Climate Prediction on Timescales of Seasons to
Decades
A tool for sustainable development in the 21st Century
T N Palmer
ECMWF
Increasing levels of CO2 are changing the probability of
occurrence of spells of cold/warm wet/dry weather.
Multiple climate forecasts (varying uncertain initial conditions and
uncertain model parameters) can be used to estimate the impact of
increasing levels of CO2 on the probability of occurrence of
drought/flood/heatwave/cold snap.
Ensemble Climate Forecasting
An ensemble is a set of predictions, each member with slightly different initial conditions and using slightly different model approximations.
Ensemble gives - most likely prediction
- estimate of uncertainty
- probability of occurrence of extreme climatic conditions.
Increasing Levels of CO2 are Predicted to Change the Risk of
Extreme Seasonal Climate Anomalies.
As part of an overall adaptation strategy to lessen the impact of inevitable climate change, particularly in developing countries, the use of climate models to predict risk of particular occurrences of seasonal climatic extremes months to seasons ahead, will be of increasing importance.
Thomson, M.C., Doblas-Reyes, F.J., Mason S.J., Hagedorn, R., Connor S.J., Phindela, T., Morse, A.P. and Palmer, T.N.
Malaria early warnings based on seasonal climate forecasts from multi-model ensembles.
Nature, 439,576-579.
Cumulative PDFs of standardised malaria incidence in Botswana five months in advance of the epidemic
-- high malaria years
-- low malaria years
ROC Score Precipitation Incidence
Event CMAP DEMETER CMAP DEMETER
Low1.00 (1.00-
1.00)0.95 (0.82-
1.00)1.00 (1.00-
1.00)1.00 (1.00-
1.00)
High1.00 (1.00-
1.00)0.52 (0.25-
0.78)0.94 (0.80-
1.00)0.84 (0.65-
0.98)
Low malaria
incidence
High malaria
incidence
Webster P.J., Anderson, D.L.T. Chang, H.-R., Grossman, R., Hoyas, C., Hopson, T., Shami, K., Subbiah, A. and Palmer, T.N.
Regional application of monsoon dynamics: implementation of a three-tier flood and precipitation forecasting scheme for Bangladesh and surrounding regions.
CLIVAR Exchanges, 9, 21-25.
Challinor, A.J., Singo, J.M., Wheeler, T.R. and Doblas-Reyes, F.J., 2005.
Probabilistic simulations of crop yield over western India using the DEMETER seaonal hindcast ensembles.
Tellus 57A, 498-512.
The LACES ProjectLarge Atmospheric Computation on the Earth Simulator
12-h development of Hurricane Earl: Sept.1, 1998: 1-km horizontal resolution
Conclusions• Increasing levels of CO2 are gradually changing the
probability of occurrence of extremes of weather. • Ensemble forecast techniques give probabilistic
estimates of climate change.• The same techniques and models can be used to
make seasonal climate forecasts - a increasingly valuable tool to help society, especially in developing countries, adapt to the changing risk of climate extremes.
• The accuracy of climate forecasts is compromised by inadequate computational resources.
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