By Maeve Dunigan
University of Maryland (UMD) Professor Ross Salawitch is an atmospheric and climate scientist, whose main research interest includes the quantification of the effect of human activity on atmospheric composition. Salawitch, who has joint appointments in the Departments of Atmospheric and Oceanic Science (AOSC), Chemistry and Biochemistry (CHEM), and the Earth System Science Interdisciplinary Center (ESSIC), was conducting research based on a class he had taught when something startling occurred.
“We came up with a rather stunning result,” he said. “Big climate models warm too quickly.”
Paris Climate Agreement: Beacon of Hope is an open access book, published earlier this year and co-written by Salawitch. The publication presents a more positive viewpoint regarding the potential success of the goals determined by the Paris Climate Agreement, signed in 2016, that is commonly appreciated.
Salawitch and other researchers realized that big climate models commonly used to predict the rise of greenhouse gasses were coming up with skewed results. Though this was fascinating information, it wasn’t going to become a book on its own.
“We believe that global warming is real, humans are responsible, we had better do something about it, but the big climate models warm too quickly,” he said. “That’s the beginning of the answer. But good luck getting that published.”
This was bad news that didn’t yet have a solution. So the team began to analyze the pledges of the Paris Climate Agreement and soon came to the conclusion that, using their framework, the parameters of the agreement could put the world on the right track to eventually lower global warming by two degrees Celsius.
“Now we go from a bad news story, that the big climate models have problems, to a good news story, that the Paris Climate Agreement may work,” he said.
Eventually, Salawitch attracted the attention of a publisher while giving a high-profile talk at a meeting of the American Meteorological Society (AMS), who agreed to let the team publish open access, meaning anyone can read the book for free.
“We’re not in it to get rich,” said Salawitch. “We’re in it to get the word out.”
The empirical model used in this new approach differs from the big climate models in a variety of ways. Big climate models are used to calculate many quantities, including precipitation, clouds, and ocean circulation response. There are about 40 of these models in the world and each of them involves a huge team of researchers.
“Our approach is very different,” said Salawitch. “What we’re doing is trying to understand one thing and one thing only, what and what exactly drives global mean surface temperature.”
Big climate models warm a factor of two too quickly. Salawitch believes that they do so because they simulate cloud feedback being strongly positive (i.e., within these models the response of clouds reinforces the global warming due to rising greenhouse gases), when in reality, the cloud feedback might be zero, or even slightly negative. The big climate models are also free running, and not trained with data.
“We train our model with data,” he said. “We’re just projecting how global mean surface temperature will evolve, but it’s a framework that’s very conducive to the Paris Climate Agreement, because the way the Paris Climate Agreement is written, it’s written to limit the rise in global mean surface temperature (GMST).”
The empirical model used in Beacon of Hope is also well-aligned with the projections of GMST presented by the Intergovernmental Panel on Climate Change (IPCC), based on their own assessment of the climate model forecasts, an agreement that Salawitch referred to as a “saving grace,” as it shows the projections provided by his group might be realistic.
A world that doesn’t so fully rely on fossil fuels is one that we will have to fight hard to achieve, but Salawitch believes that if we start working now, it can be done. The goals set by Paris, which generally stop at modest reductions in the emission of greenhouse gases by the year 2030, alone will not save the world from two degree warming. The improvements in carbon intensity of all of the world’s economies must be extended out to the year 2060, and the developed as well as developing world must be fully involved.
“We have to keep getting better,” he said. “That’s vitally important because, the big message of our book is [that] we need 50 percent of global energy to be produced by some means that doesn’t produce greenhouse gasses, 50 percent globally, by 2060 … We better start figuring this out really soon.”