Background
The authors write that "the Oriental migratory locust (Locusta migratoria manilensis) has been one of the most damaging agricultural pests throughout Chinese history."

What was done
Based on the decadal locust abundance data of Ma (1958) for the AD 950s-1950s, the decadal Yangtze Delta flood and drought frequency data of Jiang et al. (2005) for the AD 1000s-1950s, and the decadal mean temperature records of Yang et al. (2002) for the AD 950s-1950s, Zhang et al. (2009) employed wavelet analysis "to shed new light on the causal relationships between locust abundance, floods, droughts and temperature in ancient China."

What was learned
The international team of Chinese, French, German and Norwegian researchers found that coolings of 160-170-year intervals dominated climatic variability in China over the past millennium, and that these cooling periods promoted locust plagues by enhancing temperature-associated drought/flood events.

What it means
The six scientists say their results suggest that "global warming might not only imply reduced locust plague[s], but also reduced risk of droughts and floods for entire China," noting that these findings "challenge the popular view that global warming necessarily accelerates natural and biological disasters such as drought/flood events and outbreaks of pest insects," as promulgated by the most recent report of the Intergovernmental Panel on Climate Change. Indeed, they say their results are an example of "benign effects of global warming on the regional risk of natural disasters."

References
Jiang, T., Zhang, Q., Blender, R. and Fraedrich, K. 2005. Yangtze delta floods and droughts of the last millennium: abrupt changes and long-term memory. Theoretical and Applied Climatology 82: 131-141.

Ma, S. 1958. The population dynamics of the oriental migratory locust (Locusta migratoria manilensis Meyen) in China. Acta Entomologica Sinica 8: 1-40.

Yang, B., Brauning, A., Johnson, K.R. and Yafeng, S. 2002. Temperature variation in China during the last two millennia. Geophysical Research Letters 29: 10.1029/2001GL014485.