03 August 2006

Brighter Sun Driving Global Warming--Solar Driven Climate Change?

Harvard researchers are rocking the boat of climate science by claiming that changes in the brightness of the sun are driving global warming. Greenhouse gases are only secondary to the process, they say. Climate models are blind to changes in solar radiance, since they typically hold the sun's input constant while varying greenhouse gas levels. A more scientific approach than current GCMs would look at all the possible variables involved before coming to a conclusion, imply the Harvard scientists.

There is a better explanation for global warming than air pollution, two Harvard researchers say: the Sun is increasing in brightness and radiance.

"Changes in the Sun can account for major climate changes on Earth for the past 300 years, including part of the recent surge of global warming," claims Sallie Baliunas, an astronomer at the Harvard-Smithsonian Center for Astrophysics (CfA).

"We're not saying that variations in solar activity account for all of the global rise in temperature that we are experiencing," cautions her CfA colleague, astrophysicist Willie Soon. "But we believe these variations are the major driving force. Heat-trapping gases emitted by smokestacks and vehicles -- the so-called greenhouse effect -- appear to be secondary."

If that conclusion proves true, it promises a huge economic and political impact on the "third rock from the Sun." The Clinton Administration is trying to negotiate an international treaty to gradually reduce greenhouse pollutants without bringing economic havoc to industries that satisfy our enormous appetite for the energy that comes from burning oil, coal, and gas.

Other world leaders and environmentalists are pushing for immediate action, but Baliunas thinks there is time to carefully consider what action to take. "The best models of global warming call for a very slow temperature rise of less than two degrees in the next 100 years," she has told various congressional committees and briefings. "There is time for more research and a measured response because the penalty you pay in increased temperatures from greenhouse warming is small."

Anything that's cost-effective to cut emissions can be done right away, Baliunas says. Dramatic cuts with high economic penalties might be postponed in the expectation that more effective and affordable technologies will become available in the next 25 years or so.

.... Baliunas and Soon base their ideas about the cause of global warming on irrefutable evidence that sunlight is getting stronger. Since the late 1970s, three Sun-watching satellites recorded surprising changes in heat, ultraviolet radiation, and solar wind. The radiation alters the paths of winter storms; solar winds affect cloudiness and rainfall.

The increased activity, everyone agrees, is tied to a cycle that sees the Sun dimming, then brightening, every 11 years or so. From the late 1970s to mid-1980s, activity on Earth's star declined. Since then it has risen, declined, then risen again. The satellites measured an increase in brightness of as much as 0.14 percent on the latest rise.

Two unknowns, however, prevent Sun-watchers from making any useable forecasts about the next five years. No one knows why the Sun cycles like it does, or when it will reach its next maximum. The best guess is the year 2000.

.... The most striking markers of the Sun's waxings and wanings are the coming and going of black spots on its face. Sunspots mark areas where strong magnetic fields exit and enter the surface of the Sun. They are about a thousand degrees cooler than the bright areas that surround them, but are still incandescently hot.

These spots not only follow an 11-year cycle; they also cycle through longer periods of high and low magnetic activity. When the Sun boasts a maximum of spots, cycle after cycle, Earth tends to be warmer than when its face is clear.

During the years from 1640 to 1720, for example, observers counted abnormally few sunspots and Earth's climate entered a period of unusually cold weather. Since the mid-1960s, solar magnetism has been increasing along with global temperatures.

At such maximums, the wind of magnetic fields and charged particles that normally wafts across the 93 million miles from Sun to Earth blows harder. These gusts can trigger colorful displays of auroral lights during long polar nights. The strongest winds may also disrupt long-range radio communications, cause power outages, and disturb the operation of satellites.

Solar winds also produce radioactive carbon atoms in the atmosphere that eventually rain down and become assimilated into tree rings. High solar winds lead to rings with fewer radioactive atoms and vice versa. Changing levels of radiocarbon provide a natural record of magnetic changes on the Sun that can be matched with weather records of coldings and warmings.

"There have been 19 cold periods in the past 10,000 years and a decrease in solar magnetic activity can be linked to 17 of them," Baliunas notes.
Much more at the Source.

For more Al Fin postings on solar climate effects, see here and here.

Climate science is still in its infancy, and subject to making early large scale errors, as juvenile research tries to make its mark. Sadly, many politicians have jumped on the bandwagon before it was ready to be hitched to the team. In an effort to gain publicity and affect public policy, too many politicians are jumping into what should be a scientific debate. This reflects badly on them, and on a "celebrity culture" that values celebrity and notoriety over actual competence and expertise.

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“During times of universal deceit, telling the truth becomes a revolutionary act” _George Orwell

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