SEMINAR: MPO Seminar tomorrow, 10:30 MSC 343: Dr. Shukla

[ikamenkovich@rsmas.miami.edu]

MPO Seminar, MSC 343, 10:30a.m.

On the Role of Unforced Multidecadal Variability in Twentieth Century
Global Warming



Jagadish Shukla



Department of Atmospheric, Oceanic, and Earth Sciences (AOES)

George Mason University (GMU)



Center for Ocean-Land-Atmosphere Studies (COLA)

Institute of Global Environment and Society (IGES)





The problem of separating variations due to natural and anthropogenic
forcing from those due to unforced internal dynamics during the twentieth
century is addressed using IPCC climate simulations and observations. An
unforced internal component that varies on multidecadal time scales is
identified in the twentieth century IPCC climate simulations by a new
statistical method that maximizes integral time scale. This component,
called the Internal Multidecadal Pattern (IMP), is stochastic and hence
does not contribute to trends on long time scales, but can contribute
significantly to short-term trends.



The warming and cooling of the IMP matches that of the Atlantic
Multidecadal Oscillation and is of sufficient amplitude to explain the
acceleration in warming during 1977-2008 as compared to 1946-1977.  The
forced component is increasing at the same rate during these two periods.
The amplitude and time scale of the IMP are such that its contribution to
the trend dominates that of the forced component on time scales less than
16 years, implying that the lack of warming trend during the past ten
years is not statistically significant.



Furthermore, since the IMP varies naturally on multidecadal time scales,
it is potentially predictable on decadal time scales, providing a
scientific rationale for decadal predictions.



In the second part of the presentation, an attempt is made to optimize the
most predictable land surface air temperature pattern at continental
scales related to global SST. It is found that the optimized land surface
air temperature pattern has predictability of only 3 ? 5 years (for land
precipitation only 1 ? 2 years). Since this is an optimized predictable
pattern it will be difficult to find additional predictability. This
result raises some questions about the prospects for multidecadal
prediction of unforced variability over land.

-- 
Dr. Igor Kamenkovich
Associate Professor
Division of Meteorology and Physical Oceanography
Rosenstiel School of Marine and Atmospheric Science
University of Miami
4600 Rickenbacker Causeway
Miami, FL 33149

ikamenkovich@rsmas.miami.edu
Tel: (305)421-4108
Fax: (305)421-4696




---------------------------------------------------------------------
Seminars and symposia at RSMAS

To unsubscribe, e-mail: seminar-unsubscribe@lists.rsmas.miami.edu
For additional commands, e-mail: seminar-help@lists.rsmas.miami.edu
Post to: seminar@rsmas.miami.edu