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The Forum > Article Comments > The temperature trend is not as simple as Garnaut makes out > Comments

The temperature trend is not as simple as Garnaut makes out : Comments

By Tom Quirk, published 14/6/2011

Professor Garnaut's latest report relies heavily on a temperature trend which is not as solid as he says.

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A good contribution Tom, and in my view you raise some important questions.

I suggest that there are three fundamental questions underlying the carbon tax 'debate' that have not been addressed sufficiently.

1. Is warming happening? It is clear that there is some warming. But the question of how much is affected by clear evidence of manipulation of the data - unexplained 'adjustments' to the temperature series, unexplained changes in the population of temperature stations included in the temperature series, and general ignoring of delta UHI effects over time. There is likely modest warming happening, but how much?

2. What is the cause of the warming? The climate scientists and the politicians appear convinced that anthropogenic CO2 emissions are the cause of warming, but the evidence for this is far from clear. Roger Pielke Sr argues that man is having an impact on local and regional climate, but through land-use factors such as deforestation, urbanisation etc. There is a case that anthropogenic CO2 is a minor factor. Natural factors are highly likely to be important.

3. What can we do to moderate warming? A tricky question, especially if (as seems likely) the case for anthropogenic CO2 being the cause of the warming is not strong. What is the point of going to great trouble to reduce CO2 emissions if that isn't the main cause.

I would much rather my tax dollars be addressed at these fundamental questions. They have never been satisfactorily addressed in the public sphere. To press on with the CO2 tax is to put the cart before the horse.
Posted by Herbert Stencil, Tuesday, 14 June 2011 7:57:12 AM
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There are liars, damn liars and statisticians!

David
Posted by VK3AUU, Tuesday, 14 June 2011 8:29:15 AM
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Prof Garnaut is an economist and that makes him very qualified to know everything about climate,doesn't it?
Posted by Arjay, Tuesday, 14 June 2011 9:20:25 AM
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Tom Quirk makes some valuable points with his analysis, however, there has been too much emphasis on whether there has been a warming trend or not. Clearly temperatures increased between mid-70s and the end of the century and then basically flat lined. Nothing much has happened between 1998 and now except that temperatues have been pulled up and down by La Nina and El Nino effects. A La Nina has pulled down temperatures in recent months

Any forecast can only be judged on what it forecast and the first IPCC forecast was in 1990. By any fair reading of that forecast, temperatures should have increased by a MINIMUM of 0.4 degrees. The Hadley graph puts the actual increase at 0.2 degrees.
The IPCC reports in 2000 and 2007 also forecast increases which again don't seem to have happened.

Prof Garnaut should know better than to make public policy recommendations on climate models that have such a limited forecasting track record to date.
Posted by Curmudgeon, Tuesday, 14 June 2011 11:25:58 AM
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I think that on balance, it should be admitted that the long term trend of temperature is upward, even at a slower rate than has generally been predicted. One only has to look at the physical evidence of melting glaciers all around the world as well as the reduction in the amount of polar ice from year to year.

David
Posted by VK3AUU, Tuesday, 14 June 2011 11:50:59 AM
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I think one can agonise too much about the detailed meaning and statistical analysis of the graphs Tom Quirk presents. And given that we now have two sceptical contributors to these forums, of whom one (Tim Curtin) trusts only econometric analysis and the other, Tom Quirk, does not, I would suggest that anything beyond simple eyeballing is trying to do too much with the data.

The rolling 13 month average of the actual global temperatures in the bottom part of Figure 1, which is the usual method of applying a degree of smoothing to the data, looks to my eyeballs like a pretty convincing example of what one would expect to see for a steady slow temperature rise superimposed on the normal random fluctuations of climate. Only someone who does not wish to believe that simplest interpretation would bother to go further.

I think that the most fascinating aspect of the temperature data is that the same graph is used to support two completely contradictory statements about temperature trends. One group looks at it and insists there has been ‘no global warming since 1998’. The other says, as I do, that global temperatures continue on their upward trend. Remarkably, both statements can be right, depending on where your eyes rest. It’s that pesky peak in 1998 that’s the problem. However, my eyeballs have no trouble in seeing a long term upward trend as by far the more reasonable interpretation. Another 10 years or so will put 1998 into proper perspective and will almost certainly remove this little fragment of evidence from the sceptics’ armoury.
Posted by Tombee, Tuesday, 14 June 2011 12:02:37 PM
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