¿Una foto del futuro próximo para las áreas costeras del mundo?
Inundaciones recientes en el norte de Manila, Filipinas
Lo que sigue es largo y por momentos tedioso, pero vale la pena invertir unos minutos en el caso y sus implicancias. Hace poco más de un mes una serie de climatólogos estadounidenses sostuvieron que el proceso de calentamiento global actualmente en curso iba a tener consecuencias prácticas mucho más dramáticas que lo sugerido previamente en informes del Comité Internacional sobre el Cambio Climático. En particular, los climatólogos hicieron hincapié en la posibilidad de un aumento brusco, a lo largo de este siglo, del nivel del mar en varios metros (no menos de tres metros hacia fin de siglo, pero posiblemente más). Adicionalmente postularon un aumento exponencial de "supertormentas" y el eventual enfriamiento del Atlántico Norte (efecto Corriente del Golfo).
Primero vayamos al artículo en sí, del climatólogo James Hansen y otros 16 colaboradores. Los autores lo dieron a conocer en forma online antes de que el trabajo fuera arbitrado y aprobado por los árbitros (los pares de los autores, esto es, otros climatólogos) y el comité editorial de la revista Atmospheric Chemistry and Physics. No jodamos: esta práctica (publicar un paper antes de su crítica y eventual re-escritura posterior) es repudiable y debería ser eliminada de la práctica científica usual. Pero ese es tema para otra discusión. Vayamos ahora a una versión sumarizada del artículo:
Título: Ice Melt, Sea Level Rise and Superstorms: Evidence from Paleoclimate Data, Climate Modeling, and Modern Observations that 2°C Global Warming is Highly Dangerous
Autores: James Hansen, Makiko Sato, Paul Hearty, Reto Ruedy, Maxwell Kelley, Valerie Masson-Delmotte, Gary Russell, George Tselioudis, Junji Cao, Eric Rignot, Isabella Velicogna, Evgeniya Kandiano, Karina von Schuckmann, Pushker Kharecha, Allegra N. Legrande, Michael Bauer y Kwak-Wai L.
Resumen: “There is evidence of ice melt, sea level rise to +5-9 meters, and extreme storms in the prior interglacial period that was less than 1°C warmer than today. Human-made climate forcing is stronger and more rapid than paleo forcings, but much can be learned by combining insights from paleoclimate, climate modeling, and on-going observations. We argue that ice sheets in contact with the ocean are vulnerable to non-linear disintegration in response to ocean warming, and we posit that ice sheet mass loss can be approximated by a doubling time up to sea level rise of at least several meters. Doubling times of 10, 20 or 40 years yield sea level rise of several meters in 50, 100 or 200 years. Paleoclimate data reveal that subsurface ocean warming causes ice shelf melt and ice sheet discharge. Our climate model exposes amplifying feedbacks in the Southern Ocean that slow Antarctic bottom water formation and increase ocean temperature near ice shelf grounding lines, while cooling the surface ocean and increasing sea ice cover and wáter column stability. Ocean surface cooling, in the North Atlantic as well as the Southern Ocean, increases tropospheric horizontal temperature gradients, eddy kinetic energy and baroclinicity, which drive more powerful storms. We focus attention on the Southern Ocean’s role in affecting atmospheric CO2 amount, which in turn is a tight control knob on global climate. The millennial (500-2000 year) time scale of deep ocean ventilation affects the time scale for natural CO2 change, thus the time scale for paleo global climate, ice sheet and sea level changes. This millennial carbon cycle time scale should not be misinterpreted as the ice sheet time scale for response to a rapid human-made climate forcing. Recent ice sheet melt rates have a doubling time near the lower end of the 10-40 year range. We conclude that 2°C global warming above the preindustrial level, which would spur more ice shelf melt, is highly dangerous. Earth’s energy imbalance, which must be eliminated to stabilize climate, provides a crucial metric.”
Finalmente, pasemos a las Summary Implications:
“Humanity faces near certainty of eventual sea level rise of at least Eemian proportions, 5-9 m, if fossil fuel emissions continue on a business-as-usual course, e.g., IPCC scenario A1B that has CO2 ~700 ppm in 2100 (Fig. S21). It is unlikely that coastal cities or low-lying areas such as Bangladesh, European lowlands, and large portions of the United States eastern coast and northeast China plains (Fig. S22) could be protected against such large sea level rise.
Rapid large sea level rise may begin sooner than generally assumed. Amplifying feedbacks, including slowdown of SMOC and cooling of the near-Antarctic ocean surface with increasing sea ice, may spur nonlinear growth of Antarctic ice sheet mass loss. Deep submarine valleys in West Antarctica and the Wilkes Basin of East Antarctica, each with access to ice amounting to several meters of sea level, provide gateways to the ocean. If the Southern Ocean forcing subsurface warming) of the Antarctic ice sheets continues to grow, it likely will become impossible to avoid sea level rise of several meters, with the largest uncertainty being how rapidly it will occur.
The Greenland ice sheet does not have as much ice subject to rapid nonlinear disintegration, so the speed at which it adds to 21st century sea level rise may be limited. However, even a slower Greenland ice sheet response is expected to be faster than carbon cycle or ocean termal recovery times. Therefore, if climate forcing continues to grow rapidly, amplifying feedbacks will assure large eventual mass loss. Also with present growth of freshwater injection from Greenland, in combination with increasing North Atlantic precipitation, we already may be on the verge of substantial North Atlantic climate disruption.
Storms conjoin with sea level rise to cause the most devastating coastal damage. End-Eemian and projected 21st century conditions are similar in having warm tropics and increased freshwater injection. Our simulations imply increasing storm strengths for such situations, as a stronger temperature gradient caused by ice melt increases baroclinicity and provides energy for more severe weather events. A strengthened Bermuda High in the warm season increases prevailing northeasterlies that can help account for stronger end-Eemian storms. Weakened cold season sea level pressure south of Greenland favors occurrence of atmospheric blocking that can increase wintertime Arctic cold air intrusions into northern midlatitudes.
Effects of freshwater injection and resulting ocean stratification are occurring sooner in the real world than in our model. We suggest that this is an effect of excessive small scale mixing in our model that limits stratification, a problem that may exist in other models (Hansen et al., 2011). We encourage similar simulations with other models, with special attention to the model’s ability to maintain realistic stratification and perturbations. This issue may be addressed in our model with increased vertical resolution, more accurate finite differencing method in ocean dynamics that reduces noise, and use of a smaller background diffusivity.
There are many other practical impacts of continued high fossil fuel emissions via climate change and ocean acidification, including irreplaceable loss of many species, as reviewed elsewhere (IPCC, 2013, 2014; Hansen et al., 2013a). However, sea level rise sets the lowest limit on allowable human-made climate forcing and CO2, because of the extreme sensitivity of sea level to ocean warming and the devastating economic and humanitarian impacts of a multimeter sea level rise. Ice sheet response time is shorter than the time for natural geologic processes to remove CO2 from the climate system, so there is no morally defensible excuse to delay phase.out of fossil fuel emissions as rapidly as possible.
We conclude that the 2°C global warming “guardrail”, affirmed in the Copenhagen Accord (2009), does not provide safety, as such warming would likely yield sea level rise of several meters along with numerous other severely disruptive consequences for human society and ecosystems. The Eemian, less than 2°C warmer than pre-industrial Earth, itself provides a clear indication of the danger, even though the orbital drive for Eemian warming differed from today’s human-made climate forcing. Ongoing changes in the Southern Ocean, while global warming is less than 1°C, provide a strong warning, as observed changes tend to confirm the mechanisms amplifying change. Predicted effects, such as cooling of the surface ocean around Antarctica, are occurring even faster than modeled.
Our finding of global cooling from ice melt calls into question whether global temperature is the most fundamental metric for global climate in the 21st century. The first order requirement to stabilize climate is to remove Earth’s energy imbalance, which is now about +0.6 W/m2, more energy coming in than going out. If other forcings are unchanged, removing this imbalance requires reducing atmospheric CO2 from ~400 ppm to ~350 ppm (Hansen et al., 2008, 2013a).
The message that the climate science delivers to policymakers, instead of defining a safe “guardrail”, is that fossil fuel CO2 emissions must be reduced as rapidly as practical. Hansen et al. (2013a) conclude that this implies a need for a rising carbon fee or tax, an approach that has the potential to be near-global, as opposed to national caps or goals for emission reductions. Although a carbon fee is the sine qua non for phasing out emissions, the urgency of slowing emissions also implies other needs including widespread technical cooperation in clean energy technologies (Hansen et al., 2013a).
The task of achieving a reduction of atmospheric CO2 is formidable, but not impossible.
Rapid transition to abundant affordable carbon-free electricity is the core requirement, as that would also permit production of net-zero-carbon liquid fuels from electricity. The rate at which CO2 emissions must be reduced is about 6%/year to reach 350 ppm atmospheric CO2 by about 2100, under the assumption that improved agricultural and forestry practices could sequester 100 GtC (Hansen et al., 2013a). The amount of CO2 fossil fuel emissions taken up by the ocean, soil and biosphere has continued to increase (Fig. S23), thus providing hope that it may be possible to sequester more than 100 GtC. Improved understanding of the carbon cycle and non-CO2 forcings are needed, but it is clear that the essential requirement is to begin to phase down fossil fuel CO2 emissions rapidly. It is also clear that continued high emissions are likely to lock-in continued global energy imbalance, ocean warming, ice sheet disintegration, and large sea level rise, which young people and future generations would not be able to avoid. Given the inertia of the climate and energy systems, and the grave threat posed by continued high emissions, the matter is urgent and calls for emergency cooperation among nations.
Pasemos ahora al tratamiento periodístico del tema. Así lo vio Chris Mooney el 23 de Julio de 2015 en el Washington Post, un diario conservador tradicionalmente en contra del “alarmismo” de los climatólogos en torno al cambio climático:
Título: James Hansen’s controversial sea level rise paper has now been published online
Epígrafe: It has been widely discussed — but not yet peer reviewed. Now, though, you can at least read it for yourself and see what you think.
Texto: A lengthy, ambitious, and already contested paper by longtime NASA climate scientist James Hansen and 16 colleagues appeared online Thursday in Atmospheric Chemistry and Physics Discussion, an open-access journal published by the European Geosciences Union. The paper, entitled “Ice melt, sea level rise and superstorms: evidence from paleoclimate data, climate modeling, and modern observations that 2 ?C global warming is highly dangerous” is now open for comment — peer review in this journal happens in public.
And given how much attention the work has already received, it’s likely to generate plenty of comments from fellow scientists.
The study raises the possibility of a more rapid rate of sea level rise in this century than forecast by the U.N.’s Intergovernmental Panel on Climate Change, whose research is widely regarded as the gold standard of climate research — but also often criticized for being too conservative.
Moreover, the study postulates that this faster sea level rise, brought on by the melting of parts of Antarctica and Greenland, could lead to a number of climate change “feedbacks” that could shut down the oceans’ circulation; stratify the polar seas with warmer waters trapped below cold surface layers; increase the temperature difference between low and high latitudes; and generate stronger storms.
In reporting on the paper this week, The Post solicited comments from five noted climate scientists — as did other journalists — so in a sense, the peer review has already begun. One of them — Kevin Trenberth of the National Center for Atmospheric Research — strongly criticized the study, saying that “there are way too many assumptions and extrapolations for anything here to be taken seriously other than to promote further studies.”
Other researchers also expressed skepticism about some parts of the work — particularly the suggested feedbacks — but acknowledged that they, too, have great concerns about sea level rise from the melting of ice sheets, especially if global warming exceeds 2 degrees Celsius above pre-industrial levels.
So it remains to be seen what the scientific community, overall, will make of this work.
Nevertheless, it is already notable that a group of prominent scientists — not just Hansen, but also his 16 co-authors, working in fields, such as glaciology, oceanography, and paleo-climatology (or the study of the climates of past planetary eras) — are worried that sea level rise of more than 1 meter is a threat this century. Now, the question becomes to what extent the broader scientific community does — or does not — agree.
In the end, that process could very well lead many researchers to seek out a middle ground. In fact, some already have.
“There is no doubt that the sea level rise, within the IPCC, is a very conservative number,” says Greg Holland, a climate and hurricane researcher at the National Center for Atmospheric Research, who has also reviewed the Hansen study. “So the truth lies somewhere between IPCC and Jim.”
Veamos ahora cómo cuenta el caso (más sobriamente, obvio) un blog a cargo de una climatóloga profesional, Judith Curry, del sitio web Climate.etc (http://judithcurry.com):
Título: Hansen’s backfire
Epígrafe: Jim Hansen’s new paper, and his PR strategy, are raising a whole host of issues that are arguably a backfire for his objectives.
Texto: Last week, several media articles appeared about an alarming new paper by Jim Hansen, that was just being submitted to a journal and was not yet publicly available:
Washington Post: The world’s most famous climate scientist just outlined an alarming scenario for our planet’s future
National Observer: 2-degree target may still cause catastrophic sea level rise, James Hansen warns
The Daily Beast: Climate Seer James Hansen Issues His Direst Forecast Yet
My first reaction was this: Why, of all the major news outlets, is only the Washington Post carrying this? No AP, etc.? Why haven’t I received a copy of this paper (usually a reporter or one of the skeptical news outlets would send me a copy). I figured the press release and paper were sent to only a few favored journalists?
The ‘favored journalists’ hypothesis quickly evaporated as articles like this then started to appear:
The Conversation: Study predicts multi-meter sea level rise this century but not everyone agrees
Mashable: The godfather of global warming’s frightening prediction is getting the cold shoulder
The paper is in Atmospheric Chemistry and Physics Discussions, the discussion forum of the European Geosciences Union journal Atmospheric Chemistry and Physics [link]
Andy Revkin has two superb posts on the paper, which I will be referencing in my discussion below:
Whiplash warning: when climate science is publicized before peer review and publication
A rocky first review for a climate paper warning of a stormy coastal crisis
Reviews of the science
While the paper has not yet undergone formal peer review by the journal, journalists have elicited numerous reviews/comments from scientists. From the Washington Post:
Michael Mann “Their climate model scenario wherein Greenland and Antarctic meltwater caused by warming poles, leads to a near total shutdown of ocean heat transport to higher latitudes, cooling most of the globe (particularly the extratropics), seems rather far-fetched to me.” “Whether or not all of the specifics of the study prove to be correct, the authors have initiated an absolutely critical discussion.”
Kevin Trenberth, called the paper“provocative and intriguing but rife with speculation and ‘what if’ scenarios.” Trenberth objected in particular to the climate modeling scenarios used to study freshwater injection as ice sheets melt. “These experiments introduce a lot of very cold fresh water in various places, and then they see what happens.” “The question is how relevant these are to the real world and what is happening as global warming progresses? They do not seem at all realistic to me.” “There are way too many assumptions and extrapolations for anything here to be taken seriously other than to promote further studies.”
Richard Alley,“Many parts of the new paper are likely to stimulate much technical discussion and further research in our community, as we try to weave together the deep-time and recent history to provide useful projections for the future.” “This new paper is not ‘the answer,'” “Particularly, replacing the simple assumptions about doubling times of ice loss with physically based insights is a major focus of our field, but is not yet done and not likely to be ready really quickly.” Alley acknowledged that the IPCC’s sea level rise estimate “is well on the optimistic low-rise side of the possible outcomes,” and added that “the estimates in the new paper of freshening, and discussion of stabilization of the southern ocean and influences on precipitation, are interesting and important.”
From Revkin’s second post:
Tad Pfeffer: If you look at this from the point of view of somebody who’s trying to use this information for anything other than scientific satisfaction, whether or not these very, very rapid rates of sea level rise happen in the next few decades or the next few centuries makes all the difference in the world. The question of when does this start is not really addressed in this paper that I can find, and has been addressed only peripherally in most of the papers about ice sheet instability that I have seen. Ian Joughin made some statements recently [context] that I thought were pretty solid about it being a few centuries before this kind of very rapid sea level rise can take place and that makes sense to me because there are some very important things that you have to do in order to turn on the rapid response of the Antarctic ice sheet – you have to get rid of a couple of big ice shelves for starters. And it’s going to take a few centuries to do that. From a strictly geophysical, glaciological, point of view, a few centuries may not make much difference. But from the point of view of a planner, a policymaker, again these are the people who care about what exactly we’re saying. It makes all the difference in the world. And that’s the part I find missing in this paper. They have to say something about when this is going to occur. They may not be able to say with any great precision, but they have to say something. Because if this is something that’s going to happen in the next few decades, yeah, it’s something we’ve really got to wake up and pay attention about. If it’s something that’s going to happen in the next few centuries then there are a lot of other issues that we have to sort out first.
Without going into any details here, Revkin’s second post provides scientists’ comments that shows the whole section on Eemian superstorms appears to be without basis.
JC comments on the science:
This is an intriguing and wide-sweeping paper that has put together a multi-disciplinary team to examine the possibility of near term catastrophic sea level rise.
For context, Hansen et al. present a much more extreme scenario than the last report from the Intergovernmental Panel on Climate Change and the most recent assessment in 2014 “Expert assessment of sea-level rise by AD 2100 and AD 2300.”
Should we only pay attention to UN and NAS sanctioned assessments by expert teams? Absolutely not (note I will have a follow on post in a day or two that delves into this issue). As stated in my previous post What is the plausible ‘worst scenario’ for climate change?, we should be putting extreme scenarios out there and assess whether they are plausible, possible, or essentially impossible.
The biggest issue raised by Hansen is the potential (plausible? possible?) for a catastrophic >5 m sea level rise in the 21st century. Hansen et al. have proposed a a new mechanism for faster sea level rise – can we falsify this? The collapse of the West Antarctic ice sheet (WAIS) is arguably the most alarming potential impact of global warming. WAIS has collapsed before during previous interglacials, and will undoubtedly collapse again (with or without AGW), with a ~5 m sea level rise. The issue is whether the WAIS can collapse on timescales of decades to a century. Based on what we know (summarized by Tad Pfeffer above), this is a process that would take centuries.
I am not an expert on sea level rise or ice sheets, but here are a few things that frame my own understanding, including some recent research:
Sea level has been rising for millennia. I am not convinced that there is a significant acceleration of sea level rise that can be attributed to human caused global warming (see this previous post).
Recent research from Scripps finds that the Greenland ice sheet did not melt as much as expected during the Eemian but that may mean Antarctic ice sheets melted more than expected
A new paper summarized by Cato that found that the size of the Greenland ice sheet—especially the best observed portions covering the west and southwestern parts of Greenland—during the mid-Holocene was smaller than it is today—but not by a whole lot.
Study finds surprisingly high geothermal heating beneath west antarctic ice sheet [link]
So it looks like we should be more worried about WAIS than about Greenland, and it seems that natural processes (natural climate change and geothermal processes) have caused large sea level changes in the past during interglacial periods (albeit not rapid ones) and will continue to cause sea level to changes in the future. Human contribution so far to sea level rise does not seem particularly significant, given the early 20th century rate of sea level rise is about the same as the current rate. Our ways of inferring future rates of sea level rise from ice sheet melting is crude – we can speculate but not with much confidence. The danger posed by sea level rise is a function of the rate of change far more than the actual sea level itself.
Does Hansen et al. make any contribution to all this? Well their proposed mechanism with feedbacks is of interest and should be explored further. But their conclusions regarding an alarming rate of sea level rise are at best possible (and not plausible).
The policy relevance of the Hansen et al. paper is the articulation of a possible worst case scenario of sea level rise. In robust decision making, the plausible worst case scenario informs decision making but does not necessarily dominate the decision making process.
What role does a ‘possible’ worst case scenario play, apart from clarifying what is plausible? Well, to alarm people and to help build political will to ‘act’ on emissions reductions, particularly for forthcoming Paris COP.
Regarding the policy relevance of the paper, Science Insider writes:
Whether this paper will become a key point of reference in the ongoing climate talks isn’t clear. In advance of the Paris meetings, negotiators from nearly every country in the world have provisionally agreed to the 2°C target. That there is even such an agreement in the offing seems like a victory, but whether it will be reached is still up in the air. Recognizing this, 24 academic and professional institutions in the United Kingdom yesterday issued a sternly worded joint communiqué that called on the international community to take immediate action on reducing emissions. The statement suggested that to have a chance of reaching that 2°C goal, Earth must become a zero-carbon world by the second half of the century. . . But how influential this paper will be is unclear, given its flaws.
Hansen has previously suggested that scientists are often too hesitant to say just how dire the situation is. A 2007 paper he co-authored, titled “Scientific Reticence and Sea Level Rise,” suggested that scientists felt constrained from sounding a full-fledged alarm on how high the waters will get, in part because of the cautious nature of scientific inquiry and the scientific method. But, he says in that paper’s abstract, “there is a danger in excessive caution.” The new paper, he told reporters yesterday, is “significantly more persuasive than anything previously published about just how dangerous 2°C warming would be.”
Hansen’s political agenda is evident as per Revkin’s post:
The new paper, which Hansen told me he’s been working on for eight years, was being rushed into public view with the hope of influencing negotiations at the December round of talks in Parisaimed at crafting a new global climate change agreement. You can hear from Hansen on the reasoning in the recording of his phone conference call with some reporters on Monday.
Also from Revkin regarding a passage apparently in the press release:
The paper got attention in advance because of this passage:
We conclude that continued high emissions will make multi-meter sea level rise practically unavoidable andlikely to occur this century. Social disruption and economic consequences of such large sea level rise could be devastating. It is not difficult to imagine that conflicts arising from forced migrations and economic collapse might make the planet ungovernable, threatening the fabric of civilization. This image of our planet with accelerating meltwater includes growing climate chaos and storminess, as meltwater causes cooling around Antarctica and in the North Atlantic while the tropics and subtropics continue to warm. Rising seas and more powerful storms together are especially threatening, providing strong incentive to phase down CO2 emissions rapidly.
The cited criticisms of the paper all make valid points. The criticisms of Mann and Trenberth are somewhat surprising to me, since I have seen them support papers that are at least as dubious as Hansen et al. Apart from the paper’s flaws, I suspect some of the backlash from these scientists is associated with the fact that this paper has not yet been peer reviewed, and is an integrative, interdisciplinary assessment that challenges the IPCC and other established assessment reports. Revkin cites Tad Pfeffer: “One of the things that troubles me most is that the rapid-fire publication of unsettled results in highly visible venues creates the impression that the scientific community has no idea what’s going on.” There is clearly a concern that such independent assessments, especially by well known and/or reputable scientists, can undermine the authority and messaging of ‘establishment’ assessment and scientists.
Revkin provides some interesting insights into their publicity push and the media response:
But by late Tuesday, as other coverage built, so did questions about the way the study was released, and the quality of its analysis. Another sign of trouble was that, despite the publicity push, the Associated Press, The New York Times, the BBC and The Guardian (despite its yearlong push for climate action blending advocacy and reporting) were among those who steered clear of the study. Listen to the taped call to get a visceral sense of the concerns of Seth Borenstein, the longtime climate reporter at the A.P.
That portentous section above — which in many ways is the only part of the paper that is news given how it centers on the “likely” inundation of most coastal cities in this century without aggressive emissions cuts — is not in the version the journal has posted. It’s in a shorter version, lacking references, that a publicist at Glover Park told me was going into more of a lay publication.
The final draft posted for discussion has more nuanced language, in line with what those arguing for more near-term climate and coastal risk have already articulated.
Maybe we’ll all be a little slower on the draw next time when work is promoted before it is publicized or peer reviewed. There are other merits to slowing down a bit in examining an issue that will be with us for generations — long past Paris. This is amarathon, not a sprint.
I think part of the backfire is associated with having Glover Park handle the media push. Glover Park provides strategic communications campaigns for corporations, non-profit organizations and industry associations. The Group is also involved in lobbying, but it definitely seems to be non-partisan (i.e. open to pretty much all paying customers – I wonder how much Hansen paid for their services and where the funds came from).
I’m not sure I’ve ever seen publicity for a research paper being handled by such a group (Glover doesn’t seem to have prior experience with this, since they rather bungled it for Hansen). Press releases are usually issued by universities, journals or funding agencies. Advocacy groups and think tanks also issue press releases for their own reports. But what about retired or independent scientists? And for scientists whose universities won’t issue a press release? E.g., Georgia Tech declined to issue a press release on Lewis and Curry; the paper was publicized on my blog and by the GWPF. In Hansen’s case, presumably NASA or Columbia could have issued the press release. But probably not including Hansen’s most alarming statements.
In any event, it is refreshing to see the maturity shown by some journalists is handling this issue. They seem to be well trained re the ‘sanctity’ of peer reviewed papers. I am also wondering whether Hansen’s explicit policy advocacy, coupled with a scientific research paper (esp one that had not undergone peer review), contributed to distrust of the research? You would hardly expect Jim Hansen to write a paper saying AGW is less alarming than we thought.
A combination of weak/speculative science, issuing the press release prior to peer review or at least public availability of the paper, a direct challenge to establishment assessment reports, policy advocacy, and use of a professional publicity/marketing/lobbying group to handle the publicity seems to have contributed to the backfire. I doubt that this paper will have any serious influence on the Paris deliberations.
That said, I am very sympathetic to what Hansen did. I regard him as a fellow maverick – thinking for himself and not afraid to challenge the ‘consensus’ – Hansen and I are of course on opposite ends of the climate maverick spectrum, with Hansen more alarmed and myself being less alarmed.
I think what Hansen did raises a whole host of very important issues about climate research, the science-policy interface, and how research is publicized. I will be addressing these issues in a follow-on post (which should be up Mon or Tues).
Por último, reproducimos el artículo de Brian Clark Howard para National Geographic el 21 de Julio de 2015:
Título: Prediction of Rapid Sea Level Rise Won’t Change Global Climate Talks
Epígrafe: A new study predicting 10 feet of sea level rise by the century’s end isn’t supported by the mainstream scientific community.
Texto: A bombshell climate study published this week warns that sea levels may rise a catastrophic 10 feet (3 meters) by the end of this century, rather than the currently predicted 3 feet (.9 meters). But mainstream climate scientists say the report appears speculative and is not in sync with the leading understanding of melting sea ice.
As a result, the study is unlikely to change leading scientific consensus or affect the current negotiations on a comprehensive global agreement on climate change.
The new study, led by former NASA climate scientist James Hansen (now at Columbia University) is set to be published in the peer-reviewed journal Atmospheric Physics and Chemistry. Hansen and 16 colleagues argue in the paper that increasing melting of the ice sheets over Greenland and Antarctica will lead to a shutdown of the ocean’s currents. That would lead to warm waters trapped under Antarctica, which would increase the melting of ice there (if all the continent’s ice melted, it would raise sea level by around 200 feet).
Hansen’s prediction is more dire than the scenario deemed most likely by the Intergovernmental Panel on Climate Change (IPCC), which foresees no more than 3 feet of sea level rise by century’s end. (See an interactive of sea level rise.)
The 10 feet Hansen predicts would make many of the world’s coastal cities, from New York to Shanghai, unlivable. It would also flood South Florida, making everything below Interstate 75 unlivable (from Ft. Lauderdale on down). Three feet would put many of New York’s airport runways underwater, but would be much easier to mitigate with seawalls. (Learn more about the damage expected for Florida.)
A number of prominent climate scientists are skeptical of Hansen’s conclusions.
Ian Joughin, a professor of Earth sciences at the University of Washington, says melting glaciers and ice sheets contribute only about 1 millimeter (0.04 inches) of sea level rise a year.
While Hansen and team predict a doubling in the rate of ice melt in Greenland in the coming years, Joughin says that seems unlikely given past trends and what we currently know about the processes.
“I don't think you can extrapolate current melt rates to get to 10 feet,” says Joughin.
Hansen was not available to comment on the study or the reaction.
Gavin Schmidt, a climate scientist with NASA's Goddard Institute for Space Studies, says the Hansen report is merely “one scenario, and not evidence for that scenario.”
Schmidt says the study “might add to the discussions” but is far enough from conventional thinking that it is unlikely to change mainstream climate views, international negotiations on reducing carbon, or the IPCC’s recommendations to world governments.
“There's plenty of reason to worry about sea level rise, but I don't see 10 feet happening by end of century,” says Joughin.
“Ten feet is well outside the range of peer-reviewed projections and peer-reviewed scientific literature,” says Benjamin Strauss, a scientist at Climate Central, a non-profit climate research and journalism organization in Princeton, New Jersey.