C. Parmesan, G. Yohe, A globally coherent fingerprint of climate change impacts across natural systems. Nature 421, 37 (2003). doi:10.1038/nature01286 pmid:12511946
This article addresses the difficulties the Intergovernmental Panel on Climate Change had reaching an agreement (in 2001) on the extent to which climate change is causing changes in biological systems. The authors suggest that differences in approach, particularly between biologists and economists, were a source of disagreement.
To bridge the gap between the disciplines, they used several analyses, combinations of biological and economic approaches, to analyze a large set of global biological data. They concluded that there is sufficient evidence to say with very high confidence that climate change is already affecting living systems.