Thursday, February 28, 2008

Denial goes solar: Here comes the sun, again

Bad Astronomy takes on the recent recurrence of that hardy meme, the sun (not human activity) is causing climate change: 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.

…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.

This image shows the Sun as viewed by the Soft X-Ray Telescope (SXT) onboard the orbiting Yohkoh satellite, NASA Goddard Laboratory for Atmospheres, Wikimedia Commons

1 comment:

hahajohnnyb said...

For one thing you are mistating the case for solar cycle climate change. No one is saying that the change in irradiation has an serious effect on climate change, or has a strong relationship in the historical record. What is interesting is the relationship between the length of the solar cycle and climate change. While, I do not understand why the duration of the solar cycle would have an effect on the climate, there is obviously a relationship there. Perhaps it is cosmic rays, but I do not know.

Its not at all implausible that different feedback mechanisms are at play which are not at all understood. Looking at the AGW hypothesis, many different feedback mechanisms are added to the computer models that are thought to amplify the greenhouse effect, but by using Beer's law we only get a 1C degree rise in Global temperatures as a result of the logarithmic equation which defines the green house effect.

Yes, NASA's year from January-December was warm for 2007, but for the 12 month period of Febuary-January was much cooler. This cannot be entirely explained by the current La Nina, which has only recently increased in strength, and has yet to last as long or match the magnitude of the La Nina of 1998-2000. Knowing that CO2 has continued to rise, and abscent of a major volcanic eruption this would seem to question the magnitude of Global Warming which is currently attributed to mankind's fossil fuel use and the resultant carbon dioxide levels.

Global Warming has now become a political issue, which means that the masses of the people have to be able to understand what is going on. If the Global Warming people have overstated thier case, and the current cooling trend persists over a series of months or years, then your graphs start to look funny and your case for Global Warming falls apart. If you to prove AGW this is your big chance, and you best hope that Solar Cycle 24 is further delayed, then when it warms up you can say that you told us so, but right now its the skeptics time to say that we told you so. Cheers!