Tuesday, June 22, 2010

Death, doom and disaster coming soon to a planet in your neighborhood

Just when the denialists have convinced themselves that there is no problem here, keep moving, comes Steven Sherwood and Matthew Huber in the Proceedings of the National Academy of Sciences, to point out that yes Virginia (GMU) and Roger, death, doom and disaster are saddling up and while they might not arrive before a couple of hundred years, the time horizon for climate change issues extends beyond 2100 and what is out there is seriously worrying.

Despite the uncertainty in future climate-change impacts, it is often assumed that humans would be able to adapt to any possible warming. Here we argue that heat stress imposes a robust upper limit to such adaptation. Peak heat stress, quantified by the wet-bulb temperature TW, is surprisingly similar across diverse climates today. TW never exceeds 31 °C. Any exceedence of 35 °C for extended periods should induce hyperthermia in humans and other mammals, as dissipation of metabolic heat becomes impossible. While this never happens now, it would begin to occur with global-mean warming of about 7 °C, calling the habitability of some regions into question. With 11–12 °C warming, such regions would spread to encompass the majority of the human population as currently distributed. Eventual warmings of 12 °C are possible from fossil fuel burning.
Humans, and many animals upon which the world depends, must maintain core temperatures of ~ 37  °C by shedding energy via conductive, radiative and evaporative cooling. When the ambient wet bulb temperature exceeds 35  °C, core temperatures sore soar and people die fairly rapidly, in a few hours. The figure below gives you an idea of how problematic human existence would be on such a brave new world.

The consensus estimate for climate sensitivity is ~2-4.5  °C for doubling of CO2. With a bit of bad luck warmings of 8 °C are possible (Tw trails the global temperature by a bit) at 4x CO2, which is certainly within reach in a bit more than 100 years.

UPDATE: Anonymouse in the comments below points out that
It's the creeping statistical hints between the lines of this paper that really bother me. Long before or even if we never see broad areas permanently enter a existentially threatening torrid regime, what about excursions? For instance, Pakistan this year has seen record temperatures approaching 54 degrees C in places where many people live, fortunately with lower humidity and only for handful of days but what about when/if such aberrations extend to a handful of weeks and are accompanied by inexorably increasing humidity? The resulting disaster would cause migrations. The worst-case scenario in Sherwood and Huber would not have to happen before we effectively lose major swathes of territory for year-round habitability.
And if you follow the press, there have been lots of deaths in Pakistan and Northern India from these heat waves.

Sherwood and Huber are pushing the envelope here, but remind Eli again about the proper discount rate for starting to deal with climate change.

We conclude that a global-mean warming of roughly 7 °C would create small zones where metabolic heat dissipation would for the first time become impossible, calling into question their suitability for human habitation. A warming of 11–12 °C would expand these zones to encompass most of today’s human population. This likely overestimates what could practically be tolerated: Our limit applies to a person out of the sun, in gale-force winds, doused with water, wearing no clothing, and not working. A global-mean warming of only 3–4 °C would in some locations halve the margin of safety (difference between TW max and 35 °C) that now leaves room for additional burdens or limitations to cooling. Considering the impacts of heat stress that occur already, this would certainly be unpleasant and costly if not debilitating. More detailed heat stress studies incorporating physiological response characteristics and adaptations would be necessary to investigate this.

If warmings of 10 °C were really to occur in next three centuries, the area of land likely rendered uninhabitable by heat stress would dwarf that affected by rising sea level. Heat stress thus deserves more attention as a climate-change impact.

The onset of TW max > 35 °C represents a well-defined reference point where devastating impacts on society seem assured even with adaptation efforts. This reference point constrasts with assumptions now used in integrated assessment models. Warmings of 10 °C and above already occur in these models for some realizations of the future (33). The damages caused by 10 °C of warming are typically reckoned at 10–30% of world GDP (33, 34), roughly equivalent to a recession to economic conditions of roughly two decades earlier in time. While undesirable, this is hardly on par with a likely near-halving of habitable land, indicating that current assessments are underestimating the seriousness of climate change.

29 comments:

Daniel said...

It appears to this Yooper bunny that Danny Bloom's "Polar Cities" concept is coming closer to realization:

http://prpc101.blogspot.com/

Musing of the moment: Where will the snow-hares go?

Cheers,

Daniel the Yooper bunny

Daniel said...

More of the Bloom-bunny's work on Polar Cities can be found here:
http://pcillu101.blogspot.com/

and here:
http://climatechange3000.blogspot.com/

No time like the present for planning for the future, eh?

The swift bunnies get all the carrots,

Daniel the Yooper bunny

jyyh said...

That map gave an idea for a short story set in 5000 AD (if that's far enough), looks like in this scenario the Sahara Pump like conditions are going to expand somewhat and give raise to some 5 (sub)species for previously cosmopolitan species.

Anonymous said...

It's the creeping statistical hints between the lines of this paper that really bother me. Long before or even if we never see broad areas permanently enter a existentially threatening torrid regime, what about excursions? For instance, Pakistan this year has seen record temperatures approaching 54 degrees C in places where many people live, fortunately with lower humidity and only for handful of days but what about when/if such aberrations extend to a handful of weeks and are accompanied by inexorably increasing humidity? The resulting disaster would cause migrations. The worst-case scenario in Sherwood and Huber would not have to happen before we effectively lose major swathes of territory for year-round habitability.

Jonathan Gilligan said...

This is very frightening.

You write, "with a bit of bad luck warmings of 8C are possible ... at 4xCO2." The paper notes, climate sensitivity "is poorly constrained on the high side (2, 3) and according to one new estimate has a 5% chance of exceeding 7.1 °C per doubling."

Thus, if this paper and the study cited above are both correct, there's something like a 5% chance that most regions of earth currently inhabited by people would be uninhabitable.

The nagging voice in my head says, "yada yada yada ... can't trust 300-year model projections ...," which is correct. So let's posit a 95% probablity that one or both studies are wrong. That would still leave one chance in 400 (5% times 5%) that in the next few hundred years, a BAU emissions scenario would leave most places people now live too hot to survive in.

The right question is not Eli's "proper discount rate," but Harry Calahan's: "You've got to ask your self one question. 'Do I feel lucky?' Well, do ya?"

a_ray_in_dilbert_space said...

I remember when I was a Peace Corps bunny in Africa. During the hot season, temperatures would often climb to over 40 degrees C. At such times, one's daily routine became quite simple: 1)Get butt nekkid; 2)Shower with cold water; 3)stand in front of the fan; 4)Repeat until the temperature drops. At noon on such days, nothing stirred, and at night, trying to sleep was torture. Cooking? Fuggedaboudit. The hot season was sufficiently unlivable that the season before it was called the funeral season--where old people in the villages simply gave up the ghost rather than face the prospect of yet another hot season.

This is simple thermo. We are heat engines after all.

Anonymous said...

How long can we survive a wet bulb temperature of 35 C?

Weather plus global warming (or 7 degrees plus El Nino plus solar max plus a hot spell) equals ???

A scared Little Mouse

Anonymous said...

Well, the U.S. southern states become uninhabitable. Ironic, given that's where a lot of the denialist wingnuttery is coming from.

a_ray_in_dilbert_space said...

One could argue that the US South has been uninhabitable for intelligent life for a very, very long time.

Jim Eager said...

Eli, "temperatures sore" should be "temperatures soar."


BTW, had to comment using Safari as it would not work using Firefox.

Arthur said...

I believe I noted long ago that the papers Lomborg used to claim that "cold kills more than heat" or whatever it was he was saying, actually showed the opposite when you took the slope of the curve into account.

That is, yes, for any given region of the world, there's a minimum in daily mortality in some mid-range of temperatures, so that both warmer and colder temperatures are correlated with more people dying. But for each 1 degree change in temperature, on the warm side far more people start dying, than on the cold side, and the slope keeps rising with temperature. While on the cold side the slope is a pretty steady gentle one.

This was all from some long paper in BMJ that I no longer seem to have a reference too - maybe somebody can look it up? :)

Daniel said...

Arthur @ 23/6/10 11:49 AM

"This was all from some long paper in BMJ that I no longer seem to have a reference too - maybe somebody can look it up?"

Hopped to it and found two pretty quick (both should be publicly available at the URLS below):

http://www.bmj.com/cgi/reprint/321/7262/670.pdf

http://ec.europa.eu/health/ph_information/dissemination/unexpected/death_risk.pdf

Both seem to be fairly heavily cited, though you probably want the latter piece.

Cheers,

Daniel the Yooper bunny

yorksranter said...

This is...horrifying, and weirdly sf-nal.

stephenleahy.net said...

The 4C science conference in Oxford last fall was alarming enough: "+4 Degrees C By 2060? Alarming But Not Alarmist"
http://stephenleahy.net/2009/11/08/four-degrees-of-devastation/

Anonymous said...

Definitely paws for thought.

Oh for a time machine to transport the paid denialist-liars to a hot-zone, for their 'personal education'!
Instructions: Leave for one month or until well-done.

Vengeance mouse

J Bowers said...

Steven Gilligan: "The right question is not Eli's "proper discount rate," but Harry Calahan's: "You've got to ask your self one question. 'Do I feel lucky?' Well, do ya?""

I wonder if those who like to gamble with their descendants' lives would play the following version of roulette:

The rewards are very high. The wheel has four hundred slots, the croupier has a gun. If the ball falls into only one predetermined slot out of the four hundred the croupier picks up the gun and shoots the gambler in the head.

I wonder how many of these gamblers would step up to the table. I especially wonder how many would push their grandchildren to the table.

J Bowers said...

Whoops, I meant Jonathan Gilligan. Apologies Jonathan.

Anonymous said...

J Bowers @ 24/6/10 1:23 AM, a slight correction:

I suspect that: "I wonder if those who like to gamble with their descendants' lives...." should read "I wonder if those who like to gamble with everyone's descendants' lives...."

At some stage, there will come a point when everyone except the deniers accepts that mainstream science was > 90% right about the climate all along. At which point.....

Sorry Eli, but it has to be said.

Vengeance Mouse

Anonymous said...

Sherwood and Huber are optimistic.

At least, in the sense that they only consider mammalian heat tolerances, they are being optimistic.

Humans rely on the viability of planetary ecosystems, whether they acknowledge it or not. Many non-mammalian species would be profoundly affected long before a 7-8 C shift occurred, and in the process many ecosystems and their essential (to humans) functions would also be impacted - to the point of failure.

It's all well and good to think that all the people-bunnies might be able to 'adapt' to such changes by huddling in their bunkers (or whatever else works), but if one's crops, one's forests, one's soils, one's rivers and lakes, and one's flora and one's fauna are all frying to crispy bits because they do not possess the adaptability of said people-bunnies, then the whole idea of human adaptability and human levels of tolerance is a moot point.

The short version: what's bad for humans is worse for the rest of the biosphere, and what's worse for the biosphere is just as bad for humans.

Bernard J. Hyphen-Anonymouse XVII.

Anonymous said...

Question.
Many people would like to think that the heating will all be in the polar regions but the surface area of +60 deg north and +60 deg south
together only amount to 15% of the total world area and the oceans where temperatures may be moderated versus land areas are 71% of the total global area.
Doesn't this suggest that the land temperature rise will be a lot more than the global average?

Anonymous Freddy(AF)

Chris Dudley said...

Seems to me that everyone here has a luck rabbit's foot so we can discount any chance of anything bad happening?

But, we can do without any discounting if people are already dying from too much heat owing to anthropogenic warming. Which they are.

Anonymous said...

Markeymouse says: Ahem, cough, cough, hand up.... There has been no material warming for 10 years.

Anonymous said...

Markeymouse - you mean like this graph shows?

http://www.woodfortrees.org/plot/gistemp/from:2000.6/to:2010.6/mean:12/plot/gistemp/from:2000.6/to:2010.6/trend

Or perhaps you prefer the satellites?
http://www.woodfortrees.org/plot/uah/from:2000.6/to:2010.6/mean:12/plot/uah/from:2000.6/to:2010.6/trend

ahem, ahem, cough, cough...

still going up...

crazy bill

peeke said...

Four times the current CO2 level? What hubris to think that there will be enough easy fossile fuel to burn to actually reach that. To make a long story short: that would only happen in the wet dreams of Chigago School economists. The real world will see dramatic downturns of usable fossile fuels somewhere in the foreseeable future. You see, people tend to think like this: There is a shitload of clathrate. We were able to extract a tad. Therefore we will be able to use it all in an ever expanding fashion. That greatly ignores the fact that more then 9o% of clathrate is lied down in lumps in the sea floor. There is no way that will be used up by us.

Same story goes for oil shale.

We won't. I'd be surprised if CO2 levels get over 600 ppm.

EliRabett said...

Coal

a_ray_in_dilbert_space said...

Peeke,
Spoken like somebody who hasn't done the math. I have done the math, and using conservative estimates of 1)petroleum, 2)natural gas, 3)coal and 4)nontraditional sources (oil shale, tar sands, etc.)there is easily enough fossil fuel to get us abov3 1000 ppmv, even assuming that the oceans continue to take up ~50% of the CO2. That is without touching clathrates or considering outgassing of melting permafrost, etc. What is more, as we move toward lower grade fuels, the process of extracting the energy will become less efficient--resulting in higher CO2 emission per joule of energy than we have at present. There is every reason to believe that the concurrent crises of peak oil and climate change will interfere constructively rather than destructively.

Thus, the hubris, Peake, is all yours.

peeke said...

James Hansen did the math too. He came to 580 ppm CO2.

http://www.theoildrum.com/story/2006/11/18/93514/869

That scenario is Laherre's iirc. It's quite mild. It peaks 2050 and gently goes down the slope.

O, and I leave you and your hubris remark alone. My reference to hubris was made simply to bring under your attention that horror scenario's expect mankind to continue growth at the same rate as ever: Assumptions like that used to be considered pipe dreams.

a_ray_in_dilbert_space said...

Peeke,
Hansen's calculation looks mainly at coal, petroleum and natural gas. It does not look an nonconventional fossil fuels. There is more petroleum in the Orinoco than in all of the Middle East. It is not necessary to assume continual growth--merely that humans will attempt to maintain continual growth. With human population reaching ~10 billion by mid century and us being dependent on fossil fuel just to produce enough calories to feed even 7 billion, I'd call that a good bet.

In India, first they burned all the wood; then they burned all the brush. Now they burn dung for their cooking fires. I haven't looked at how much the wood in the Amazon will add, but I suspect we will find out empirically before humans are done.

Anonymous said...

J Bowers said...
"I wonder if those who like to gamble with their descendants' lives would play the following version of roulette:

The rewards are very high. The wheel has four hundred slots, the croupier has a gun. If the ball falls into only one predetermined slot out of the four hundred the croupier picks up the gun and shoots the gambler in the head.

I wonder how many of these gamblers would step up to the table. I especially wonder how many would push their grandchildren to the table."

Chances of death in an auto...1 in 100 over a life time, yet we allow our kids to drive, I am neither for nor against warming theories...but we can not live our lives based on what might, could, possibly happen. Time will tell this tale and I think we will find that man kind does not "control" everything. Nature does....NavyVette