Tag Archives: tropical cyclones

Hurricane Sandy and the Climate Hens

Image courtesy of NASA, used under Creative Commons

Hurricane Sandy is one for the record books in a number of senses, and as New York and the world struggle to grapple with its enormity, some discussion has turned to climate change. A topic that has been damningly absent from discussion in the U.S. Presidential election.

It is inevitable that when anyone anywhere tries to talk about climate change in relation to things in the here and now rather than some murky, distant future, a particular group descends to cluck their tongues and admonish everyone that climate change can’t be tied to any individual event (a proposition that is not true, and grows increasingly less defensible as the field of fractional attribution matures). This group includes many who also fall into the camp of those who style themselves as non-partisans or above the “tribal” nature of climate debates. The parallels with Jay Rosen’s larger media critique of the View from Nowhere have been noted by Michael Tobis among others.

Dave Roberts has a thoughtful piece about this phenomenon. He refers to this group as climate “scolds” in contrast to climate hawks (and yes, I do have my own problems with the latter moniker). And while I do think that “scold” captures a lot of the flavor of the group Roberts is describing, I think the hawk vs. “___” setup favors a different term for the group: climate hens.

Image courtesy of Flickr user “Ann Blair”, used under Creative Commons

Climate hens by and large acknowledge the human perturbation of the climate system. But they are very, very hesitant to highlight (or are even downright resistant to) the idea that humans are shaping the present climate in ways that are affecting the public now. This may be because it doesn’t jibe with what they learned about climate years ago. It may be because they view erring on the side of making climate change seem more serious than it is to be as bad or worse than denying that it’s a problem. It may be because they don’t really understand climate science very well- Eric Berger and Roger Pielke Jr., for instance, are two climate hens that have displayed a remarkable ignorance about basic aspects of climate science pertaining to natural variability in a warming world. (Pielke Jr. is also infamous for playing bait and switch by turning conversations about human contribution to extreme events into discussions about an economic signal in normalized disaster losses.) Whatever the reason, climate hens are just plain uncomfortable with people attempting to tie extreme events to our increasing influence on the planet’s climate.

Roberts points out, correctly and convincingly, that the climate hens are clucking about a problem that doesn’t really exist- at least not the one that they’re ostensibly worried about. When the general public sees something like the record US heat, the summer drought, or a hurricane like Sandy, and they start asking about global warming, they don’t really want a belabored lecture on fractional attribution or paleoclimatic precedents that the climate hens think should determine the answer. What the public is looking for is some way to connect this thing- that scientists are telling them is real and a real problem- to their own experiences of the world. That’s what we humans do. Climate hens are, by mistake or by design, frustrating one of the best avenues of facilitating public recognition of climate change as a problem they need to take seriously. Roberts frames it this way:

That’s the key missing ingredient on climate change: not a technical understanding of stochastic modeling, forensic attribution, and degrees of probability, but a visceral, more-than-intellectual sense of what climate change means. Most people simply lack a social and ethical context for it, so they end up jamming it into other, more familiar contexts (“big government,” “environmental problem,” “liberal special interest group”).

A storm like Sandy provides an opportunity for those who understand climate change to help construct that context. It provides a set of experiences — a set of images, sounds, smells, feelings, experiences — that can inscribe climate change with the cultural resonance it lacks. That’s what persuades and motivates people: not the clinical language of science, but experiences and emotions and associations. Of course communicating scientific facts is important too, but it’s not the primary need, nor the standard by which other communications should be judged. What scolds often do is interpret the language of emotion and association through the filter of science. That’s neither helpful nor admirable.

And this perspective has supporters amongst those studying climate communication. Elke Weber (2010) makes this point:

Behavioral research over the past 30 years strongly suggests that attention-catching and emotionally engaging informational interventions may be required to engender the public concern necessary for individual or collective action in response to climate change… To the extent that time-delayed consequences of our actions do not attract the attention or generate the concern ex-ante that they would seem to warrant ex-post, behavioral research provides some corrective actions. The concretization of future events and moving them closer in time and space seem to hold promise as interventions that will raise visceral concern.

The science of tropical cyclogenesis in a warming world is undoubtedly complex and uncertain- a point I’ve been making for years. But when the public starts asking questions about climate after an event like Hurricane Sandy, they aren’t looking for navel-gazing about ensembles of modeling runs, wind shear, and overwash sediment coring. They are asking for a way to connect something they keep hearing they are supposed to care about to things they already do. The proper response to such questions is not, as the climate hens would have it, to shut them down and turn them away. And it should go without saying that nor is it a reason to overstate the connections between our increasingly heavy influence on the climate and extreme events like Hurricane Sandy. Rather, the appropriate response is to treat the questions for what they are: an invitation to talk about climate change in a way that is meaningful to a curious but decidedly lay public. Climate change means sea levels rising, it means storm surge increases, it means heavier precipitation events (Schaeffer et al., 2012; Sriver et al., 2012; Shepard et al., 2012; Min et al., 2011). If Hurricane Sandy makes these threats more concrete, if it moves them closer in time and space, if- in Roberts’ words- it provides “a set of images, sounds, smells, feelings, experiences”, we should absolutely be talking about it. And perhaps something good will come of this disaster. Clucking from the climate hens be damned.


  • Min, S.-K., X. Zhang, F. W. Zwiers, and G. C. Hegerl (2011), Human contribution to more-intense precipitation extremes, Nature, 470(7334), 378–381, doi:10.1038/nature09763.
  • Schaeffer, M., W. Hare, S. Rahmstorf, and M. Vermeer (2012), Long-term sea-level rise implied by 1.5 °C and 2 °C warming levels, Nature Climate Change, doi:10.1038/nclimate1584.
  • Shepard, C., V. Agostini, B. Gilmer, T. Allen, J. Stone, W. Brooks, and M. Beck (2012), Assessing future risk: quantifying the effects of sea level rise on storm surge risk for the southern shores of Long Island, New York, Natural Hazards, 60(2), 727–745, doi:10.1007/s11069-011-0046-8.
  • Sriver, R., N. Urban, R. Olson, and K. Keller (2012), Toward a physically plausible upper bound of sea-level rise projections, Climatic Change, 1–10, doi:10.1007/s10584-012-0610-6.
  • Weber, E. U. (2010), What shapes perceptions of climate change?, Wiley Interdisciplinary Reviews: Climate Change, 1(3), 332–342, doi:10.1002/wcc.41.

Tropical cyclones, climate, and consensus, cont’d

I’ve written about what I’ve called the “proto-consensus” on tropical cyclones (AKA hurricanes, typhoons) under anthropogenic warming before (e.g. here and here). On Sunday, Nature Geoscience published a Review entitled “Tropical cyclones and climate change” [full paper here] by Thomas Knutson, John McBride, Johnny Chan, Kerry Emanuel, Greg Holland, Chris Landsea, Isaac Held, James Kossin, A. K. Srivastava, and Masato Sugi that succinctly covers the state of play, reiterating that the evidence seems to be increasingly pointing to a warmer world with less frequent yet more powerful hurricanes:

…future projections based on theory and high-resolution dynamical models consistently indicate that greenhouse warming will cause the globally averaged intensity of tropical cyclones to shift towards stronger storms, with intensity increases of 2–11% by 2100. Existing modelling studies also consistently project decreases in the globally averaged frequency of tropical cyclones, by 6–34%. Balanced against this, higher resolution modelling studies typically project substantial increases in the frequency of the most intense cyclones, and increases of the order of 20% in the precipitation rate within 100 km of the storm centre…

More if/when I have time.

[h/t Andrew Freedman]

Tropical cyclones, climate, and consensus

A favorite denialist canard goes something like this: “You alarmists swore that your global warming caused Katrina and would cause more hurricanes every year, but the last few years have been a bust. Yet another algore lie exposed!” If you think I’m unfairly exaggerating, read the comments section of any major newspaper article or online forum discussing climate change.

Lest you believe that this (genuine or otherwise) confusion about the mainstream view of climate change and hurricanes is restricted to random commenters, you see something similar (although less frothy) from even mainstream science writers, like the Houston Chronicle’s science blogger, Eric Berger [emphasis mine]:

When An Inconvenient Truth came out I believed the movie to be scientifically accurate. Carbon dioxide levels were rising and so were temperatures. And hurricane activity, especially after the disastrous 2005 season, was out of control.

But a funny thing happened on the way to the end of the world: hurricane activity on the global scale is near historical lows. And the Earth seems to have, at least temporarily, stopped warming.

This, despite the fact that some of the country’s leading climate scientists say there is unequivocally a link between major hurricanes and climate change. And despite the fact that other leading climate scientists predicted 2009 or 2010 will go down as the warmest year in recorded history. Either prediction, if true, would be alarming.

Yet both of these predictions seem, at the present moment, to be off.

We’re in some familiar denialist territory here- even if there were an alleged consensus about an increase in “hurricane activity”, drawing conclusions based on a period of 2005-2009 is, well, inexcusable. Especially for a science writer. Similarly, he seems to believe that global warming should likewise be monotonic– which is to say that Mr. Berger can’t seem to understand that there can be long term upward trends despite substantial year-to-year variation.

In any event, the idea that there was even a robust, precise consensus about the current and future impacts warming is supposed to have on hurricanes (tropical cyclones, typhoons, etc.) is easily refuted by simply looking at the relevant sections of the IPCC Fourth Assessment Report, which I’ll add to the end of this post.

Whenever someone asks me “What happened to all the hurricanes?” or “What’s the consensus on climate and hurricanes?”, my stock answer is something like this-

First, in terms of a broad, robust consensus- such as those around the issues of whether or not the planet is warming, and the anthropogenic nature of that warming- one doesn’t exist for tropical cyclones. To grossly oversimplify, we could say that in a warming world- all other things being equal– we would expect warmer sea surface temperatures (SSTs) to contribute to an increase in tropical cyclone intensity. However, not all other things will be equal. While SSTs play an enormous role in cyclogenesis, they are not the only factor in play. For example, wind shear is another huge player in tropical cyclone behavior– too much wind shear can both prevent the formation of  and destroy tropical cyclones- and we expect wind shear to increase in a warming world. And of course there are “unknown unknowns”, as well as some known unknowns like the behavior of relevant ocean-atmosphere patterns (like ENSO* and the NAO) in a warmer world.

So roughly speaking, I think it would be fair to say that (setting aside the unknowns) while warmer SSTs imply an increase in intensity, increased wind shear implies a decrease in total storms, so that we’re left with the possibility of a warming world with fewer but more intense hurricanes- something that I’ve categorized in the past as a “proto-consensus”.

There have been a number of recent high profile attempts to model tropical cyclone behavior from some of the big names in the field, like Knutson 2008 and Emanuel 2008. Although Knutson 2008’s and Emanuel 2008’s findings were misrepresented by some in the media and governmental offices as evidence of a shift in opinion that GHGs had little effect on the behavior of tropical cyclones, both papers supported this proto-consensus, albeit with significant caveats and from different angles. One of the biggest areas of concern in these kinds of studies is that the models used often didn’t have the resolution necessary to look at the behavior of the strongest (Cat 3 and higher) storms, which seem to be getting stronger as we warm.

Knutson is part of a new study in Science (or here), lead by Morris Bender, which seeks to remedy this flaw entitled “Modeled Impact of Anthropogenic Warming on the Frequency of Intense Atlantic Hurricanes”. Bender et al. use a downscaling process to examine the effect of anthropogenic warming in GCMs on the behavior of Atlantic storms in an operational hurricane model. They find that while the total number of storms decreases, there is “nearly a doubling of the frequency of category 4 and 5 storms by the end of the 21st century”.

Tracks for all storms reaching category 4 or 5 intensity, for the control and the warmed 18-model ensemble conditions, as obtained using the GFDL/NWS hurricane model.

This has serious implications for policy-makers, especially in the US, where the strongest storms (Cat 3+) are responsible for the overwhelming majority (80%) of economic losses from Atlantic hurricanes.

So- is this the last word? Have we reached A Consensus? Of course not- although this paper certainly adds weight to the proto-consensus, there is still a tremendous amount of uncertainty on this issue. But the next time someone tries to tell you about how “climate science got it all wrong re: hurricanes”, you’ll know more or less where things stand.

*Intriguingly, while normal El Niños tend to suppress Atlantic hurricanes, so-called Modoki El Niños are actually positively correlated with them, and as the planet warms it looks as though Modoki El Niños are becoming more common.

Relevant sections from the AR4 are below the fold:

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1500-year Atlantic hurricane record

One of the most common and easily debunked claims by denialists is that there is a massive global conspiracy on the part of the climate science community to deliberately and fraudulently overstate the severity of present climatic conditions (e.g. temperature, CO2 levels, etc.) relative to the paleoclimatic record in order to make the (non-existent in their minds) threat of anthropogenic climate change more frightening to the public.

The climate community is doing this presumably to continue their grant-funded lives of obscene wealth and debauchery. Or to cripple the American economy by destroying capitalism [ha!] in order to further a UN-run, communist world government.  Or something. In any event, among their frequent targets for such ludicrous conspiracy theories are Jim Hansen (who they believe in his spare time has single-handedly “fabricated” global warming by altering the GISTEMP temperature record; presumably his free time and mendacity are so great that he has been able to similarly propagate this faked warming signal throughout the biosphere), Phil Jones (likewise, but for the HadCRUT record instead), and perhaps most of all Michael Mann- for his temperature reconstructions of North America over the past two millennia. The steady blast of fetid hot air directed at Mann for his imagined attempts to exaggerate current climatic conditions relative to the past could, redirected through a turbine, easily comprise a stabilization wedge all its own.

So it is with much amusement that those in the reality-based community note papers like the one  published in today’s issue of Nature here (or here) entitled “Atlantic hurricanes and climate over the past 1,500 years” by one Michael Mann- along with coauthors Jeffery Donnelly, Jonathan Woodruff, and Zhihua Zhang. The Mann et al. paper is a relatively straightforward attempt to reconstruct Atlantic hurricane activity over the past 1.5 ka, employing multiple (although admittedly sparse) regional overwash sediment records in an attempt to create a basin-wide record of landfalling hurricanes. This reconstruction is then compared against statistical modeling based on reconstructions of several climatic (sea surface temperature, Nino 3, and North Atlantic Oscillation) records.

Naturally Mann- no doubt twirling his mustache and laughing manically- has determined through premeditation and statistical voodoo that recent Atlantic hurricane activity is completely unprecedented in the paleoclimatic record, in furtherance of his dastardly fearmongering agenda. Wait- what’s that? Mann et al. actually found that around 1000 AD hurricane activity may actually have equaled and possibly exceeded that of today?!

But that doesn’t fit conveniently into my demonization of Mann or preconceived notions about the global climate conspiracy at all! No fair.

In all seriousness this is an interesting paper as despite some very serious caveats, it seems to indicate that we’ve got a decent grasp of the main drivers of hurricane activity for the region. Obviously it would be nice to increase the number of overwash records used, especially for the southeast US, the Gulf coast, and the Caribbean– for which we only have a single record per region.

The peak in medieval hurricanes is associated with persistent La Niña-like conditions in the Pacific and warmer tropical Atlantic SSTs– conditions that also notably produced a series of megadroughts in the US southwest and Mexico. Has anyone done comparisons between modern Atlantic hurricane activity and southwest drought conditions?

Modoki El Niño increasing frequency and North Atlantic tropical cyclones

Place holder: “Impact of Shifting Patterns of Pacific Ocean Warming on North Atlantic Tropical Cyclones”. Abstract here. Paper here.

[Judy isn’t being blasted on CA as much as I’d have guessed (with some notable exceptions).]


Eye of Hurricane Isabel, courtesy of NASA

“Hurakan” (also Huracan; Jun Raqan) is the name of a Maya storm/Creator god that is the probable origin of the English word “hurricane”. In the Popol Vuh, the first men that populated the Earth (there existed an even earlier, failed attempt to create men out of mud) were made of wood. Although they could speak and reproduce, and multiplied across the face of the Earth, they forgot their Creators and had no minds or souls. Hurakan and the other Creator gods exacted retribution on them, sending a great deluge and other punishments. Not only did the beasts wild and domestic turn on these first men for their mistreatment of them, so too did their own tools and trappings of civilization.

Atlantic tropical cyclones comprise only a fraction of global storms, and land-falling Atlantic hurricanes make up an even smaller number. Since the record 2004 and 2005 Atlantic hurricane seasons and the Katrina disaster however, Atlantic hurricanes have received an amount of press greatly disproportionate to their global number- often in the context of anthropogenic warming.

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