March 8, 2008

"The sun is the primary driver"

Alan Sullivan has posted a very long piece on Climate. He's a weather-nut, has been studying this for a lifetime, and knows a lot. Well worth reading...

....But why are ice ages occurring now, and why at other times in earth’s history, has warmth predominated, with only a few previous cycles of widespread glaciation? At last the information from the various sciences offers a coherent explanation of paleoclimate, with which we can better understand the present, and take more educated guesses at the future.

There is one essential truth to emphasize: the sun is the primary driver. All other factors affecting climate are trivial in comparison, though sometimes they may briefly override the solar homeostasis. Virtually all Earth’s thermal energy derives from the sun; only the tiniest traces leach from the planet’s interior. But the sun’s output is not perfectly constant. Its immense thermonuclear furnace fluctuates, with short-term and long-term cycles. We scarcely understand the former, and the latter we don’t understand at all.

Our time-line of sophisticated solar study is very brief. Only in the last few years have instruments been deployed that can probe the sun’s innards more precisely. Even with super-computers, scientists will need some time to integrate the new information into theories that might help us comprehend Sol’s long-term behavior, and its peculiar short-term changes.

The first solar cycle known to astronomers was the sun-spot cycle, which was found to peak at eleven-year intervals. We have decent records of sunspot count going back to the 1500’s. They show something very odd: the Maunder minimum. During the 1600’s, the sunspot cycle collapsed, and hardly any sunspots were observed for the better part of a century. Then the cycle resumed and gradually sharpened. The peaks of the Twentieth Century appear to be the highest in the record, even when weighted for the limitations on the older counts.

The Little Ice Age happened during the Maunder Minimum. Europe and other parts of the world suffered crop failures and food crises. Winters were fierce; snows deep; ice covered the rivers; and we inherited pretty paintings of people ice-skating on canals of the Netherlands. This is not a coincidence. Solar radiance peaks with the flares that accompany sunspots. When solar storms quit entirely for decades on end, Earth’s energy balance changes. There is less input from the primary driver. The effects come promptly, and pass when the sunspot cycle resumes.....
Posted by John Weidner at March 8, 2008 7:41 PM
Weblog by John Weidner