James Hansen, NASA's former top climate scientist, is joined by 16 other leading climate scientists in a paper with some alarming conclusions. The gist is that the glaciers in Antartica and Greenland are melting so much faster than previously predicted that the global sea level will rise more than 10 feet in as little as 50 years, rendering many coastal cities uninhabitable. From Eric Holthaus in Slate:
The study -- written by James Hansen, NASA's former lead climate scientist, and 16 co-authors, many of whom are considered among the top in their fields -- concludes that glaciers in Greenland and Antarctica will melt 10 times faster than previous consensus estimates, resulting in sea level rise of at least 10 feet in as little as 50 years. The study, which has not yet been peer reviewed, brings new importance to a feedback loop in the ocean near Antarctica that results in cooler freshwater from melting glaciers forcing warmer, saltier water underneath the ice sheets, speeding up the melting rate. Hansen, who is known for being alarmist and also right, acknowledges that his study implies change far beyond previous consensus estimates. In a conference call with reporters, he said he hoped the new findings would be "substantially more persuasive than anything previously published." I certainly find them to be.
That's the thing about nonlinear systems like the Earth's climate: things happen gradually, then suddenly. This is much more terrifying to me than the Pacific Northwest earthquake. BTW, as a reminder, here's what NYC and the surrounding area looks like with 10 more feet of water. Goodbye JFK Airport.
Update: The paper is now available online.
Update: In the New Yorker, Elizabeth Kolbert provides a bit more explanation and context about Hansen's paper.
What the new paper does is look back at a previous relatively warm period, known as the Eemian, or, even less melodically, as Marine Isotope Stage 5e, which took place before the last ice age, about a hundred and twenty thousand years ago. During the Eemian, average global temperatures seem to have been only about one degree Celsius above today's, but sea levels were several metres higher. The explanation for this, the new paper suggests, is that melt from Antarctica is a non-linear process. Its rate accelerates as fresh water spills off the ice sheet, producing a sort of "lid" that keeps heat locked in the ocean and helps to melt more ice from below. From this, the authors conclude that "rapid sea level rise may begin sooner than is generally assumed," and also that a temperature increase of two degrees Celsius would put the world well beyond "danger."
"We conclude that the 2°C global warming 'guardrail,' affirmed in the Copenhagen Accord, does not provide safety, as such warming would likely yield sea level rise of several metres along with numerous other severely disruptive consequences for human society and ecosystems," Hansen and his colleagues wrote.
A recent paper by three climate scientists concludes there's a high risk of an unprecedented drought in the Southwest and Midwest United States later this century, even if we manage to get our carbon emissions under control. The scientists say it'll be drier in the Western US than at any point in the past 1000 years.
In the Southwest and Central Plains of Western North America, climate change is expected to increase drought severity in the coming decades. These regions nevertheless experienced extended Medieval-era droughts that were more persistent than any historical event, providing crucial targets in the paleoclimate record for benchmarking the severity of future drought risks. We use an empirical drought reconstruction and three soil moisture metrics from 17 state-of-the-art general circulation models to show that these models project significantly drier conditions in the later half of the 21st century compared to the 20th century and earlier paleoclimatic intervals. This desiccation is consistent across most of the models and moisture balance variables, indicating a coherent and robust drying response to warming despite the diversity of models and metrics analyzed. Notably, future drought risk will likely exceed even the driest centuries of the Medieval Climate Anomaly (1100-1300 CE) in both moderate (RCP 4.5) and high (RCP 8.5) future emissions scenarios, leading to unprecedented drought conditions during the last millennium.
Eric Holthaus has the layperson's explanation of the study and its implications.
Smerdon's study is the first to examine the future risk of "megadrought" in the southwest and central United States in the context of historical episodes of drought in the same regions. Smerdon's study suggests that the coming years are likely to see droughts worse than the epic dry periods that are thought to have caused profound changes to human settlement in the region over the last millennium.
"They're 'mega' because they are droughts that lasted in these regions for multiple decades," said Smerdon in an interview with Slate. "We haven't seen anything like this since at least the 1400s." In comparison, the current California drought is four years old, though drought has been present in most of the last 15 years somewhere in the West.
Update: This NASA video provides a quick overview of this study and what it means for our climate.
The headline from Eric Holthaus' latest piece is arresting: The Last Time There Was This Little Arctic Ice, Modern Humans Didn't Exist.
Ice has been a relatively constant feature of the Arctic for most of the past 36 million years, but there have been some gaps. Scientists aren't exactly sure what happened during the most recent major ice-free period, but it's often considered an analog to our future, warmer Earth. The only difference is, this time, the gap in Arctic sea ice is being caused by us.
Greenland has been covered in dark ice this summer. Why is that such a problem? Because dark things absorb more heat than lighter colored things, causing the dark ice to melt faster than white ice would. Eric Hotlhaus explains.
There are several potential explanations for what's going on here. The most likely is that some combination of increasingly infrequent summer snowstorms, wind-blown dust, microbial activity, and forest fire soot led to this year's exceptionally dark ice. A more ominous possibility is that what we're seeing is the start of a cascading feedback loop tied to global warming. Box mentions this summer's mysterious Siberian holes and offshore methane bubbles as evidence that the Arctic can quickly change in unpredictable ways.
This year, Greenland's ice sheet was the darkest Box (or anyone else) has ever measured. Box gives the stunning stats: "In 2014 the ice sheet is precisely 5.6 percent darker, producing an additional absorption of energy equivalent with roughly twice the US annual electricity consumption."
Perhaps coincidentally, 2014 will also be the year with the highest number of forest fires ever measured in Arctic.
The internet's resident meteorologist Eric Holthaus (who incidentally has given up flying because of climate change) warns that a major storm could be on its way to the East Coast in time for Thanksgiving and Hanukkah (which overlap this year and then not again until the year 79811).
Technically, the storm is a nor'easter but is looking more like a tropical storm in the computer models:
At this point, the most likely scenario would be cold, wind-driven rain in the big coastal US cities, with up to a foot of snow stretching from inland New England as far south as the Carolinas. The cold would stick around after the storm exits, with high temperatures in the 20s and wind chills possibly in the single digits as far south as New Jersey on Black Friday.
According to this afternoon's iteration of the Euro model (a meteorological model that famously predicted superstorm Sandy's rare left hook into New Jersey six days out), at the storm's peak, wind gusts on Cape Cod could approach hurricane force.
We're still a ways out, so things might change, but travel safely next week, folks. (via @marcprecipice)
There's a blizzard bearing down on the northeastern United States and here's some essential information you need to know if you live in an affected area:
But seriously, you should follow @EricHolthaus for the latest storm info. (Ok, so we have our first celebrity Twitter weatherman. Weather and climate are going to become a lot more important in American pop culture...at what point do Gawker or Buzzfeed launch their climate verticals?)
Update: Gawker now has a climate vertical, The Vane. (via @bgporter)