Space.com has an interesting report on the variability of the solar constant (them scientists are really good with the non-sequiturs).
In what could be the simplest explanation for one component of global warming, a new study shows the Sun's radiation has increased by .05 percent per decade since the late 1970s.Difficult to quantify. I think that represents the current state of climate science in a nut shell. There are a lot of things difficult to quantify given the current state of climate science. Like cloud feedback for instance. We do not know whether clouds are a positive or negative feedback element in the climate equation. Convieniently it is assumed positive and a value is assigned which makes the effect of CO2 more intense.
The increase would only be significant to Earth's climate if it has been going on for a century or more, said study leader Richard Willson, a Columbia University researcher also affiliated with NASA's Goddard Institute for Space Studies.
The Sun's increasing output has only been monitored with precision since satellite technology allowed necessary observations. Willson is not sure if the trend extends further back in time, but other studies suggest it does.
"This trend is important because, if sustained over many decades, it could cause significant climate change," Willson said.
In a NASA-funded study recently published in Geophysical Research Letters, Willson and his colleagues speculate on the possible history of the trend based on data collected in the pre-satellite era.
"Solar activity has apparently been going upward for a century or more," Willson told SPACE.com today.
Further satellite observations may eventually show the trend to be short-term. But if the change has indeed persisted at the present rate through the 20th Century, "it would have provided a significant component of the global warming the Intergovernmental Panel on Climate Change reports to have occurred over the past 100 years," he said.
That does not mean industrial pollution has not been a significant factor, Willson cautioned.
Scientists, industry leaders and environmentalists have argued for years whether humans have contributed to global warming, and to what extent. The average surface temperature around the globe has risen by about 1 degree Fahrenheit since 1880. Some scientists say the increase could be part of natural climate cycles. Others argue that greenhouse gases produced by automobiles and industry are largely to blame.
Willson said the Sun's possible influence has been largely ignored because it is so difficult to quantify over long periods.
A separate recent study of Sun-induced magnetic activity near Earth, going back to 1868, provides compelling evidence that the Sun's current increase in output goes back more than a century, Willson said.So if we have no data or poor data an effect is ignored.
It then means you have to increase your uncertainty bands. By how much?
Well that is uncertain.
Now all this would be academic except we are basing policy decisions on where to spend real money extracted by force by governments based on models that are clearly inadequate.
Cross Posted at Classical Values and at The Astute Bloggers