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Climate changes in Southern Africa; downscaling future (IPCC) projections Olivier Crespo

Climate changes in Southern Africa; downscaling future (IPCC) projections Olivier Crespo Thanks to M. Tadross Climate Systems Analysis Group University of Cape Town. Historical change. Coherent regional increases in temperature attributable to human emissions.

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Climate changes in Southern Africa; downscaling future (IPCC) projections Olivier Crespo

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  1. Climate changes in Southern Africa; downscaling future (IPCC) projections Olivier Crespo Thanks to M. Tadross Climate Systems Analysis Group University of Cape Town

  2. Historical change Coherent regional increases in temperature attributable to human emissions Increase in temperatures ≈ 2°C since 1900 over central southern Africa

  3. Historical change - rainfall • Observed changes in rainfall: • Increase in length of dry season and daily rainfall intensity over central region (Kruger, 2006) • Later onset of rains over eastern lowland regions (Tadross et al., 2005) • Both the above are observable over parts of southern Africa but very heterogeneous in space and time and the physical mechanisms for the changes are poorly understood

  4. Future change - scenarios A1: A world of rapid economic growth and rapid introductions of new and more efficient technologies A2: A very heterogenous world with an emphasis on familiy values and local traditions B1: A world of dematerialization and introduction of clean technologies B2: A world with an emphasis on local solutions to economic and environmental sustainability

  5. Future change - scenarios

  6. Future change - temperature

  7. Future change Southern Africa projected temperature change at the large scale • Regional temperature: • Historical observed (Black line) • Historical simulated by 21 global models (Red envelope) • Projected ranges by 21 global models • red: A2 • orange: A1B • blue: B1

  8. Future change Changes in rainfall from global models Summer (SH) Winter (SH) White areas are where less than two thirds of the models agree in the direction (+/-) of the change After IPCC AR4: SPM 7

  9. What are GCMs Good For? IPCC AR4 WG1: Ch 1

  10. Scales and resolution

  11. Future change Downscaling The challenge of bring confident large scale projections to scales of adaptation and policy

  12. Statistical and RCM downscaling An empirically derive stochastic or quantitative transfer function conditioned by the large-scale fields from the GCM or A regional climate model (RCM) nested within the GCM fields

  13. Future change • Potential changes in rainfall: • Decreases in winter rainfall over SW Cape • Increases in summer rainfall over eastern regions Winter rainfall change Summer rainfall change

  14. Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Downscaling to a 0.1º precipitation grid: 6 GCMs SRES A2 forcing Future – Control anomaly

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