Julie Loisel is wary of expert scientific opinion, but not because she’s a climate change denier.
She researches expert opinion, when it is useful and when it is potentially harmful. The Texas A&M University geography professor outlined the difference in a talk at the University of Wyoming Geology building Monday.
Expert opinion, compiled by asking multiple scientists for their interpretation of data, helps government officials and other decision makers take action when the data on an issue is unclear or incomplete. The first danger of it, though, is who counts as an expert.
“You may have heard the White House has its own experts,” Loisel said, to audience chuckles.
Experts should be leading research in their fields, Loisel said, and also represent a variety of viewpoints. One well-known expert assessment, the climate change report put out by the United Nations’ Intergovernmental Panel on Climate Change (IPCC), screens contributors for competence and seeks contributors with varied scientific backgrounds, countries of origin, age and gender.
Another hazard of expert opinion is the pressure to build consensus. Reports like the IPCC’s look at increasingly stringent “layers of judgment,” starting with the level of agreement among experts on evidence. If experts agree on the evidence, they assess their confidence in conclusions, and if they agree in confidence, they assess the likelihood of the conclusion.
So, the statement “It is very likely human activity is causing climate change” reflects the highest level of agreement, confidence and likelihood among experts.
The problem is when a report publicizes a consensus on a specific number, say “The climate will warm two degrees celcius in the next century,” when this number may represent the average of expert predictions or even be flat out wrong. If the climate warms but not that exact amount, people tend to lose faith in science itself.
“If you have consensus and it turns out to be wrong, to the public that puts everyone in the bucket of ‘Scientists don’t know what they’re talking about,’” Loisel said. “And that’s dangerous.”
In a your-opinion-against-mine era, Loisel said, some people believe expert opinion is elitist and prefer to support views that counter it. This happens with climate change when people prefer to believe the 3 percent of scientists who deny the planet is warming because of human activities, opposed to the 97 percent who agree.
Media coverage that gives equal attention to supporters and deniers of climate change undermines this robust consensus, and some researchers are pushing back.
“There are some scientists who refuse to participate in climate change debates because it’s not a debate,” Loisel said.
On the flip side, other researchers object to participating in expert assessments at all, Loisel said, for fear it gives the impression science on a particular issue is finalized when in fact good science is a continual work in progress.
“They pretty much think once we have an expert assessment it’s ‘case closed,’” she said, “but that’s not how we think of it.”
Instead, Loisel views expert assessments as a way to find out the state of knowledge in a particular area, including possible gaps. Questions that emerge from expert assessments drive future research questions.
Expert opinion has other uses as well. One pillar of scientific knowledge is modeling, but when models are incomplete experts can provide more accurate information or analysis.
This is the case with Loisel’s research on peatlands, a type of land that can trap a significant amount of carbon. Most earth systems models for climate change don’t take peatlands and their carbon sink function into account.
Peatlands won’t save humanity from global warming, however. Peatlands around the world are being destroyed by land use, pollution, fire, permafrost and other factors. This shrinkage is not taken into account in peat carbon sink models, which themselves are not accounted for in earth system models.
The complexity of science means expert opinion, though it has limitations, is still valuable.
