May 22, 2006

Earth-solar cycle spurs greenhouse gases – studies

By Deborah Zabarenko

WASHINGTON (Reuters) - Greenhouse gases are known to spur
global warming, but scientists said on Monday that global
warming in turn spurs greenhouse gas emissions -- which means
Earth could get hotter faster than climate models predict.

Two scientific teams, one in Europe and another in
California, reached the same basic conclusion: when Earth has
warmed up in the past, due to the sun's natural cycles, more
greenhouse gases have been spewed into the atmosphere.

As greenhouse gas levels rose, so did Earth's temperature,
the scientists reported.

Earth has not endlessly warmed up, though, because these
natural solar cycles ended, letting the planet cool down and
prompting a corresponding drop in greenhouse gas emissions, the
scientists reported.

But these previous periods of heating and cooling were not
influenced by the burning of fossil fuels, and the current
resulting trend toward higher global average temperatures,
according to Margaret Torn of Lawrence Berkeley National

"It means the warming is happening faster, each decade is
actually warming faster than it would have," Torn said in a
telephone interview. "It's the pace of change that will be one
of the big problems. It's how humans adapt and the cost that
will depend on the rate of change of climate."


Global warming is caused in part by the emission of
greenhouse gases, including carbon dioxide and methane. These
gases are emitted naturally but are also the result of the
burning of fossil fuels, especially coal and petroleum
products. These gases swaddle Earth in a layer that lets the
sun's warmth in but does not allow it to easily escape.

Over the past 30 years, Earth has warmed by 1.08 degrees
Fahrenheit (0.6 degrees Celsius), NASA has reported. Over the
past 100 years, it has warmed by 1.44 degrees F (0.8 degrees
C), indicating a recent acceleration in warmth.

Current climate models predict temperature increases of 2.7
to 8.1 degrees F (1.5 to 4.5 degrees C), but Torn's team found
that additional carbon dioxide caused by the natural solar
cycle could push those estimates higher.

Taking this into account could mean temperature increases
of 2.9 to 11 degrees F (1.6 to 6 degrees C), the scientists
said. The higher temperatures are more likely, they said in a

The European team estimated that global warming in the next
century may be 15 percent to 78 percent higher than current
estimates because these predictions fail to take into account
the feedback mechanism involving carbon dioxide emissions.

Both articles are to be published on Friday in Geophysical
Research Letters.