July 23, 2020 by Steve Hanley
In 1979, a National Research Council study prepared by lead author Jule Charney exposed what would likely happen to average global temperatures if the amount of carbon dioxide in the atmosphere doubled compared to pre-industrial levels. Earth’s climate is incredibly complex, making any accurate analysis extremely difficult.
Image credit: WCRP
According to the Washington PostClimate scientists face the difficult task of dealing with uncertainties about how the oceans and the atmosphere respond to historical changes in solar production, the planet’s orbit, past periods with higher amounts of carbon dioxide in the air as well as feedback on how cloud formations act to trap or reflect thermal energy.
The best that Charney and his colleagues were able to do in 1979 was to suggest a variety of possible scenarios, from a low of 1.5 ° Celsius to a maximum of 4.5 ° Celsius. For those of you who prefer the Fahrenheit scale, that is a range of 2.7 to 8.1 degrees. The 1979 numbers became the focus of attention at the COP 22 conference in Paris in 2015, when the overwhelming majority of the world’s nations agreed to take action on our planet by warming more than 1.5 ° C.
Four years later, the latest climate report prepared on behalf of the World Climate Research Program takes a close look at three climate models and concluded that the best 1.5 ° C path is extremely unlikely to occur. In fact, the report states that there is a 66% chance that the planet will warm up in the next 5 decades between 2.6 and 3.9 degrees Celsius. If warming reaches the midpoint of this new range, it would be extremely damaging, said Kate Marvel, a physicist at the Goddard Institute for Space Studies at NASA and Columbia University. If that happens, it will be the equivalent of a “five alarm fire” for the planet, he warns.
If there is no decrease in the rate of carbon emissions, there is a 6 to 18% chance that average global temperatures will rise by more than 4.5 ° C, in which case the Human Goose will be well-cooked, literal and figuratively. Research says there is a very small chance that global temperatures could rise by more than 5 ° C.
S for carbon sensitivity
The problem for climate scientists is determining the sensitivity of the atmosphere to the concentration of carbon dioxide, which climate scientists define in the letter. S. The new study finds that the atmosphere is more sensitive to carbon dioxide than previously thought. The peer-reviewed study was recently published by the journal. Geophysical Comments. Here is the plain language summary:
Earth’s global “climate sensitivity” is a fundamental quantitative measure of Earth’s climate susceptibility to human influence. A historical report in 1979 concluded that it is likely to be between 1.5-4.5 ° C due to doubling of atmospheric carbon dioxide, assuming other influences on the climate remain unchanged. In the 40 years since then, it seems difficult to reduce this range of uncertainty. In this report we comprehensively evaluate all lines of evidence, including some new developments. We find that a large volume of consistent evidence now points to a more secure view of climate sensitivity near the middle or upper part of this range. In particular, it now seems extremely unlikely that climate sensitivity could be low enough to prevent substantial climate change (well above 2 ° C warming) in a future high emission scenario. We still cannot rule out that sensitivity could be above 4.5 ° C by doubling carbon dioxide levels, although this is not likely. Continuous research is needed to further reduce uncertainty and we identified some of the most promising possibilities in this regard.
Dr. James Hansen, the leading climate scientist who testified about the danger of global warming before Congress in 1988, says Science magazine The new study is the result of decades of advancement in climate science. “It is an impressive and comprehensive study, and I am not saying this just because I agree with the result. Whoever guided this deserves our gratitude. Hansen’s granddaughter is one of the young plaintiffs in the innovative climate justice lawsuit. Juliana vs. US. His investigation was the basis of Charney’s original report.
Three streams of research
The 25 researchers analyzed three streams of research: data from 1800 to the present, contributions from the study of clouds and how they can cool or warm the planet, and historical data from 25,000 years ago at the peak of the last Ice Age and 3 million Years ago, when carbon dioxide levels were similar to those on Earth today. The data from all three approaches were then subjected to Bayesian statistics to create a unified end result.
Co-authors often collide heads, says Kate Marvel. “It was such a long and painful process.” The new result narrows the range of what Charney and colleagues calculated by raising the lower limit. In other words, that 1.5 ° C lower limit that everyone has been talking about since 1979 is not realistic. The actual amount of warming will probably be significantly higher.
To reach their new authoritative estimates, the researchers required that multiple lines of evidence point to the same general conclusion and can be explained without being the result of a bias that influences one or more sources of evidence, the Washington Post says. “An important part of the process was ensuring that the lines of evidence were more or less independent,” says lead author Steven Sherwood, a climate scientist at the ARC Center for Excellence in Climate Extremes at the University of New South Wales in Australia in press release. “You can think of it as the mathematical version of trying to determine if a rumor you hear separately from two people could have come from the same source or if one of the two eyewitnesses to a crime has been influenced by hearing the other’s story,” he said.
Andrew Dessler, a climate scientist at Texas A&M University, said in an email to Send“It would have been great if the skeptics had been correct and the climate sensitivity was, say, 1.5 ° C, but that’s not the world we live in.” In other words, people like Rex Tillerson, who mocked climate science by claiming that people will simply adapt to slightly higher temperatures, are wrong. Evil dead, as it turns out.
Looking at the clouds from both sides
Climate skeptics like to say that Earth has basic feedback responses that will limit the amount of warming to less than 1.5 ° C. They argue that higher temperatures will lead to more clouds that will reflect more sunlight into space, which will cause lower temperatures. Cloud dynamics was extensively studied by the researchers, who found no evidence that this feedback loop is powerful enough to affect global temperatures. “There is a growing consensus that the [cloud] the feedback is positive, but not great, “says Thorsten Mauritsen, climate scientist at Stockholm University. Science magazine.
“We found that total negative cloud feedback is highly unlikely,” the study authors write. “The uncertainty is really asymmetric here,” said Kate Marvel in an interview. “We can be very confident in ruling out sensitivities at the low end. Basically, what we are saying here is that there really is no evidence of any kind of natural response, any kind of large and stabilizing feedback, that in the absence of human actions, will save us from climate change. ”
The bottom line
Gavin Schmidt is co-author of the study and a colleague of Kate Marvel at NASA. He sums up the situation perfectly by pointing out that the collective action of nations could prevent the duplication of carbon dioxide in the atmosphere. “The main determinant of future climate is human actions,” he says. Translation? Stop burning fossil fuels, people. You are killing Earth and all living things on it! Is it so hard to understand?
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About the Author
Steve Hanley Steve writes about the interface between technology and sustainability from his homes in Florida and Connecticut or anywhere else Singularity can take him. You can follow him on Twitter but not on any social media platform run by evil lords like Facebook.
