Amplification of wet and dry month occurrence over tropical land regions in response to global warming

摘要: [1] Quantifying how global warming impacts the spatiotemporal distribution of precipitation represents a key scientific challenge with profound implications for human welfare. Utilizing monthly data from Coupled Model Intercomparison Project (CMIP3) climate change simulations, results here show that occurrence very dry ( 10 mm/day) months comprises straightforward, robust metric anthropogenic on tropical land region rainfall. In particular, differencing tropics-wide frequency histograms 25-year periods over late 21st and 20th centuries shows increased late-21st-century histogram extremes both in model ensemble across individual models. Mechanistically, such differences are consistent view enhanced spatial gradients. Similar diagnostics calculated two 15-year subperiods 1979–2008 CMIP3 models three observational products to assess whether signature has already emerged response recent warming. While observations ensemble-mean hint at similar amplification warmer (1994–2008) subinterval, changes not robust, as substantial evident among intraensemble spread is large. Comparing computed warmest coolest years period further demonstrates effects internal variability, notably El Nino/Southern Oscillation, which appear oppose impact quasi-uniform wet tail distribution. These identify increase occurrences potential but also highlight continuing dominance variability even bulk measures