News and Outreach: Kerry Emanuel

Climate scientists disagree on the impact of the Atlantic Multidecadal Oscillation—a 25-to-40-year cycle of cooling and warming of the Atlantic Ocean—on the frequency of hurricanes. Some expect the AMO to drive cooler sea surface temperatures and fewer hurricanes in coming decades, but others do not think the AMO works this way. EAPS Professor Kerry Emanuel, who is affiliated with the MIT Joint Program, believes that another factor—air pollution—has played a significant role in reducing hurricane activity.

Helen Hill | EAPS

The MIT Department of Earth, Atmospheric and Planetary Sciences (EAPS), together with the Lorenz Center and the MIT Alumni Association, are hosting a climate symposium on Jan. 27 in the Kirsch Auditorium of the Stata Center (Room 32-123).

While this event is now fully subscribed, the day's proceedings will be available via a live webcast. (Register to watch.)

Taking action on climate change has become a dominating issue — globally, nationally, locally, and even here at MIT. Yet so many questions remain. How much and how quickly will climate change? How will these changes manifest, and where? What are the greatest risks posed by a changing climate and how likely are these worst-case outcomes? What is the science behind climate change, and how can basic research inform our efforts to avert, mitigate and adapt to its impacts?

Essential knowledge built through basic climate research lies at the core of all these questions. We would not even recognize that Earth’s climate is changing were it not for the cumulative efforts of climate scientists over the past five decades, many of them here at MIT. And we cannot hope to improve the climate outcome for ourselves and future generations without the vital, ongoing contributions of fundamental climate science research.

Touching on everything from the essentials of planetary climate through the complexities of Earth’s climate system to the challenges of finding the will to act on our knowledge to address current climate change, the symposium features talks and discussion by faculty experts from across the spectrum of climate research at MIT, plus keynote speakers Marcia McNutt (editor-in-chief of Science) and Justin Gillis (environmental science writer for The New York Times).

Speakers include:

Daniel Cziczo, MIT Department of Earth, Atmospheric and Planetary Sciences
Elfatih A. B. Eltahir, MIT Department of Civil and Environmental Engineering
Lindy Elkins-Tanton, Arizona State University
Kerry Emanuel, MIT Earth, Atmospheric and Planetary Sciences
John Fernandez, MIT Environmental Solutions Initiative
W. Eric L. Grimson, MIT Chancellor for Academic Advancement
Valerie Karplus, MIT Sloan School of Management
Thomas Malone, MIT Sloan School of Management
John Marshall, MIT Department of Earth, Atmospheric and Planetary Sciences
David McGee, MIT Department of Earth, Atmospheric and Planetary Sciences
Ronald Prinn, MIT Department of Earth, Atmospheric and Planetary Sciences
Sara Seager, MIT Department of Earth, Atmospheric and Planetary Sciences
Noelle Selin, MIT Institute for Data, Systems and Society and Department of Earth, Atmospheric and Planetary Sciences
Lawrence Susskind, MIT Department of Urban Studies and Planning
Dennis Whyte, MIT Department of Nuclear Science and Engineering
Maria Zuber, MIT vice president for research

For more information and a detailed agenda, visit the EAPS symposium website.

Image: Jennifer Fentress/EAPS

MIT events throughout climate talks underscore Institute's global perspectives and partnerships

Jennifer Chu | MIT News Office

"Grey swan" cyclones — extremely rare tropical storms that are impossible to anticipate from the historical record alone — will become more frequent in the next century for parts of Florida, Australia, and cities along the Persian Gulf, according to a study published today in the journal Nature Climate Change.

In contrast with events known as “black swans” — wholly unprecedented and unexpected occurrences, such as the 9/11 attacks and the 2008 financial collapse — grey swans may be anticipated by combining physical knowledge with historical data.

In the case of extreme tropical cyclones, grey swans are storms that can whip up devastating storm surges, beyond what can be foreseen from the weather record alone — but which may be anticipated using global simulations, along with historical data.

In the current paper, authors Kerry Emanuel, the Cecil and Ida Green Professor in Earth and Planetary Sciences at MIT, and Ning Lin of Princeton University simulated the risk of grey swan cyclones, and their resulting storm surges, for three vulnerable coastal regions. They found a risk of such storms for regions such as Dubai, United Arab Emirates, where tropical storms have never been recorded. In Tampa, Florida, and Cairns, Australia — places that experience fairly frequent storms — storms of unprecedented magnitude will be more likely in the next century.

“These are all locations where either no one’s anticipated a hurricane at all, such as in the Persian Gulf, or they’re simply not aware of the magnitude of disaster that could occur,” Emanuel says.  

Beyond forecasts

To date, the world has yet to see a black swan or grey swan cyclone: Every hurricane that has ever occurred in recorded history could, in retrospect, have been predicted, given the previous pattern of storm activity.

“In the realm of storms, I can’t really think of an example in the last five or six decades that anybody could call a black swan,” Emanuel says. “For example, Hurricane Katrina was anticipated on the timescale of many years. Everybody knew New Orleans was going to get hammered. Katrina was not meteorologically unusual at all.”

However, as global warming is expected to significantly alter the Earth’s atmosphere and oceans in the coming decades, the track and magnitude of hurricanes may skew widely from historical patterns.

To get a sense of the frequency of grey swan cyclones in the next century, Emanuel and Lin employed a technique that Emanuel’s team developed 10 years ago, in which they embed a detailed hurricane model into a global climate model.

For this paper, the team embedded the hurricane model into six separate climate models, each of which is based on environmental data from the past, or projections for the future. For each simulation, they generated, or “seeded,” thousands of randomly distributed nascent storms, and observed which storms produced unprecedented storm surges, given environmental factors such as temperature and location.

From their simulations, the researchers observed that storm surges from grey swan cyclones could reach as high as 6 meters, 5.7 meters, and 4 meters in Tampa, Cairns, and Dubai, respectively in the current climate. By the end of the century, surges of 11 meters and 7 meters could strike Tampa and Dubai, respectively.

Changing risk

To put this in perspective, the last big hurricane to hit Tampa, in 1921, produced a devastating storm surge that measured 3 meters, or about 9 feet high.

“A storm surge of 5 meters is about 17 feet, which would put most of Tampa underwater, even before the sea level rises there,” Emanuel says. “Tampa needs to have a good evacuation plan, and I don’t know if they’re really that aware of the risks they actually face.”

Emanuel says that Dubai, and the rest of the Persian Gulf, has never experienced a hurricane in recorded history. Therefore, any hurricane, of any magnitude, would be an unprecedented event.

“Dubai is a city that’s undergone a really rapid expansion in recent years, and people who have been building it up have been completely unaware that that city might someday have a severe hurricane,” Emanuel says. “Now they may want to think about elevating buildings or houses, or building a seawall to somehow protect them, just in case.”

Upper limit shift

The team also found that as storms grow more powerful in the coming century, with climate change, the most extreme storms will become more frequent.

The team’s results show that the expected frequency for a grey swan cyclone with a 6-meter storm surge in Tampa would fall from 10,000 years today to as little as 700 years by the end of the century. Put another way, today Tampa has a one in 10,000 chance of being struck by a devastating grey swan cyclone in any given year — odds that will remain the same next week, or next year.  

“Hurricanes, unlike earthquakes, are like a roll of the die,” Emanuel says. “Just because you had a big hurricane last year doesn’t make it more or less likely that you’d have a big hurricane next year.”

But in 100 years, Tampa’s odds of a 6-meter storm surge will be 14 times higher, as the world’s climate shifts.

“What that really translates to is, you’re going to see an increased frequency of the most extreme events,” Emanuel says. “Whereas the upper limit of hurricane wind speeds today might be 200 mph, 100 years from now it might be 220 mph. That means you’re going to start seeing hurricanes that you’ve never seen before.”

The group’s estimates of extreme storm intensity, while high, are not unrealistic for the coming century, says Greg Holland, senior scientist at the National Center for Atmospheric Research.

“This is an excellent example of the type of study needed to fill out our knowledge of what is possible with damaging events such as storm surge,” says Holland, who was not involved in the study. “Although the events listed are … rare, a knowledge of their possibility helps considerably with assessing more likely events in planning.”

This research was funded in part by the National Science Foundation.

David L. Chandler | MIT News Office

Panelists at an MIT discussion yesterday on how to improve communication about climate change said that while serious obstacles remain in making the issues and potential solutions clear to the public and political leaders, there is some cause for optimism, especially when the messages focus on readily available solutions.

The discussion, part of the MIT Conversation on Climate Change, was moderated by John Durant, director of the MIT Museum, and introduced by Nate Nickerson, MIT’s vice president for communications. The event — titled “Getting Through on Global Warming: How to Rewire Climate Change Communication” — featured journalists, scientists, and policy experts who deal with the issue of climate change. Durant opened the session by asking, given the often-polarizing nature of the subject, “how the MIT community … can do a better job of contributing to the discussion.”

Chris Mooney, an environmental reporter at the Washington Post, pointed out that rhetoric can quickly give way to action when people are confronted by serious impacts in their own backyards. For example, in Florida, four southern counties most affected by rising sea levels and storm surges are proceeding with serious countermeasures.

In that part of Florida, Mooney said, “the climate debate is not particularly partisan”:  People see the need for action to protect vulnerable coastal lands, and have focused on specific solutions — such as installing one-way valves in storm drains to prevent storm surges from backing up into homes.

Such contrasts between rhetoric and action provide a ray of hope, panelists said. Drezen Prelec, the Digital Equipment Corp. Leaders for Global Operations Professor of Management at MIT’s Sloan School of Management, said that sudden and unexpected shifts in public opinion — on issues such as smoking and gay marriage — show that rapid changes are possible, even in the face of strong resistance from political leaders.

Judith Layzer, a professor of environmental policy in MIT’s Department of Urban Studies and Planning, said that politicians will begin to take action on issues such as limiting greenhouse-gas emissions when it becomes clear that their constituents take the issue seriously enough to vote accordingly. “We only will make progress if we let them know we will vote them out of office,” she said.

Tom Levenson, a professor of science writing and head of MIT’s Graduate Program in Science Writing, said that a key to getting people to internalize the importance of climate change is through memorable storytelling. “If you wish to communicate with human beings in ways that they will remember, you need a story,” he said.

Susan Hassol, director of the nonprofit group Climate Communication, said that research has shown that when Republicans who had resisted climate change are presented with potential solutions based on free-market mechanisms, they are three times more likely to accept those rather than solutions based on government regulations or taxes.

“We all want clean air and water and a better world for our kids,” she added — so it’s important to stress “how climate change is affecting these things.”

Kerry Emanuel, the Cecil and Ida Green Professor in Earth and Planetary Sciences at MIT, whose research has shown the potential for stronger hurricanes as a result of climate change, said that he has made a particular effort “not to preach to the converted, but to go to the heart of skepticism.”

Emanuel said he has spoken to numerous groups known for their opposition to measures to curb greenhouse gases, and for skepticism about the human influence on climate — including conservative think tanks such as the Heritage Foundation and the American Enterprise Institute. He believes that such groups’ resistance has to do with their sense of possible solutions involving government actions.

“They have a very narrow perception of what the range of possible solutions is,” Emanuel said. “Once they understand there are solutions out there that they can embrace, then suddenly they start to accept the science.”

These audiences are much more receptive when presented with a panoply of possible actions, Emanuel added, including ones based on market forces, entrepreneurship, and national competitiveness. “There are a lot of things we ought to be embracing that are worth doing anyway,” he said, such as developing low-carbon energy technology that the U.S. might “sell to other countries, instead of buying it from them.”

Such technologies, Emanuel said, could include next-generation nuclear reactors and carbon-capture systems that could allow fossil-fuel power plants to operate with drastically reduced emissions.  

Hassol summed up lessons she has learned from her attempts to communicate about climate change: “We need to stop trying to give science lessons, and talk about the solutions. The sweet spot is on the solution side.”

When it comes to solutions, panelists said, MIT is especially well positioned to take a leadership role. Among many proposals that have been made through MIT’s “Idea Bank” on climate change, the panel discussed the possibility of opening an MIT facility in Washington to educate political leaders and their staffs on climate and energy topics. Another suggestion was the creation of a rapid-response team of impartial experts who could quickly respond to media reports that contain misleading or incorrect information.

By Angela Fritz | The Washington Post

Late last week, one of the strongest tropical cyclones on record in the South Pacific made a direct hit on the island nation of Vanuatu, leaving more than 20 people dead and massive destruction in its wake.

Tropical Cyclone Pam’s sustained winds of 165 mph and gusts nearing 200 ripped trees from the ground and flattened homes. In the course of a day, Tropical Cyclone Pam intensified from the equivalent of a category 2 hurricane to a category 4, before going on to become just the second category 5 on record to directly hit an island in the South Pacific. At the time, Pam was the strongest of four concurrent cyclones in the western Pacific and Indian oceans.

It was “one of the largest and most intense cyclones” the region has seen, says Greg Holland, a senior scientist at the National Center for Atmospheric Research who has specialized in South Pacific tropical storms. “Taken together I have not seen a storm with higher damage potential in the region,” Holland told The Washington Post, “and this shows in the extensive damage that Vanuatu has suffered.”

Now, as the death toll grows and the people of Vanuatu pick up the pieces of their devastated lives, scientists are pondering what role Earth’s changing climate may have had in the destructive potential of the storm.

In a post on the climate science blog RealClimate, MIT meteorologist Kerry Emanuel dissects the science embodied in the question, coming to the conclusion that “while Pam and Haiyan, as well as other recent tropical cyclone disasters, cannot be uniquely pinned on global warming, they have no doubt been influenced by natural and anthropogenic climate change and they do remind us of our continuing vulnerability to such storms.”

Read the full article on the Washington Post

by Peter Dizikes

Powerful, destructive tropical cyclones are now reaching their peak intensity farther from the equator and closer to the poles, according to a new study co-authored by an MIT scientist.

The results of the study, published today in the journal Nature, show that over the last 30 years, tropical cyclones — also known as hurricanes or typhoons — are moving poleward at a rate of about 33 miles per decade in the Northern Hemisphere and 38 miles per decade in the Southern Hemisphere.

“The absolute value of the latitudes at which these storms reach their maximum intensity seems to be increasing over time, in most places,” says Kerry Emanuel, an MIT professor and co-author of the new paper. “The trend is statistically significant at a pretty high level.”

And while the scientists who conducted the study are still investigating the atmospheric mechanisms behind this change, the trend seems consistent with a warming climate.

“It may mean the thermodynamically favorable conditions for these storms are migrating poleward,” adds Emanuel, the Cecil and Ida Green Professor of Earth and Planetary Sciences at MIT.

The implications are serious, since the movement of peak intensity means regions further north and south of the equator, which have not previously had to face many landfalls by violent cyclones, may now have greater exposure to these extreme weather events. That, in turn, could lead to “potentially profound consequences to life and property,” the paper states. “Any related changes to positions where storms make landfall will have obvious effects on coastal residents and infrastructure.”

Moving with the trade winds?

The paper, “The Poleward Migration of the Location of Tropical Cyclone Maximum Intensity,” was co-written by James P. Kossin — who is the lead author — of the National Oceanic and Atmospheric Administration's National Climatic Data Center; Gabriel A. Vecchi of the National Oceanic and Atmospheric Administration; and Emanuel.

To conduct the study, the scientists used international data from 1982 to 2012, collected by NOAA’s National Climatic Data Center. They used the location of peak intensity of cyclones as a benchmark because it is a more consistent metric than statistics such as storm duration: The duration can be harder to estimate because of difficulties in establishing precisely when a storm should first be considered a tropical cyclone.

While there are regional differences in the poleward movement of cyclones, the fact that every ocean basin other than the northern Indian Ocean has experienced this change leads the researchers to suggest, in the paper, that this “migration away from the tropics is a global phenomenon.”

However, Emanuel notes, the global mechanisms underlying the trend are a matter for further research.

“We think, but have not yet been able to establish, that this is connected to independently observed poleward expansion of the Hadley circulation,” Emanuel says, referring to a large-scale pattern of global winds, which in recent years has also moved further poleward. The paper notes the potential impact of vertical wind shear, which inhibits cyclone formation; data suggests a decrease in wind shear in the tropics and an increase at higher latitudes.

Emanuel notes that researchers in the field are continuing to examine the links between storm migration and global warming. Over the past three decades, the incidence of cyclones in the tropics has actually diminished — because while tropical cyclones may become more intense in a warmer climate, it is actually more difficult to generate them.

Ocean temperatures between 82 and 86 degrees Fahrenheit seem to be “ideal for the genesis of tropical cyclones,” Emanuel says, “and as that belt migrates poleward, which surely it must as the whole ocean warms, the tropical cyclone genesis regions might just move with it. But we have more work to do to nail it down.”

Michael Mann, a professor of meteorology and director of the Earth System Science Center at Penn State University, says the matter of cyclone migration is “a very interesting new angle on the larger issue of how climate change may be impacting tropical cyclone activity.”

Overall, Mann adds, “The findings seem quite plausible. We know that human-caused climate change is leading to a poleward shift in certain features of the atmospheric circulation. … It would be surprising if these shifts were not influencing tropical cyclones. This study shows that they are, by causing a poleward migration in the zones where atmospheric shear is either favorable or prohibitive to tropical cyclone formation.” In practical terms, he says, the result may have “considerable implications” for coastal cities in the long term.

In many public discussions of climate change, science takes a back seat to political agendas and rhetoric. But 12.340x (Global Warming Science), a new massive open online course from MITx now open for enrollment on the edX platform, aims to change that dynamic by providing a solid scientific view of what is really happening with global warming.

“We are trying to bring back some of the intellectual excitement that belongs to the field,” says Professor Kerry Emanuel, a co-teacher of the course whose research focuses on hurricanes. “This is a serious science course.”

The MITx course will use many of the lecture materials developed for the on-campus version of the course, along with new videos and visuals. The course will also include new exercises, problem sets, and a final exam, all tailored to the assessment tools available on the edX platform and developed with an eye on preserving the rigor of the course. “You have to have a background in mathematics up through differential equations, and a background in physics,” says Emanuel, the Cecil and Ida Green Professor of Atmospheric Science. “Our intent is that it will be as challenging as the classroom course.”

12.340x will also bring simulations used in the MIT residential course to a wider audience, including the single-column model simulation. Emanuel describes this unique tool as “a computer climate model that takes inputs such as solar radiation and atmospheric greenhouse gas content and calculates the temperatures of the surface and atmosphere, and the moisture and cloud distributions in the atmosphere. Students can change the intensity of sunlight, the time of year, the greenhouse gas concentrations, and other inputs to see how they affect climate change.”

Emanuel expects a wide range of people to take 12.340x. “You’re going to find a lot of students in climate and energy. They will want to know the physics, chemistry, and biology (of climate change).” He also expects professionals working in energy and public policy to be interested in the course. Even a politician has expressed interest in 12.340x, but Emanuel is keeping the individual’s name confidential.

Emanuel and the Department of Earth, Atmospheric and Planetary Sciences also hope to change the dynamic around the study of climate change on the MIT campus. In part because the course is not a requirement, and in part because of the perception among students that climate-change study is mostly about politics and not hard science, the on-campus course has not seen the enrollment levels Emanuel would like to see. “Part of the problem is all the publicity of global warming has sent out a message that global warming is highly politicized, and has nothing to do with science,” he says. “Nothing could be further from the truth.”

Editor's note: Climate and energy scientists James Hansen, Ken Caldeira, Kerry Emanuel and Tom Wigley released an open letter Sunday calling on world leaders to support development of safer nuclear power systems.

(CNN) -- To those influencing environmental policy but opposed to nuclear power:

As climate and energy scientists concerned with global climate change, we are writing to urge you to advocate the development and deployment of safer nuclear energy systems. We appreciate your organization's concern about global warming, and your advocacy of renewable energy. But continued opposition to nuclear power threatens humanity's ability to avoid dangerous climate change.

We call on your organization to support the development and deployment of safer nuclear power systems as a practical means of addressing the climate change problem. Global demand for energy is growing rapidly and must continue to grow to provide the needs of developing economies. At the same time, the need to sharply reduce greenhouse gas emissions is becoming ever clearer. We can only increase energy supply while simultaneously reducing greenhouse gas emissions if new power plants turn away from using the atmosphere as a waste dump.

Renewables like wind and solar and biomass will certainly play roles in a future energy economy, but those energy sources cannot scale up fast enough to deliver cheap and reliable power at the scale the global economy requires. While it may be theoretically possible to stabilize the climate without nuclear power, in the real world there is no credible path to climate stabilization that does not include a substantial role for nuclear power.

We understand that today's nuclear plants are far from perfect. Fortunately, passive safety systems and other advances can make new plants much safer. And modern nuclear technology can reduce proliferation risks and solve the waste disposal problem by burning current waste and using fuel more efficiently. Innovation and economies of scale can make new power plants even cheaper than existing plants. Regardless of these advantages, nuclear needs to be encouraged based on its societal benefits.

Quantitative analyses show that the risks associated with the expanded use of nuclear energy are orders of magnitude smaller than the risks associated with fossil fuels. No energy system is without downsides. We ask only that energy system decisions be based on facts, and not on emotions and biases that do not apply to 21st century nuclear technology.

While there will be no single technological silver bullet, the time has come for those who take the threat of global warming seriously to embrace the development and deployment of safer nuclear power systems as one among several technologies that will be essential to any credible effort to develop an energy system that does not rely on using the atmosphere as a waste dump.

With the planet warming and carbon dioxide emissions rising faster than ever, we cannot afford to turn away from any technology that has the potential to displace a large fraction of our carbon emissions. Much has changed since the 1970s. The time has come for a fresh approach to nuclear power in the 21st century.

We ask you and your organization to demonstrate its real concern about risks from climate damage by calling for the development and deployment of advanced nuclear energy.

Sincerely,

Dr. Ken Caldeira, Senior Scientist, Department of Global Ecology, Carnegie Institution

Dr. Kerry Emanuel, Atmospheric Scientist, Massachusetts Institute of Technology

Dr. James Hansen, Climate Scientist, Columbia University Earth Institute

Dr. Tom Wigley, Climate Scientist, University of Adelaide and the National Center for Atmospheric Research

With global warming, a study finds, tropical cyclones may become more frequent and intense.

(Also covered by USA Today)

By: Bryan Walsh

Maybe Mayor Michael Bloomberg would have gone through the troubling of putting together a 430-page report outlining a $19.5 billion plan to save New York from the threat of climate change had Hurricane Sandy not hit  last year and inflicted some $20 billion in New York City alone. But somehow I doubt it. There’s a reason that a satellite image of Hurricane Katrina highlighted the poster for An Inconvenient Truth, or that belief in man-made global warming tends to spike after extreme weather. Heat waves are uncomfortable and drought is frightening, but it’s superstorms—combined with the more gradual effects of sea-level rise—that can make climate change seem apocalyptic. Just read Jeff Goodell’s recent piece in Rolling Stone about what a major hurricane might be able to do to Miami after a few decades of warming.

But there was one hopeful side effect to climate change, at least when it came to tropical storms. The prevailing scientific opinion—seen in this 2012 report from the Intergovernmental Panel on Climate Change—is that while tropical storms are likely to become more powerful and rainier as the climate warms, they would also become less common. Bigger bullets, slower gun.

A new study in the Proceedings of the National Academy of Sciences, however, suggest that we may not be so lucky. Kerry Emanuel, an atmospheric scientist at the Massachusetts institute of Technology (MIT) and one of the foremost experts on hurricanes and climate change, argues that tropical cyclones are likely to become both stronger and more frequent as the climate continues to warm—especially in the western North Pacific, home to some of the most heavily populated cities on the planet. But the North Atlantic—meaning the U.S. East Coast and Gulf Coast—won’t be spared either. Bigger bullets, faster gun

Emanuel is going up against the conventional wisdom and much of the published literature with this paper. But the reality is that we don’t have a very good grasp of how tropical cyclone formation or strength might change in the future. As Adam Freedman points out at Climate Central, hurricanes may be huge, but they’re still too small to be easily tracked by computer climate models, which do better on a larger scale. Emanuel embedded higher-resolution regional and local models into an overarching global framework. Emanuel’s “downscaled” model simulates the development of tropical cyclones at a resolution that will increase as the storm gets stronger. For each of the six IPCC global climate models, Emanuel simulated 600 storms every year between 1950 and 2005, then ran the model forward to 2100, using an IPCC forecast that has global carbon dioxide emissions tripling by the end of the century. 

Emanuel’s simulations found that the frequency of tropical cyclones will increase by 10 to 40% by 2100. And the intensity of those storms will increase by 45% by the end of the century, with storms that actually make landfall—the ones that tend to smash—will increase by 55%. As Emanuel told LiveScience:

We see an increase, in particular, toward the middle of the century. The results surprised us, but we haven’t gotten so far as to understand why this is happening.

OK, big caveats here. Emanuel is a very well-respected climatologist, but it always takes more than a single study to overturn existing scientific opinion—especially if that opinion is itself a little wobbly. Georgia Tech climatologist Judith Curry, who falls on the more skeptical side of the scientific debate on climate change, told this to Doyle Rice of USA Today:

The conclusions from this study rely on a large number of assumptions, many of which only have limited support from theory and observations and hence are associated with substantial uncertainties. Personally, I take studies that project future tropical cyclone activity from climate models with a grain of salt. 

We’ll see in the decades to come whether Emanuel is right. But in a way, it may not matter all that much. As Sandy showed, hurricanes already pose a tremendous threat to our coastal cities. And that threat will continue to grow no matter what climate change does to tropical storm frequency or intensity because we’re putting more and more people and property along the water’s edge. Remember Miami? In 1926 the city was devastated by a Category 4 hurricane. (Sandy barely ranked as a Category 1 by the time it made landfall.) The difference is that there wasn’t much of a Miami back in 1926—the city’s population had just passed 100,000. Today more than 2.5 million people call Miami-Dade county home, and a hurricane of the same sort that hit in 1926 that hit now would cause $180 billion in damages. Whatever climate change does to hurricanes, we need to be ready.