Blue Marble

We’re Still Losing Ice at the Poles

| Tue Dec. 17, 2013 7:00 AM EST
Arctic sea ice reached its minimum extent in Sep. 2013, two days earlier than usual. The orange line is the median minimum extent from 1981 - 2010; note how much lower the ice was this year.

This story first appeared on Slate and is reproduced here as part of the Climate Desk collaboration.

One of the key indicators and consequences of global warming is ice loss at the Earth's poles. As the planet warms, on average and over time, every summer more ice melts. It refreezes in the winter, but again as temperatures rise, in general we'll see less ice at any given time as compared to the year before.

The situation for the two poles is different. In the north the Arctic ice floats on the ocean, and on the south the Antarctic ice is over land and sea. This means that they way they melt—how quickly, how much, even where specifically in those regions—are different. Still, the fact is the ice at both poles is melting. We've known this for quite some time.

And some new data show it's even worse than we thought.
 

Bad News, Australis Edition

ice loss in Antarctica
Ice loss in Antarctica; blue shows where ice is thinning, red where it's growing. Note the imbalance. CPOM / ESA

Measurements of Antarctic ice made by the European Space Agency's CryoSat satellite show that it's losing about 150 cubic kilometers (36 cubic miles) of ice on average every year just from the West Antarctica ice sheet alone. This is notably more than what had been previously estimated, and is likely to be more accurate due to the satellite's better coverage and use of radar to measure ice thickness.

The bulk of this loss is from melting glaciers, with their runoff flowing into the sea. This in turn is raising the sea level by about 0.3 millimeters per year (again, just from the West Antarctic ice sheet alone). It's unclear if this increase in ice loss is due to faster thinning of the ice, or due to better coverage of the satellite in regions otherwise difficult to access. Either way, the ice is melting more rapidly than previously thought.

This amount of loss is staggering; it's equivalent to about a hundred billion tons. That's equivalent in volume to a mountain about four kilometers (2.5 miles) high, roughly the size of a medium-size mountain in the Rockies.

I'll note that some people who deny global warming like to talk about ice in Antarctica increasing, not decreasing. This is at best misleading; the sea ice fluctuates every year, and has grown marginally recently, but this is tiny compared to the loss of land ice. Overall, Antarctica is losing ice, rapidly, with more melting every year.

 

Bad News, Borealis Edition

Maps of ice loss in the Arctic show it dwindling over time. A fair question to ask is, when will we see an ice-free summer there?

This question isn't all that easy to answer; it depends on past measurements as well as models of how the ice melts. Most conservative models estimate it will happen before the end of this century, but how long before? Some say it may be 50 years or more, some much sooner.

In the Guardian, Nafeez Ahmed reports on a study funded by the U.S. Department of Energy and undertaken by scientists with the U.S. Navy has shown that the Arctic could see its first nearly ice-free summer in just three years, in 2016. These results actually came out last year, and are based on ice loss from a few years back, using a relatively straightforward extrapolation.

In the paper, the scientists claim that ice loss is underestimated by most models because they don't include feedback mechanisms; that is, processes in the system that amplify other processes. For example, as water warms it cannot hold as much dissolved carbon dioxide. That CO2 is released in the air, accelerating the warming process because it's a greenhouse gas.

I'm not sure how much stock to put in a prediction of an ice-free Arctic in just a few years, but that day is clearly coming, and soon. Looking at the sea ice extent (essentially, how much area is covered by ice) over the past few years, we've lost about 2 million square kilometers over 15 years.* The extent is at roughly 10 million sq. km now, so extrapolating we have 75 years left. I'll note that's very rough, and I'd consider that only a decent upper limit to how long it will take. With feedback processes, that's likely to be a severe overestimate.

Arctic ice loss from 1978 throught the end of 2013. Note the trend. NSIDC
 

To give you a more visceral sense of just how much trouble we're in, Andy Robinson, who created a video earlier this year showing the ice loss, has updated it with data including this year's minimum:

Note that this is volume of ice, not extent, which is a better measure of real loss. Extent fluctuates more, and doesn't include the thickness of the ice; you can get very thin ice in the winter adding to the extent but not really adding to the total amount of ice. Plus, thin ice melts more readily in the summer.

And, of course, this puts lie to the whole idea that sea ice in the Arctic is "recovering", which we knew was more hot air from the deniers all along anyway.


Double Pole Loss, What Does It Mean?

So, we're losing ice, and fast. But what does it mean?

First, again, it's a clear indicator of the reality of global warming. Second, melting ice means rising sea levels. That means loss of land area, more flooding, and bigger storm surges from hurricanes (like with supertyphoon Haiyan in November).

There's another potential issue, too: This melting ice can indirectly cause weirder weather. As the ice melts, more ocean surface is exposed to the Sun, warming it further. Moreover, as more fresh water is dumped into the salty ocean from the polar ice, the currents in that water change, bringing with them different temperatures to different places. The flow of the jet stream over the pole depends on temperature, and that can change as the temperature changes. You see bigger dips in the stream, bringing cold weather south, and warm weather north. This can also create what are called blocking patterns; high pressure systems that block the normal movement of air, creating stagnant conditions over a region. Alaska's heat wave over the summer was one from one such blocking pattern, as was Greenland's last year. A vicious cold snap in the US in March 2013 was also due to such an event.

Unfortunately, from what I can tell, it's not clear what exactly will happen as more ice is lost at the poles; but it's a safe bet we'll get more extreme weather as it occurs. And it's also a safe bet these changes won't be beneficial. They're happening too quickly. Plants, animals, humans: We can't adapt quickly enough to our rapidly fluctuating environment.

That's what worries me. Not so much cripplingly hot summers or more severe winters—as bad as those will be—but also the changes in rainfall, flooding, fires, and more. Our ability to feed ourselves depends very strongly on the weather, and that weather is changing. The house odds are getting worse, and the stakes are very high indeed.

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Pushing Poor People to the Suburbs Is Bad for the Environment

| Mon Dec. 16, 2013 5:47 PM EST

This story first appeared on the Grist website and is reproduced here as part of the Climate Desk collaboration.

In recent years, an overhyped counterrevolution has emerged in America. Millennials from the suburbs and their empty-nester parents have been flocking to certain desirable urban neighborhoods. This has led to a lot of chin-pulling about "demographic inversion,"wherein the cities become richer and whiter and the suburbs more non-white and poor. Skeptics note that suburbs are in the aggregate still richer and whiter than central cities and most middle-class families still settle in suburbia.

This sociological debate misses the important environmental question: What will we have achieved if we simply change the demographic complexion of who lives in walkable urban areas and who doesn't? The answer is nothing. For the urbanist movement to be worthy of its name, the end result has to be that a higher percentage of Americans are actually living in central cities, and that the residents of both cities and suburbs represent the full spectrum of American life.

The evidence suggests that a combination of bad public policies is instead causing poor residents to be priced out of the most popular cities by well-heeled newcomers. Consider Annie Lowrey's report on low-income renters in Tuesday's New York Times. They are being squeezed by an economy where all the gains accrue to the top and new housing is built at the high end. Gentrification also brings wealthier renters into poor urban neighborhoods, bidding up the price of existing housing. Writes Lowrey:

The number of renters with very low incomes—less than 30 percent of the local median income, or about $19,000 nationally—surged by 3 million to 11.8 million between 2001 and 2011, according to a report released Monday by the Joint Center for Housing Studies at Harvard. But the number of affordable rentals available to those households held steady at about 7 million. And by 2011, about 2.6 million of those rentals were occupied by higher-income households.…

Many of the worst shortages are in major cities with healthy local economies, like Seattle, San Francisco, New York and Washington.

Coincidentally, the Times is also running a moving, deeply reported five-part series this week on the life of Dasani, a homeless girl living in a shelter in Brooklyn. Her family lost their housing subsidy in 2010, when the New York state program was canceled for lack of funds. Dasani, her parents, and her seven siblings now crowd into one room in a squalid, vermin-infested building next to the Walt Whitman Houses, a vast public housing project in the swiftly gentrifying Fort Greene neighborhood.

From a housing perspective, three things stand out about Dasani's family:

  • They would rather live in the projects than in a shelter. Public housing projects are supposedly a discredited form of big-government liberalism, and the federal government no longer appropriates much money at all for their construction. But in New York City, there are 167,353 families on the waiting list for public housing. (New York also has 123,533 families on the waiting list for Section 8 housing vouchers.)
  • Their homelessness is the direct result of being ejected from Advantage, a government rental assistance program. "By August 2010, bedbugs had infested the family's house, just as their rent subsidy once again expired," writes the Times' Andrea Elliot. "The city's shelters were filling with former Advantage recipients—families who had been homeless before taking the rent subsidy, only to become homeless again."
  • Their dream is to move to the Poconos because they could never afford an apartment in New York. The Poconos region in Pennsylvania has long been a rural area best known in New York City as a relatively cheap vacation spot. Now it is filling up with working-class New Yorkers priced out of the five boroughs. In other words, it's the exurbs.

Living in the Poconos, where driving is a necessity and a commute to New York takes 90 minutes, is not environmentally efficient. If the wealthy in-migration to New York City forces an equal out-migration, there has been no environmental gain.

To provide affordable apartments in thriving inner cities and their inner-ring suburbs, we need to adopt both the conservative free-market and liberal big-government approaches to expanding housing supply. Zoning restrictions on density must be lifted, so that developers can increase supply to meet demand. But we must also realize that the market isn't providing housing at the price points low-income families need. As Roger K. Lewis notes in The Washington Post, "there is not a single state in the United States where a person working full time and earning minimum wage can afford to rent, at fair-market value, a two-bedroom apartment or home."

Slate's Matthew Yglesias makes the point about zoning in reference to Lowrey's article. Lowrey illustrates her story with a 54-year-old nanny facing skyrocketing rents in Columbia Heights, a neighborhood of Washington, D.C., that was predominantly low-income just a decade ago and is now heavily gentrified. Yglesias writes:

[T]here are two questions unanswered… With demand surging, why doesn't construction surge enough to keep vacancy rates roughly stable. The other: If builders are always aiming at that high end, why are they building in Columbia Heights rather than in the traditionally fancier and more expensive neighborhoods west of Rock Creek Park.

The answers are "zoning" and "zoning."…

[Y]ou have a twofold limitation on supply. On the one hand, the total number of new units is capped so people only want to build luxury. On the other hand, new construction in the fancy neighborhoods is absolutely prohibited.

For example, you might walk up Connecticut Avenue just west of Rock Creek Park in D.C.'s tony Cleveland Park neighborhood and think it is fully built up because there are no empty lots. But why are all the buildings merely six or 10 stories tall? Why not 40, when the prices indicate that the demand is there? This is why D.C. must eliminate its building height restriction. But it's also a matter of local zoning ordinances. The side streets in Cleveland Park are dominated by low-density single-family homes. If the market could support replacing them with apartment buildings, why shouldn't developers be allowed to do that? D.C.'s density is only about one-third that of New York's, and its population is only about three-quarters as high as its peak 50 years ago. So clearly there is room for more development, as there is in other expensive cities such as San Francisco and Boston.

At the same time, it makes no sense to assume the market will provide the poor with housing any more than it will provide them with health insurance. It's true that massive, isolated housing projects have often bred social ills. But as the demand to live in New York's projects demonstrates, it is better than forcing people to live in homeless shelters or more than an hour's drive from the city where their jobs and social networks are located. The projects in New York are so destigmatized that developers are going to build market-rate housing right in their footprint. And housing projects no longer all look like vertical prisons. Innovative design can make subsidized housing green, human-scaled, attractive, and integrated into the streetscape.

Since even some conservatives agree with liberals that Section 8 vouchers, which allow low-income renters to find apartments on the market, are both the most efficient means of providing affordable housing and the best approach to encourage economic integration, we should appropriate more money for them.

Too often, after years of neglect, depopulation, crime, and disinvestment, cities have viewed recruiting richer residents as the essence of successful renewal. But a revival of urban America as a whole means that more people, from all walks of life, should be able to live safely, affordably, and comfortably in our cities.

This Interactive Map Shows Exactly How Hot Your Hometown Will Get

| Mon Dec. 16, 2013 7:00 AM EST

Climate scientists are fond of global models that try to answer how much the whole planet is going to warm up in a given time period. That's all well and good, but it doesn't do much for a mayor or city planner trying to prepare for the future in her own city. But a new map from the US Geological Survey (screenshot below) combines a group of the top climate models and matches them with high-resolution NASA climate data to project exactly how much hotter your county will be by the end of the century.

The map shows how temperature and precipitation will change based on your selection of a timescale (in a few years, a few decades, or by century's end) and a future emissions scenario (higher or lower emissions). You can see averages for the whole country, individual states (minus Alaska and Hawaii... sorry y'all), and individual counties. My home of Pima County, Arizona, for example, will see a rise of 8.8 degrees Fahrenheit in maximum temperature but no change in precipitation in the longest-term, high emissions projection. The map shows some of the biggest changes are in store for the upper Midwest. Northern Minnesota's Kittson County, for example, is in for a 10.6 degree F rise under this same scenario. (Because the map was made by scientists, all the temperatures are in Celsius; if you want to convert to Fahrenheit, remember that change in temperature uses a different equation than simply converting between units. There's a good calculator here).

map
USGS

Temperatures like that won't just make you sweatier: Climate policymakers at the UN have long agreed on 2 degrees C (3.6 degrees F) as the maximum threshold for avoiding the worst global impacts of climate change, including droughts and extreme storms. Steve Hosteler, the USGS scientist who designed the map, says that local officials could use the statistics to plan for future electricity use (hotter days means more A/C) and water drainage infrastructure (if more rain is the forecast).

While working to compile climate data on the US, he said, "it became pretty apparent that there was a need to take this data out of the modeling realm and make it useful for other people."

Are Hurricanes Getting Stronger? Science May Finally Be Approaching an Answer

| Mon Dec. 16, 2013 7:00 AM EST

For more than a decade, the question of how global warming is affecting the scariest storms on the planet—hurricanes—has been shot through with uncertainty. The chief reason is technological: In many parts of the world, storm strengths are estimated solely based on satellite images. Technologies and techniques for doing this have improved over time, meaning that there is always a problem with claiming that today's storms are stronger than yesterday's. After all, they might just be better observed.

That's why, despite expectations that global warming will make hurricanes stronger—as well as massive societal consequences if more powerful storms are slamming coastlines—scientific authorities like the United Nation's Intergovernmental Panel on Climate Change have demurred on the hurricane/climate question. Most recently, the IPCC earlier this year said it had "low confidence" that global warming is worsening hurricanes.

Hurricane Wilma, 2005
Hurricane Wilma of 2005, which set the Atlantic Basin record for the lowest pressure recorded in a hurricane at 882 millibars NOAA/Wikimedia Commons

But just maybe, a new scientific paper has managed to get past this long-standing data problem. The study, just out in the Journal of Climate from hurricane and satellite expert Jim Kossin of the National Climatic Data Center and his colleagues, seeks to create a completely consistent database of hurricane satellite images that will finally allow for apples-to-apples comparisons. How? "We can't take bad data and make it good, because that's adding information that we don't have," explains Kossin. "But we can take the good information and make it worse."

That's the surprising solution that the scientists implemented in their paper. Data that was too "good"—for instance, because the satellite images were too high in resolution—was degraded to what Kossin calls the "lowest common denominator": one satellite image of each storm taken every three hours, with a pixel size no greater than eight kilometers by eight kilometers. Using this technique, Kossin and his colleagues at NCDC created a 28-year record of storm images across the world's seven hurricane basins, from 1982 to 2009. Then they used a computer algorithm to compute each storm's maximum strength, removing human error and unpredictability from the equation.

The result? The scientists found that globally, hurricane wind speeds are increasing at a rate of a little more than two miles per hour per decade, or just faster than six miles per hour over the entire period. There are some key caveats, though, the biggest being that the trend they found was not statistically significant at usually accepted levels. (For nerds: the p value was 0.1). But there were strong and significant trends in some hurricane basins of the world, especially the North Atlantic (the region encompassing the Caribbean, Gulf of Mexico, and open Atlantic north of the equator), where storms have been strengthening at the rate of nearly nine miles per hour per decade (see chart above). But other basins offset that, including the western North Pacific, which showed a negative trend.

The punch line, then, could hardly be called overwhelming. But as Kossin explains, that may be precisely what you expect to see once you're finally analyzing the troublesome hurricane data reliably. These results, after all, are quite consistent with the idea that the signal of hurricane intensification might be just now emerging from the "noise" of natural climate variability. "What we're observing could very easily fit into an assumption of this greenhouse gas forced trend in the tropics and the effect that it has on tropical cyclone intensity," says Kossin.

Perhaps the best news is that if scientists continue adding to the new database of homogenized satellite images—starting with the years 2010-13, which were not part of this study—the chance of finding a significant trend (or showing that there just isn't one to be found) will increase. "I think every year, we'll get a little bit closer to the truth," says Kossin.

At that point, perhaps we can finally can leave the sound and fury to the hurricanes themselves, rather than the debate over what's happening to them.

Yes, It Really Just Snowed in Egypt (Even If That Sphinx Photo Is Fake)

| Sat Dec. 14, 2013 5:31 PM EST
Is this really in Egypt?

Yesterday Twitter was lit up by images of a snowy Egypt. Like this one:

The cause, according to the Weather Underground, was a stalled area of low pressure.

However, there were also more dubious tweets, especially of this image:

According to some sleuthing by Buzzfeed, that image actually seems to be of a theme park in Japan—where snow would be decidedly less extraordinary—that contains a sphinx replica.

Meanwhile, just how rare is snow in Egypt, anyway? Capital Weather Gang and New York Magazine have called into question assertions that it has not occurred in 112 years. Still, snow is extremely uncommon—as is rain, for that matter: According to Wunderground, Cairo receives less than an inch of rain per year.

And what of the global warming snark? Actually not that far off: The snowy weather does seem tied to a weirdly behaving jet stream, and one prominent scientific idea of late is that global warming is interfering with the jet stream, leading to "stuck" weather and all kinds of extremes. 

Scientists Find That Polluted Oceans Could Make Fish Anxious

| Sat Dec. 14, 2013 7:00 AM EST
It's okay, Mr. Rockfish–ocean acidification makes me anxious, too.

This article originally appeared on The Atlantic and is reproduced here as part of the Climate Desk collaboration.

We've known for a while that the ocean is rapidly becoming too acidic for some forms of marine life to survive. We know that this is caused by continued rising emissions of carbon dioxide, which dissolves from the atmosphere into the ocean to form carbonic acid, which in turn dissolves/corrodes calcium carbonate-based coral reefs and shellfish.

Now we also know that ocean acidification does more than break down marine skeletons—it can actually cause behavioral changes in individual organisms. Simply stated, ocean acidification is making fish anxious—or, at least, anxiety as we measure it in fish.

"They would go to the dark part of the tank and they wouldn’t move. They just stayed there."

Scientists from UCSD's Scripps Institution of Oceanography and Canada's MacEwan University recently published this surprising finding in Proceedings of the Royal Society B: Biological Science. But what does it mean for fish to be anxious? According to this study, all it takes is observing how much time the fish choose to spend in dark versus light areas of their habitats. The test subjects were juvenile rockfish, whose natural environments—kelp forests—off the California coast offer varying levels of shade and sunlight. The researchers put a control group of rockfish in a tank with "normal," or unaltered, seawater and observed the fish moving continuously between the light and dark areas of the tank. They put a second group of rockfish in a tank with seawater of elevated acidity, meant to approximate the expected pH of the ocean one hundred years from now, and observed something different.

Previous studies have shown that fish dosed with anxiety-inducing drugs will, instead of moving continuously around their tanks, prefer to dwell in the dark spots. Turns out, putting fish in slightly more acidic water is just like administering an anxiety-inducing drug. "They would go to the dark part of the tank and they wouldn’t move. They just stayed there," study co-author Martín Tresguerres told the L.A. Times last week.

"If the behavior that we observed in the lab applies to the wild during ocean acidification conditions, it could mean that juvenile rockfish may spend more time in the shaded areas instead of exploring around," Tresguerres said in a press release last Wednesday. "This would have negative implications due to reduced time foraging for food, or alterations in dispersal behavior, among others."

Notice that we're not even talking about shellfish like lobsters or shrimp, who may or may not be experiencing mental anguish in awareness of their threatened bodily integrity. Let it be said, though, that a future study on anxiety in lobsters is not out of the question. "Behavioral neuroscience in fish is a relatively unexplored field, but we do know that fish are capable of many complicated cognitive tasks of learning and memory," according to Trevor James Hamilton, another of the study's co-authors.

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CHART: How Much Do Exxon and Google Charge Themselves for Climate Pollution?

| Wed Dec. 11, 2013 7:00 AM EST
companies' carbon prices
Tim McDonnell/Climate Desk

Most experts agree that slowing climate change is going to have to involve some kind of price on carbon dioxide pollution. Although the last attempt to pass a federal carbon price in the US failed in 2009, some of the world's most-polluting companies haven't let down their guard. A report last week from the nonprofit Carbon Disclosure Project found that 29 companies that operate or are headquartered in the US are planning for the future by using their own internal carbon price.

So how much do these companies think carbon pollution is worth? Not every company released a specific number, but we plotted those that did on the chart above. As you can see, there's quite a broad range, with the price officially recommended by the Obama White House ($37 per metric ton of carbon) falling north of the middle. For comparison, we also included the current prices in British Columbia (which levies a flat tax) and the European Union (which operates a carbon credit-trading market). An oversupply of credits on the EU market has recently driven the price to record lows, below where most economists believe it can be effective in curbing emissions. But a decision yesterday by the European Parliament to slash the number of available credits is expected to drive the price up 35 percent over the next year.

Remembering Nelson Mandela and His Fight for Climate Justice

| Tue Dec. 10, 2013 7:00 AM EST

This story first appeared on the Grist website and is reproduced here as part of the Climate Desk collaboration.

Nelson Mandela, who died last week, is best known for his fight against South African apartheid. But his long walk to freedom also included steps toward solving this mammoth problem called climate change. He envisioned a world where all people are able to live a fully dignified life, with clean air to breathe and clean water to drink—and where poor countries are not left with the repercussions of rich nation's dirty ways.

Six years ago, Mandela founded The Elders, a cross-cultural group of leaders from across the globe, including former President Jimmy Carter and former United Nations Chief Kofi Annan, to forge human rights-based solutions to worldwide problems. One of the group's top priorities is climate justice, which is not only about reducing greenhouse gas emissions, but also about ensuring the protection of those people and regions most vulnerable to the worst of climate change's impacts.

Why the EPA Chief Needs China's Help to Tackle Global Warming

| Mon Dec. 9, 2013 11:59 AM EST

Environmental Protection Agency Administrator Gina McCarthy is in China this week for her first international trip as the head of the agency. During her four-day tour she'll stop by Beijing, Shanghai and Hong Kong and will meet with her counterparts in the Chinese government to discuss how the two countries might reduce their carbon footprint. "The U.S. and China represent the world's largest economies, the world's largest energy consumers, and the world's largest emitters of carbon pollution," McCarthy said last week in a speech previewing her trip. "I'd rather not be the largest energy consumers or the largest emitters of carbon pollution, but since we are we're going to get together and we're going to talk."

The world better hope the planet's two dominant superpowers can find a way to curb their pollution. The US, which is responsible for much of the rise in emissions during the twentieth century, is certainly one of the world's leading villains when it comes to global warming. But China is now, by far, the world's top producer of climate-destroying pollutants. The country claimed the top spot in global carbon emissions in 2007, nabbing the reins from the US. (To be fair to China, the US emits far more carbon per capita.)

Combined, China and the US produce nearly half of the world's carbon emissions. This chart breaks down the percentage of global CO2 emissions from 2008 by country:

 

 

China once lagged far behind the other major polluters in the world. But as this chart from the Yale Forum on Climate Change and the Media shows, the country's emissions have risen steeply ever since the late 1990s:

 

 

As things stand, China's exponential increase in emissions won't abate anytime soon. Even as the country leads research in renewable energy and explores a carbon tax, it's not enough. "Over the next two decades or so, China will belch out nearly as much CO2 as it did over the entire previous 160 years combined," the Economist wrote last month.

Carbon emissions from the US have leveled off and even dropped slightly in recent years, thanks to increased fuel efficiency in cars and cheaper natural gas. Good news, but the US will need to reduce, not just flat line, its carbon use if the worst calamities of global warming—cities wiped out by rising sea levels, volatile storms, droughts, etc.—are to be averted. But even if US politicians can muster the will to pass meaningful legislation tackling climate change, it will all be for naught if China's emissions rate continues to skyrocket.

 

Which Hollywood-Style Climate Disasters Will Strike in Your Lifetime?

| Thu Dec. 5, 2013 7:00 AM EST
How likely are extreme climate scenarios like those featured in The Day After Tomorrow?

In a just-released report, the National Academy of Sciences (NAS) has taken an extensive look at the scary side, the dramatic side…let's face it, the Hollywood side of global warming. The new research falls under the heading of "abrupt climate change": The report examines the doomsday scenarios that have often been conjured in relation to global warming (frequently in exaggerated blockbuster films), and seeks to determine how likely they are to occur in the real world.

So here's a list of some of the most dreaded abrupt changes (where abrupt means occurring within a period of a few decades or even years), and the probability that they'll happen—even if nothing like the Hollywood version—before the year 2100:

 

Global warming freezes the Earth in 2004's The Day After Tomorrow.
20th Century Fox/Wikimedia Commons

Disruption of the Ocean's "conveyor belt"

As seen in: The scientifically panned 2004 blockbuster The Day After Tomorrow.

What would happen: The great overturning circulation of the oceans, driven by the temperature and the salt content of waters at high latitudes, transports enormous amounts of heat around the planet. If it is disrupted or comes to a halt, there could be stark changes in global weather patterns.

Chances it will happen this century: Low. For future generations, however, The Day After Tomorrow might be slightly less laughable (if still wildly exaggerated). In the longer term, the NAS rates the probability of a disruption as "high."

 

CBS/Wikimedia Commons

A sharp increase in extreme precipitation events

As seen in: The over-the-top Category 7 and the even more over-the-top Sharknado.

What would happen: The frequency and/or intensity of extreme precipitation events—including heavy rains, damaging flooding, droughts, and hurricanes—would show a relatively sudden increase. The consequence would be not only the potential for more weather disasters and their associated costs but also, the NAS warns, the possibility of "increased conflict" following disasters. No Category 7s, but still something worth worrying about.

Chances it will happen this century: According to the NAS, we can already detect a clear trend towards more extreme flooding, although trends in other extreme weather phenomena, such as droughts and hurricanes, are more murky for the moment. As for an abrupt change this century? NAS rates the outlook as "moderate."

 

Universal/Wikimedia Commons

Extreme Sea Level Rise Due to Polar Ice Sheet Collapse

As seen in: The 1995 Kevin Costner classic Waterworld.

What would happen: Here is arguably the scariest global warming scenario—the collapse of all or part of the ice sheets of Greenland and Antarctica, leading to rapid and extreme sea level rise. (But no, the continents would not disappear as in Waterworld. Not remotely.)

Chances it will happen this century: Fortunately, this risk is not likely to materialize before 2100, according to the NAS—with one possible exception, the West Antarctic Ice Sheet, which contains the equivalent of three to four meters of sea level rise. The NAS judges that an abrupt change here during this century is "plausible, with an unknown although probably low probability." In the longer term, meanwhile, the probability is high that some of the great ice sheets of the planet will indeed melt substantially and drive sea level rise on a scale measured in meters, rather than inches.

 

Universal/Wikimedia Commons

Worse Heat Waves, More Often

As seen in: Spike Lee's Do the Right Thing (which isn't directly about global warming, of course, but is definitely about heat).

What would happen: Heat waves can be devastating. Not only can they kill significant numbers of people (and spark conflict), but they also can imperil agriculture and water supplies.

Chances it will happen this century: According to the NAS, a climate-related trend towards more intense and frequent heat waves has already been detected. And the outlook for an abrupt change for the worse in this century is "moderate."

 

Catastrophic Methane Release from the Arctic

As seen in: Amazingly, to our knowledge Hollywood hasn't made use of this one yet.

What would happen: One oft-touted climate fear is that undersea Arctic deposits of methane hydrate will be destabilized or even explode, releasing large volumes of gas into the atmosphere that, in turn, trigger rapid global warming. This scenario is particularly frightening because methane is a much more potent greenhouse gas than carbon dioxide. By worsening global warming, an Arctic methane "bomb" would also increase the risk of other dangerous abrupt climate changes.

Chances it will happen this century: "Low," says the NAS. Over the longer term, however, the risk rises to "moderate"; and when it comes to a related threat—the release of stored carbon from the thawing of northern permafrost, which would also amplify global warming—the long-term risk is "high."

 

Warner Bros.

disappearing Arctic sea ice

 
 
 
 

As seen in: The 2012 Imax film To the Arctic (yes, a documentary).

What would happen: The loss of summer Arctic sea ice has profound effects, ranging from opening up dramatic new opportunities for shipping and resource exploitation, to reshaping ecosystems and native cultures, to changing global weather patterns.

Chances it will happen this century: The NAS considers the ongoing changes in the Arctic region to be an abrupt climate change that is already upon us. So you can watch this one in a documentary, or even in satellite images.