The Economist’s new article (7/18/13) on climate science focuses narrowly on a critically important but also complex piece of scientific inquiry – the climate’s sensitivity to carbon pollution – without a wider look at the science around it and observations of accelerating climate change impacts worldwide. The article relies on a single chart in a leaked draft of the forthcoming IPCC Fifth Assessment Report.
[Updated July 19 with quotes from scientists.]
The following is a guest post by Climate Nexus:
The Economist Zeroes in on Climate Sensitivity
but Misses Bigger Picture
The Economist’s new article (7/18/13) on climate science relies on leaked pieces of two draft reports (the first due in September, the second later next year) to question some issues on the margins of climate change science. It focuses narrowly on a critically important but also complex piece of scientific inquiry – the climate’s sensitivity to carbon pollution – without a wider look at the science around it and observations of accelerating climate change impacts worldwide.
At the core of this article is the relevance of the internationally agreed-upon goal to keep global warming below 2˚ C, and how fast we will surpass it, which in turn depends upon how sensitive the climate is to carbon pollution. While the entire possible range of climate sensitivity is important information, neither this article nor any peer-reviewed science disputes that this year the world witnessed the highest level of CO2 in 15 million years. Current government policies for controlling pollution lead us to the high projections of temperature rise — with catastrophic repercussions – regardless of the exact sensitivity of the climate. We are already seeing the impacts now, from Superstorm Sandy to megafires and severe droughts.
The Economist reports that a new limit for carbon pollution could inform discussions about whether “it is safe to let CO2 concentrations climb” above current levels. The article focuses on a proposed update to the estimated range of climate sensitivity (also called the equilibrium climate sensitivity or ECS), an update that would slightly lower the lower end of the possible range of climate sensitivity.
Climate sensitivity is often calculated by a complex mathematical projection of how much the Earth will warm in response to a doubling of CO2 concentration in the atmosphere. Although it is an important figure to consider when designing climate policy, ECS exists primarily as an abstract number that reflects how scientists anticipate the climate will behave in the future. In general, scientists offer a range of temperatures to estimate climate sensitivity, not a single figure.
Shifting the lower end down, the article explains, could provide an impetus to adjust the ceiling for amount of pollution required to keep global warming below the 2˚ C goal.
The article leaves out critical context – and cannot be fact-checked since it relies on a single chart of an early draft of an unpublished science report.
The Economist story ignores the high end of the estimated range for climate sensitivity. While a new low end would suggest the climate might be slightly less sensitive to carbon pollution than previously thought, the other possibility — that the climate is much more sensitive to carbon pollution than the middle of the range — is still a very real threat.
The story also leaves out the accelerating rate of change observed in key climate indicators: Arctic sea ice melting decades faster than expected, sea levels rising faster and faster, and glaciers dissolving several times faster than before.
The article also ignores the enormous costs already incurred due to climate change. From megafires ravaging the western U.S. — one recent Colorado fire cost insurers more than $290 million — to Superstorm Sandy’s damage to shores of New York and New Jersey, climate change is causing a range of problems. Unfortunately, those bills and the possibility of more in the future won’t decrease whatever range is ultimately determined for climate sensitivity.
Regardless of the exact sensitivity, carbon pollution is currently on track to skyrocket over the limit for avoiding catastrophic climate change.
15 million years ago was the last time the planet had CO2 levels equal to current ones. It was 3-6 ˚C (5-10 ˚F) warmer then, which meant the sea was 75 to 120 feet higher than today.
From the scientists:
Andrew Dessler, professor of atmospheric sciences at Texas A&M:
“The Economist is wrong, predicted warming from the models has NOT declined. The reduction in the prediction of future warming is not due to a reduction in the estimates of sensitivity. The AR5 models have similar climate sensitivities to the AR4 models. Rather, they are due to the fact that the emissions scenario has changed and the RCP2.6 scenario discussed in the article has more aggressive mitigation than the lowest SRES scenario used in the AR4.
Overall, predicted warming from the models has NOT declined — what's declined is lowest emissions scenario. That's an important point to make. And, frankly, the RCP2.6 scenario is pure fiction — unless something happens soon, we'll be far above that scenario.”
“Among other things, the author hopelessly confuses transient warming (the warming observed at any particularly time) with committed warming (the total warming that you’ve committed to, which includes warming in the pipeline due to historical carbon emissions). Even in the best case scenario, business as usual fossil fuel burning will almost certainly commit us to more than 2C (3.6 F) warming, an amount of warming that scientists who study climate change impacts tell us will lead to truly dangerous and potentially irreversible climate change. The article does a disservice to Economist readers by obscuring this critical fact. Sadly, it is hardly the first time in recent history that the Economist has published flawed and misleading stories about climate change.”
“This draft, like any IPCC draft, is the result of the IPCC's iterative process of writing and review process and thus a work in progress. The text is likely to change in response to comments from government and expert reviewers. It is therefore premature and can be misleading to attempt to draw conclusions. Draft reports are intermediate products and do not represent the scientific view that the IPCC provides on the state of knowledge of climate change and its potential environmental and socio-economic impacts at the conclusion of the process.”
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UPDATE July 19:
Joe Romm at Climate Progress eviscerates The Economist piece: Nonsense And Sensitivity: Top Climatologist Slams The Economist For Yet Another ‘Flawed And Misleading’ Piece
As does Dana Nucitelli at Skeptical Science: The Economist Screws Up on the Draft IPCC AR5 Report andClimate Sensitivity
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Earlier guest posts by Climate Nexus: