Sun's Cycles Can Forecast Floods, Drought?

Carolyn Barry, National Geographic News 10 Dec 08;

The sun's fluctuations can help predict extreme climatic events on Earth decades ahead of time, new research suggests.

Solar cycles are 11-year phases during which the sun's activity ebbs and flows, accompanied by an increase in sunspots on the sun's surface. (Watch a video of how solar storms cause "sun quakes.")

The cycles, which are driven by the sun's magnetic turbulence, may influence weather systems on Earth, particularly the El Niño-Southern Oscillation, a periodic climatic system associated with floods and droughts mostly in the Southern Hemisphere.

"The sun is the engine of our climate," said lead study author Robert Baker, of the University of New England in Australia.

"It's like a vibrating string—its past vibrations can be used to predict future vibrations."

Those vibrations are the cyclical "twisting and untwisting" of magnetic fields that cause the sun's poles to flip at the start of each new cycle.

Climate and Sun Similarities

Longer magnetic cycles of about 90 years and 400 years are also found in astronomy records.

The Southern Oscillation Index, which measures the El Niño-Southern Oscillation system, seems to correspond with a 90-year sun cycle, Baker found.

For instance, the current index reading closely follows a trend observed in the 1920s.

Periods of greater solar disturbances are associated with rainy periods, whereas a calmer sun dovetailed with times of drought in Australia, Baker said.

The research appears in a recent edition of the journal Geographical Research.

Floods of the Future?

Data from the 1940s, coupled with astrophysicists' calculations of future solar cycles, could predict droughts and floods as far off as 2030, Baker said.

"We can look into the future based on the past to make predictions 10 to 20 years ahead."

El Niño and La Niña, which creates opposite climatic effects from El Niño, also affect North America.

That means long-range forecasting is possible for water availability in Mexico and the western United States, where droughts are often severe, Baker said.

How solar cycles may influence Earth's weather systems is not well understood, but Baker speculated that cosmic radiation is a factor.

For instance, Baker's research shows that periods of high cosmic radiation coincide with particularly long La Niñas, Baker said.

"This [area of research] is something that warrants further investigation," he said.

If the current index continues to mimic the 1920s cycle, then 2009 is set to be another cool year relative to the 1990s.

However, the next few years may be a little harder to predict, he added.

That's because the sun has already defied its typical 11-year cycle: The new round was supposed to begin in 2007, but only recently got underway.

Longer-term trends may also be influencing the timing of the new cycle, Baker said. The larger 400-year magnetic cycle, for instance, is expected to end in 2020.

Doubtful

However, other scientists have misgivings about the strength of the research and its value in predicting climate events.

Stuart Larsen, a climate ecologist at Monash University in Melbourne, Australia, believes that solar cycles may "play a role in driving climatic variation."

But he's doubtful of Baker's work, calling it "statistically flawed."

"No causal link between El Niño events and solar variability has been demonstrated, and I think it is very unlikely that any direct link exists," said Larsen, who was not involved in the research.

Julie Arblaster is a climatologist at the Bureau of Meteorology in Melbourne.

"While there may be some influence of the solar and magnetic cycles on the [Southern Oscillation Index] and Australian rainfall," Arblaster said, "the magnitude of the signal is quite small."