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

From: Schwarzwald <>
Date: Fri Aug 28 2009 - 00:07:52 EDT

Thanks for the additional information, Rich! Just goes to show how much more
we need to learn about these varied effects to truly understand just what's
going on with our environment. The fact that we still have a vastly long way
to go when it comes to getting all these details straightened out must make
climate science research an exciting time - plenty of opportunities to
investigate aspects of the climate that are poorly understood or not
understood at all.

On Thu, Aug 27, 2009 at 11:54 PM, Rich Blinne <> wrote:

> From the paper today in *Science*:
> It has long been noted that the 11-year cycle of solar forcing is
> associated with various phenomena in Earth’s climate system, in both the
> troposphere and stratosphere (*1*<>
> –*9* <>). Because
> the amplitude of the solar cycle (solar maximum to solar minimum) is
> relatively small, about 0.2 W m–2 globally averaged (*10*<>),
> and the *observed global sea surface temperature** **(SST) response of
> about 0.1°C* would require more than 0.5 W m–2 (*11*<>),
> there has always been a question regarding how *this small solar signal*could be amplified to produce a
> *measurable* response.
> From the July report of NCDC:
> El Niño persisted across the equatorial Pacific Ocean during July 2009.
> Related sea-surface temperature (SST) anomalies increased for the sixth
> consecutive month in this ENSO domain, where *July SSTs were more than
> 0.5°C (0.9°F) above average*. If El Niño conditions continue to mature, as
> now projected by NOAA, global temperatures are likely to exceed previous
> record highs.
> To put this in perspective the difference in SST from solar minimum to
> solar maximum is 5 times smaller than the current deviation from average.
> Which stands to reason given the amplitude of the solar variation of
> 0.2W/m^2 is much smaller than the CO2 forcing of 1.6 W/m^2. Large is
> relative to what was expected (that it was so small an effect that it was
> *immeasurable*) given the small solar variation but not large when
> compared to the effects of CO2.
> Rich Blinne
> Member ASA
> On Aug 27, 2009, at 9:25 PM, Schwarzwald wrote:
> Also from Physorg:
> Study: Small fluctuations in solar activity, large influence on the climate
> *( -- 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<>respond during solar
> maximum <> in a way that
> amplifies the Sun's influence on some aspects of air movement. This can
> intensify winds and 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 <>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 <>wrote:
>> 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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Received on Fri Aug 28 00:08:46 2009

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