The New York Times has a must-read article on how and why the Intergovernmental Panel on Climate Change “seems to be bending over backward to be scientifically conservative” in its forthcoming assessment.
Climate Progress has explained many times why the IPCC’s Fifth Assessment Report (AR5) is “an instantly out-of-date snapshot that lowballs future warming because it continues to ignore large parts of the recent literature and omit what it can’t model.” For instance, we have known for years that perhaps the single most important carbon-cycle feedback is the thawing of the northern permafrost. The AR5′s climate models completely ignore it, thereby lowballing likely warming this century.
The Times explains what the AR5 is doing:
In one case, we have a lot of mainstream science that says if human society keeps burning fossil fuels with abandon, considerable land ice could melt and the ocean could rise as much as three feet by the year 2100. We have some outlier science that says the problem could be quite a bit worse than that, with a maximum rise exceeding five feet.
The drafters of the report went with the lower numbers, choosing to treat the outlier science as not very credible.
In the second case, we have mainstream science that says if the amount of carbon dioxide in the atmosphere doubles, which is well on its way to happening, the long-term rise in the temperature of the earth will be at least 3.6 degrees Fahrenheit, but more likely above 5 degrees. We have outlier science that says the rise could come in well below 3 degrees.
In this case, the drafters of the report lowered the bottom end in a range of temperatures for how much the earth could warm, treating the outlier science as credible.
… Is it right to throw out bleeding-edge science in the one case while keeping it in the other?
I’m not certain that the upper ranges of sea level rise projections are an “outlier.” A good discussion of the recent literature can be found in this January 2013 RealClimate post by Stefan Rahmstorf. His and other research suggests sea level rise could easily be 5 feet if we don’t reverse emissions trends soon.
Similarly, plenty of recent research supports a higher than expected warming this century — see “Science Stunner (11/12): Observations Support Predictions Of Extreme Warming And Worse Droughts This Century” and, from August, “Ocean Acidification May Amplify Global Warming This Century Up To 0.9°F.”
The key point is that while many in the media seem to buy into the myth that the IPCC overstates future impacts, the NY Times points out “it is interesting to see that in these two important cases, the panel seems to be bending over backward to be scientifically conservative.” The NYT notes “there are climate scientists not serving on the committee this year” whose “fear is that the intergovernmental panel might be pulling punches.”
The question, then, is why is the IPCC so conservative, why does it appear to be pulling its punches? True, a certain degree of caution is inherent in science, which is by nature skeptical. That goes double in a consensus-based process where any member country can object to any number. But the Times goes further:
It turns out that the Nobel Prize, welcome as it might have been back in 2007, served the same function it has for many other scientists who have won it over the years: it painted a fat target on the committee’s back. The group has been subjected to attack in recent years by climate skeptics. The intimidation tactics have included abusive language on blogs, comparisons to the Unabomber, e-mail hacking and even occasional death threats.
Who could blame the panel if it wound up erring on the side of scientific conservatism? Yet most citizens surely want something else from the group: an unvarnished analysis of the risks they face.
It would certainly be a shame if the IPCC felt in the least bit cowed by the shameless tactics of the most successful disinformation campaign in history. The IPCC does science no favor by pulling its punches. Future generations are all but certain to suffer through the worst-case scenario — multiple, simultaneous catastrophes — if we keep taking no serious action. They won’t much care why the scientific community pulled its punches, only that they are stuck with the grim consequences for decades if not centuries.
To its credit, the New York Times doesn’t end its story there:
To be clear, even if the Intergovernmental Panel on Climate Change ends up sticking with the lowball numbers in these two instances, they are worrisome enough. As best scientists can tell, the question with sea level is not whether it is going to get to three feet and then five feet of increase, but merely whether it will happen in this century or the next.
Likewise, with temperature, the panel is saying only that the lowball numbers are possible, not that they are likely. In fact, the metric used in the scientific literature, the temperature effect of doubled carbon dioxide, is merely a convenient way of comparing studies. Many people make the mistake of thinking that is how much of a global temperature increase will actually occur.
At the pace we are going, there is no reason to think that we will stop burning fossil fuels when carbon dioxide doubles. We could be on our way to tripling or quadrupling the amount of that heat-trapping gas in the atmosphere. In that case, experts believe, even an earth that turns out to be somewhat insensitive to carbon dioxide will undergo drastic changes.
Precisely. Climate Progress and others have been endeavoring to make this point for years.
In terms of real world warming and its impact on humans, the equilibrium climate sensitivity (ECS) is a mostly theoretical and oversimplified construct. The ECS tells you how much warming you would get IF we started slashing emissions asap and stabilized carbon dioxide concentrations in the air around 550 parts per million (they are currently at 400 ppm, rising over 2 ppm a year, and accelerating) — AND IF there were no slow feedbacks like the defrosting permafrost (or acidification slowing the uptake of carbon by the ocean).
Obviously, the high estimates are even scarier. So it would be nice to hear an explanation from the drafters of this coming report as to why they made decisions that effectively play up the low-end possibilities. But with the report still officially under wraps, they are not speaking publicly. We are thus left wondering whether it is a matter of pure professional judgment — or whether they have been cowed by the attacks of recent years.
Even better would be if the IPCC fixed the problem in the final draft.
View full post on ThinkProgress » Climate