Reference
Xu, X., Piao, S., Wang, X., Chen, A., Ciais, P. and Myneni, R.B. 2012. Spatio-temporal patterns of the area experiencing negative vegetation growth anomalies in China over the last three decades. Environmental Research Letters 7: 10.1088/1748-9326/7/3/035701.
Background
The authors note "there is wide concern about how terrestrial ecosystems respond to extreme climatic events in the context of global warming," with their most immediate concern being the fact that "large increases of dry areas in Northeast, North and eastern Northwest China since the 1990s are unprecedented during the past half century."
What was done
As they describe it, Xu et al. employed "a time series dataset of satellite vegetation greenness, Normalized Difference Vegetation Index (NDVI) available from 1982 to 2009 (Tucker et al., 2005), precipitation, temperature, and Palmer Drought Severity Index (PDSI) datasets to investigate anomalies of vegetation greenness linked with extreme climatic events, particularly with drought."
What was learned
Quoting the six scientists, "at the national scale, we found that China experienced an increasing trend in heat waves and drought events during the study period." More precisely, they report that "the average fraction of climate stations with drought events detected increased from 8% in the 1980s, to nearly 20% in the 2000s." Yet in spite of this increase in drought stress, they found that areas exhibiting negative anomalies of vegetation greenness decreased at the rate of 0.9% per year from 1982 to 2009.
What it means
Apparently, the (1) aerial fertilization effect of the concomitant increase in the atmosphere's CO2 concentration, together with its (2) water-use-efficiency enhancement effect, combined with the (3) tendency for most plants to shift their optimal temperature for photosynthesis upwards at higher atmospheric CO2 concentrations, were sufficient to more than overcome the negative effects of the increased heat and drought stress experienced in China over the last three decades of the 20th century.
Reference
Tucker, C.J., Pinzon, J.E., Brown, M.E., Slayback, D.A., Pak, E.W., Mahoney, R., Vermote, E.F. and El Saleous, N. 2005. An extended AVHRR 8 km NDVI dataset compatible with MODIS and SPOT vegetation NDVI data. International Journal of Remote Sensing 26: 4485-4498.