(From a 'climate skeptic' approach):

Climate science is never settled

Geoffrey Kearsley

There's no point ruining the economy pursuing carbon neutrality if carbon is not the main culprit or the climate is on a new trend.

IT IS now pretty much taken for granted that global warming is ongoing, that climate change is being driven by human activity and that it is critically important that fundamental changes be made to our economy and way of life.

On the small scale, people plant trees, examine food miles, purchase carbon offsets and modify travel behaviour.

Cities and even countries vie with one another to become carbon neutral; as a nation, we are contemplating emission controls, taxes and carbon-trading schemes that will have a profound effect on individual households and the national economy.

When linked with the other great crisis of our times — peak oil — it has become not only socially desirable to embrace all of this, but sustainability has achieved the status of a higher morality. It has become politically unacceptable to doubt any of the current dogma.

It is said that we are now beyond the science and that the science of global warming has been finalised or determined and that all scientists agree. Sceptics and deniers are simply cynical pawns in the pockets of the big oil companies. This is unfortunate.

Science is rarely determined or finalised. Science evolves and the huge complexity of climate science will certainly continue to evolve in the light of new facts, new experiences and new understandings.

For example, early in the 1900s, Alfred Wegener proposed that the continents were once joined up; their coastlines seemed to match, there appeared to be great rifts and tears in the continental fabric.

This view was ridiculed; how could the continents move? What possible force could transport the unimaginable mass of Africa or Australia hundreds and thousands of kilometres across the earth? Today, of course, plate tectonics is well understood. We know that continents move and we know the consequences.

Global warming seemed sewn up as well in the year 2000. Michael Mann's hockey-stick graph showed centuries of modest change culminating in an explosive temperature growth in recent decades, leading to terrifying projections of a climate out of control, with the sea rising to drown us all. Al Gore's apocalyptic images of tsunami-like flooding and dying polar bears brought global warming into every home.

Today, the hockey stick has gone. Its basic data was flawed and the statistical processes inadequate; it failed to describe known climate changes from the historically recorded past, so how could it be a reliable predictor? Although Gore received the Nobel Peace Prize, his celebrated documentary has been shown to be riddled with inaccuracies, distortions and misrepresentations; it cannot be shown in British schools without a comprehensive explanation of its mistakes and an acknowledgement that it is advocacy, not science.

There is no doubt that the climate is changing; it always has done. We have become familiar with the regularly repeating glaciations of the past. Human history has mainly occupied an exceptionally warm interglacial peak in a world that, for the last half million years at least, has generally been much cooler, although, in deep time, the world has been much warmer than now.

In the 1970s, climate science was concerned about when the next ice age might commence; we may have to return to that position.

There have been considerably warmer eras in the past couple of thousand years. In both the Roman and medieval warm periods, vineyards flourished as far north as York in England; Greenland was indeed green, at least in parts. By contrast, just 400 years ago, there was a Little Ice Age in America and Europe, at least, that lasted until well into the 1800s. The historic record confirms this.

What we also know, by historical record and by proxy calculation, is that these large swings in temperature closely correlate with the frequency of sunspots, which are a visible indicator of activity in the sun. Sunspots vary in number according to a series of cycles. In periods of high temperature, sunspots proliferated, but during the Little Ice Age, there were few or none for many decades, a phenomenon known as the Maunder Minimum; the last quarter of the 20th century saw a flurry of activity.

The last cycle was at its energetic peak in 1998, our warmest year for some time. The mechanism is unclear, but it seems related to solar magnetic influences and the amount of gamma radiation that reaches the earth. The last 10 years have seen a static or even cooling trend as the sunspot cycle ran down; 2007 saw bitter weather around the world and the mean global temperature dropped by an unprecedented amount. It is not picking up. The Antarctic winter sea ice was at its largest extent since satellite observation began, and it snowed in Baghdad and Buenos Aires for the first time in living memory. China's winter was awful.

And now the scary news. The latest sunspot cycle should have started up around the middle or end of 2006; it didn't. According to NASA's forecasts, there should be a sunspot index of 70 or more, as the new cycle ran up.

I looked at a real-time photo of the sun on a recent morning; there are no sunspots at all. There have only been a couple of brief, tiny ones since the last cycle ended. Not only that, but the longer trends tell us that by 2020, we will be experiencing an unusually low-energy sun. Apparently, these are exactly the conditions that preceded the Maunder Minimum and ushered in the Little Ice Age.

There is much more yet to learn. My point is this: It may well be that human activity is indeed changing the climate, at least in part, but there is an increasing body of science that says that the sun may have a greater role.

If it does have, then global warming is likely to stop, as it appears to have done since 1998, and if the current sunspot cycle fails to ignite, then cooling, possibly rapid and severe cooling, may eventuate. The next five years will tell us a great deal. In these circumstances, we should wait and see.

With China and India churning out new thermal power stations at assembly-line speed, our influence on the global climate is negligible. Surrounded as we are by great oceans, even the alarmist predictions will have relatively minor consequences for us for some time.

We can afford to wait. There is no point in decimating our economy in the pursuit of carbon neutrality if carbon is not the main culprit or if the climate is now on a new trend.

Instead, now is the time to moderate the pseudo-religious and uncritical belief that global warming is still as we once thought it might have been.

Professor Geoffrey Kearsley is a geographer developing a program in environmental communication at the University of Otago in New Zealand.

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