More on sunspots: response to a comment

[slide: before getting thrown by this slide, read the post below ... i'll explain.]

By John Sutter

I think my last post may have left some undue confusion about the role of sunspots in temperatures here on Earth.

The post got this comment from a user who identified himself or herself as "skeptic":

If you plot the average mean temperature variance by decade alongside the average mean sunspot activity, you'll clearly see a correlation. I've plotted this data going back to 1890 and was shocked at how the averages moved in tandem.

I very much appreciate the comment and the opportunity for clarification. While there is some weak correlation between the absence of sunspots -- how blank the sun looks -- and increased temperatures way over here on our planet, the scales of both phenomenons don't match up. The amount of increased energy coming to the Earth from a blanker-looking sun is not nearly powerful enough to account for the increased temperatures that are being observed and projected. Something else has to be at play. Based on physical properties of heat-trapping gases like carbon-dioxide, and the massive quantities at which we're spewing them into the sky, scientists say these industrial emissions are by far the main cause of climate change.

The changes due to a doubling CO2 in the atmosphere (which is what we're doing) causes temperatures to rise 27 times higher than sunspots could account for, according to George Kling, a professor at the University of Michigan.

So, it's definitely a confusing point, but one that makes sense when you think about it. Sunspots can affect global temperatures, but their impact isn't strong enough to account for climate change. Hope that clears it up some. Let me know if you all have further questions. Also, if you have any good articles on this subject, I'd be interested to read them. Feel free to post in the comments section.

The sun is neat, confusing

By John Sutter

Check out these awesome pictures of the sun, from The Big Picture, on the Boston Globe's Web site. Pretty cool.

Of note is the fact that scientists don't know what the deal is sunspots lately. There appear to be fewer of them now than at any time since early in the 1900s. Some climate change skeptics have posited that the sun spots, instead of human emissions of heat-trapping gases, explain warming temperatures. Here's an NYT article about the uncertainty surrounding that claim. Another period of low solar activity coincided with global cooling and an Ice Age:

Scientists are not sure why this minimum has been especially minimal, and the episode is even playing into the global warming debate. Some wonder if this could be the start of an extended period of solar indolence that would more than offset the warming effect of human-made carbon dioxide emissions. From the middle of the 17th century to the early 18th, a period known as the Maunder Minimum, sunspots were extremely rare, and the reduced activity coincided with lower temperatures in what is known as the Little Ice Age.

A University of Michigan scientist I spoke with last week said that linking climate change to sunspots is misleading and irresponsible because the scale of the effects are so different and because sunspot patterns vary wildly over short periods of time. It's clear that heat-trapping gases emitted by our industries are to blame for climate change, he said.