Last week the Washington Post’s energy and environment reporter, Chris Mooney, reported on climate scientist James Hansen’s alarming new report.
The world’s most famous climate scientist just outlined an alarming scenario for our planet’s future:
James Hansen has often been out ahead of his scientific colleagues.
With his 1988 congressional testimony, the then-NASA scientist is credited with putting the global warming issue on the map by saying that a warming trend had already begun. “It is time to stop waffling so much and say that the evidence is pretty strong that the greenhouse effect is here,” Hansen famously testified.
Now Hansen — who retired in 2013 from his NASA post, and is currently an adjunct professor at Columbia University’s Earth Institute — is publishing what he says may be his most important paper. Along with 16 other researchers — including leading experts on the Greenland and Antarctic ice sheets — he has authored a lengthy study outlining an scenario of potentially rapid sea level rise combined with more intense storm systems.
It’s an alarming picture of where the planet could be headed — and hard to ignore, given its author. But it may also meet with considerable skepticism in the broader scientific community, given that its scenarios of sea level rise occur more rapidly than those ratified by the United Nations’ Intergovernmental Panel on Climate Change in its latest assessment of the state of climate science, published in 2013.
The authors conclude that 2 degrees Celsius global warming—the widely accepted international target for how much the world should limit global warming—is “highly dangerous.”
The new paper by Hansen and colleagues can be read online here.
The new paper takes, as one of its starting points, evidence regarding accelerating ice loss from some parts of the planet’s ice sheets, especially West Antarctica. One of Hansen’s co-authors on the new paper, Eric Rignot of NASA, was the lead author of a 2014 study suggesting that, as one NASA press release put it, the decline of West Antarctica could now be “irreversible.”
In the new study, Hansen and his colleagues suggest that the “doubling time” for ice loss from West Antarctica — the time period over which the amount of loss could double — could be as short as 10 years. In other words, a non-linear process could be at work, triggering major sea level rise in a time frame of 50 to 200 years. By contrast, Hansen and colleagues note, the IPCC assumed more of a linear process, suggesting only around 1 meter of sea level rise, at most, by 2100.
“If the ocean continues to accumulate heat and increase melting of marine-terminating ice shelves of Antarctica and Greenland, a point will be reached at which it is impossible to avoid large scale ice sheet disintegration with sea level rise of at least several meters,” the new paper says.
Using climate models and an analogy with the so-called Eemian period or “Marine isotope stage 5e” — an interglacial period some 120,000 years ago that featured considerable sea level rise — the paper goes on to suggest that major ice loss from both Antarctica and Greenland will change the circulation of the oceans, as large volumes of cold, fresh water pour into the seas. This freshening or decreasing saltiness of the ocean, at both poles, could ultimately block the oceans’ overturning circulation, in which (in the northern hemisphere) warm water travels northward, and then colder, denser water sinks and travels back south again.
As the paper notes, there is already evidence of such cooling in the north Atlantic — presumably due to ice loss from Greenland.
Around Antarctica, meanwhile, sea ice has been growing — potentially another indicator of cooling and freshening at the ocean surface due to ice loss from the frozen continent.
In the model employed by Hansen and his coauthors, this cooling and freshening of the oceans eventually leads to a shutdown of the oceans’ circulation, and warm waters trapped at depth below a cold fresh surface layer in the Antarctic region, continually eating away at ice sheets from below. It also triggers a globe with ever-warming tropics but cold poles — leading to a large contrast in temperatures between the mid-latitudes and the polar regions.
A larger temperature contrast between the tropics and the poles, the researchers posit, would then strengthen winter storms or so-called extratropical cyclones, which draw their energy from such contrasts. The study therefore contemplates more powerful storms.
There is much more detail in Chris Mooney’s report.
Andrew Revkin, the New York Times’ “Dot Earth” blogger, reported after the release of the report, A Rocky First Review for a Climate Paper Warning of a Stormy Coastal Crisis:
On Thursday, I wrote about the rocky rollout, prior to peer review, of “Ice Melt, Sea Level Rise and Superstorms: Evidence from Paleoclimate Data, Climate Modeling, and Modern Observations that 2°C Global Warming is Highly Dangerous.”
The 66-page, 17-author paper was posted Thursday in Atmospheric Chemistry and Physics Discussions, the pre-publication forum for papers submitted to the European Geosciences Union journal Atmospheric Chemistry and Physics. (You’ll hear more on the benefits and problems of such open-review journals toward the end of this post.)
The paper is a sweeping cross-disciplinary challenge to status-quo science on risks posed by the building greenhouse effect. The authors, led by James E. Hansen, the veteran climatologist-turned-campaigner, stitch a variety of findings and simulations into a worrisome vision of a looming and abrupt collapse of Antarctic ice sheets and a multi-meter rise in storm-raked seas. They directly call for urgent action by the world’s nations at the Paris treaty talks in December.
It’s no wonder the paper made headlines.
But, after less than two days of public review, the paper is being revealed as much more of a rough sketch, a provocation, than a thorough, deeply grounded new thesis.
In science, that’s not a bad thing. It is how progress gets made. Dip the gutsy new idea in the acid bath of peer review. What’s left is new knowledge.
But in the public sphere, with consequential science, the result can be whiplash, at best, and confusion and disengagement at worst.
Don’t take my word for it.
Below you’ll hear from scientists with significant concerns about keystone sections of the paper — on the evidence for “superstorms” in the last warm interval between ice ages, the Eemian, and on the pace at which seas could rise and the imminence of any substantial uptick in the rate of coastal inundation. Reviewers have until mid September to post comments at the discussion site. I hope the scientists below, and others, do so. As the Montell Jordan song goes, “This is How We Do it.”
As Revkin notes: Jim Hansen has posted an essay pressing his argument for urgency. A very positive review was posted Sunday on the journal website by David Archer of the University of Chicago; Judith Curry of Georgia Tech lauds Hansen’s sweep and “maverick” approach, but isn’t impressed with the sea-level conclusion.
James Hansen writes at The Huffington Post, Disastrous Sea Level Rise Is an Issue for Today’s Public — Not Next Millennium’s:
We can always say that more research is needed. Yet as the evidence accumulates at some point a scientist must say it is time to stop waffling so much and say that the evidence is pretty strong. In my opinion, we have reached that point on the sea level issue.
My conclusion, based on the total information available, is that continued high emissions would result in multi-meter sea level rise this century and lock in continued ice sheet disintegration such that building cities or rebuilding cities on coast lines would become foolish.
That brings me to the other reason for publishing in an open-access “discussion” journal, in addition to wanting to give the sea level rise issue more prominence prior to Paris meetings. There is a danger that the public — not too familiar with the scientific method — may misinterpret criticisms, which are natural and healthy for science. I’m hoping that this publication process will make that process clearer and thus also make the reality of the climate situation clearer.
A startling conclusion of our paper is that effects of freshwater release onto the Southern Ocean and North Atlantic are already underway and 1-2 decades sooner in the real world than in the model (Fig. 2). Observed effects include sea surface cooling and sea ice increase in the Southern Ocean around Antarctica and cooling in the North Atlantic. We suggest that the sluggishness (delayed response) of the climate models may be a result of a common excessive small scale mixing in many ocean models, including ours, as discussed previously. One of our objectives is to draw attention to this — I also hope to get support for our group to do climate modeling to investigate the issue, because we recognize several ways that we could improve the model.
Here, I expand on our conclusion that the science indicates 2°C is not a safe target. Indeed, 2°C is not only a wrong target, temperature is a flawed metric due to meltwater effect on temperature. Sea level, a critical metric for humanity, is at least on the same plane. Earth’s energy imbalance is a critical metric, because energy balance must be restored to stabilize climate, which thus informs us about the required limit on greenhouse gases (GHGs). The Framework Convention on Climate Change, agreed upon at Rio in 1992, defines GHGs as the critical metric, saying that GHGs must be stabilized at a level that avoids “dangerous anthropogenic interference” with climate. Why have policymakers turned away from GHG amount to temperature as the metric with a value (2°C) seemingly pulled from a hat? Could it be because 2°C allows politicians to set emission targets to be achieved in the future when they will be out of office? If we stick to the Framework Convention’s GHG metric, we find that the CO2 stabilization level is not 450 ppm or 400 ppm, it is 350 ppm and possibly lower with immediate implications for policy.
The bottom line message scientists should deliver to policymakers is that we have a global crisis, an emergency that calls for global cooperation to reduce emissions as rapidly as practical. We conclude elsewhere and reaffirm in our present paper that the crisis calls for an across-the-board rising carbon fee and international technical cooperation in carbon-free technologies.
Despite the increased threat of sea level rise, I believe that it is still possible to keep impacts of human-made climate change moderate. However, that optimism is based on the assumption that we are close to the point when it is widely recognized that a policy with an across-the-board rising carbon fee that rapidly phases down carbon emissions also makes good economic sense.
Of course, good economics, science and just common sense are in short supply in the Congress.