Warmer and wetter or warmer and dryer? Observed versus simulated covariability of Holocene temperature and rainfall in Asia

• Temperature and precipitation are investigated in proxy, instrumental and model data.
• Holocene temperature and precipitation variability is strongly linked in Asia.
• The observed relationship is timescale-dependent and positive on centennial scale.
• In contrast, the relationship is always negative in Global Climate Model results.
• We support the proxy view, that warm related to wet, and cold to dry conditions.

Temperatures in Asia, and globally, are very likely to increase with greenhouse gas emissions, but future projections of rainfall are far more uncertain. Here we investigate the linkage between temperature and precipitation in Asia on interannual to multicentennial timescales using instrumental data, late Holocene paleoclimate proxy data and climate model simulations. We find that in the instrumental and proxy data, the relationship between temperature and precipitation is timescale-dependent. While on annual to decadal timescales, negative correlations dominate and thus cool summers tend to be rainy summers, on longer timescales precipitation and temperature are positively correlated; cool centuries tend to be dryer centuries in monsoonal Asia. In contrast, the analyzed CMIP5/PMIP3 climate model simulations show a negative correlation between precipitation and temperature on all timescales. Although many uncertainties exist in the interpretation of the proxy data, there is consistency between them and the instrumental evidence. This, and the persistence of the result across independent proxy datasets, suggests that the climate model simulations might be considerably biased, overestimating the short-term negative associations between regional rainfall and temperature and lacking long-term positive relationships between them.