© Crown copyright Met Office Regional/local climate projections: present ability and future plans Research funded by Richard Jones: WCRP workshop on regional climate, Lille, June 2010

© Crown copyright Met Office Outline – version 1 Regional climate projections and predictions: present ability Detailed (spatially and temporally) climate projections: present ability Regional and detailed climate projections and predictions: future plans Expected outcomes of these plans and the resulting implications

© Crown copyright Met Office Outline – version 2 What we can say and why What we cannot say and why What we are planning next What will this (not) deliver

© Crown copyright Met Office Regional climate projections and predictions: present ability Large-area “average” indications of ranges of plausible (and in some cases “likely”, i.e. predicted) climate changes for all regions via e.g. CMIP3, other (ensemble) global models IPCC AR4 states that there will likely (or very likely) be : seasonal temperature increases in all regions sea-level rises in all regions seasonal precipitation changes (either increased or decreases) in many regions

© Crown copyright Met Office Observed, simulated and projected temperature ranges with human and natural forcings Significant “predicted” regional temperatures rises, “likely” ranges given by IPCC based on model responses to observed forcing etc.

© Crown copyright Met Office Global to regional sea level rise ratio in 11 CMIP3 models Regional sea-level rise - China

© Crown copyright Met Office Temperature/precipitation changes: Asia, A1B emissions, 2090s, CMIP3 Significant high- latitude precip. increase via moister atmosphere; West Asian dries via warming- driven lower relative humidity and surface drying in spring

© Crown copyright Met Office Regional climate projections – what we can say and why The following broad overview of likely sub-continental changes (i.e. a range of values in which the observed change is expected to lie), i.e.: seasonal temperature increases in all regions – we understand the processes and models respond correctly to observed forcings sea-level rises in all regions – likely range for global average from observations and process understanding with regional wider due to model-dependent variability in patterns seasonal precipitation in many regions – confident where we understand the processes and when the dominant ones are driven by warming

© Crown copyright Met Office Detailed climate projections: present ability and limiting factors Detailed temperature changes (including extremes) can often be inferred from the large-scale changes Similarly, some detailed precipitation changes can be inferred but sampling issues often limit the information Various factors, including climate variability and processes that are poorly understood or not represented, act to limit the information that can be obtained

© Crown copyright Met Office Changes in Caribbean islands in global and regional models ECHAM4 – B2 ECHAM4- A2 HADCM3 – A2 HADCM3 – B2 Pattern of change over the sea- surface is very different using different GCMs Temperature changes over the islands are larger, more consistent and we are confident of the processes involved

© Crown copyright Met Office The influence of internal variability Changes in average intensity of top 5% of wet days, SRES A2, 2080s forecast with 3-member ensemble Many areas of significant change in each ensemble member Key point is not where change is significant but reliable Changes similar on large-scales Locally considerable differences between 3 realisations Run 1, winter Run 2, summer Run 3, winter Run 2, winter Run 1, summer Run 3, summer Change (%)

© Crown copyright Met Office Use signal to noise analysis for robust changes Can discern significant changes over much of Europe in winter and parts of Europe in summer Changes quantified with reasonable accuracy where |SNR|>, i.e. only in limited areas Robust change limited even in mean with 3-member ensemble and is less for extremes Mean, winter Top 5%, summer Top 1%, winter Top 5%, winter Mean, summer Top 1%, summer Kennett, E. J., D. P. Rowell, R. G. Jones, and E. Buonomo, 2008: Robustness of future changes in local precipitation extremes. J. Climate, doi: /2008JCLI

© Crown copyright Met Office Climate variability and information available from a climate projection Single 30 year integrations can be insufficient to infer detailed changes in precipitation With 3-member ensemble sampling top 5%, changes at grid box level discernible over much of Europe in winter, but less than half of Europe in summer Changes quantified only in some northern European locations More than 3x30yr ensemble integrations needed for significant local changes over large parts of Mediterranean in winter and central and eastern Europe in summer

© Crown copyright Met Office Future precipitation: a regional example – the Indian monsoon Changes over India are mostly large and positive, supported by physical insight

© Crown copyright Met Office Top 5% precipitation change drivers – 3 member ensemble experiments Winter Summer Percentage change in extreme precipitation for each mechanism Warming Large-scale Soil moisture Total change

© Crown copyright Met Office Some information on changes in top 5% daily precipitation intensity Increases across much of Europe in winter are dominated by increasing atmospheric moisture in a warmer climate The prediction of increased extreme precipitation for Europe as a whole in winter is reliable At the regional scale (~1000 km or less) an enhanced increase or a decrease due to changing circulation patterns is possible. In summer there are competing processes which tend to respectively enhance and reduce precipitation

© Crown copyright Met Office Contributions to the ranges in projected winter precipitation changes for relative to at selected 25km grid squares in an ensemble global/regional projection. Internal variability, carbon cycle, downscaling, account for ~50%, i.e. not accounting for these reduces range of change around projected or likely value by factor of 2 Factors influencing ranges of local precipitation projections

© Crown copyright Met Office Detailed climate projections – what we cannot say and why Regional patterns of changes, even in the mean, for a given decade or thirty-year period under transient climate change are affected by sampling (only small areas of change in precipitation quantified with a 3x30y sample) – and the situation is worse for extremes Spatially and temporally detailed changes are often unclear because they results from: (a)processes we are uncertain about, e.g. large-scale circulation changes, (b)a combination of processes which we cannot quantify or do not represent

© Crown copyright Met Office What we are planning next CMIP5 will deliver, for centennial projections, an increase in the processes simulated and more models with higher resolution CMIP5 will deliver ensemble decadal projections initialised from the observed state of the system including 30-year projections from 2005 CORDEX is providing a framework for, and will deliver for Africa, coordinated downscaling of the CMIP5 centennial projections using the rcp4.5 and rcp8.5 concentration scenarios

© Crown copyright Met Office CMIP5 Experiments

© Crown copyright Met Office What this will (not) deliver A broad picture of sub-continental changes likely to lie in given ranges (similar to those in AR4) from the CMIP5 GCMs This information on changes will include more spatial detail and a greater range of processes and thus provide a more realistic range of possible outcomes around the likely value The CMIP5 30-year initialised ensembles should provide reasonable sampling of patterns of near-term projected climate change where downscaling would not add information CORDEX will further enhance the realism of ranges around likely centennial climate changes for Africa Little additional information will be provided on other aspects of detailed climate change

© Crown copyright Met Office Conclusions To provide information on detailed patterns of even mean climate change for periods under transient climate change requires sample-sizes that can only be derived from ensembles Even with ensemble sampling, uncertain aspects of climate change such as possible circulation change or the magnitude of competing processes (even if we have confidence in their sign of change) will limit what we can say with confidence on detailed climate change AR5 is likely to improve on the picture of area-averaged regional climate change providing some increases in spatial detail and more realistic range of possible outcomes around the likely value (from including more processes) and, for the near term, ensemble 30-year initialised projections – but little will be provided on other aspects of detailed climate change