NOAA CSI Meeting

1
Plateaued Warming of the Globe ---
Why? --- What Relation of Ocean Land?
JFM 2009
--- OBS Conditions ---
Attributable effects of SSTs


NOAA CSI Meeting May 14 2009
2


What is Causing Recent Global Temperature
Variations?












GLOBE





3


Recent popular press questions Is Global
Warming Over? What Do Humans Have To Do With The
Warming?






The 21st century standstill 8 years of
temperature decline, which has occurred at a
time when global CO2 emissions have been
rising faster than ever, is something that the
conventional wisdom, and the computer models on
which it relies, completely failed to predict."
(Lawson, 2008 page 6)




All-Natural The Earth is warming but physical
evidence from around the world tells us that
human-emitted CO2 (carbon dioxide) has
played only a minor role in it. Instead, the
mild warming seems to be part of a
natural 1,500-year climate cycle that goes back
at least one million years. (Singer and Avery
2007, Ch 1)



4




May 5 2009 Hearing On The National Climate
Service


California Congressman Rohrbacher challenges
Lubchenco about whether global warming is
indeed occurring in light of the recent
global cooling trend. He challenged the
assertion that CO2 is driving climate change in
light of his understanding that ice core
records indicate past interglacial warming
led CO2 changes.


5


So, What About Recent Coolness Is
Global Warming Over?













6


How Unusual is Decadal Cooling?



Easterling and Wehner, 2009 GRL



PDF of Decadal Trends of Global Temperature
In Climate Models




It is not unusual to experience a decade of
cooling, even within an epoch of strong warming
trend Natural variability can overwhelm the
GHG warming trend for a decadal period, and
climate models can be used to estimate the
probability of decadal cooling.



7


Radiative Forcing of Temperature In The Last
Millenium










Jansen et al. 2007


GHGs must be included among radiative forcings
to simulate temperature variability since
1000AD It is very unlikely that recent
observed warming is a recovery from pre-20th
Century coolness.

8



The Maunder Minimum 17th Century



Peak-to-trough variation in solar irradiance
during recent sunspot cycles 0.2 w/m2, Solar
activity is exceedingly unlikely the cause for
post-1975 global warming Recent sunspot
minima and reduced solar irradiance coincide with
recent decade of global averaged cooling, but
was very likely a minor factor.

9











Hoerling et al 2008 GRL




10











Hoerling et al 2008 GRL

Most of the increase in global mean land
temperature has occurred after 1975. Most of
the observed warming is very likely due to
anthropogenic GHGs. The increase in global
mean land temperature is directly attributable to
ocean warming.



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Virtually all of the variability in tropical
land temperatures is directly attributable to SST
variability.



12


Variations in Global Mean Sea Surface
Temperatures The Natural ENSO Cycle A Key
Player in Yearly Fluctuations












Courtesy of J. Hansen

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Observed January- March 2009 Anomalies





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Observed January-March 2009 200Z Anomalies





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Observed January- March 2009 Anomalies





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Simulated January- March 2009 Anomalies
GOGA, 150-member multi-model





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Simulated JFM 2009 150-member multi-model


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Observed Temperature JFM 2009
32


What are the Official Forecast for US winter
climate?




0.5 month Lead DJF
0.5 month Lead JFM
33






Observed Precipitation JFM 2009