If July felt horrendously hot， that’s because it was。
Today, over a dozen federal agencies released the Climate Science Special Report, which is a product of the National Climate Assessment -- a congressionally mandated review that takes place every four years. In it, hundreds of scientists from dozens of government agencies and academic institutions present evidence that supports the existence of a human-caused warming planet and all of the consequences that come with it. "This assessment concludes, based on extensive evidence, that it is extremely likely that human activities, especially emissions of greenhouse gases, are the dominant cause of the observed warming since the mid-20th century," the report stated. "For the warming over the last century, there is no convincing alternative explanation supported by the extent of the observational evidence."
Tom Yulsman| February 8, 2018 5:39 pm177
The special report notes that each of the last three years have set temperature highs and that global temperature averages have risen by 1.8 degrees Fahrenheit over the last 115 years. It also warns that weather disasters like hurricanes and floods that have cost the US $1.1 trillion since 1980 could become more commonplace if action isn't taken to reduce our emissions. "The frequency and intensity of extreme high temperature events are virtually certain to increase in the future as global temperature increases (high confidence). Extreme precipitation events will very likely continue to increase in frequency and intensity throughout most of the world (high confidence)," said the report.
Arctic Sea Ice Just Set Another Record Low—In Winter
NASA and the National Oceanic and Atmospheric Administration ― two leading global authorities on climate ― both say July 2016 was not only the hottest July on record， but the most sizzling month in the history of record-keeping。
Also noted, was the importance of reducing emissions for any hope of curtailing the negative outcomes of climate change. "The magnitude of climate change beyond the next few decades will depend primarily on the amount of greenhouse gases (especially carbon dioxide) emitted globally. Without major reductions in emissions, the increase in annual average global temperature relative to preindustrial times could reach 9°F (5°C) or more by the end of this century," the report stated.
And what’s happening in the New Arctic isnot staying there
I shot thisiPhone photo of Arctic sea ice in the Davis Strait between Greenland and Baffin Islandwhile flyingfrom Icelandto Denver on Jan. 30,
- (Photo: ©Tom Yulsman)
Another month, yet another record low forArctic sea ice extent in a warming world.
January’saverage ice extent in the Arctic was 525,000 square miles below the 1981-to-2010 average, making it the lowest January extent in the satellite record. This is an astonishingly large loss of ice — equivalent to 80 percent of Alaska.
趣味研究。But what happened in January was equally, if notmore significant, for its timing. Ithappened when the Arctic was grippedby frigid, polar weather.
Record lows in the Arcticonce occurred mostly in September — at the end of summer when relatively warm temperatures naturally cause the frozen lid of sea ice to shrink to an annual minimum extent. With human-caused warming added on top of relatively mild summertemperatures, recordmelt-backs in summer perhaps arenot sosurprising.
But now, dramatic reductions in sea ice are occurring more and more often during the cold season.
“Now we are seeing winter really get into the act as well,” says NSIDC director Mark Serreze. “The shrinking Arctic sea ice cover is no longer something that just stands out in summer.”
Thisshift to record lows in winter,scientists say, is yet another indication that human activities have already transformed the region into what they’re calling “the new Arctic.”
必发娱乐手机版，No surprises here: average January #Arcticsea ice extent was the lowest in the satellite record…
— Zack Labe February 2, 2018
Why should those of us who don’t live in the Arctic care about what’s happening up there?
Péter Szijjártó, Minister of Foreign Affairs and Trade for Hungary — obviously not an Arctic nation — answered that question in this way, during an address to theArctic Frontiers conferencein Norway last month: “Whatever happens here in the Arctic has a direct and immediate impact on the rest of the world, and especially Europe.”
I don’t know about “immediate,” but there are myriadways that changes in the Arctic are affecting the rest of the world — for example, changes to fisheries as fish stocks move north, and possible (but still unproven) effectson weatherfar to the south.
Shrivelingsea ice also has turnedthe region into something of a new frontier. Many nations are eyeing the Arctic’s opening sea routes, its strategic position between Eurasia and North America, and its potentially hugereserves of oil and gas, as well as other resources.
This, in turn, is having geopolitical consequences. Among them: Russian military moves that some analysts believe are designedto bring down an “ice curtain” in the region — intended todeny other nations access to large swaths of the Arctic.
As sea ice growth last monthwas lagging far behind normal and heading for its record low, politicians andscientistsattending the Arctic Frontiers conference were discussing the ramifications of thenew Arctic. Among the scientists was Ingrid H. Onarheim,a researcher atthe University of Bergen and Bjerknes Centre for Climate Research.
She began anoverview talk about Arctic sea ice by putting the trendinto a long-term context: “The recent sea ice loss is unprecedented,” she said, at least during the last 160 or so years.
Modern satellite monitoring of sea ice could not by itself reveal that insight, because it dates back only to 1979. So fora longer term perspective,researchers fromNSIDC and elsewhereturned to noveldata sources. These includedwhaling ship logs,sea ice chartsfrom the Danish Meteorological Institute, compilations by U.S. Navy oceanographers, observations from aircraft, and other sources. All of this disparate informationhad to be digitized and then synthesized to be compatible with one another.
The resulting database, going all the way back to 1850, showsthat at least since then “we’ve never had as little ice as we have now,” Onarheim told her colleagues at Arctic Frontiers.
Here’s what that looks like in graphic form:
Source:“A database for depicting Arctic sea ice variations back to 1850,” John E. Walsh et al, Geographical Review, 11 July 2016
Before getting into what these maps show,I shouldpoint out that there is a typo in the oneon the left. It should be 1850-1900.
With that correction in mind, let’s turn to the details. The left-handmap above shows the concentration of sea ice during September of1854. Thenew databaseshows thatthis month had the smallest ice extent duringthe entire 1850-1900period.
The other maps in the triptych show what sea ice looked like for the lowest September in each of those respective periods.
The take-away message from the triptych is pretty clear. As theauthors of the paper describing the new long-term database wrote:
It is apparent that the recent September minimum of 2012 is far less than the minima of the two earlier . . . periods. This comparison indicates that the summer ice minima of the past decade have no precedents in earlier decades back to 1850.
But as last month’s record low ice extent shows, significant sea ice losses are no longer mostly confined to the warmer months. I think you can see that pretty well in this graphicshowing how Arctic sea ice fared during each of the 1,956months between1850 and2013:
The status of Arctic sea ice month-by-month (vertical axis) and year-by-year (horizontal axis). Blues indicate ice extent that’s below the long-term mean. Reds indicate the opposite. (Source: Cooperative Institute for Research in Environmental Sciences, after a figure by Julienne Stroeve, National Snow and Ice Data Center)
The first thing that jumps out atme is the dominanceof blue, meaning lower than average sea ice, starting around 1975. It’s most pronounced during July, August and September, the warm months. But recently, deeperblues have been spreading out into the cold season months ofNovember through April.
“We are losing sea ice in all seasons now,” Onarheimsaid, echoing the NSIDC’s Mark Serreze. “The changes in ice are spreading from the summer to winter season.”
There is no doubt as to what’s behind the accelerating decline of the sea ice at the top of the world: warming fromhumankind’s emissions of carbon dioxide and other greenhouse gases. There is also no doubt that the Arctic is actually ground zero for climate change — it’swarming twice as fast as the globe as a whole.
But the Arctic is a very big place, and the regional patterns are just as important as the overall trend.
No region has been affected more than the Barents Sea, located north of Norway and Russia, and the nearby waters just north of the archipelago of Svalbard. And as it turns out, thestrongesteffect in this part of the Arctichas been — you guessed it — during winter, according to Onarheim.
Scientists are working hard to explainwhy this is so, and research suggests that the answer can be summed upthis way: In this region, the Arctic isexperiencing what some call “Atlantification.”
The Gulf Stream, carrying warm Atlantic water, moves north along the Norwegian coastanddivides into two main branches, one on either side side of the island archipelago of Svalbard. In the Arctic Ocean, this Atlantic water becomesdenser as it cools and therefore sinks. After circulating, the now cold water leaves the Arctic Ocean, mainly through the Fram Strait between Svalbard and Greenland.(Illustration: Audun Igesund, Norwegian Polar Institute).
Scientists have known for 100 years that warm Atlantic water rides north on the back of the Gulf Stream, and that extensions of that massive current take it all the way up into the Barents Sea and over the top of Svalbard. (See the map above.) Research has shownthat increasingly warmAtlantic Ocean water carried on thesecurrents — about 1 degree C warming since 1979 — isinhibitingsea ice from forming, even as winter air temperatures continue to plunge well below freezing.
Research by Onarheim and her colleaguesshowsthat warming Atlantic waters arriving north of Svalbard on the currents are having several specific impacts. To start with, theypush underthe sea ice that does form, inhibiting further growth and even causing it to melt from underneath. This leaves the ice thinner and less extensive than it otherwise would be.
With less floatingice forming a cap on the sea during winter, the relatively warm sea water is able to give upmore heat to the atmosphere. And that helps explain a nearly 7degree C increase in mean air temperature north of Svalbard in winter, according to Onarheim’s research.
As air temperatures naturally warm in the spring, the thinner ice can melt out faster. That leaves the water exposed to sunlight for longer periods. So it absorbs more energy and heats up— inhibiting the formation of ice when cold air temperatures return with a vengeance in the fall. And that means still less sea ice in the winter months.
Here is how energy has been accumulating within Earth’s climate system, thanks to humankind’s emissions of greenhouse gases. As the graph shows, most of the energy has been been absorbed by the oceans. The rest has gone to melting ice, warming continental land masses and the atmosphere. (Source: Intergovernmental Panel on Climate Change Fifth Assessment Report)
The oceans make up 70 percent of our planet’s surface.And water is particularlyadept at soaking up heat. So much so, in fact,that Earth’s oceans have absorbed more than 90 percent of the heat that has accumulated in theplanet’s climate system due to our emissions of greenhouse gases.
As we’ve now seen, some of that heat has a tendency to come out — nowhere more readily than in the Arctic, where the frigid atmosphere is practically begging to absorb heat, and where the Gulf Stream’s northernmost extensions have been only too happy to oblige.
Onarheim’s overarching take-away message during her Arctic Frontiers talk was this: Computer modeling of the climate system suggests that unless we significantly rein in CO2 emissions soon, Arctic waters could be sea-ice free during summer by about mid-century. Sea ice would still form in winter. But the models also predict that continuing warming would lead to ice-free Arctic watersin winterbetween 2061 and 2088. (The rather large range represents the possible impact of natural climate processes.)
In other words, the models are saying that in just a little more than forty years, Arctic waters could be ice freeyear ’round. That would give us a radically new Arctic — and a verydifferent planetthan the one we live on today.
One lastthing: Sofar, Arctic sea ice has been disappearing more quickly than the models have predicted. So we may not have to wait four decades for completely ice-free Arctic waters.
“If we want to keep the ice cover, we have to reduce the CO2emissions,” Onarheim says. “The faster we emit the CO2, the faster we will lose the sea ice.”
The report released today -- an exhaustive compilation of research totaling over 600 pages and peer reviewed by the National Academy of Sciences -- is just the first of two. A second, longer volume detailing the regional impacts of climate change is not yet finalized, but is open for public comment and will soon undergo peer review. Somewhat surprisingly, today's report was approved by the White House even though the Trump administration has repeatedly worked against efforts to combat climate change including removing the US from the Paris Accord, placing a climate change denier at the helm of the Environmental Protection Agency (EPA), and nominating one to lead NASA. Under the Trump presidency, the EPA has stopped researchers from speaking about climate change and deleted climate change information from its website while the Department of Agriculture has pressed its staff to not refer to climate change in their communications.
NOAA on Wednesday said July’s global average temperature was 62.01 degrees， 1.57 degrees above the 20th-century average。 NASA， which uses a slightly different methodology， said the average global temperature in July was 1.51 degrees above average。 Both agencies pegged July as the hottest month since monitoring began in 1880。
In regards to the report released today, Penn State University geoscientist Richard Alley told NPR, "This is good, solid climate science. This has been reviewed so many times in so many ways, and it's taking what we know from ... a couple of centuries of climate science and applying it to the U.S." Michael Mann, director of the Earth System Science Center at Penn State University told the New York Times, "This new report simply confirms what we already knew. Human-caused climate change isn't just a theory, it's reality. Whether we're talking about unprecedented heat waves, increasingly destructive hurricanes, epic drought and inundation of our coastal cities, the impacts of climate change are no longer subtle. They are upon us. That's the consensus of our best scientists, as laid bare by this latest report."
You can read the full Climate Science Special Report here.