The Sciences

Here comes the Sun… again

Bad AstronomyBy Phil PlaitFeb 27, 2008 11:00 PM


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For some reason, people want to blame the Sun for global warming. This, despite there being no evidence for it, and plenty of evidence against it.

The latest round was brought to my attention from DarkSyde, a science blogger at DailyKos. In an article he put up last night, he notes that an online mag called Daily Tech has a blogger who is claiming that last year was cooler than average... which contradicts a study by NASA's Goddard Institute for Space Studies that shows that last year was among the hottest on record. Which one is right? Duh. NASA. The Daily Tech columnist evidently confused a below-average January temperature for an entire year's worth. Oops. He also quotes anecdotal data about places having cooler than normal weather. While he acknowledges this is only anecdotal data (though it's his biggest paragraph in the story), he forgets that scientists have been saying for years now that global warming does not mean every place on Earth gets hotter. Some places get colder, much colder. The weather patterns changes, and arctic air can be brought down to areas on the planet that don't usually get them. Ironically, a few years ago global-warming deniers tried to frame the debate by changing the phrase "global warming" to "climate change", because it sounds less threatening. It's ironic because it probably is a better term: the climate is changing. It's getting hotter in some places, colder in others. Wetter in some places, drier in others. In some ways I wish it were as a simple as things warming up. It's not. We depend critically on huge areas of this planet being stable and capable of supporting crops. Ask a Kansas farmer what happens when it doesn't snow all winter, or a citrus grower in California what happens when it gets unusually cold. The Daily Tech article is very misleading -- even plain old wrong -- and that hurts the rational discourse on this topic... especially when garbage hounds like Matt Drudge pick up on it, as he did on his website today. The comments on the Daily Tech article are full of errors, too: several people are saying it's the Sun causing this climate change. That is utter baloney. Let me make that clearer: BALONEY. I wrote about this extensively in my upcoming book, so I talked to quite a few solar astronomers about this very topic. In general the solar output varies very little over the course of a year, less than 1%. Over the whole sunspot cycle, though, it's a little more complicated. The sunspots darken the Sun by about 1%, but they are surrounded by regions called faculae, which are actually brighter in the visible and ultraviolet. So when the Sun is its spottiest, it's actually brighter than average by about 0.1%. At most, this would raise the temperature of the Earth on average by 0.2 degrees Celsius (and it's generally less), and we are measuring increases much larger than that (not to mention the trending just keeps going up, and doesn't rise and fall with the sunspot cycle). People have also tried to tie global warming to sunspots by invoking cosmic rays; when sunspots are at a minimum the Sun's magnetic field is weakest, and it lets subatomic particles from outer space into the solar system. This can seed clouds (so it's claimed) and cool the Earth. Maybe, kinda, sorta. The evidence for this is incredibly weak, and it's not taken very seriously yet. People who try to tie global warming to the Sun are in for a losing fight, it seems, though in many cases this just makes them scream all the louder. But they have very very spotty (har har) evidence, and what they do have does not come close to explaining the rise in temperature we see on Earth.

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