Duck Season

Finally took the time to find all the relevant links. Previous post here.

Almost all scientists acknowledge that the earth has been getting warmer recently. But for global warming to be a problem about which something should be done, all of the following must be true:

1. The earth has been consistently getting warmer, not just recently.
2. The source of this warmth is human activity.
3. The warmth comes from a greenhouse effect.
4. Global warming is harmful overall.
5. Humans can prevent global warming by changing their behavior.

Now some of these points are in dispute. First, a recent study shows that the earth was warmer than it is now in the Middle Ages:

Claims that man-made pollution is causing "unprecedented" global warming have been seriously undermined by new research which shows that the Earth was warmer during the Middle Ages.

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This announcement followed research published in 1998, when scientists at the Climatic Research Unit at the University of East Anglia declared that the 1990s had been hotter than any other period for 1,000 years.

Such claims have now been sharply contradicted by the most comprehensive study yet of global temperature over the past 1,000 years. A review of more than 240 scientific studies has shown that today's temperatures are neither the warmest over the past millennium, nor are they producing the most extreme weather - in stark contrast to the claims of the environmentalists.

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The findings prove that the world experienced a Medieval Warm Period between the ninth and 14th centuries with global temperatures significantly higher even than today.

They also confirm claims that a Little Ice Age set in around 1300, during which the world cooled dramatically. Since 1900, the world has begun to warm up again - but has still to reach the balmy temperatures of the Middle Ages.

The timing of the end of the Little Ice Age is especially significant, as it implies that the records used by climate scientists date from a time when the Earth was relatively cold, thereby exaggerating the significance of today's temperature rise.

According to the researchers, the evidence confirms suspicions that today's "unprecedented" temperatures are simply the result of examining temperature change over too short a period of time. (Via Robert Musil)

And it turns out that some of the warming of the earth is caused by the sun:

Humans may be shouldering too much of the blame for global warming, according to a new look at data from six sun-gazing satellites. They suggest that Planet Earth has been drenched in a bath of solar radiation that has been intensifying over the past 24 years--an increase of about 0.05 percent each decade. If that trend began early last century, it could account for a significant component of the climatic warm-up that is typically attributed to human-made greenhouse gases, says Richard C. Willson of Columbia University's Center for Climate Systems Research in Coronado, Calif. Willson concedes that the climate's sensitivity to such subtle solar changes is still poorly understood, but the evidence merits keeping a close eye on both the sun and humans to better gauge their relative influences on global climate. "In 100 years I think we'll find the sun is in control," he says. His team's report appears in the March 4 Geophysical Research Letters. (Via Zonitics)

This is supported by the fact that Mars is getting warmer too, and I'm quite sure humans don't have anything to do with that:

The March 2003 Astronomy has an article by Peter Thomas titled, "Mysteries of the Martian Poles." Among the other interesting aspects of the article is the repeated mention that the polar ice caps "are receding at rates up to 15 feet (4 meters) a year."

Lately, high temperatures in Europe is taken as a sign of global warming. Bjorn Lomborg, author of the Skeptical Environmentalist, in an op-ed today in the Telegraph, says not so fast:

... it is simply not correct to claim that global warming is the primary explanation of the kind of heatwave we are now experiencing. The statistics show that global warming has not, in fact, increased the number of exceptionally hot periods. It has only decreased the number of exceptionally cold ones. The US, northern and central Europe, China, Australia and New Zealand have all experienced fewer frost days, whereas only Australia and New Zealand have seen their maximum temperatures increase. For the US, there is no trend in the maximum temperatures - and in China they have actually been declining.

Having misidentified the primary cause of the heatwave as global warming, we then tend to make another mistake: we assume that as the weather gets warmer, we will get hotter and more people eventually will die in heatwaves. But, in fact, a global temperature increase does not mean that everything just becomes warmer; it will generally raise minimum temperatures much more than maximum temperatures.

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If the goal is to reduce our vulnerability to extreme weather, limiting carbon emissions is certainly not the most cost-effective way.

In the Kyoto Protocol, industrialised countries have agreed to cut carbon dioxide emissions by 30 per cent by 2010. This will be very expensive and will only have a negligible effect. Estimates from all macro-economic models show a global cost of $150 billion-$350 billion every year. At the same time, the effect on extreme weather will be marginal: the climate models show that Kyoto will merely postpone the temperature rise by six years from 2100 to 2106. (Via The Corner)

We know that predictions for the temperature of the earth based on the greenhouse effect have always been wrong. An adjustment to the greenhouse effect theory also takes into account the role of aerosols of smoke. According to this revision, the reason why predictions about temperature based on the greenhouse effect are wrong is that aerosols masks the effects of the greenhouse effect:

Smoke is clouding our view of global warming, protecting the planet from perhaps three-quarters of the greenhouse effect. That might sound like good news, but experts say that as the cover diminishes in coming decades, we are in for a dramatic escalation of warming that could be two or even three times as great as official best guesses.

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IPCC scientists have suspected for a decade that aerosols of smoke and other particles from burning rainforest, crop waste and fossil fuels are blocking sunlight and counteracting the warming effect of carbon dioxide emissions. Until now, they reckoned that aerosols reduced greenhouse warming by perhaps a quarter, cutting increases by 0.2 °C. So the 0.6 °C of warming over the past century would have been 0.8 °C without aerosols.

But the Berlin workshop concluded that the real figure is even higher - aerosols may have reduced global warming by as much as three-quarters, cutting increases by 1.8 °C. If so, the good news is that aerosols have prevented the world getting almost two degrees warmer than it is now. But the bad news is that the climate system is much more sensitive to greenhouse gases than previously guessed.

Sounds like bad new, but Iain Murray (from the Volokh link above) has another perspective:

The original short Perspectives piece in Science magazine the workshop was based on had said that this might mean either that the earth’s temperature is more naturally variable than thought or that the climate is more sensitive to forcing than thought. The Berlin workshop settled on the latter, and produced the prediction that, when sulfate aerosol production wanes, the earth might warm between 7-10° C. based on the IPCC’s worst-case scenario. The worst-case scenario is based on the improbable idea that the entire world will raise itself to the economic output levels of the United States.

New Scientist admits that the calculations on which these dire predictions were “back-of-the-envelope” figures. Despite this extreme uncertainty, Will Steffen of the Swedish Academy of Sciences was quoted as saying that “the message for policy makers is clear: ‘We need to get on top of the greenhouse gas emissions problem sooner rather than later.’”

This is a perfect illustration of the way the greenhouse theory is manipulated. The base theory suggests warming that isn't happening to the extent it should. Science then suggests something else. A new theory is produced, or an old one updated, to make the new data fit with the base theory. Worst-case scenarios are dreamed up and promulgated, normally worse than before. Action is then demanded now from policy-makers to avert the worst-case scenario.

All this seems to fit Thomas Kuhn's idea of paradigms in science. In The Structure of Scientific Revolutions, Kuhn argues that science advances not by a slow addition of facts and discoveries, but by a rise and decline of overarching paradigms. Scientists abide by a paradigm in a field of science, and work to solve the minor problems, the facts that do not fit in with the paradigm. Usually scientists solve these problems by making slight adjustments and additions to the paradigm, but other problems go unsolved, and they accumulate. Eventually, scientists acknowledge that the existing paradigm has major problems, and the field of science is in crisis, until someone proposes a new paradigm, a new way to organize known facts within a new theory. If other scientists find that the new paradigm is able to solve the problems left unsolved by the old paradigm, they will become adherents of the new paradigm.

Global warming by greenhouse effect seem to be in the stage where unsolved problems keep cropping up. Perhaps scientists who adhere to this theory will find the solution to these problems and show the theory conclusively to be correct, but right now, we just do not know.

POSTSCRIPT The following is purely anecdotal, so I decided not to put it in the main post, but it is too funny not to be included. The European Union missed it target for greenhouse emissions last winter. The reason--it was too cold:

European Union greenhouse gas emissions rose for the second year running in 2001, the European Environment Agency said Tuesday in its annual report on the bloc's strategy to curb global warming.

Ten of the EU's 15 states overshot national targets, increasing total emissions by 1 percent in the last year for which data is available.

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The EEA says the latest increase is due to a cold winter in many EU countries, higher emissions from the transport sector and greater use of fossil fuels in electricity production. (Via Clayton Cramer)