Meshing Opposing Methods of Climate Change Measurement

by Tyler Dean

Camille Parmesan and Gary Yohe describe the reasoning and results of the IPCC’s method of measuring the fingerprint of climate change. Their goal was to “improve communication, provide common ground for discussion, and give a comprehensive summary of the evidence.” The IPCC’s method mitigates the result abnormality from the opposing methods and views of biologists and economists by implementing both of their techniques into IPCC’s. The need for the IPCC’s approach comes from both of the existing results being beneficial, but flawed to the point that citizens, readers and policy makers must remain dubious of the results. Economists focus on direct evidence, in the moment and apply time discounting in order to account for their lack of quality control. From this, they conclude that climate change is only important if it is responsible for the current biotic changes; which leads economists to the conclusion that climate change’s fingerprint is weak.

The reason for this is that most short term local changes are not caused by climate change, but by changes in the abundance and allocation of species; ergo economists can argue that climate change is if little importance to wild systems. The problem with this is it ignores the fact that over time, several small incidents or changes compile and yield large problems. Another problem with this is the inability to measure whether or not the changes to the environment over time are caused by climate change or by land-use change and natural fluctuations in the abundance and distributions of species. Biologists focus on minimizing the confounding factors by searching for trends in undisturbed environments and testing for the effects of climate change. Economists view this as a biased, while biologists view this as a pure analysis, free of non-climatic disruption. Biologists’ methods allow them to implement a quality control that eradicates their need of the time discount used by economists. The IPCC utilizes the biologists’ confidence assessment for “statistical meta-analyses of effect size and more comprehensive categorical analysis of the full literature.” They then create a model of probability that considers “proportion of observations, matching climate change predictions, numbers of competing explanations for each of those observations, and casual attribution of each observation to climate change” for both the biologists’ results. They use the same model and variables to consider the economists’ confidence assessment. Last, IPCC explore the sign switching patterns that are predicted by and/or result from climate change. From this process, the IPCC concludes very high confidence levels, supported by their analysis results.

Parmesan, Camille, and Gary Yohe. 2003. “A globally coherent fingerprint of climate change impacts across natural systems.” Nature 42. 37-42.


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