Three key anniversaries in the history of climate change science are recognized this week in a commentary published by nearly a dozen climate researchers, including five from Lawrence Livermore National Laboratory.
LLNL authors are Ben Santer, Celine Bonfils, Jeffrey Painter, Stephen Po-Chedley and Mark Zelinka.
The commentary appears in the February 25 edition of Nature Climate Change, a leading climate journal.
Each anniversary discussed in the commentary recognizes an influential event that occurred 40 years ago, at a time when climate science did not yet have overwhelming evidence that human activities are dramatically changing Earth’s climate.
Today, that evidence is widely accepted by the scientific community, from broad brush observations of rising oceans and shrinking ice sheets to more subtle measurements of how heat is distributed in the upper versus the lower atmosphere.
In 1979, however, thousands of studies were still to be done. Each event commemorated in this week’s Nature Climate Change helped pave their way.
One event was the 1979 publication of a National Academy of Sciences study called the Charney report, which forecast changes that would help guide future scientific efforts.
Its predictions have largely been validated. For example, it forecast a probable global temperature rise of about 3ºC (5.4ºF) if carbon dioxide levels double compared to pre-industrial levels.
The levels haven’t doubled yet and may not if societies take certain actions – if fossil fuel burning is curtailed, for example – but the pace of warming has occurred much as predicted to date.
The Charney report recognized that cloud behavior would be a source of uncertainty in future climate assessments, giving scientists a focus for key studies. It foresaw the importance of developing powerful computer models and then validating them with actual observations.
It observed that the oceans absorb so much heat energy from the atmosphere that they may hide signs of warming until there is so much carbon dioxide in the atmosphere that “appreciable climate change is unavoidable.”
The commentary called the Charney report “the handwriting on the wall.” The warning it set forth “was accurate and remains more relevant than ever.”
The second anniversary marks the publication of a technical paper by Klaus Hasselmann of the Max Planck Institute for Meteorology in Germany.
Using methods that originated in the electronics industry, Hasselmann developed a statistical system that could extract telltale signs of human-caused warming from the background fluctuations of a climate that also fluctuates for natural reasons.
The effort was “a statistical roadmap for hundreds of subsequent climate change detection and attribution studies,” according to the Nature Climate Change paper.
These studies have identified human fingerprints in a wide range of “independently monitored” climate observations.
Hasselmann showed that it was possible to look at the importance of global climate patterns rather than study localized climate fluctuations in a piecemeal and disconnected manner, the custom at that time.
The third 1979 milestone was the beginning of 24/7 satellite measurement of the atmosphere, an effort carried out today by NASA and the National Oceanic and Atmospheric Administration.
Before satellites, weather and therefore climate data were spotty, readily available in populated regions but sparse (if they existed at all) in rarely traveled places, like the southern oceans or the frozen mountain plateaus of Asia.
The satellites and their microwave sensors improved and generated more and higher quality data with the passing years. They made it possible to estimate sea surface temperature, temperatures aloft, humidity, wind speed and other atmospheric characteristics nearly everywhere, continuously and systematically.
The U.S. made the information available to scientists around the globe, helping to standardize climate science generally and providing “a useful test-bed for Hasselmann’s signal detection strategy,” the commentary said.
Among many other findings, the studies “revealed that human fingerprints were identifiable in the warming of the troposphere (lower atmosphere) and cooling of the lower stratosphere.”
This separation of warming and cooling zones had been predicted more than a decade before the satellites were launched, and the measurements were one important confirmation of the reality of climate change.
In addition to LLNL, climate research authors of the commentary came from the University of Washington, the Canadian Centre for Climate Modeling and Analysis, the University of Edinburg, Remote Sensing Systems, and the National Oceanic and Atmospheric Administration.
In an interview, Ben Santer, the prominent LLNL climate scientist and first author of the commentary, said the authors knew each other from various past research associations.
“The more we talked about these three anniversaries, the more it became clear that they were interrelated,” he said.
“Charney said there will be warming. Hasselmann said, ‘Here’s how to look for it.’ And (the satellites) provided the data to enable scientists like us at Lawrence Livermore National Laboratory to search for a human caused warming signal.”
While the science involved has been academically satisfying, he said, “there is no joy in telling the story” because of the damage already done, and rapidly getting worse as a result of the changing climate.