Ep 25 – Dr. Benjamin Santer, Part 1: Finding climate fingerprints

Dr. Benjamin D. Santer is one of the most decorated and published climate scientists in the world. Most of his historic work has taken place at the Lawrence Livermore National Laboratories. He holds a Ph.D. in Climatology from the University of East Anglia, England. He spent five years at the Max-Planck Institute for Meteorology in Germany, where he worked on the development and application of climate fingerprinting methods. Santer served as convening lead author of the climate-change detection and attribution chapter of the 1995 IPCC report. 

“To prevent dangerous anthropogenic interference with the climate system” 

In 1992, the United Nations Framework Convention on Climate Change, ratified under the elder Pres. Bush, enlisted nearly 200 nations in a mission to “prevent dangerous anthropogenic interference with the climate system.” It was understood then, by scientists in many fields, and by nearly all of the governments in the world, that there would be a chemical threshold after which excess emissions of heat-trapping gases would heat the planet and destabilize the climate system. 

What we didn’t have in 1992 was the clear readable signal showing anthropogenesis, or human cause. 

Like our host Don Shelby, Dr. Santer grew up reading the detective stories of Sherlock Holmes. Holmes famously admonished his investigative partner Watson: “It is a capital mistake to theorize in advance of the facts.” Don became an investigative reporter, and Dr. Santer became one of the most eminent and accomplished climate scientists in the world. Their respective life’s work has been the pursuit of evidence. 


Fingerprinting climate change 

Dr. Santer set out to find the “fingerprints”—the clear readable evidence of what was driving rising levels of heat-trapping gases in Earth’s atmosphere. In 1995, he led a team of scientists who wrote Chapter 8 of the 2nd Assessment Report (AR2) of the Intergovernmental Panel on Climate Change. The core finding of that report was: 

The balance of evidence suggests a discernible human influence on global climate.

That “discernible human influence” finding marks a turning point in the history of human civilization. There was no longer anything like “plausible deniability”. No one could argue legitimately that they “did not know” routine, pervasive, and escalating emissions of carbon dioxide and other heat-trapping gases would destabilize the climate.


Beyond even a sliver of doubt 

In 2019, Dr. Santer and a team of scientists reached a conclusion based on a complete analysis of all relevant data, and found to a “five sigma” level of certainty that human activity was causing climate change, primarily emissions from fossil fuels and land use. The five sigma “gold standard” means only 1 out of 3.5 million times could the observation in question occur by chance.

Dr. Santer says the historic findings would not have been possible without decades of work of teams of scientists and engineers supporting satellite temperature measurements of global warming in the lowermost layer of the Earth’s atmosphere. He describes those satellite observations as “things of beauty”. They measure microwave emissions from oxygen molecules. Those emissions depend on the temperature at different levels in the atmosphere. This makes it possible to accurately measure temperature variations at deep layers of the atmosphere, from space. 

The evidence is conclusive: we now have the signal detection capability to “fingerprint” climate change, with consideration for complex fluid dynamic interactions in the atmosphere and ocean. 


Endangerment is pervasive; we need to step up climate protection. 

The Charney Report—produced by a group of eminent scientists, led by Jule Charney of MIT—had found in 1979 that probable warming of global average surface temperatures was 3ºC. Even at the lower end of probability of 1.5ºC, they found such global heating would result in significant socio-economic impacts. 

The 1992 Climate Convention requires preventing dangerous human-caused climate disruption. In 1995, we detected the clear signal of human cause. In 2019, we confirmed that evidence beyond a sliver of a doubt. So, it is important to note that in 2013, the IPCC’s 5th Assessment Report (AR5) found that fingerprints of human-caused climate disruption were ubiquitous. The AR5 also found that serious climate impacts were already pervasive and having “widespread impacts on human and natural systems”.

Just this week, we learned that Germany’s Constitutional Court had ruled that climate protection is a basic, and universal, human right. The ruling also held that mitigation of dangerous climate-destabilizing emissions must be enshrined in law, not only as an outcome of enabling policies. 

What Part 1 of our conversation with Dr. Santer highlights is the need for more people to understand how complex, multifaceted, and comprehensive an investigation of Earth systems is behind these scientific findings. We can avoid and reduce pervasive climate danger, because of the work of thousands of hard-working scientists, whose collective body of work is establishing a scientific foundation for the future wellbeing of people and Nature. 


Please listen, subscribe, and share, and join us next week for Part 2, when we talk about the more personal side of our responsibility to each other.

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