Title: Fingerprinting the Climate System
Abstract: Fingerprint research seeks to improve understanding of the nature and causes of climate change. The basic strategy is to search for model-predicted patterns of climate change (“fingerprints”) in observed climate records. Such studies exploit the fact that different factors affecting climate have different characteristic signatures. These unique attributes are clearer in detailed patterns of climate change than in global-mean climate information. Fingerprinting is a powerful tool for separating human and natural climate-change signals. Results from fingerprint research provide scientific support for findings of a “discernible human influence” on global climate.
In 1996, at the time of publication of the Second Assessment Report of the Intergovernmental Panel on Climate Change, most fingerprint studies relied on surface temperature. Critics of this work argued that a human-caused fingerprint should be identifiable in many different aspects of the climate system, and not in surface thermometer records alone. Climate 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. The message of this body of work is that human-caused fingerprints are ubiquitous in the climate system.
My lecture looks back at over two decades of efforts to fingerprint the climate system, and will attempt to tell the story of how the scientific community identified a human-caused warming signal.