Thursday, October 02, 2008
The solar minimum and what it means for climate change
The Financial Times has rounded up some of the questions that arise from our quiet sun, which has recently produced fewer sun spots than at any time in at least a century. The article is worth reading for the sake of its main subject matter -- it is, after all, hard to imagine a more fundamental subject than the condition of our star -- but also for its acrobatic discussion of the sun's impact on climate change.
First, there is an early paragraph that hints at scientific controversy (emphasis added):
Experts are reluctant to predict the consequences for Earth and its inhabitants because there are so many complex interactions between the Sun’s output, the planet’s atmosphere and magnetic field, and cosmic radiation from outer space. Some climatologists say that, over a period of decades, a quieter Sun means a cooler Earth, although the relationship between solar activity and climate is particularly controversial.
Fine. Students of climate change activism and its critics know that the argument over "solar forcing" is central to the debate over the extent of anthropogenic forcings. This is because the climate models used to forecast climatic disaster, or not, use a "budgeting system," whereby they account for all the energy put into the Earth's system, the energy subtracted from it, and the effects of other influences. From this they calculate that part of the warming in the last half-century which comes from surplus greenhouse gases. Because the anthropogenic global warming is, in effect, the residual that is left over after accounting for all other factors, it is essential that the other factors be measured accurately.
Sadly, the FT never explains why "the relationship between solar activity and climate is particularly controversial." It simply serves up these question-begging paragraphs (emphasis added again):
The relationship between solar variability and climate remains a mystery, says Jamie Casford, a climate researcher at Durham University. While the Sun’s magnetic field and the solar wind change remarkably over the years – the Ulysses satellite measurements show that they are 20 to 30 per cent weaker now than at the last solar minimum in 1996-97 – the accompanying changes in the Sun’s total energy output are tiny.
When the Sun is very quiet, the amount of energy that reaches Earth is only 0.1 per cent less than when it is very active – a change too small to produce significant global cooling on its own. “I would say that solar variability does feed into the climate system but we really do not know what the mechanism is,” Dr Casford says.
There are several theories. A controversial one comes from Henrik Svensmark, a physicist at the Danish National Space Centre in Copenhagen; he believes increased cosmic radiation, hitting the atmosphere when the Sun is quiet, stimulates cloud formation – which cools the planet. Paul Mayewski, director of the University of Maine Climate Change Institute, says the primary impact of solar variability is on atmospheric circulation, which then affects temperature.
Although some people who are sceptical about the human influence on global warming like to emphasise the link between solar variability and climate, Prof Mayewski turns their argument on its head: “The fact that we are not in conditions like the little ice age today shows that the atmosphere is being perturbed by human activities,” he says.
So, let me get this straight:
Call me a bonehead, but I would have thought that these bombshells -- which call into question both the accuracy of the climate models and the quantum of damage done by AGW -- would have warranted some elaboration.
5 Comments:
By 
, at
Thu Oct 02, 12:52:00 PM:
Call me a bonehead as well, and I have been forever on this issue. In fact I am sure that we could somehow, someway be deemed racist for this view as well. Just don't ask me why on the later.
By , at
Thu Oct 02, 01:06:00 PM:
Quite simple.
People who don't believe in AGW = science-hating knuckle draggers
George Bush = person who doesn't believe in AGW = science hating knuckle dragger = racist
Therefore, people who don't believe in AGW = racists
Quite simple, indeed.
By , at
Thu Oct 02, 01:18:00 PM:
Elaboration would show AGW for the fraud it is. Facts should be no obstacle to the spread of official truth.
By , at
Thu Oct 02, 04:19:00 PM:
By 
Brian, at
Sun Oct 05, 02:16:00 AM:
George Bush now believes in AGW.
The point is that the 50-year low in solar wind isn't accompanied by a 50-year low in temps, but rather by temps just a little below the record, in a La Nina-year climate system. So hanging your hat on the idea that solar wind has determined climate change in the last 50 years is a very bad idea.
Mayewski isn't saying that pollution is stopping the ice age, but rather that the fact of no ice age shows the solar wind theory is bunk.
