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25 September 2009

How natural and anthropogenic influences alter global and regional

GEOPHYSICAL RESEARCH LETTERS, VOL. 35, L18701, doi:10.1029/2008GL034864, 2008

How natural and anthropogenic influences alter global and regional
surface temperatures: 1889 to 2006
Judith L. Lean1 and David H. Rind2
Received 2 June 2008; revised 1 August 2008; accepted 8 August 2008; published 16 September 2008.

Abstract
To distinguish between simultaneous natural and
anthropogenic impacts on surface temperature, regionally
as well as globally, we perform a robust multivariate
analysis using the best available estimates of each together
with the observed surface temperature record from 1889 to
2006. The results enable us to compare, for the first time
from observations, the geographical distributions of
responses to individual influences consistent with their
global impacts. We find a response to solar forcing quite
different from that reported in several papers published
recently in this journal, and zonally averaged responses to
both natural and anthropogenic forcings that differ distinctly
from those indicated by the Intergovernmental Panel on
Climate Change, whose conclusions depended on model
simulations. Anthropogenic warming estimated directly
from the historical observations is more pronounced
between 45S and 50N than at higher latitudes whereas
the model-simulated trends have minimum values in
the tropics and increase steadily from 30 to 70N.
Citation: Lean, J. L., and D. H. Rind (2008), How natural and
anthropogenic influences alter global and regional surface
temperatures: 1889 to 2006, Geophys. Res. Lett., 35, L18701,

14 September 2009

How will Earth's surface temperature change in future decades?

How will Earth's surface temperature change in future decades?

Judith L. Lean
Space Science Division, Naval Research Laboratory, Washington, D. C., USA

David H. Rind
NASA Goddard Institute for Space Studies, New York, New York, USA

Reliable forecasts of climate change in the immediate future are difficult, especially on regional scales, where natural climate variations may amplify or mitigate anthropogenic warming in ways that numerical models capture poorly. By decomposing recent observed surface temperatures into components associated with ENSO, volcanic and solar activity, and anthropogenic influences, we anticipate global and regional changes in the next two decades. From 2009 to 2014, projected rises in anthropogenic influences and solar irradiance will increase global surface temperature 0.15 ± 0.03°C, at a rate 50% greater than predicted by IPCC. But as a result of declining solar activity in the subsequent five years, average temperature in 2019 is only 0.03 ± 0.01°C warmer than in 2014. This lack of overall warming is analogous to the period from 2002 to 2008 when decreasing solar irradiance also countered much of the anthropogenic warming. We further illustrate how a major volcanic eruption and a super ENSO would modify our global and regional temperature projections.

Received 29 April 2009; accepted 9 July 2009; published 15 August 2009.

Citation: Lean, J. L., and D. H. Rind (2009), How will Earth's surface temperature change in future decades?, Geophys. Res. Lett., 36, L15708, doi:10.1029/2009GL038932.

03 September 2009

Amplifying the Pacific Climate System Response to a Small 11-Year Solar Cycle Forcing

Science 28 August 2009:
Vol. 325. no. 5944, pp. 1114 - 1118
DOI: 10.1126/science.1172872

REPORTS
Amplifying the Pacific Climate System Response to a Small 11-Year Solar Cycle Forcing
Gerald A. Meehl,1,* Julie M. Arblaster,1,2 Katja Matthes,3,4 Fabrizio Sassi,5 Harry van Loon1,6
One of the mysteries regarding Earth’s climate system response to variations in solar output is how the relatively small fluctuations of the 11-year solar cycle can produce the magnitude of the observed climate signals in the tropical Pacific associated with such solar variability. Two mechanisms, the top-down stratospheric response of ozone to fluctuations of shortwave solar forcing and the bottom-up coupled ocean-atmosphere surface response, are included in versions of three global climate models, with either mechanism acting alone or both acting together. We show that the two mechanisms act together to enhance the climatological off-equatorial tropical precipitation maxima in the Pacific, lower the eastern equatorial Pacific sea surface temperatures during peaks in the 11-year solar cycle, and reduce low-latitude clouds to amplify the solar forcing at the surface.
1 National Center for Atmospheric Research, Post Office Box 3000 Boulder, CO 80307, USA.
2 Center for Australian Weather and Climate, Bureau of Meteorology, Melbourne, Australia.
3 Helmholtz Centre Potsdam – GFZ German Research Centre for Geosciences, Potsdam, Germany.
4 Institut für Meteorologie, Freie Universität Berlin, Berlin, Germany.
5 Naval Research Laboratory, Washington, DC 20375, USA.
6 Colorado Research Associates, Boulder, CO 80301, USA.