Re: [asa] Crop Yields Face Non-Linear Effects Due to Climate Change

Also from Physorg:

http://www.physorg.com/news170601993.html

Study: Small fluctuations in solar activity, large influence on the climate

*(PhysOrg.com) -- Subtle connections between the 11-year solar cycle, the
stratosphere, and the tropical Pacific Ocean work in sync to generate
periodic weather patterns that affect much of the globe, according to
research appearing this week in the journal Science. The study can help
scientists get an edge on eventually predicting the intensity of certain
climate phenomena, such as the Indian monsoon and tropical Pacific rainfall,
years in advance.*

An international team of scientists led by the National Center for
Atmospheric Research (NCAR) used more than a century of weather observations
and three powerful computer models to tackle one of the more difficult
questions in meteorology: if the total energy that reaches Earth from the
Sun varies by only 0.1 percent across the approximately 11-year solar cycle,
how can such a small variation drive major changes in weather patterns on
Earth?

The answer, according to the new study, has to do with the Sun's impact on
two seemingly unrelated regions. Chemicals in the stratosphere and sea
surface temperatures in the Pacific
Ocean<http://www.physorg.com/tags/pacific+ocean/>respond during solar
maximum <http://www.physorg.com/tags/solar+maximum/> in a way that amplifies
the Sun's influence on some aspects of air movement. This can intensify
winds and rainfall <http://www.physorg.com/tags/rainfall/>, change sea
surface temperatures and cloud cover over certain tropical and subtropical
regions, and ultimately influence global weather.

"The Sun, the stratosphere, and the oceans are connected in ways that can
influence events such as winter
<http://www.physorg.com/tags/winter/>rainfall in North America," says
NCAR scientist Gerald Meehl, the lead
author. "Understanding the role of the solar cycle can provide added insight
as scientists work toward predicting regional weather patterns for the next
couple of decades."

---
Interesting stuff. Glad to see impacts and effects of variables in earth's
climate are being investigated all around.
On Thu, Aug 27, 2009 at 10:40 PM, Rich Blinne <rich.blinne@gmail.com> wrote:
> http://www.physorg.com/news170350697.html
>
> In a paper published online this week in Proceedings of the National
> Academy of Sciences, North Carolina State University agriculture and
> resource economist Dr. Michael Roberts and Dr. Wolfram Schlenker, an
> assistant professor of economics at Columbia University, predict that U.S.
> crop yields could decrease by 30 to 46 percent over the next century under
> slow global warming scenarios, and by a devastating 63 to 82 percent under
> the most rapid global warming scenarios. The warming scenarios used in the
> study - called Hadley III models - were devised by the United Kingdom's
> weather service.
>
> The study shows that crop yields tick up gradually between roughly 10 and
> 30 degrees Celsius, or about 50 to 86 degrees Farenheit. But when
> temperature levels go over 29 degrees Celsius (84.2 degrees Farenheit) for
> corn, 30 degrees Celsius (86 degrees Farenheit) for soybeans and 32 degrees
> Celsius (89.6 degrees Farenheit) for cotton, yields fall steeply.
>
> "While crop yields depend on a variety of factors, extreme heat is the best
> predictor of yields," Roberts says. "There hasn't been much research on what
> happens to crop yields over certain temperature thresholds, but this study
> shows that temperature extremes are not good."
>
> Roberts adds that while the study examined only U.S. crop yields under
> warming scenarios, the crop commodity market's global reach makes the
> implications important for the entire world, as the United States produces
> 41 percent of the world's corn and 38 percent of the world's soybeans.
>
> "Effects of climate change on U.S. crop production will surely be felt
> around the globe, especially in developing countries," he says.
>
> More information: "Nonlinear temperature effects indicate severe damages to
> U.S. crop yields under climate change" Wolfram Schlenker, Columbia
> University and Michael Roberts, North Carolina State University; Published:
> Aug. 24, 2009, in the online version of Proceedings of the National Academy
> of Sciences.
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