainly not a climate sceptic, concedes that part of the warming between 1975 and the end of the century may have been due to a climate cycle known as the North Atlantic Oscillation (NAO). In a speech at the World Climate Conference in Geneva in September, called by the World Meteorological Organisation, Latif also concedes that as the NAO was in a cooling phase temperatures would cool for the next few years.

Now we are back to the oceans and they are in a cooling phase, rather than warming up. This is a consensus? This is settled science?

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About the Author

Mark Lawson is a senior journalist at the Australian Financial Review. He has written The Zen of Being Grumpy (Connor Court).

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