Re-Assessing Climatic Warming in China since 1900

The regional mean surface air temperature (SAT) in China has risen with a rate of 1.3-1.7 degrees C (100 yr)(-1) since 1900, based on the recently developed homogenized observations. This estimate is larger than those [0.5-0.8 degrees C (100 yr)(-1)] adopted in the early National Reports of Climate Change in China. The present paper reviews the studies of the long-term SAT series of China, highlighting the homogenization of station observations as the key progress. The SAT series of China in early studies showed a prominent warm peak in the 1940s, mainly due to inhomogeneous records associated with site-moves of a number of stations from urban to outskirts in the early 1950s, thus leading to underestimates of the centennial warming trend. Parts of China were relatively warm around the 1940s but with different-phase interdecadal variations, while some parts were even relatively cool. This fact is supported by proxy data and could partly be explained by interdecadal changes in large-scale circulation. The effect of urbanization should have a minor contribution to the observed warming in China, although the estimates of such contributions for individual urban stations remain controversial. Further studies relevant to the present topic are discussed.