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On global warming, public policy is where the science was in 1998. Due to new evidence, science has since moved off in a different direction.

The UN science body on this matter, the IPCC, is a political body composed mainly of bureaucrats. So far it has resisted acknowledging the new evidence. But as Lord Keynes famously asked, "When the facts change, I change my mind. What do you do, sir?"

Four things have changed since 1998.

First, the new ice cores shows that in the six global warmings over the past half a million years, temperature rises and falls occurred on average 800 years before the accompanying rises and falls in atmospheric carbon. The carbon rises could not have either started or ended the temperature rises. So there must be natural influences on global temperatures that are more powerful than atmospheric carbon levels.

This 800 year lag became known and past dispute by 2003, which is significant. The old ice core data, collected from 1985 to 1998, was low resolution: the data points were more than a thousand years apart. It showed carbon and temperature moving in lockstep, and it was the only supporting evidence we ever had for the notion that carbon caused temperature. It seemed too good to be true—it appeared we could control the temperature of the planet just by adjusting the levels of a minor gas!

Watch Al Gore’s movie carefully. The old ice core data is the only evidence he presents for believing that carbon emissions cause global warming. But by 2003 we had found the 800 year lag, so then we knew that temperature caused carbon, not the other way around as previously assumed. Al Gore’s movie was made in 2005 so it was misleading of him not to mention the new ice core data. Would anyone have believed his pitch if he had mentioned that the alleged cause (rising and falling carbon levels) happened 800 years after the effect (rising and falling temperatures)?

Secondly, with the reversal of the ice core evidence, there is now no evidence that carbon emissions cause significant global warming. None.

Evidence is a set of observations by people of events. The scientific method demands evidence—theory, politics, and vested interests are all trumped by evidence. The scientific method evolved as our best method for obtaining reliable information, precisely because it was immune from forces such as power and superstition.

It is important to realize what is not evidence that carbon emissions cause global warming. There is ample evidence that global warming has occurred, but it says nothing about the causes of that warming. Serious theoretical calculations for the amount of warming by 2100 range from an inconsequential 0.24°C to a catastrophic 6.2°C, but theory (including computer models) is not evidence. Comparison of model outputs to observed results is not evidence, because it cannot prove that the model is always right, only that it was right in that instance. Existing computer models treat clouds simplistically and unrealistically, and omit the effects of cosmic rays on clouds, so we cannot begin to be confident that they might approximate reality.

Western governments have spent $50b on global warming since 1990, yet have found no evidence. We are constantly bombarded with evidence that the world has warmed. Don’t you think we would have heard all about any evidence that carbon emissions cause global warming, if there was any?

Thirdly, the warming trend that started in 1975 ended in 2001. The global temperature has been flat since 2001, and has dipped sharply in the last few months. The warmest recent year was 1998. This is a very different picture from that presented by the IPCC in 2001, of overpowering warming due to carbon emissions for the foreseeable future. Obviously there is some other influence on global temperatures at work, more powerful than our carbon emissions. The IPCC are silent on what those causes might be (hint: probably something to do with clouds).

So why do some people say temperatures are still rising, apart form being out of date? Satellite data is the only temperature data we can trust, but it only goes back to 1979. The satellites go around 24/7, measuring the temperature across broad swathes of the world, everywhere except the poles. Three of the four world temperature records use satellite data partly or exclusively, and they all say that the world stopped warming in 2001 and that temperatures have recently dipped.

NASA GISS, the home of the global warming scare, only uses land based thermometers (and a few ocean thermometers)—despite being a space agency. Land thermometers are housed in little boxes a few feet off the ground. They were mainly put in place decades ago, on the outskirts of towns or cities so it was convenient to go and read the temperature each day. But urban growth has changed the microclimate around many of these thermometers, due to concrete, asphalt, vegetation changes, houses, air conditioners, and so on. In contrast to the satellite data, NASA GISS reports a continued warming trend since 2001. But their data is likely just measuring urban growth around some of their thermometers.

Fourthly, we looked for the greenhouse signature and could not find it. Each possible cause of global warming heats the atmosphere in a different pattern. Increased greenhouse warming causes a hotspot 10 km up over the tropics. The hotspot is central to our understanding: if there is no hotspot then either there is no significant increased greenhouse warming, or we don’t understand greenhouse and all our climate models are rubbish anyway.

Decades of measurements with thermometers in weather balloons have been unable to find even a small hotspot. So we now know for sure that carbon emissions are not a significant cause of the recent global warming. I would switch back to being an alarmist if we had found a strong greenhouse signature. (By the way, our carbon emissions have no doubt caused some underlying warming, but not enough to create a hotspot that we have been able to detect so far.)

These four changes have rendered our current debate over carbon emissions obsolete. The changes occurred slowly as the science on each item became more settled, so there was no sudden news flash to make us sit up and take notice.

But now that we are finally coming to terms with how exp ensive it will be to cut back our carbon emissions, the causes of global warming have suddenly become a topic of major economic importance.

Policy makers must grapple with the possibility that global temperatures don’t rise over the next decade, and that the recent rises were predominately not due to our carbon emissions. Deliberately wrecking the economy for reasons that later turn out to be bogus hardly seems like a recipe for electoral success. 

Obviously the onus is on the Government to clearly set out the evidence for believing carbon emissions are the main cause of global warming before embarking on an ETS.

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