Tuesday 11 November 2014

Near-term human extinction and Wet-bulb temperature

Reading the vicious ad hominem attacks you would think that Guy McPherson is the only one guilty of realism with his “death cult” (Nicole Foss)

Will Climate Change Cause Human Extinction?

by Chris Clarke

Will we greenhouse gas ourselves right off the planet? | Photo: neeravbhatt/Flickr/Creative Commons License

27 August, 2013

In the last few days an alarming article making the rounds on social media has revived the idea that our species might be doing itself in by changing the global climate. The article, by vice.com's Nathan Curry, minces no words in its title: "Humanity Is Getting Verrrrrrry Close to Extinction," with the extra rs in the original.

Curry cites sources ranging from climatologist James Hansen to admitted doomsayer Guy McPherson to advance a startling notion: human society has triggered enough irrevocable climate change mechanisms that we're locked in to warming temperatures sufficient to kill us off.

It's alarming, but is it alarmist? Could we really heat ourselves to extinction? Maybe, but that's asking the wrong question.

All species eventually go extinct, and things can always go badly wrong when you're futzing with your life support system. But if a few things happen that aren't accounted for in climate forecasts -- like a wholesale release of methane from permafrost and seabed deposits, there's a significantly larger chance that most of what we humans currently think of as good places to live will become literally uninhabitable for at least part of the year.

Doomsday scenarios have their fans, the aforementioned McPherson among them. In a January post from his blog Nature Bats Last, McPherson suggested that Obama had turned his back on a 2009 global climate conference because he had inside information that it was all pointless:

In other words, Obama and others in his administration knew near-term extinction of humans was already guaranteed. Even before the dire feedbacks were reported by the scientific community, the Obama administration abandoned climate change as a significant issue because it knew we were done as early as 2009. Rather than shoulder the unenviable task of truth-teller, Obama did as his imperial higher-ups demanded: He lied about collapse, and he lied about climate change. And he still does.


To be fair, McPherson does allow in that same post that a colleague's prediction that all life on Earth will die before mid-century "appears premature."


But running through articles like Curry's and websites like McPherson's is a startling scientific claim that has merit: there's a chance that large parts of the world will get hot enough to kill humans outright.

Climate change threatens to alter the way we live our lives in a whole lot of ways, from changing the frequency and severity of storms and droughts to causing crop failures to promoting increases in pest animals and diseases. Clever animals like us may well be able to come up with ways to mitigate such horrors.

But as global temperature warms, some reserachers have said that some places run the risk of getting too hot and humid for humans to survive in for more than a few days.

Humans, like other mammals, generate heat just by being alive, and we rely on our surroundings as sinks for that heat. Even if the air is considerably hotter than our body temperature, we can cool ourselves by sweating: water evaporating from our bodies takes a lot of heat with it.

At 100 percent humidity, a temperature of 35°C -- 95°F -- proves fatal within days or hours to people in good health in ideal theoretical conditions -- as James Hansen puts it in a passage quoted by Curry, "even a person lying quietly naked in hurricane force winds would be unable to survive" such temperatures. If we can't shed our waste heat, our organs fail and death results.

And that's for a healthy person tring to get as cool as possible while relaxing. People who aren't in top physical condition or who must continue to work can drop dead from less extreme conditions.

That "temperature at 100 percent relative humidity" is referred to as a "wet bulb temperature," a slightly confusing mathematical concept named for the easiest way to measure it: draping a thermometer bulb with a wet, non-insulating cloth. 

As almost everyone reading this will know from personal experience, temperatures of 35°C by themselves aren't uniformly deadly: it is, as they say, not so much the heat as the humidity. That world record air temperature set a century ago in Death Valley of 132°F would have needed an accompanying atmospheric humidity of 26 percent to work out to that fatal 35° wet bulb level. As I write this in Joshua Tree on August 27, in the days after a series of tropical storms dumped water into the desert, the relative humidity is 52 percent, it's 86°F, which works out to a slightly muggy but still comfortable wet bulb temperature of 22.5°C. Los Angeles, at 83° and 44 percent humidity, is a comfortable 19.7°C wet bulb.

Very few places on the planet ever exceed a wet bulb temperature of 30° or 31°C. 


But a study released in 2010 by researchers Steven C. Sherwood and Matthew Huber of the University of New South Wales and Purdue University suggests that if the global climate increases by an average of about 10°C, which is not completely implausible by the year 2200, vast areas of the planet could regularly exceed that deadly 35°C wet bulb temperature, making them essentially uninhabitable, at least for part of the year for anyone without abundant reяources.


Increases in wet bulb temperature don't track directly to increases in air temperature for a couple reasons. For one thing, wet bulb temperature is also influenced by barometric pressure. More importantly, if you heat a mass of air, its relative humidity will decrease unless you add more water to it. What that means is that even with global temperature increase, the parts of the planet that are now deserts generally won't see much of an increase in wet bulb temperatures.

What parts of the world will approach that fatal 35°C? Places where there's a lot of water laying around for that heated air to suck up. Places like India. West Africa. The Amazon. Coastal China and southeast Asia. And essentially all of what is now the eastern United States.
Areas shaded in lavender and purple may become uninhabitable with a 10°C global temperature rise | Photo: Purdue University

As Sherwood and Huber said in 2010, our technology may not offer those trying to live in these affected areas much help:
In principle humans can devise protections against the unprecedented heat such as much wider adoption of air conditioning, so one cannot be certain that... 35°C would be uninhabitable. But the power requirements of air conditioning would soar; it would surely remain unaffordable for billions in the third world and for protection of most livestock; it would not help the biosphere or protect outside workers; it would regularly imprison people in their homes; and power failures would become lifethreatening. Thus it seems improbable that such protections would be satisfying, affordable, and effective for most of humanity.

If temperatures increase by 11° or 12°C, said Sherwoood and Huber, we'd lose most of our species' habitat.

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.


How likely is an increase of 10°C by 2200? The Intergovernmental Panel on Climate Change (IPCC) offered a number of scenarios in its Fourth Assessment Report in 2007, one of which was based on the assumption of "a future world of very rapid economic growth, global population that peaks in mid-century and declines thereafter, and the rapid introduction of new and more efficient technologies." If that world was primarily focused on fossil fuel use, said that report, the road ours seems to be headed down, temperatures could be as much as 6.4° higher by 2100. In a renewable-centered world, that increase could be kept to 4°C or lower. But few expect temperatures to stop rising in 2100, regardless of the scenario.

The website Skeptical Science offered a look at best- and worst-case climate scenarios in February, with the best-case scenario modeled on the assumption that doubling our atmospheric CO2 will cause 2°C of global temperature increase, and the worst case scenario making that 4°C for the same input of CO2. Their best-case scenario showed between 2° and 3°C increase by 2150 for the two most likely industrial strategies for emitting carbon, and their worst-case scenario pumped that up to a range of 5° to 7°C.


Skeptical Science offers two sobering caveats for this data:

There is a critical point that must be made here -- the worst case scenario is just as likely as the best case scenario... And remember, we haven't accounted for account for possible changes in the carbon cycle, like reduced ocean carbon absorption or releases from melting permafrost, or slow feedbacks which may amplify global warming further in the future.


The total eventual effect of those complicating factors Skeptical Science omitted from its calculations is unknown, but it's near certain that at least some will occur, and it's also near certain that their cumulative impact on global temperatures will be unpleasant. For instance: one of the more likely effects of a very optimistic 2°C global increase in temperature will be that polar regions increase by 4°C. That means that huge areas of permafrost soild will be altered. Permafrost is thought to hold about twice as much carbon as the atmosphere does at present: when it melts, that carbon enters the atmosphere either as methane, a devastatingly potent greenhosue gas, or as carbon dioxide. Methane once sequestered in permafrost is already entering the atmosphere. Even if our greenhouse gas emissions stopped today, the UN Environment Programme estimates it would take a century for the resulting permafrost emissions to peak, and another century to drop back down to anywhere close to their current levels.

The IPCC will be releasing its Fifth Assessment Report in stages coming next month, so we'll see how the world's leading climate science body has updated what it thought in 2007. A 10°C increase in global temperatures by 2200 would seem far more likely than any of us would like. Which means that, according to Sherwood and Huber's projections, 58 percent of the world's current population now lives in areas with a good chance of being uninhabitable in 190 years.

Loss of habitat is the major cause of extinction, and a species that loses 58 percent of its habitat is in trouble. The Sumatran elephant is now considered critically endangered after losing 70 percent of its original habitat. We're better than any other species at shifting from one habitat to another, but even those skills have limits. How well will our descendants on the U.S. Pacific Coast fare when they're faced with accomodating migrants from all of North America east of the Missouri River? Or from the likely Death Zone in Asia?


Conflict over resources and space leads to wars and other conflict, and it's very likely that if Sherwood and Huber's projections come to pass, life will be excruciatingly bad, even in places where the wet bulb temperatures never get close to 35°C.

Will we go extinct? There's some thought that humans have already passed through a near-extinction event, related to the Toba eruption about 70,000 years ago, that may have reduced our total global population down to 15,000 people or fewer in southern Africa. That theory is questioned by some who cite the possibility of other survivng bands of humans. Either interpretation offers us hope for our species: humans can survive horrible catastrophes and rebuild.

Which means the question may not be so much "will we die out" as "will we wish we had." If humans were to go extinct, the earth would at least have a chance to repair itself, evolve new biodiversity, and move on. But having the globe sprinkled with scattered bands of a few hundred survivors, each desperately scraping whatever sustenance might come from the planet their ancestors ruined? That's a much more frightening prospect for both the planet and our great great grandchildren.

Chris Clarke is a natural history writer and environmental journalist currently at work on a book about the Joshua tree. He lives in Joshua Tree

From summer, last year

Ocean Heat Dome Steams Coastal China: Shanghai to Near Very Dangerous 35 Degree Celsius Wet Bulb Temperatures This Week

13 August, 2013

Shanghai Under Ocean Heat Dome
Shanghai, southeast China swelter under Ocean Heat Dome.
(Image source: NASA/Lance-Modis)
An ocean heat dome that formed over a broad area of the Pacific Ocean, the South and East China seas, and a large stretch of coastal China during late July continues to create a dangerous combination of record hot temperatures and high humidity.

According to reports from AccuWeather, the sweltering coastal China town of Shanghai hit a new all-time record high temperature of 105.8 degrees Fahrenheit (41 degrees C) on Tuesday. But this marker may just be a milepost to what is predicted to be a 107-108 degree scorcher on Wednesday and Friday. With humidity predicted to be around 50% and barometric pressure readings expected to hit 1005 millibars, these represent extraordinarily dangerous conditions.

The human wet bulb limit: 35 C

One implication is that if we should “succeed” in digging up and burning all fossil fuels, some parts of the planet would become literally uninhabitable, with some time in the year having wet bulb temperature exceeding 35°C. At such temperatures, for reasons of physiology and physics, humans cannot survive, because even under ideal conditions of rest and ventilation, it is physically impossible for the environment to carry away the 100 W of metabolic heat that a human body gene rates when it is at rest.

Different from direct air temperature, wet bulb readings measure what air feels like on the surface of the skin. The measure simulates the cooling effect caused by human sweat evaporating from the skin surface. In very dry, hot conditions, human skin temperature can remain below this lethal level as the rate of evaporation increases due to dryness. Since most of the world’s hottest regions are very dry, humans can withstand air temperatures of 120 degrees (Fahrenheit) and above. Thankfully, it is very rare that extraordinarily hot and humid conditions occur in the same locations. This is generally due to a cooling affect provided by an adjacent ocean mass — as most damp regions are also near or surrounded by cooler ocean air.

The Ocean Heat Dome

Enter the weather conditions forecast for Shanghai tomorrow and Friday…
A massive heat dome high pressure system has settled, not just over land areas of China, but directly over a large region of the Pacific Ocean and adjacent China seas. The result is that sea surface temperatures are now ranging 1-4 degrees Celsius above the already warm 1971-2000 average with a large area showing temperatures above 30 degrees Celsius (86 Fahrenheit). This large region of hot water and corresponding hot ocean air is pumping both heat and humidity into the Shanghai region. Hot ocean air is being pumped over Southeast Asia where it mixes with the already baking land mass air to form a brutal brew of very high heat and high humidity. The clockwise flow of the heat dome then pulls this mixture of record hot and humid air over the highly populated regions of Shanghai.
These ocean-based heat dome conditions are not normal, with typical heat dome conditions usually forming over land. The danger in this particular set of conditions is that very high heat combines with higher than usual humidity to result in much greater heat injury risks for humans.

Ocean heat dome
Sea surface temperatures under Ocean Heat Dome
(Image source: Weather Online)
Forecasts for tomorrow and Friday are showing Shanghai temperatures will probably reach at least 107-108 degrees Fahrenheit (42 C) in an area where relative humidity is forecast to be 50% and where barometric pressures are forecast to remain around 1005 millibars of mercury. This brings us to the extraordinarily dangerous high wet bulb temperature of 33 degrees Celsius. And should thermometers crack 113 degrees (F) under those same temperature and pressure conditions, Earth will have achieved a new and very ominous wet bulb temperature record of 35 degrees Celsius.

Please do your best to stay safe

In such instances, the best defense is to find a cool, shaded location and limit exposure to heat during the hottest times of the day. Drinking cold fluids can also aid in reducing core body temperatures. A common heat mitigation aid is freezing a bottle of water and carrying it in a pocket next to your thigh. The cold bottle will contact the skin near the femoral artery, cooling blood there and transporting this cooler blood throughout the body. If extreme heat is still too much, placing the bottle in direct contact with the large veins in the neck will provide even more efficient cooling. This simple cooling pack also doubles as a means to replenish vital fluids.

Under such conditions, it is also important to be alert for signs of heat exhaustion and heat stroke to include:
  • Confusion
  • Dark-colored urine (a sign of dehydration)
  • Dizziness
  • Profuse sweating
  • Weakness
  • Muscle cramps
  • A lack of sweating
China has also activated emergency operations facilities and is providing information and aid in the hardest hit regions.

Unfortunately, record heat is expected to continue over Shanghai through at least next Wednesday with only one day expected to see below 100 degree (F) readings. With so many already dealing with heat stress, our best hopes are that all there will have the means to remain safe.

Hat Tips and People I Just Feel Like Promoting:

China Falls Under Suspicion of Covering Up Deaths as Ocean Heat Dome Expands to Blanket Korea and Japan


13 August, 2013

US Weather Fatalities by Type
US Weather Fatalities by Type
(Image source: NOAA)

According to recent reports from NOAA and the CDC, heat is the most lethal form of weather in the United States. Death and injury rates have been on the rise as human-forced temperature increases have expanded, surging northward into major metro areas such as New York City. The CDC report showed a growing number of heat deaths and injuries for this northern region, with the New York Metro area seeing an average of 13 deaths and over 440 heat injuries each year during the period from 2000 to 2011. Nationwide, the average number of heat fatalities surged to 117 during a period from 2003 to 2011.

Heatwaves have hit the NYC region time and time again over the past decade, driving the death and injury rate inexorably higher. However, the heat impacting that area is paltry when compared to the extreme and deadly temperatures that have broiled southeastern China since late July. For more than three weeks, the Shanghai region of China has experienced almost daily temperatures in excess of 100 degrees Fahrenheit and sweltered under very high humidity for such hot conditions. This combination has pushed wet bulb temperatures (a measure that simulates the temperature of human skin) into a range of 29 to 32 degrees Celsius, very close to the lethal human limit of 35 degrees C.

On Sunday, an extreme heat pulse sent thermometers soaring to 109 degrees Fahrenheit in the city of Shengxian — its hottest temperature ever recorded and a scorching 32.3 degree wet bulb temperature. Meanwhile, on the same day, Hangzhou had hit a new all time record high temperature of 105.8 degrees Fahrenheit, the twelfth time since July 24th that Hangzhou has tied or broken its old all time temperature record which, in some cases, was set just the day before.

High heat and humidity of this kind is deadly to humans because as temperatures approach 35 degree C wet bulb readings, it is nearly impossible for the human body to carry away the excess heat it generates through evaporation. Never has a wet bulb temperature of 35 degrees C been recorded by humans. However, climate scientists such as James Hansen have asserted that it’s just a matter of time under the current regime of human-caused warming before we hit that ominous mark.

So have thousands died?
Road Sing Burns in Shanghia Region
Road Sign Burns Under Record Heat in Shanghai Region
(Image source: Shenzhen Daily)
As reports of vehicle fires and sporadically smoldering infrastructure in the massive Chinese heatwave flared, suspicions emerged that Chinese officials are covering up what are potentially thousands of heat-related deaths.

According to Chinese news agencies, the official report is that about two dozen have died so far in Shanghai’s record-shattering heatwave. But similar heat in Europe and Russia resulted in tens of thousands of deaths over the past decade. At issue is the fact that China’s current record heat and humidity are at levels never before experienced in its weather history and that this event is even more intense than the deadly heatwaves of Europe and Russia. Add to this extraordinarily dangerous event the fact that more than 400 million people live in the region of China currently being socked by record heat and the vague reports coming out of China seem highly incongruent.

Never before has such high wet bulb temperatures hit a region of so dense a population. Yet China has only continued to report the vague ‘dozens’ estimate.  It was this discrepancy that caused WeatherUnderground Historian Christopher Burt to speculate that China may be covering up a catastrophic rash of fatalities:

Eastern China, where about 30% of the population of the country and 5% of the global population reside (approximately 400 million people) has undergone a heat wave unprecedented in its history. No one really knows how many have died as a result of the heat wave (Chinese news sources claim ‘about two dozen’), but statistically it is almost certain that many thousands must have perished as the result of the heat over the past month.

If Christopher Burt’s, quite rational, analysis ends up proving true, we can expect reports of fatalities to begin to slowly trickle out of China. Misreporting and under-reporting of Chinese heatwave casualties would also be yet one more instance of government officials and mainstream media downplaying and under-reporting the effects of catastrophic events related to human-caused climate change. Such under-reporting is yet one more manifestation of a dangerous and paralyzing denial that has so hampered an effective response to these increasingly dangerous and self-inflicted events.

Making such a call, however, is possibly premature as residents of this region are more acclimated to excessive heat than Europeans or Russians. As Burt notes:
One thing to keep in mind, however, is that it is ALWAYS hot and humid in eastern China during the summer (unlike Russia and Western Europe), so perhaps the population has learned to adapt to extreme heat.
The Ocean Heat Dome Expands to Cover Korea and Japan
Ocean Heat Dome
Ocean Heat Dome Over China, Korea and Japan
(Image source: NASA/Lance-Modis)
A sprawling heat dome high pressure system that has scorched a region stretching from coastal China to a large expanse of the Pacific Ocean shifted eastward into Korea and Japan over the weekend. Southern Japan saw temperatures surge into the 100s with Shimanto recording the highest temperature ever measured in Japan of 105.8 degrees Fahrenheit (41 degrees Celsius). Tokyo, meanwhile, broke the record for its hottest minimum temperature at 86.7 degrees Fahrenheit (30.4 C).

South Korea, over the same period, reported 8 deaths as temperatures soared to 102.2 degrees Fahrenheit (39 C) in Busan. Temperatures in Seoul hit the still hot, but more moderate, 90s (32 C +).
Both South Korea and Japan are surrounded on multiple sides by water. This geographic feature would usually provide a cooling effect as ocean temperatures are typically many degrees cooler than land temperatures. But, in this case, a massive heat dome is baking the ocean itself to unprecedented high surface water temperatures. As a result, a large area of open ocean now shows readings above 30 degrees Celsius ( 86 Fahrenheit). This extremely hot, near 90 degree water, has formed the central pulse of the current heatwave even as it has pumped extraordinarily humid air for such hot conditions over adjacent land areas. A shift to the north of this large and still growing region of extraordinarily hot ocean water led to the record steamy conditions over Japan and Korea during the past few days — both of which can expect little relief from the now, very hot, water.
Asia in Hot Water
Ocean Heat Dome Puts Asia in Hot Water
(Image source: Weather Online)
Forecasts for Shanghai, Korea, and Japan call for slightly less sweltering temperatures in the upper 90s with more isolated readings in the 100s as clouds are expected to move in and increase chances of rainfall by later this week. A slight improvement but a welcome change, nonetheless. Meanwhile, hot ocean conditions create a risk for continued very hot temperatures for much of this coastal region.

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