Thursday, 15 May 2008

Climate doing what the experts said it would, part II

There's been some fuss about the supposed tailing off in global warming. This is, of course, a favourite topic of the deniers, who regularly recite that the Earth has been cooling since 1998 (not true (1)). Recently, they've been given fresh ammunition following a study (2) suggesting that the Earth global temperatures may remain stable until 2015 (2).

I don't know if the studies are valid or not. That's for climateologists to work out. The reaction has been predictable, of course. The qualified comments of the report are immediately re-interpreted as certainty, and the essential point - that the combination of several cooling cycles (low solar activity, la Nina and so on) are being held in check by the influence of anthropogenic global warming - is missed.

That last bit is the most important. Sometimes the Earth gets hot, due to various nartural factors. Other times, it gets cool due to various natural factors. Right now, the latter should be happening - there is low solar activity, natural climate cooling through la Nina and the meridional overturning circulation (3) - but instead the temeprature is being held in status. Instead of being pushed back, we're virtually motionless, while anthropogenic climate change strives to shove us one way, natural cooling tries to force us another. As long as they are in opposition, the temperature will remain stable - but the natural cooling cycles are short term. When they switch back to warming tendencies, then the statis will be resolved and we can expect temperature to rise rapidly as AGW and natural warming work in unison, rather than opposition.

Or, to look at it in simple arthmetical terms:

If there were no AGW, then the equation would look like this:

0 -2 = -2 (Natural cooling, unmitigated by any other factors, reduces the global temperature.)

Instead, we have this situation:

2 - 2 = 0 (The current situation, where the balance between AGW and natural cooling cancel each other. Temporary statis is achieved.)

And we can look forwards to this once the cooling cycle reverses:

2 + 2 = 4 (Where AGW and natural heating complement each other)
Simple enough for yah?

Another tactic that the deniers are deploying is undermining the reliablity of climate models. Looking back through the archives of Real Climate (4), I was delighted to find an examination of how well the earliest modelings of likely warming, from the late 80s, have proven to be accurate (5). This was based on Hansen's modelling in 1988 - so that's 20 year old data that's proved robust:

Best of all, however, the B and C scenarios Hansen prepared (B being the one he identified as most likely to occur) both indicated a plateau in global temperature between 2005-2020 (scenario C) and 2010-2020 (Scenario B). Which is pretty impressive, really, given that the limitations on the models and computing power, and climate knowledge and resourcing, available back then.

So, basically, the climate is doing pretty much what the experts said it would. Not just as the Hadley Centre (6) predicted last year, but as they said it would back in the 1980s. Expect to hear the scratching of denier-Ostriches burying their heads in the sand.

1 - As described previously on lefthandpalm:
2 - "Global warming may 'stop', scientists predict," by Charles Clover in The Telegraph, 30th of April, 2008. (
3 - No, I'd never heard of it before, either.
4 -
5 - 'Hansen’s 1988 projections,' by Gavin Schmidt, posted on Real Climate blog, 15th of May, 2007. (
6 - 'Ten-year climate model unveiled,' unattributed BBC article, 9th of August, 2007. (

1 comment:

Anonymous said...

The real cooling has yet to begin.

Still at the minimum, two years late...

And yes, the earth does revolve around the sun and climate change does not cause solar variance, as the Sacred Consensus would say.

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