Leading global forecasts widely underestimate the future costs of climate change, a new paper warns.
The findings, to be released Monday in the Review of Environmental Economics and Policy, say projections used by the United Nations Intergovernmental Panel on Climate Change rely on outdated models and fail to account for “tipping points” ― key moments when global warming rapidly speeds up and becomes irreversible.
The IPCC, established in 1988, is the leading international body for assessing climate change, and took on an expanded role after every country on Earth signed the Paris Agreement, the first global pact to cut greenhouse gas emissions. By relying on inaccurate economic models, the organization is misleading policymakers around the world about the risks of climate change, according to the researchers at the Environmental Defense Fund, Harvard University and the London School of Economics who co-authored the paper.
Current estimates for how much climate change will cost take different forms. One recent study looked at projected damage by U.S. county, finding that some counties in low-lying Florida, for example, would see costs of up to 30 percent of their gross domestic product. Other projections are more broad, putting the worldwide figure at $535 trillion by the end of this century.
“It’s difficult to quantify that,” said study co-author Thomas Stoerk, an economist at the Environmental Defense Fund, when asked to give his own estimate. “That’s part of the point of the paper. It could be a lot more than the consensus.”
The paper breaks down into three main points:
• Current projections virtually ignore a very real possibility: that events such as the melting of the Antarctic ice sheet or the faster-than-expected thawing of Arctic permafrost will act like kerosene on a bonfire. These could increase the rate of climate change astronomically.
• These forecasts are based on an average of all possible climate change scenarios, even though newer models account for the increased likelihood of more warming.
• The newer models are still largely abstract, but they also factor in how human uncertainty over climate change can potentially cause even more damage in the future.
All the tools that we argue for already exist. The IPCC could really just go out and use them.Thomas Stoerk, study author and economist at the Environmental Defense Fund
“We have models that allow us to rank the probabilities,” Stoerk said. “There are some models out there that quantify how much the uncertainty itself ― not knowing what’s going to happen ― drives economic estimates.”
Models that rely on averages of warming possibilities fail to factor in new data that show the continued rise in emissions makes the lower-end projections impossible, he said. Newer models, however, account for that reality.
“All the tools that we argue for already exist,” he added. “The IPCC could really just go out and use them.”
The findings come as policy attempts to rein in the world’s greenhouse gas output fall flat. Fossil fuel emissions hit an all-time high last year, causing global carbon dioxide pollution to surge for the first time in three years ― dashing hopes that the production of planet-warming pollution peaked.
In fact, 2017 was the world’s second-hottest year on record and the third-warmest in U.S. history. Climate-fueled natural disasters caused $330 billion in losses from uninsured damages just last year, according to a report from the world’s biggest reinsurer.
In the United States alone, extreme weather events caused $306.2 billion in damages and killed at least 362 people outright during the worst wildfire and hurricane seasons in modern history, the National Oceanic and Atmospheric Administration found in January.
In perhaps the most dramatic demonstration of domestic policymakers’ failure to account for climate change-fueled devastation, Harvard researchers found that 4,645 people died in Puerto Rico in the aftermath of Hurricane Maria last year ― mostly as a result of the failure to provide medication, treatment and electricity ― more than 70 times the official death toll.