© Crown copyright Met Office Regional Temperature and Precipitation changes under high- end global warming Michael Sanderson, Deborah Hemming, Richard Betts Met Office Hadley Centre, 12 May 2010

© Crown copyright Met Office Contents This presentation covers the following areas Introduction Methodology Temperature and Precipitation changes Regions most strongly impacted Summary

© Crown copyright Met Office Introduction

© Crown copyright Met Office AR4 Projections EU Limit High- End

© Crown copyright Met Office Current global temperature projections IPCC AR4: Temperatures will rise between 1.6 and 6.9  C by 2100 (relative to preindustrial). Much EU political attention focused on 2  C warming. However, climate projections clearly indicate greater levels of global warming are possible. Projections of 4  C or more termed ‘high-end’. This work was funded by the Joint DECC and Defra Integrated Climate Programme - DECC/Defra (GA01101) (and contributes to the AVOID project).

© Crown copyright Met Office High-End Climate Change 1.Are high-end climate projections notably different to the non high-end projections? 2.Which regions are likely to be most affected by high-end changes? AR4 model ensemble analysed, focusing on results using SRES A2 scenario (19 models). Analysed monthly mean data. 2 m Temperature, Total Precipitation.

© Crown copyright Met Office Methodology (1) Calculate annual global average temperature for preindustrial control run and If more than 1 model realisation, each one treated independently. 40 projections analysed. If temperature difference is 4  C (to 1 d.p.) or more, that projection classed as high-end.

© Crown copyright Met Office Summary of Global Mean Temperature Changes 21 model projections classed as high-end 19 projections are non high-end. In high-end projections 4ºC first reached between 2083 and s mean temperature changes lie between 4.0 and 4.8ºC A few other models reach or exceed 4ºC in individual years during 2090s but are not classed as high-end.

© Crown copyright Met Office Model biases Correlation between temperature change and preindustrial mean temperature examined using all projections. Models which simulate the large areas of ice in the polar regions will have coldest temperatures for the preindustrial period Only these models could produce a large warming as the ice sheets recede. No correlation observed, indicating that any relationship between preindustrial ice sheet extent and temperature increases is complex and non-linear.

© Crown copyright Met Office PI Mean temperature vs T change (2090s A2 – PreInd)

© Crown copyright Met Office Methodology (2) Examined changes in temperature and precipitation between pre-industrial and future. December, January and February (DJF) and June, July and August (JJA). For future used average of Changes scaled with that model’s global warming. Medians of high-end and non high-end models examined.

© Crown copyright Met Office DJF Scaled Temperature changes + model range

© Crown copyright Met Office JJA Scaled Temperature changes + model range

© Crown copyright Met Office Summary of Temperature Changes Very large warming projected over much of high northern latitudes in DJF (4ºC per degree). Range of temperature changes from models larger than median temperature rise. Large biases in modelled ice sheet extents Many land areas warm by ºC in JJA. Area of cold water projected to form in North Atlantic and southern ocean (vertical mixing). Regional response of high-end and non high- end models is similar, except over Asia.

© Crown copyright Met Office Precipitation Changes (%)

© Crown copyright Met Office Summary of Precipitation Changes Patterns of precipitation changes from high-end models similar to non high-end models. Large reductions in many areas between 45 ºN and 45 ºS. Bigger reductions in high-end models. Precipitation increases north of 45 ºN and south of 50 ºS.

© Crown copyright Met Office Regions impacted by high- end climate change High-end and non high-end models project similar patterns of temperature and precipitation change. Results from all models scaled to a global average temperature rise of 4ºC. Looked for regions where temperature rise by at least 6ºC and precipitation changes by ±10%.

© Crown copyright Met Office Areas where:  P  ±10%  T  6ºC

© Crown copyright Met Office Summary Many high northern latitudes projected to incur large temperature and precipitation increases. Mexico and northern Africa projected to be at risk from high-end climate change in DJF. Southern Europe and the adjacent part of central Asia, and southern Africa at risk in JJA. Regional temperature response of high-end models and non high-end models very similar. DJF, uncertainty mostly from temp changes. JJA, uncertainty mostly from precip changes.

© Crown copyright Met Office Questions and answers