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Climate change and decadal variability of Chinese summer rainfall: a modelling study Yonghui Lei, Brian Hoskins, Julia Slingo and Andy Turner Observed decadal variability in the period 1958-2007 Decadal variability in the period 1901-2002 using CRU dataset Outline Can HadCM3 simulate the observed decadal variability of Chinese summer rainfall without additional forcing? How may Chinese summer rainfall respond to doubled CO2 according to HadCM3? • Changes in the mean state • Changes in extreme • Changes in variability Internal decadal variability in the 1000-year control run of HadCM3 Observation-like decadal variability identified in the 1000-year control run Observation-like decadal variability in the 51-year period (the model year 590±25) Regressions of surface temperature on decadal rainfall time series in the 51-year period Regression on PC1 Regression on PC2 Summary I Can HadCM3 simulate the observed decadal variability of Chinese summer rainfall without additional forcing? Yes! • In general, internal decadal variability of Chinese summer rainfall is associated with decadal variability in the tropics. • A particular 51-year period has remarkable similarity with observations in the recent 50 years for both Chinese summer rainfall and other large-scale variables. Changes in the climate of Chinese summer rainfall in the 2xCO2 run (I) Amount 2xCO2 2xCO2 - control percentage Intensity Frequency Changes in the climate of Chinese summer rainfall in the 2xCO2 run (II) Changes in the climate of Chinese summer rainfall in the 2xCO2 run (III) Changes in extreme events of Chinese summer rainfall in the 2xCO2 run mm/day Percentile (%) The dominant Chinese rainfall patterns in the control and 2xCO2 runs (I) 1xCO2 2xCO2 The dominant Chinese rainfall patterns in the control and 2xCO2 runs (II) 1xCO2 2xCO2 1xCO2 2xCO2 The dominant Chinese rainfall patterns in the control and 2xCO2 runs (III) Uncertainty of decadal variability in the control and 2xCO2 runs (I) Uncertainty of decadal variability in the control and 2xCO2 runs (II) Summary II How may Chinese summer rainfall respond to doubled CO2 according to HadCM3? Mean: • Chinese summer rainfall increases, except the Yangtze River valley; • Intensity increases everywhere; • Decreases in the frequency over the east and increases over the northwest. Summary II How may Chinese summer rainfall respond to doubled CO2 according to HadCM3? Increases in extreme events, consistent with the ClausiusClapeyron relationship Variability: • Increases in interannual variability are very likely with global warming, which may be associated with the strengthened El Nino events. • Changes in decadal variability are unclear.