Blame the Sun for a Cloudy Day?

ScienceNOW Daily News ^ | 17 December 2008 | Phil Berardelli

[neverdem]

Enlarge Image

Linked? Drought patterns across Australia (orange) seem to closely follow solar magnetic cycle activity.

Credit: Robert Baker (Geographical Research 46 (4): 396)

An Australian researcher has linked the sun's magnetic activity to rainfall patterns in his country over the past century. The connection is solid enough that meteorologists might be able to use it to make better long-term weather predictions. But experts remain cautious about the wider implications of the findings.

Scientists have long known that the sun plays a key role in Earth's weather patterns. For example, the number of sunspots on its surface--dark zones of intense magnetic activity--peaks about every 11 years, followed by a period of dormancy. The cycle causes swings in sea-surface temperatures--more sunspots mean warmer oceans, and fewer mean chillier waters--but the effect is small. There's also a 22-year cycle, in which the sun changes the polarity of its magnetic field, but it's unclear how that phenomenon affects Earth.

Now geographer Robert Baker of the University of New England, Armidale, in Australia, has linked solar magnetic activity to Earth's climate--at least regionally. Using sunspot counts and Australian meteorological data, as well as NASA satellite data for more recent years, he tracked sunspots and rainfall in Australia from 1876 to 2006. In this month's issue of Geographical Research, Baker reports that the amount of rainfall in most regions of the country tracked the 22-year magnetic cycle almost exactly. "It was unbelievable," Baker says. At the height of magnetic activity, rainfall across most of the country was plentiful. At the other end of the cycle, many of those same regions experienced severe droughts. The findings are particularly compelling, Baker says, because even though the lengths of the magnetic cycles are not precise and can vary by several years, the rainfall patterns followed them.

So what's behind the connection? Baker thinks it has to do with the amount of ultraviolet (UV) radiation hitting Earth. When the reversing of polarity approaches, he explains, the sun's magnetic field weakens, allowing more UV energy to reach our planet. More UV radiation kills off some of the oceans' plankton, which produce dimethyl sulfide, one of the primary atmospheric chemicals involved in cloud formation, and fewer clouds mean less rainfall.

Based on the 130 years of data, Baker predicts that the current solar cycle, which reached a minimum in 2007, will continue a bit longer. In fact, he says, "there could be a 100-year minimum in solar activity," meaning much of Australia could experience a prolonged drought.

"This could be an important paper," says climatologist John Christy of the University of Alabama, Huntsville. He explains that current climate models don't give the solar effect much weight in general, because scientists think it is overwhelmed by the buildup of greenhouse gases in the atmosphere. But if there's a mechanism by which the sun's variations are tied directly to weather patterns, such as the effect of UV radiation on cloud formation, he says, the sun may have a greater impact than the models are showing. As a result, the models might not be creating an accurate picture for the future.

Solar-terrestrial physicist Mike Lockwood of the University of Southampton in the U.K. says that the paper suggests a previously unknown effect caused by the solar magnetic cycle. "If the connection [between UV radiation and precipitation] proposed here were real," he says, "it would be both highly significant and very illuminating." On the other hand, Lockwood says, the paper contains no statistical tests, and connections such as the one it suggests "can arise readily by chance, even for extended intervals."

[GOPJ]

IMHO, it's another feedback loop that is fascinating, elegant and unlikely to happen by dumb luck.

It does seem the earth is set up in a beautiful balance - with nice little balancing agents for when things get out of kilter. Gore is such a pompous as_.

[Alamo-Girl]

Thanks for the ping!

[SunkenCiv]

“More UV radiation kills off some of the oceans’ plankton, which produce dimethyl sulfide, one of the primary atmospheric chemicals involved in cloud formation, and fewer clouds mean less rainfall.”

...and...

“The findings indicate that phytoplankton will then produce more DMS(dimethyl sulfide) in response to this increased ultraviolet radiation, causing increasing cloudiness and mitigating the effects of global warming.”

More UV results in more plankton, and also simultaneously results in less?

[neverdem]

More UV results in more plankton, and also simultaneously results in less?

Go to the second link.

[SunkenCiv]

> observational evidence showing that the DMS-anti-oxidant mechanism closes the DMS-climate feedback loop

Thanks!