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Dr. David Evans

Show us the Evidence!

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I devoted six years to carbon accounting, building models for the Australian Greenhouse Office. I am the rocket scientist who wrote the carbon accounting model (FullCAM) that measures Australia’s compliance with the Kyoto Protocol, in the land use change and forestry sector. FullCAM models carbon flows in plants, mulch, debris, soils and agricultural products, using inputs such as climate data, plant physiology, and satellite data. I’ve been following the global warming debate closely for years.

When I started that job in 1999 the evidence that carbon emissions caused global warming seemed pretty good—CO2 is a greenhouse gas, the old ice core data, no other suspects. The evidence was not conclusive, but why wait until we were certain when it appeared we needed to act quickly? Soon government and the scientific community were working together, and lots of science research jobs were created. We scientists had political support, the ear of government, big budgets, and we felt fairly important and useful (well, I did anyway). It was great. We were working to save the planet!

But since 1999 new evidence has seriously weakened the case that carbon emissions are the main cause of global warming, and by 2007 the evidence was pretty conclusive that carbon plays only a minor role and is not the main cause of the recent global warming. As Lord Keynes famously said, When the facts change, I change my mind. What do you do, sir?

There has not been a public debate about the causes of global warming and most of the public and our decision makers are not aware of the most basic salient facts:

1. The greenhouse signature is missing. We have been looking and measuring for years, and cannot find it.

Each possible cause of global warming has a different pattern of where in the planet the warming occurs first and the most. The signature of an increased greenhouse effect is a hotspot about 10 km up in the atmosphere over the tropics. We have been measuring the atmosphere for decades using radiosondes—weather balloons with thermometers that radio back the temperature as the balloon ascends through the atmosphere. They show no hotspot whatsoever. Not a little hotspot, but none at all.

If there is no hotspot then an increased greenhouse effect is not the cause of the global warming. So we now know for sure that carbon emissions are not a significant cause of the global warming. If we had found the greenhouse signature then I would be an alarmist again.

When the signature was found to be missing in 2007 (after the latest IPCC report), alarmists objected that maybe the readings of the radiosonde thermometers might not be accurate and maybe the hotspot is there but went undetected. Yet hundreds of radiosondes have given the same answer, so statistically it is not possible that they missed the hotspot. Recently the alarmists have suggested we ignore the radiosonde thermometers, but instead take the radiosonde wind measurements, apply a theory about wind shear, and run the results through their computers to estimate the temperatures. They then say that the results show that we cannot rule out the presence of a hotspot. If you believe that you believe anything.

2. There is no evidence to support the idea that carbon emissions cause significant global warming. None.

There is plenty of evidence that global warming has occurred, and theory suggests that carbon emissions should raise temperatures (though by how much is hotly disputed), but there are no observations that implicate carbon emissions as a significant cause of the recent global warming. The world has spent $50b on global warming since 1990, and we have not found any actual evidence that carbon emissions cause global warming. Evidence consists of observations made by someone at some time that support the idea that carbon emissions cause global warming. Computer models and theoretical calculations are not evidence, they are just theory.

3. The satellites that measure the world’s temperature all say that the warming trend ended in 2001, and that the temperature has dropped about 0.6C in the last year (to the temperature of 1980). Land based temperature readings are corrupted by the ‘urban heat island’ effect—urban areas encroaching on thermometer stations warm the micro-climate around the thermometer, due to vegetation changes, concrete, cars, houses. Satellite data is the only temperature data we can trust, but it only goes back to 1979. NASA report only land based data, and report a modest warming trend and recent cooling. The other three global temperature records use a mix of satellite and land measurements, or satellite only, and they all show no warming since 2001 and a recent cooling.

4. The new ice cores shows that in the past six global warmings over the past half a million years, the temperature rises occurred on average 800 years before the accompanying rise in atmospheric carbon. Which says something important about which was cause and which was effect.

None of these four points are controversial. The alarmist scientists agree with them, though they would dispute their relevance.

The last point was known and past dispute by 2003, yet Al Gore made his movie in 2005 and presented the ice cores as the sole reason for believing that carbon emissions cause global warming. In any other political context our cynical and experienced press corps would surely have called this dishonest and widely questioned the politician’s assertion.

Until now the global warming debate has merely been an academic matter of little interest. Now that it matters, we should debate the causes of global warming.

So far that debate has just consisted of a simple sleight of hand: show evidence of global warming, and while the audience is stunned at the implications, simply assert that it is due to carbon emissions. In the mind of the audience, the evidence that global warming has occurred becomes conflated with the alleged cause, and the audience hasn’t noticed that the cause was merely asserted, not proved. If there really was any evidence that carbon emissions caused global warming, don’t you think we would have heard all about it ad naseum by now?

Labour Governments in Australia and New Zealand are about to deliberately wreck their economies in order to reduce carbon emissions. If the reasons later turn out to be bogus, the electorates are not going to re-elect those Labour parties to government for a long time. When it comes to light that the carbon scare was known to be bogus in 2008, the Labour parties are going to be regarded as criminally negligent or ideologically stupid for not having seen through it. And if the Oppositions support the general thrust of their actions, they will be seen likewise. The onus should be on those who want to change things to provide evidence for why the changes are necessary. The public is eventually going to have to be told the evidence anyway, so it might as well be before wrecking the economy. It is the job of our opposition politicians and press to demand the evidence from their governments.

And what is going to happen over the next decade as the global temperature continues not to rise? When the public find out that all the above points were known in 2008, might they feel deceived, furious at the futility of the economic sacrifices?

Who is going to be held responsible? Perhaps the political class, for not having the wit to examine the evidence? Maybe the press, for not have not done even the most elementary job of informing a debate and asking questions? (If any of the missing signature, the lack of actual evidence, the lack of temperature rises since 2001, or the 800 year lag of CO2 in the ice cores are news to you, then no, your press has not been keeping you well informed.)

Don’t you think some evidence is required before wrecking the economy? Someone simply has to demand to see evidence. You will find that there is none.

Further research:

The Missing Greenhouse Signature

Links to Evidence


A slightly shorter version of this article appeared in The Australian newspaper on Friday 18 July 2008.