Aug
31
2009

Link between sunspots and weather explained

The Sun in more active times: Sunspot activity, which is linked to weather and other phenomena on Earth, peaked in 2001. But for the last two years there’s been almost nothing.
The Sun in more active times: Sunspot activity, which is linked to weather and other phenomena on Earth, peaked in 2001. But for the last two years there’s been almost nothing.Courtesy NASA

Our Sun has been burning brightly for some five billion years. But the rate of its burning has not been steady. The Sun goes through a regular 11-year cycle of active periods and quiet periods. The active periods are marked by an increase in sunspots—dark regions of intense magnetic activity on the surface of the Sun.

Now, “active” and “quiet” are relative terms. The amount of energy released by the Sun in its “active” phase is only 1/10th of 1% more than that released during its “quiet” phase. In other words, a quiet Sun is still putting out 99.9% as much energy as an active Sun.

Yet, scientists have long noted a connection between activity on the Sun and temperatures here on Earth. (We have discussed this phenomenon before, here and here.) And the impact is much greater than that 1/10th of 1% would have you believe. How could such a small increase in solar output have such a large effect on Earth?

Well, it looks like we finally have an answer. A new study by the National Center for Atmospheric Research and published in the journal Science argues that the increased solar output warms ozone in the upper atmosphere. This extra energy creates more ozone, which traps more heat, which creates more ozone, which… you get the idea. It’s a feedback loop. The end result is stronger winds. These winds reduce clouds over the Pacific Ocean, allowing it to warm up as well. So you’ve got heat coming down from the sky, and more heat coming up from the ocean, the end result of which is that the Earth warms more than twice as much as you would expect from the increased Sun activity alone.

(The low number of sunspots over the last couple of years may at least partially explain our unusually cool summer.)

The researchers are careful to say that this work does not explain long-term climate change, but simply periodic weather patterns. However, sunspots have been linked to major climate events of the past, such as the Little Ice Age. Finding the exact mechanism of their influence may simply be a matter of more research.

Your Comments, Thoughts, Questions, Ideas

bryan kennedy's picture

It's cool to read how they combined two computational models to help create a super model in the process of figuring out this problem. This very process leads to one of the criticisms of the findings, in which a detracting scientist didn't feel like they ran the model's simulations enough times.

Nevertheless, it seems that this is an example of these sorts of models helping us to understand how our global climate works on a short and long time scale.

posted on Mon, 08/31/2009 - 2:40pm

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