Unobserved time effects confound the identification of climate change impacts.
A recent study by Feng et al. [Feng S, Krueger A, Oppenheimer M (2010) Proc Natl Acad Sci USA 107:14257-14262] in PNAS reported statistical evidence of a weather-driven causal effect of crop yields on human migration from Mexico to the United States. We show that this conclusion is based on a different statistical model than the one stated in the paper. When we correct for this mistake, there is no evidence of a causal link.
Department of Agricultural and Resource Economics, University of California, Berkeley, CA 94720, USA. auffhammer@berkeley.edu
Maximilian
M
Auffhammer
Jeffrey R
JR
Vincent
D015984:Causality; D057231:Climate Change; D018556:Crops, Agricultural / Q000254:growth & development*; D004641:Emigration and Immigration / Q000706:statistics & numerical data*; D006801:Humans