Transcript Mann, ME, Emanuel, KA, Atlantic Hurricane Trends linked to Climate

The Atlantic Multidecadal
Oscillation, Climate Change,
and Atlantic Hurricanes
Michael E. Mann
Department of Meteorology/Earth and
Environmental Systems Institute/Department
of Geosciences
Pennsylvania State University
Dept. of Geography Coffee Hour
September 25, 2006
Climate Change
Influence on the
Destructive
Potential of
Atlantic
Hurricanes?
Katrina (Aug 28 ’05)
Climate Model Predictions
Knutson, T. K., and R. E. Tuleya, 2004: Impact of CO2-induced warming on
simulated hurricane intensity and precipitation: Sensitivity to the choice of climate
model and convective parameterization. Journal of Climate, 17(18), 3477-3495.
Observed Trends
P. J. Webster, G. J. Holland, J. A. Curry, H.-R. Chang Changes in Tropical
Cyclone Number, Duration, and Intensity in a Warming Environment, Science,
309, Issue 5742, 1844-1846 , 2005.
Observed Trends
Emanuel, K. (2005), Increasing destructiveness of tropical cyclones over the past 30 years,
Nature, online publication; published online 31 July 2005 | doi: 10.1038/nature03906
Climate Change?
OR
natural variability?
Emanuel, K. (2005), Increasing destructiveness of tropical cyclones over the past 30 years,
Nature, online publication; published online 31 July 2005 | doi: 10.1038/nature03906
EL NINO/SOUTHERN OSCILLATION (“ENSO”)
Multivariate ENSO Index (“MEI”)
Secular Warming Pattern
Mann, M.E., Park, J., Oscillatory
Spatiotemporal Signal Detection in
Climate Studies: A Multiple-Taper
Spectral Domain Approach, Advances in
Geophysics, 41, 1-131, 1999.
Multidecadal Pattern
Cold season
Mann, M.E., Park, J.,
Oscillatory Spatiotemporal
Signal Detection in Climate
Studies: A Multiple-Taper
Spectral Domain Approach,
Advances in Geophysics, 41,
1-131, 1999.
Warm season
Multidecadal Pattern
Mann, M.E., Park, J.,
Bradley, R.S., Global
Interdecadal and
Century-Scale Climate
Oscillations During the
Past Five Centuries,
Nature, 378, 266-270,
1995.
“Atlantic
Multidecadal
Oscillation”
(AMO)
Model
Model
Influence of AMO and Hurricanes?
Mann, M.E., Emanuel, K.A.,
Atlantic Hurricane Trends linked
to Climate Change, Eos, 87, 24, p
233, 238, 241, 2006.
Influences on tropical Atlantic SST
Global Mean Aug-Oct SST [G(t)] (Aug-Oct)
T(t) = aG(t)
trop Atl (6-18N, 20-60W)
Aug-Oct SST
Mann, M.E., Emanuel, K.A., Atlantic Hurricane Trends linked to
Climate Change, Eos, 87, 24, p 233, 238, 241, 2006.
Estimation of AMO Influence
Residual [R(t)]
Mann, M.E., Emanuel, K.A., Atlantic Hurricane Trends linked to
Climate Change, Eos, 87, 24, p 233, 238, 241, 2006.
Estimation of AMO Influence
Spectrum of Residual (1870-1999)
Mann, M.E., Emanuel, K.A., Atlantic Hurricane Trends linked to
Climate Change, Eos, 87, 24, p 233, 238, 241, 2006.
Estimation of AMO Influence
Spectrum of Residual (1870-1949)
Mann, M.E., Emanuel, K.A., Atlantic Hurricane Trends linked to
Climate Change, Eos, 87, 24, p 233, 238, 241, 2006.
Estimation of AMO Influence
Residual [R(t)]
Mann, M.E., Emanuel, K.A., Atlantic Hurricane Trends linked to
Climate Change, Eos, 87, 24, p 233, 238, 241, 2006.
Hansen, J. et al, Efficacy of climate forcings. J. Geophys.
Res. 110, D18104, doi:10.1029/2005JD005776 (2005).)
Influences on tropical Atlantic SST
T(t) = aG(t)+bS(t)
bS(t)
aG(t)
trop Atl (6-18N, 20-60W)
Aug-Oct SST
Mann, M.E., Emanuel, K.A., Atlantic Hurricane Trends linked to
Climate Change, Eos, 87, 24, p 233, 238, 241, 2006.
Influences on tropical Atlantic SST
T(t) = aG(t)+bS(t) (full data)
trop Atl (6-18N, 20-60W)
Aug-Oct SST
Mann, M.E., Emanuel, K.A., Atlantic Hurricane Trends linked to
Climate Change, Eos, 87, 24, p 233, 238, 241, 2006.
Influences on tropical Atlantic SST
T(t) = aG(t)+bS(t) (full data)
T(t) = aG(t)+bS(t) (predicted 1970-1999)
T(t) = aG(t)+bS(t) (fit to 1870-1969)
trop Atl (6-18N, 20-60W)
Aug-Oct SST
Mann, M.E., Emanuel, K.A., Atlantic Hurricane Trends linked to
Climate Change, Eos, 87, 24, p 233, 238, 241, 2006.
Estimation of AMO Influence
Residual [R(t)]
Mann, M.E., Emanuel, K.A., Atlantic Hurricane Trends linked to
Climate Change, Eos, 87, 24, p 233, 238, 241, 2006.
Estimation of AMO Influence
Spectrum
Spectrumof
ofResidual
Residual(1870-1999)
(1870-1999)
“Before”
Mann, M.E., Emanuel, K.A., Atlantic Hurricane Trends linked to
Climate Change, Eos, 87, 24, p 233, 238, 241, 2006.
Estimation of AMO Influence
Spectrum of Residual (1870-1999)
“After”
Mann, M.E., Emanuel, K.A., Atlantic Hurricane Trends linked to
Climate Change, Eos, 87, 24, p 233, 238, 241, 2006.
AMO Influence on TCs?
TC #s vs T(t)
TC #s vs R(t)
CONCLUSIONS
•AMO does not significantly project onto tropical North
Atlantic SST
•Apparent multidecadal oscillation in tropical Aug-Oct
Atlantic SST an artifact of late 20th century aerosol forcing
•Anthropogenic climate change (including tropospheric
aerosol trends) appears primary factor influencing tropical
Aug-Oct Atlantic SST and North Atlantic Tropical Cyclones
(TCs)
•Late 20th century tropospheric aerosol cooling has offset
a substantial amount of anthropogenic greenhouse gas
warming in the region and has thus likely suppressed even
greater potential increases in TC activity.
“Atlantic
Multidecadal
Oscillation”
(AMO)
Observations
Observations
Model
“Pacific
Decadal
Oscillation”
(PDO)