In an interesting article in New Scientist magazine (16 September 2006), Stuart Clark looks at evidence that the sunspot activity may strongly influence the Earth’s warming and cooling cycles. When sunspot activity is high, global temperatures go up. When sunspot activity is low, little ice ages occur.
In fact, the first evidence of the role of sunspots came as researchers noticed that periods of extremely low sunspot activity corresponded to two recent mini Ice Ages: the Little Ice Age of the late 1600s – when the Thames regularly froze over, and you could walk from Manhattan to Staten Island during the winter - and a similar period from the mid 14th to mid 15th centuries.
Turns out there is a boom-bust sunspot cycle with a duration of about 200 years or so where periods of high sunspot activity are followed by a crash. We’ve been in a high-activity period for a while now, but activity levels are the lowest they’ve been in 50 years. We’re about due for a crash.
Don’t pull out the extra winter coats just yet, though. Recent sunspot activity and global temperatures were pretty well correlated until 1970 or so, an indicator that human-generated warming has overwhelmed the sunspot cycle’s influence. Best guess: a sunspot activity crash might cool off the planet by about 0.2 degrees Centigrade. And these sunspot lulls don’t last that long – in 50 to 100 years, the sunspots will be back as strong as ever.
At best, we might get a little breathing room, a little extra time for the politicians to quit being political and start being leaders. A little extra time to overcome the economic inertia and get serious about reducing greenhouse gas emissions.
At worst, a “natural cycle” slowdown in global warming will give the naysayers just the ammunition they need to stonewall our efforts for another 50 years – so that when the sun rejoins the global heating party we’re even worse off than we are today.