Is Weird Winter Weather Related to Climate Change?
Fred Pearce
By Fred Pearce
24 Feb 2014:
Analysis
http://www.e360.yale.edu/feature/is_weird_winter_weather_related_to_climate_change/2742/
This winter’s weather has been weird across much of the Northern Hemisphere. Record storms in Europe; record drought in California; record heat in parts of the Arctic, including Alaska and parts of Scandinavia; but record freezes too, as polar air blew south over Canada and the U.S., causing near-record ice cover on the Great Lakes, sending the mercury as low as minus 50 degrees Celsius in Minnesota, and bringing sharp chills to Texas.
Everyone is blaming the jet stream, which drives most weather in mid-latitudes. That would be a significant development. For what happens to the jet stream in the coming decades looks likely to be the key link between the abstractions of climate change and real weather we all experience. So, is our recent strange weather a sign of things to come? Are we, as British opposition leader Ed Milliband put it this month while surveying a flooded nation, "sleepwalking to a climate crisis"?
The story gets tangled because trying to identify long-term trends amid the noise of daily weather is hard.
The U.K. Met Office, which keeps a global weather watch, said in a rush report put out in mid-February <http://www.metoffice.gov.uk/media/pdf/n/i/Recent_Storms_Briefing_Final_07023.pdf> that we are experiencing a "hemispheric pattern of severe weather," and that the events are linked. The most extreme days of the U.S. cold event, for instance, coincided with some of the most intense storms over the U.K. And physically the connection is through the polar jet stream, which the report said showed a "persistent pattern of perturbations" — in other words, it ran wild.
The polar jet stream is a narrow stream of fast wind circling the globe from west to east at the top of the troposphere from 7 to 12 kilometers up, and usually between 50 and 70 degrees north. It forms where cold, dense air from the Arctic meets warmer and less dense air from mid-latitudes. At the boundary, winds rush in to equalize the pressure difference. The earth's rotation diverts these winds to travel eastward.
As the jet roars around the world, it drags weather systems with it. Most of Europe's weather rides in under the jet stream from the Atlantic, and most of the western U.S.'s weather comes from the Pacific in a similar manner.
This year, the jet has been unusually far north in the Pacific, bringing balmy weather to Alaska. But across the Atlantic it has been unusually far south, unusually persistent, and 30 percent faster than normal. It has sent more than 30 storms, many of them much larger and more intense than normal, crashing into the shores of Britain in the past three months. With the storms have come high winds and heavy rains almost every day, delivering amounts of precipitation unseen in records going back more than a century — and probably exceeding anything else in the last 250 years, according to the Met Office report.
At the annual meeting of the American Association for the Advancement of Science in Chicago this month, climatologist Jennifer Francis of Rutgers University linked "this bizarre winter" to climate change, and in particular to changes in the jet stream <http://www.bbc.co.uk/news/science-environment-26023166> caused by a warming Arctic. "Weather patterns are changing," she said. "We can expect more of the same."
Francis notes <http://e360.yale.edu/feature/linking_weird_weather_to_rapid_warming_of_the_arctic/2501/> that the Arctic has been warming faster than the rest of the planet in recent decades, driven by melting ice that replaced reflective white surfaces with dark, energy-absorbing ocean. That is expected to continue. While lower latitudes will also warm, the result will be to reduce the temperature gradient between polar and mid-latitude air that drives the jet. So, says Francis, we can expect the jet to slow. A slower jet is generally more meandering and inclined to get "stuck," delivering unchanging weather.
There is one problem with this analysis as regards recent events, says Tim Woollings <http://www2.physics.ox.ac.uk/contacts/people/woollings> , who researches atmospheric dynamics at Oxford University in England. While the jet stream has indeed been "stuck" for the past two months, delivering cold weather to North America and storms across the Atlantic, it is not slow and meandering. Across the Atlantic at least, it has been fast and remarkably straight. "That is the exact opposite to the weak meandering jet of your hypothesis," Woollings told Francis in an email exchange last week that both shared with Yale Environment 360.
That certainly doesn’t prove Francis wrong. Woollings agrees that Francis’s prediction of a stuck meandering jet looks very like the situation in the Pacific this winter. But it does complicate claims that this winter’s extremes can be blamed on man-made climate change.
So what is going on? The Met Office came to the conclusion that the real driver of the action in recent months was not in the Arctic or the Atlantic, but far away in the western Pacific Ocean. The jet stream, remember, is a global wind, circling the earth. This winter, the jet stream over the Pacific has been deflected much further north than usual. This, according to the Met Office, is likely a consequence of some combination of heavy rains over Indonesia, warm Pacific waters, and unusual pressure systems.
The displaced Pacific leg of the jet stream dragged warm air up over Alaska. But, once east of the Rockies, it met the dense cold air of the Arctic and plunged south. A long way south — as far as Texas at times. This southward excursion of the jet brought freezing weather across much of the U.S. But it also brought that cold polar air into contact with warm southerly breezes. Thus the temperature gradient at the boundary between polar and non-polar air was exceptionally great. At times, says Francis, Arctic air was meeting tropical air as the polar jet coalesced with the sub-tropical jet, which forms where tropical air meets air from the north.
The scientists agree that this exceptional temperature difference dramatically speeded up the jet stream as it pushed out over the Atlantic on its unusually southerly trajectory. A fast jet stream is usually also a straight jet stream. And the southerly route allowed the surface air it pulled along to pick up unusual amounts of moisture evaporating from the warm waters of the Atlantic.
The result was that the jet slammed a long succession of intense storms into southern England, where they would normally hit Scotland or miss the U.K. altogether. The storms contained huge volumes of moisture. And, to add to the tumult, the fast winds across the Atlantic also whipped up big waves and tidal surges; so in places record flood flows coming down rivers met flood waters coming off the sea. Parts of Britain were submerged.
Where does this leave us on climate change? It is no great surprise that there is confusion. Weather is weather. It is always changeable, with a large random element. Stuff happens. The Met Office notes that the winter’s weird weather has a range of causes besides the jet stream, including unusual upper atmosphere winds over the North Pole, and anomalies in the eastern Pacific that have delivered severe drought to California. There is, the Met Office says, no compelling evidence from this winter to suggest that there is a new emerging pattern.
But that doesn’t mean nothing is going on. Long-term trends are hard to spot, and natural variability is still generally dominant over the subtle changes in climate, or "average weather."
Yet there are some instances where attribution is possible. For example, climate researchers have persuasively argued that a few intense heat waves — such as the one that killed 70,000 people in western Europe in 2003 — would have been highly unlikely without the added impetus of global warming. But for weather extremes other than rising temperatures, unambiguous attribution of even extreme events is very hard to make, whatever the suspicions that something is up.
Climate scientists remain very uncertain about how most of the major features of the world’s weather will respond to global warming. The climate will change, for sure, but exactly how is a tough call.
El Niño, the Asian and African monsoons, Atlantic hurricanes, the jet streams: The most recent report of the Intergovernmental Panel on Climate Change (IPCC), issued last October, puts a big question mark over the likely trends for all of them. And while Francis suggests the polar jet stream should slow as the Arctic warms, the IPCC noted <http://www.ipcc.ch/report/ar5/wg1/docs/WGIAR5_SPM_brochure_en.pdf> that most climate models predict a faster polar jet.
Actual trends so far don’t tell us much. According to the Met Office, the number of storms crossing the Atlantic in a normal year is no higher today than 150 years ago. But Xiaolan Wang of Environment Canada, a government agency, last year reported evidence <http://link.springer.com/article/10.1007%2Fs00382-012-1450-9#> that winter storms are becoming stronger over the North Atlantic. This may not have anything to do with the jet stream, however. These storms could just be picking up more moisture from an Atlantic that is now substantially warmer than in past decades.
Data from weather stations around the world reveal more extreme precipitation events — and more droughts, too. This is firmly in line with the predictions of climate models and is "what is expected from fundamental physics," says the Met Office. A warmer atmosphere will contain more energy, and more moisture from evaporation, says Woollings. It already does. And, in general, more energy and moisture will mean wetter storms in many places.
Weird weather is definitely on the agenda, and the jet stream is very likely to be an important part of it. The nightmare scenario is that Francis will be proved right about the jet stream becoming more "stuck" in a particular trajectory, but that, as happened this winter, it will get stuck while traveling at express speed and bringing strong winds and heavy rain with it. The Met Office says the Francis scenario "raises the possibility that disruption of our usual weather patterns may be how climate change may manifest itself." If so, that would indeed unleash the perfect storm.
Solar Geoengineering:
Weighing Costs
of Blocking
the Sun’s Rays
With prominent scientists now calling for experiments to test whether pumping sulfates into the atmosphere
could safely counteract global warming, critics worry that the world community may be moving
a step closer to deploying this controversial technology.
By Nnicola Jones
09 Jan 2014: Report
http://e360.yale.edu/feature/solar_geoengineering_weighing_costs_of_blocking_the_suns_rays/2727/
In 1991, Mount Pinatubo in the Philippines erupted in one of the largest volcanic blasts of the 20th century. It spat up to 20 million tons of sulfur into the upper atmosphere, shielding the earth from the sun’s rays and causing global temperatures to drop by nearly half a degree Celsius in a single year <http://www.thefreelibrary.com/Mt.+Pinatubo%27s+cloud+shades+global+climate.-a012467057> . That’s more than half of the amount the planet has warmed due to climate change in 130 years
Now some scientists are thinking about replicating Mount Pinatubo’s dramatic cooling power by intentionally spewing sulfates into the atmosphere to counteract global warming. Studies have shown that such a strategy would be powerful, feasible, fast-acting, and cheap, capable in principle of reversing all of the expected worst-case warming over the next century or longer, all the while increasing plant productivity. Harvard University physicist David Keith <http://www.seas.harvard.edu/directory/dkeith> , one of the world’s most vocal advocates of serious research into such a scheme, calls it "a cheap tool that could green the world." In the face of anticipated rapid climate change, Keith contends that the smart move is to intensively study both the positive and negative effects of using a small fleet of jets to inject sulfate aerosols high into the atmosphere to block a portion of the sun’s rays.
Yet even Keith acknowledges that there are serious concerns about solar geoengineering, both in terms of the environment and politics. Growing discussion about experimentation with solar radiation management has touched off an emotional debate, with proponents saying the technique may be needed to avert climate catastrophe and opponents warning that deployment could lead to international conflicts and unintended environmental consequences — and that experimentation would create a slippery slope that would inevitably lead to deployment. University of Chicago geophysicist Raymond Pierrehumbert <http://geosci.uchicago.edu/%7Ertp1/> has called the scheme "barking mad." Canadian environmentalist David Suzuki <http://www.davidsuzuki.org/david/> has dismissed it as "insane." Protestors have stopped even harmless, small-scale field experiments that aim to explore the idea. And Keith has received a couple of death threats from the fringe of the environmentalist community.
Clearly, there are good reasons for concern. Solar geoengineering would likely make the planet drier, potentially disrupting monsoons <http://onlinelibrary.wiley.com/doi/10.1029/2008JD010050/abstract> in places like India and creating drought in parts of the tropics <http://iopscience.iop.org/1748-9326/9/1/014001/article> . The technique could help eat away the protective ozone shield of our planet, and it would cause air pollution. It would also do nothing to counteract the problem of ocean acidification, which occurs when the seas absorb high levels of CO2 from the atmosphere.
Some worry that solar geoengineering would hand politicians an easy reason to avoid reducing greenhouse gas emissions. And if the impacts of climate change worsen and nations cannot agree on what scheme to deploy, or at what temperature the planet’s thermostat should be set, then conflict or even war could result as countries unilaterally begin programs to inject sulfates into the atmosphere. "My greatest concern is societal disruption and conflict between countries," says Alan Robock <http://www.envsci.rutgers.edu/%7Erobock/> , a climatologist at Rutgers University in New Jersey.
As Keith himself summarizes, "Solar geoengineering is an extraordinarily powerful tool. But it is also dangerous."
Studies have shown that solar radiation management could be accomplished and that it would cool the planet. Last fall, Keith published a book, A Case for Climate Engineering <https://mitpress.mit.edu/books/case-climate-engineering> , that lays out the practicalities of such a scheme. A fleet of ten Gulfstream jets could be used to annually inject 25,000 tons of sulfur — as finely dispersed sulfuric acid, for example — into the lower stratosphere. That would be ramped up to a million tons of sulfur per year by 2070, in order to counter about half of the world’s warming from greenhouse gases. The idea is to combine such a scheme with emissions cuts, and keep it running for about twice as long as it takes for CO2 concentrations in the atmosphere to level out.
Under Keith’s projections, a world that would have warmed 2 degrees C by century’s end would instead warm 1 degree C. Keith says his "moderate, temporary" plan would help to avoid many of the problems associated with full-throttle solar geoengineering schemes that aim to counteract all of the planet’s warming, while reducing the cost of adapting to rapid climate change. He estimates this scheme would cost about $700 million annually — less than 1 percent of what is currently spent on clean energy development. If such relatively modest cost projections prove to be accurate, some individual countries could deploy solar geoengineering technologies without international agreement.
The idea of solar geoengineering dates back at least to the 1970s; researchers have toyed with a range of ideas, including deploying giant mirrors to deflect solar energy back into space, or spraying salt water into the air to make more reflective clouds. In recent years the notion of spraying sulfates into the stratosphere has moved to the forefront. "Back in 2000 we just thought of it as a ‘what if’ thought experiment," says atmospheric scientist Ken Caldeira <http://dge.stanford.edu/labs/caldeiralab/> of the Carnegie Institution for Science, who did some of the first global climate modeling work on the concept.
"In the last years, the thing that’s surprising is the degree to which it’s being taken more seriously in the policy world."
In 2010, the first major cost estimates of sulfate-spewing schemes <http://www.scribd.com/doc/53418122/AuroraGeoReport> were produced. In 2012, China listed geoengineering among its earth science research priorities. Last year, the Intergovernmental Panel on Climate Change’s summary statement for policymakers controversially mentioned geoengineering for the first time <http://heliophage.wordpress.com/2013/09/28/the-ipcc-and-geoengineering/> in the panel’s 25-year history. And the National Academy of Sciences is working on a geoengineering report <http://www8.nationalacademies.org/cp/projectview.aspx?key=49540> , funded in part by the U.S. Central Intelligence Agency.
Solar geoengineering cannot precisely counteract global warming. Carbon dioxide warms the planet fairly evenly, while sunshine is patchy: There’s more in the daytime, in the summer, and closer to the equator. Back in the 1990s, Caldeira was convinced that these differences would make geoengineering ineffective. "So we did these simulations, and much to our surprise it did a pretty good job," he says. The reason is that a third factor has a bigger impact on climate than either CO2 or sunlight: polar ice. If you cool the planet enough to keep that ice, says Caldeira, then this dominates the climate response.
But there are still problems. Putting a million tons of sulfur into the stratosphere each year would probably "contribute to thousands of air pollution deaths a year," Keith acknowledges. Because solar geoengineering doesn’t affect the amount of carbon dioxide in the air, ocean acidification would continue unabated. And sulfates would alter atmospheric chemistry toward formation of ozone-destroying chlorine compounds, which could lead to a moderate increase in skin cancers or ultraviolet damage to plant life. Sulfates would also make the sky a little whiter than usual <http://onlinelibrary.wiley.com/doi/10.1029/2012GL051652/abstract%20> and sunsets more dramatic, scientists say.
Basic physics shows that warming from sunlight boosts the planet’s water cycle more than warming from carbon dioxide. This is because sunlight adds more energy to the system, like turning up the heat on a stove under a pot of water, while carbon dioxide simply puts a lid on the pot. So counteracting greenhouse warming by reducing sunlight would likely make the planet drier <http://www.earth-syst-dynam.net/4/455/2013/esd-4-455-2013.html> — models predict a 1 percent reduction in rainfall for every degree Celsius of warming counteracted, says Axel Kleidon <http://www.bgc-jena.mpg.de/index.php/BTM/AxelKleidon> of the Max Planck Institute for Biogeochemistry in Jena, Germany. "When you try to fix one problem you create other problems," says Kleidon, who opposes pursuing such techniques.
The Geoengineering Model Intercomparison Project <http://climate.envsci.rutgers.edu/GeoMIP/> (GEOMIP) recently looked at how solar alterations might affect regional climate patterns <http://onlinelibrary.wiley.com/10.1002/%28ISSN%292169-8996/specialsection/GEOMIP1> . It concluded that the tropics would be over-cooled and the poles under-cooled. While the project concluded that solar radiation management would likely protect more than 90 percent of the globe from the serious changes in rainfall predicted from climate change, summer monsoons might start to dry up, requiring a change in agriculture or water storage systems to adapt to the new climate.
The upshot is that things would get better for some people and worse for others, though the details are hard to predict. Rice production might go down in China because of water cycle changes for example, but could increase because of increased carbon dioxide to feed the plants, says Caldeira. Despite the drop in sunshine, crop productivity would probably increase worldwide because of higher atmospheric concentrations of CO2.
Because sulfates only remain in the atmosphere for a few years, a geoengineering program could be stopped at any time if unanticipated disaster ensues. But then the temperature would race upward as the planet readjusts to the amount of carbon dioxide in the air. If geoengineering were used to counteract 2 degrees C of warming over 50 years, for example, that 2 degrees of warming would come back quickly once the geoengineering stops. And there is no governance system at present to oversee if and how a program should start or stop. A group called The Solar Radiation Management Governance Initiative <http://www.srmgi.org> has held a few workshops in recent years to discuss these questions.
Such concerns have led some people to take a hard-line stance against any kind of geoengineering. This started with environmental organizations like ETC Group <http://www.etcgroup.org/> protesting against iron fertilization of the seas — an idea meant to stimulate phytoplankton growth and so suck up carbon dioxide from the air, which controversially interferes with the base of the ocean’s food chain. This led to a 2008 Convention on Biological Diversity moratorium against iron fertilization <https://www.cbd.int/decision/cop/default.shtml?id=11659> , which in 2010 was expanded to any geoengineering <http://www.cbd.int/climate/geoengineering/> .
These agreements are non-binding, but still have influence, even on apparently harmless experimentation. When the Stratospheric Particle Injection for Climate Engineering <http://www2.eng.cam.ac.uk/%7Ehemh/SPICE/SPICE.htm> (SPICE) research group attempted to run a small field experiment in 2011 to spray water into the air from balloons as a way of testing a stratospheric delivery system, protestors forced the group to stop <http://www.handsoffmotherearth.org/hose-experiment/spice-opposition-letter/> . This irritates Caldeira. "I think it’s very dangerous
To date, no solar geoengineering field trials have taken place, aside from a study or two looking at the idea of seeding more reflective clouds. Keith argues that some experiments would be good to test the risks and efficacy of such a strategy, and he has proposed a meeting of researchers to hash out a list of suitable work that should be done. He and his colleagues are currently planning experiments that would inject less than a hundred kilograms of aerosol material into the stratosphere in order to investigate some of the ensuing chlorine chemistry. They haven’t yet gotten to the stage of an official proposal.
But Robock argues that while modeling and indoor experiments should be pursued, outdoor field trials are problematic.
"You can’t see a climate response unless an experiment is so large as to actually be geoengineering," Robock says.
Keith concludes that it "makes sense to move with deliberate haste towards deployment of geoengineering," so long as early work supports the theoretical promise of the technique.
Caldeira is less bullish, saying, "Climate change is not going to extinguish us as a species. Geoengineering will always be a decision, not a necessity."