A Brief History of Climate Fingerprinting

Fingerprint research seeks to improve understanding of the nature and causes of climate change. The basic strategy is to search observed climate records for patterns of climate change (“fingerprints”) predicted by computer models. The underlying premise in fingerprinting is that different factors affecting climate have different characteristic signatures. These unique attributes are clearer in detailed patterns of climate change than in records like global-mean surface temperature. Fingerprint research provided support for the finding of a “discernible human influence on global climate” in the IPCC's Second Assessment Report. At the time of publication of this finding in 1995, most fingerprint studies relied primarily on surface temperature. Critics argued that a human-caused fingerprint should be identifiable in many different aspects of the climate system, and not in surface thermometer records alone. Scientists responded to this justifiable criticism by moving beyond early “temperature only” fingerprint studies, interrogating modeled and observed changes in rainfall, water vapor, river runoff, snowpack depth, atmospheric circulation, salinity, and many other climate variables. As the Sixth IPCC Assessment report concluded in 2021, it is now “unequivocal” that there are human-caused fingerprints in the climate system.