Arctic warming is causing organic carbon deep-frozen in the soil for millennia to be released rapidly into the air as CO2, with potentially catastrophic impacts on climate

by Tim Radford, Climate News Network, May 14, 2015

LONDON − An international team of scientists has settled one puzzle of the Arctic permafrost and confirmed one long-standing fear: the vast amounts of carbon now preserved in the frozen soils could one day all get back into the atmosphere.

Since the Arctic is the fastest-warming place on the planet, such a release of greenhouse gas could only accelerate global warming and precipitate catastrophic climate change.

That the circumpolar regions of the northern hemisphere hold vast amounts of deep-frozen carbon is not in question.

The latest estimate is 17 billion tonnes, which is twice the level of carbon dioxide in the atmosphere and perhaps 10 times the quantity put into the atmosphere by burning fossil fuels since the start of the Industrial Revolution.

Hazard underlined

In recent weeks, researchers have already underlined the potential hazard. But the big question has been that if some of the trapped carbon must be escaping now, where is it going?

Researchers have checked the mouths of the Arctic rivers for the telltale evidence of ancient dissolved organic carbon – partly-rotted vegetable matter deep-frozen more than 20,000 years ago − and found surprisingly little.

Now Robert Spencer, an oceanographer at Florida State University, and colleagues from the US, UK, Russia, Switzerland and Germany report in Geophysical Research Letters that the answer lies in the soil − and in the headwater streams of the terrestrial Arctic regions.

Instead of flowing down towards the sea, the thawing peat and ancient leaf litter of the warming permafrost is being metabolised by microbes and released swiftly into the atmosphere as carbon dioxide.

The scientists conclude that the microbes, once they get a chance to work at all, act so fast that half of all the soil carbon they can get at is turned into carbon dioxide within a week. It gets into the atmosphere before it has much chance to flow downstream with the soil meltwater.

The researchers centred their study on Duvanny Yar in Siberia, where the Kolyma River sluices through a bank of permafrost to expose the frozen organic carbon.

They worked at 19 different sites − including places where the permafrost was more than 30 metres deep − and they found tributary streams made entirely of thawed permafrost.

Measurement of the carbon concentration confirmed that it was indeed ancient. The researchers analysed its form in the meltwater, then they bottled it with a selection of local microbes, and waited.

Used by microbes

“We found that decomposition converted 60% of the carbon in the thawed permafrost to carbon dioxide in two weeks,” says Aron Stubbins, assistant professor at the University of Georgia’s Skidaway Institute of Oceanography. “This shows that permafrost carbon is definitely in a form that can be used by the microbes.”

The finding raises a new – and not yet considered – aspect of the carbon cycle jigsaw puzzle, because what happens to atmospheric and soil carbon is a huge element in all climate simulations.

At he moment, permafrost carbon is not a big factor in projections by the Intergovernmental Panel on Climate Change.

Dr Spencer says: “When you have a huge frozen store of carbon and it’s thawing, we have some big questions. The primary question is, when it thaws, what happens to it?

“Our research shows that this ancient carbon is rapidly utilised by microbes and transferred to the atmosphere, leading to further warming in the region, and therefore more thawing. So we get into a runaway effect.” 

May 2015 posts

• Right now we are in the 6-sigma risk zone of clima...
• MUST SEE: The most amazing global animation I have...
• Joe Romm: The Really Awful Truth About Climate Cha...
• Why the 97 per cent consensus on climate change st...
• Jeff Masters: extreme, record-breaking temperature...
• When nutcases and idiots are elected to Congress, ...
• Stefan Rahmstorf: What's going on in the North Atl...
• Super El Nino Likely as Huge Warm Water Wave Hits ...
• World headed for an El Nino and it could be a big ...

Right now we are in the 6-sigma risk zone of climate change

The Choice Part 1 from Bru Pearce on Vimeo.

MUST SEE: The most amazing global animation I have ever seen!

DOUBLE CLICK TO VIEW IN FULL SCREEN HIGH DEFINITION.

NASA's Earth Science News Team

This video shows aerosol emission and transport from September 1, 2006, to April 10, 2007. Also included are locations, indicated by red and yellow dots, of wildfires and human-initiated burning as detected by the MODIS instrument on NASA's Terra and Aqua satellites. Credit: NASA Goddard Space Flight Center. Download the animation here.

The residents of Beijing and Delhi are not the only ones feeling the effects of Asian air pollution — an unwanted byproduct of coal-fired economic development. The continent's tainted air is known to cross the Pacific Ocean, adding to homegrown air-quality problems on the U.S. West Coast.

But unfortunately, pollution doesn't just pollute. Researchers at NASA's Jet Propulsion Laboratory and the California Institute of Technology, both in Pasadena, California, are looking at how Asian pollution is changing weather and climate around the globe.

Scientists call airborne particles of any sort — human-produced or natural — aerosols. The simplest effect of increasing aerosols is to increase clouds. To form clouds, airborne water vapor needs particles on which to condense. With more aerosols, there can be more or thicker clouds. In a warming world, that's good. Sunlight bounces off cloud tops into space without ever reaching Earth's surface, so we stay cooler under cloud cover.

But that simplest effect doesn't always happen. If there's no water vapor in the air — the air is dry — aerosols can't make clouds. Different types of aerosols have different effects, and the same aerosol can have different effects depending on how much is in the air and how high it is. Soot particles at certain altitudes can cause cloud droplets to evaporate, leaving nothing but haze. At other altitudes, soot can cause clouds to be deeper and taller, producing heavy thunderstorms or hailstorms. With so many possibilities, aerosols are one of the largest sources of uncertainty in predicting the extent of future climate change.

The experiments and result

During the last 30 years, clouds over the Pacific Ocean have grown deeper, and storms in the Northwest Pacific have become about 10 percent stronger. This is the same time frame as the economic boom in Asia. JPL researcher Jonathan Jiang and his postdoctoral fellow, Yuan Wang, designed a series of experiments to see if there was a connection between the two phenomena.

They used a numerical model that included weather factors such as temperature, precipitation and barometric pressure over the Pacific Ocean as well as aerosol transport — the movement of aerosols around the Earth. They did two sets of simulations. The first used aerosol concentrations thought to have existed before the Industrial Revolution. The other used current aerosol emissions. The difference between the two sets showed the effects of increased pollution on weather and climate.

An extra-tropical cyclone seen in the Pacific Ocean off the coast of Japan on March 10, 2014, by NASA's GPM Microwave Imager.

"We found that pollution from China affects cloud development in the North Pacific and strengthens extratropical cyclones," said Wang. These large storms punctuate U.S. winters and springs about once a week, often producing heavy snow and intense cold.

Wang explained that increased pollution makes more water condense onto aerosols in these storms. During condensation, energy is released in the form of heat. That heat adds to the roiling upward and downward airflows within a cloud so that it grows deeper and bigger.

"Large, convective weather systems play a very important role in Earth's atmospheric circulation," Jiang said, bringing tropical moisture up to the temperate latitudes. The storms form about once a week between 25 and 50 degrees north latitude and cross the Pacific from the southwest to the northeast, picking up Asia's pollutant outflow along the way.

Wang thinks the cold winter that the U.S. East endured in 2013 probably had something to do with these stronger extratropical cyclones. The intense storms could have affected the upper-atmosphere wind pattern, called the polar jet stream.

Jiang and Wang are now working on a new experiment to analyze how increased Asian emissions are affecting weather even farther afield than North America. Although their analysis is in a preliminary stage, it suggests that the aerosols are having a measurable effect on climatic conditions around the globe.

Conceptualizing Earth differently

How much these climate effects will increase in the coming decades is an open question. How much they can be reversed if emissions are reduced in Asia also remains unclear.

The researchers pointed out that their work should raise even more red flags about aerosol-based geoengineering solutions — interventions in the Earth system intended to counteract global warming. Some groups have suggested that we could inject sulfate aerosols into the stratosphere to block incoming sunlight, but Jiang and Wang found that sulfates are the most effective type of aerosol for deepening extratropical cyclones. Ongoing injections would bring more stormy winter weather globally and would likely change the climate in other ways we cannot yet foresee.

Jiang noted that Asian emissions have made him and some other climate researchers conceptualize Earth differently. "Before, we thought about the North-South contrast: the Northern Hemisphere has more land, the Southern Hemisphere has more ocean. That difference is important to global atmospheric circulation. Now, in addition to that, there's a West-East contrast. Europe and North America are reducing emissions; Asia is increasing them. That change also affects the global circulation and perturbs the climate."

http://climate.nasa.gov/news/2218/

Joe Romm: The Really Awful Truth About Climate Change

by Joe Romm, Climate Progress, May 18, 2015

Cary Grant and Irene Dunne in a scene from the movie “The Awful Truth.” (AP Photo)

So Vox ran a story Friday, “The awful truth about climate change no one wants to admit” by former Grist columnist Dave Roberts. While I’m a longtime fan of Roberts, the piece is filled with inaccurate and misleading statements, historical revisionism, and a fatally flawed premise.

The premise comes from an equally flawed commentary in Nature, “Policy: Climate advisers must maintain integrity” in which German analyst Oliver Geden argues that climate scientists (and others) have been “spreading false optimism,” about our chances of stabilizing below 2°C total global warming. Geden’s piece has drawn significant criticism from scientists on BuzzFeed, ClimateWire, and here, as Roberts notes.

But Roberts asserts, “the heated reactions elicited by Geden’s piece do show that he’s on to something.” Dave, Dave, Dave, if heated reactions proved someone is “on to something,” then I guess Fox News is fair and balanced after all….

So what is “The awful truth about climate change no one wants to admit”? Roberts asserts that no one wants to admit “The obvious truth about global warming is this: barring miracles, humanity is in for some awful shit.”

No. And by “no” I mean that, setting aside the vagueness of the word “miracles,” lots of people have been saying in recent years that humanity faces some awful shit if we don’t don’t adopt super-aggressive action ASAP. But they have not been saying it’s scientifically hopeless or requires religious miracles — since that isn’t true, though it seems to be what Geden and Roberts want them to be saying.

No, the really awful truth about climate change is that while climate scientists, the International Energy Agency, and many others have been increasingly blunt about how dire our situation is — and what needs to be done ASAP to avoid catastrophe — much of the so-called intelligentsia keep ignoring them.

The most recent example comes in a report out earlier this month from 70 leading climate experts (click here). The parties to the U.N. Framework Convention on Climate Change (aka the world’s leading nations) set up a “structured expert dialogue” from 2013 to 2015 to review the adequacy of the 2°C target. Early this month, the experts reported back. Thoughtfully, they simplified their key conclusions into 10 core messages. Among them:

• Message 1: “Parties to the Convention agreed on an upper limit for global warming of 2°C, and science has provided a wealth of information to support the use of that goal.” Incorporating concerns about ocean acidification and sea level rise, “only reinforces the basic finding emerging from the analysis of the temperature limit,namely that we need to take urgent and strong action to reduce GHG emissions” (emphasis in original).
• Message 2 (again, original emphasis): “Limiting global warming to below 2°C necessitates a radical transition (deep decarbonization now and going forward),not merely a fine tuning of current trends.”
Yeah, scientists just love to spread false optimism.
• Message 4: “Significant climate impacts are already occurring at the current level of global warming” (which is about 0.85°C) and so additional “warming will only increase the risk of severe, pervasive and irreversible impacts. Therefore, the ‘guardrail’ concept, which implies a warming limit that guarantees full protection from dangerous anthropogenic interference, no longer works.“
• Message 5: “The 2°C limit should be seen as a defence line … that needs to be stringently defended, while less warming would be preferable.”
• Message 6 (from the 2014 IPCC mitigation report): “Limiting global warming to below 2 °C is still feasible and will bring about many co-benefits, but poses substantial technological, economic and institutional challenges.”

I reviewed all the mitigation literature in my January post, “It’s Not Too Late To Stop Climate Change, And It’ll Be Super-Cheap.”

Again, no one is saying it would be easy, but it is straightforward, and the literature couldn’t be clearer on how low-cost it is. Geden asserts, “The climate policy mantra — that time is running out for 2 °C but we can still make it if we act now — is a scientific nonsense.” Even Roberts points out, “No. It may be a nonsense, but it’s not a scientific nonsense. No branch of science, certainly not climatology, can tell us what the humans of 2050 are capable of.”

Almost. Thank goodness these pundits weren’t around when we had to do somethingreally difficult, like suffer millions of casualties and remake our entire economy almost overnight to win World War II.

It may well be true that policymakers are unlikely to do what is scientifically, technologically, and economically possible (and morally necessary). But what precisely would Geden have climate scientists tell policymakers — “You folks can’t stop unimaginable catastrophe because you’re simply too greedy and myopic so we’re not even going to tell you how you could do it?” In fact, Geden never tells us what he thinks the advice should be nor what target he would recommend to policymakers (which makes his piece mostly a time-waster).

Note: Geden conflates climate scientists with climate advisers, so he can make it sound like climate scientists are overly optimistic about our ability to hit the 2C target. Even today, most climate scientists didn’t consider themselves experts on energy technology or economic analysis or policy — their job in the IPCC was to tell policymakers what the science says will happen if we act and if we don’t. The job of economists, energy experts, and their ilk has been to tell policymakers what different scenarios entail and how much they would cost, which turns out to be virtually nothing in the 2C case.

Again, that doesn’t mean 2C is easy to do or that we will do it — just that if we ever got off of our asses the way the Greatest Generation did, it would require us to invest only a smidgen of our wealth to make the transition, and we’d be paid back again and again in productivity gains and health gains and energy security gains. And of course there’s that whole not destroying a livable climate thing.

The reality of the transition is no longer theoretical. Last fall, China pledged to “increase the share of non-fossil fuels in primary energy consumption to around 20% by 2030.” That “will require China to deploy an additional 800-1,000 gigawatts of nuclear, wind, solar, and other zero emission generation capacity by 2030 — more than all the coal-fired power plants that exist in China today and close to total current electricity generation capacity in the United States.”

Over the next 15 years, the Chinese will build enough clean electricity to power America. So how exactly is it “nonsense” to think the U.S., EU, or even India could not do the same over, say, twice as much time? Answer: It isn’t.

Here’s Message 8 from the world’s leading climate experts: “The world is not on track to achieve the long-term global goal, but successful mitigation policies are known and must be scaled up urgently.”

Such Polyannas, these climate experts.

Roberts writes of Geden’s piece, “Politicians, he says, want good news. They want to hear that it is still possible to limit temperature to 2°C. Even more, they want to hear that they can do so while avoiding aggressive emission cuts in the near-term — say, until they’re out of office.”

This is no doubt true of many politicians, yet last year the entire EU pledged to cut total emissions 40 percent below 1990 levels by 2030, which is pretty aggressive. And last month, Governor Jerry Brown (D-CA) issued an executive order setting the same goal for California.

But it’s where Roberts (and Geden) leap next that bears scrutiny:

Climate scientists, Geden says, feel pressure to provide the good news. They’re worried that if they don’t, if they come off as “alarmist” or hectoring, they will simply be ignored, boxed out of the debate. And so they construct models showing that it is possible to hit the 2°C target. The message is always, “We’re running out of time; we’ve only got five or 10 years to turn things around, but we can do it if we put our minds to it.”

That was the message in 1990, in 2000, in 2010. How can we still have five or 10 years left? The answer, Geden says, is that scientists are baking increasingly unrealistic assumptions into their models.

No, no, and not quite. This is a complete revision of history.

Climate scientists were not saying in 1990, “we’ve only got five or 10 years to turn things around.” Read the IPCC’s Overview of its 1990 First Assessment Report here. Warning: It’s a yawner.

But that’s no surprise since the UNFCCC wasn’t even negotiated and ratified until 1992. That treaty’s goal was to set up an international process to “stabilize greenhouse gas concentrations in the atmosphere at a level that would prevent dangerous anthropogenic [human-caused] interference with the climate system.” The UNFCCC did not define what that level was at the time. It wouldn’t officially pick 2°C for almost two decades!

And so climate scientists were not saying in 2000, “we’ve only got five or 10 years to turn things around.” Read the IPCC’s entire 2001 Third Assessment Report here. Another yawner.

There are, however, two specific and synergistic reasons why scientists became increasingly concerned during the 2000s.

First, in that decade, Chinese emissions soared, taking us off of more moderate pathways that scientists had been anticipating. You can see that in a chart Roberts posts.

Historical emissions have of late been tracking RCP8.5, catastrophic 4°C warming. But until 2000, emissions were tracking scenarios of much less warming

CREDIT: GLOBAL CARBON PROJECT

Second, at the very end of the 2000s, the world community finally settled on 2°C as the threshold for dangerous warming, which meant CO2 levels in the air needed to be stabilized below 450 parts per million. That consensus, as many people have explained, solidified with the IPCC’s 2007 Fourth Assessment Report.

That’s why, for instance, in 2004, when Princeton Professors published a landmark paper in Science, “Stabilization Wedges: Solving the Climate Problem for the Next 50 Years with Current Technologies,” they wrote: “Proposals to limit atmospheric CO2 to a concentration that would prevent most damaging climate change have focused on a goal of 500 +/- 50 parts per million (ppm).”

So it was only around late 2007 that people paying very close attention, like climate scientists, could see that (1) emissions were veering onto a worse case scenario track (2) just as a scientific and political consensus was forming around the need to set the bar at 2°C, which was now starting to look like a best-case scenario.

That’s why in 2010, a previously reticent Lonnie Thompson explained why previously reticent climatologists had begun speaking out: “Virtually all of us are now convinced that global warming poses a clear and present danger to civilization.” It’s why, when I launched Climate Progress nine years ago, I created a category called “uncharacteristically blunt scientists.”

But again, it wasn’t actually until December 2010 that the parties to the UNFCCC officially adopted 2°C as the upper limit.

Besides climate scientists, many other climate advisers were becoming increasingly blunt, such as the International Energy Agency, which warned in 2009 “The world will have to spend an extra $500 billion to cut carbon emissions for each year it delays implementing a major assault on global warming.”

Their 2011 World Energy Outlook [WEO] release should have ended once and for any notion that climate advisors were pulling their punches. The U.K. Guardian’s (misleading) headline captured the urgency: “World headed for irreversible climate change in five years, IEA warns … If fossil fuel infrastructure is not rapidly changed, the world will ‘lose for ever’ the chance to avoid dangerous climate change.”

Half right. Yes, rapid change is needed. But the IEA did not say the climate change would be irreversible in five years. They wrote:

If internationally co-ordinated action is not taken by 2017, we project that all permissible emissions in the 450 Scenario would come from the infrastructure then existing, so that all new infrastructure from then until 2035 would need to be zero-carbon, unless emitting infrastructure is retired before the end of its economic lifetime to make headroom for new investment. This would theoretically be possible at very high cost, but is probably not practicable politically.

Yes, shutting down existing fossil fuel infrastructure is much more costly than not building it in the first place. It is politically difficult (see U.S. coal plants), but it also happens all the time (see U.S. and China coal plants).

Everything about the 450 (or lower) scenario is politically difficult as I (and many others) have been saying for years. In one 2008 post, “Is 450 ppm (or less) politically possible? Part 1,” I answered the headline question, “Not today — not even close.”

People can use the political difficulty of averting catastrophe as a reason to express hopelessness if they think that is productive, but don’t try to pin this on climate scientists or climate advisors.

There’s an old saying “it’s better to light a candle than curse the darkness” that is based on a Chinese proverb, “Don’t curse the darkness – light a candle.”

But it turns out there is a third option. You can curse the candle lighters, maybe because you have your eyes closed. And that’s the really awful truth.

http://thinkprogress.org/climate/2015/05/18/3644824/really-awful-truth-about-climate-change/

Why the 97 per cent consensus on climate change still gets challenged

BY ANDY SKUCE, climate and carbon, corporate knights, MAY 14, 2015

Active misinformation campaigns by those seeking to oppose or delay climate policy has created a persistent “consensus gap.”

Illustration by Lisk Feng

In 2004, science historian Naomi Oreskes published a short paper in the journal Science concluding there was an overwhelming consensus in the scientific literature that global warming was caused by humans.

After the paper’s release, there was some unexpectedly hostile reaction. This prompted Oreskes and her colleague Erik Conway to go even deeper with their research, leading to the publication of the book Merchants of Doubt. It documents how a small group of scientists with links to industry were able to sow doubt about the scientific consensus and delay effective policy on DDT, tobacco, acid rain and, now, global warming.

Fast forward to two years ago: a team of volunteer researchers (myself included) associated with the website Skeptical Science decide to update and extend Oreskes’ research. Led by University of Queensland researcher John Cook, we analyzed the abstracts of about 12,000 scientific papers extracted from a large database of articles, using the search terms “global warming” and “global climate change.” The articles had been published over a 21-year period, from 1991 to 2011.

As an independent check on our results, we also sent emails to the more than 8,500 scientist authors of these articles. (These were the scientists whose e-mail addresses we were able to track down). We asked them to rate their own papers for endorsement or rejection of man-made global warming.

Both approaches yielded a very similar result: 97 per cent of the scientific literature that expresses an opinion on climate change endorses the expert consensus view that it is man-made. The results were published in May 2013 in the journal Environmental Research Letters.

We were astonished by the positive reception. Mention of the paper was tweeted by U.S. President Barack Obama, Al Gore and Elon Musk, among others. Obama later referenced it in a speech at the University of Queensland, while U.S. Secretary of State John Kerry has referred to the 97 per cent consensus in recent speeches. John Oliver based an episode of his HBO comedy show Last Week Tonight around it, a clip viewed online more than five million times.

The paper has been also been downloaded over 300,000 times – so far – which makes it a blockbuster for a science paper.

Tol fails to make the case

We knew that our paper would be unpopular among climate contrarians, but we were taken aback by the ferocity of the attack and the obsessiveness of some of our critics.

One of the most persistent among them is Professor Richard Tol, an econometrician who teaches at the University of Sussex. Over the past two years, Tol has published numerous blog articles, written letters and submitted Freedom of Information requests to lead author John Cook’s employer, the University of Queensland. Tol has also petitioned the publisher of the article, the Institute of Physics, to have the paper withdrawn.

Expert reviewers at the journal Environmental Research Letters rejected the rebuttal that Tol submitted. After shopping his rebuttal around to other journals, Tol found one, Energy Policy, which agreed topublish his comment. The journal gave us the right to reply, but we didn’t have enough space to do so and we needed a supplementary publication to fully detail the many errors in his analysis.

Tol is no stranger to controversy. He had a vicious public dispute with economist Frank Ackerman, in the course of which he badgered Ackerman’s employer and tried to get Ackerman fired. Eventually, a group of eminent economists published an extraordinary open letter where they upbraided Tol for his unprofessional conduct.

He also wrote a series of letters to the Stockholm Environmental Institute (SEI), which was first to publish the article co-authored by Ackerman. The SEI issued a public statement, which supported Ackerman. “Professor Tol’s repeated, groundless attacks on this article, and on SEI for its association with the article, have violated the norms of civility and scholarly debate,” it said. “We urge Professor Tol to stop attacking the motivations and reputations of others, and to return to the academic community that accepts disagreement and engages in substantive debate.”

More recently, Tol has had some bitter exchanges with Bob Ward, of the London School of Economics, who had pointed out that one of Tol’s published papers contained serious errors. The errors were eventually formally corrected in the original journal (the correction was itself later corrected) and the IPCC had to change its report that had referenced Tol’s paper. The corrections related to a claim by Tol that small amounts of global warming have a beneficial effect, a false result that has been widely promoted by climate contrarians.

What is astonishing about Tol’s campaign is that he does not himself deny the physical science of global warming and also admits that the percentage consensus on man-made climate change is in the high nineties. His criticism consists of a long list of trivial and tendentious comments on methodology, the consequences of which he concedes—either explicitly or by default—have no significant impact on the outcome.

Mind the gap

It came as no surprise to anyone working in climate research that there is an overwhelming scientific consensus on human-caused global warming. Our result was consistent with the outcomes of earlier studies that had measured scientific agreement by other means.

There are many areas in climate science that are not settled and that need more research. But mainstream scientists don’t waste their time arguing about whether or not humans are causing climate change. Increasingly, as we found, many scientists no longer even mention the human cause of modern climate change in their papers. It is taken for granted as are, for example, natural selection in the life sciences and plate tectonics in geology.

However, surveys show that the general public is misinformed about the degree of scientific agreement on global warming. People who do not accept human-caused climate change generally believe that a large fraction of scientists disagree with the basic notion of man-made warming. But even among people who accept the scientific consensus, there’s a false belief that there is significant disagreement among the experts.

Some of this difference of opinion can be explained by politics and culture, with conservatives tending to favour a low estimate of the perceived consensus and liberals a higher one. But there remains a gap – independent of politics – between how much the public thinks scientists agree on the fundamentals of climate change and what the actual level of agreement is.

We call this the “consensus gap” and it is that misunderstanding we are trying to correct. Part of that gap is due to people simply not being sufficiently informed, but part of it is because they have been actively misinformed by those seeking to oppose or delay public policy.

Recent social-science research has shown that the acceptance of the existence of the expert consensus on climate change is a gateway belief. If somebody is not aware, or refuses to accept that there is an overwhelming majority of experts who agree that humans have caused global warming, you are unlikely to be able to persuade them about the more uncertain future consequences of climate change. And you certainly won’t be able to persuade them to support policies to reduce emissions.

Convincing people that the experts agree on the fundamentals of the science is not, of course, sufficient to solve the climate problem, but it is a necessary step.

Tol is not the only one who has tried and failed to show our results are flawed. Climate contrarians everywhere protest there is no scientific consensus. If that were true, they should easily be able to show there is indeed a significant body of work that challenges mainstream science. Yet they haven’t and can’t, because a robust and coherent denial of man-made global warming does not exist.

Our study describes the state of expert opinion, it does not define scientific truth nor does it tell people what to think. Climate scientists today overwhelmingly endorse the consensus view that humans are the cause of most of recent global warming. That’s a fact.

If the goal is to sell doubt and delay action on climate, it’s a fact that has to be denied.

http://www.corporateknights.com/channels/climate-and-carbon/97-per-cent-consensus-climate-change-still-gets-challenged-14315868/

Jeff Masters: extreme, record-breaking temperatures in Spain

All-Time May Heat Record for Europe Falls For the 2nd Time This Month

by Jeff Masters, wunderblog, May 14, 2015

An extreme May heat wave unprecedented in European recorded history has invaded Spain and Portugal, bringing the hottest May temperatures ever recorded on the continent. According to the Spanish meteorological agency, AEMET, at least four stations in the Valencian Community of eastern Spain hit temperatures today in excess of the previous European May heat record set just eight days ago -- a 41.9 °C (107.4 °F) reading at Catenanuova, Sicily (Italy) on May 6. Today's European record-breaking May temperatures in Spain included:

Carcaixent: 42.9 °C (109.2 °F)
Xativa: 42.7 °C (108.9 °F)
Algemesi: 42.6 °C (108.7 °F) 
Valencia: 42.6 °C (108.7 °F)

Many stations in Spain's Valencian community went above their June records, and were near their all-time records for any month. The record set at Valencia Airport today was 6.6 °C (11.9 °F) above the previous highest May temperature, was 4.4 °C (7.9 °F) higher than the record for June, and was the 3rd hottest temperature since records began in 1869 for any month! This week's heat wave began yesterday, when hot air from North Africa flowed northwards over Spain and Portugal, setting all-time May heat records at Madrid, Sevilla, Cordoba, Ciudad Real, Granada, and many other cities. Portugal beat its all-time May heat record with a 40.0 °C (104.0 °F) reading at Beja EMA (old record: 39.5 °C, 103.1 °F, at Regua on May 28, 2001). The most remarkable record yesterday, however, was from the Canary Islands to the southwest of Spain, where Lanzarote Airport hit 42.6 °C (108.7 °F), breaking its old record for the entire month of May by 6 °C (10.8 °F)! The old record was 36.6 °C (97.9 °F) on May 24, 1986. 


Figure 1. Predicted high temperatures for Thursday, May 14, 2015, for Spain from AEMET. Temperatures of 42.0 °C are hotter than any May readings on record for Spain.

According to weather records researcher Maximiliano Herrera, Europe also had its earliest 40 °C temperature ever recorded this month -- a 40.4 °C (104.7 °F) reading at San Priamo in southeastern Sardinia on May 5. Prior to 2015, the previous all-time hottest May temperature recorded in Europe was 41.7 °C (107.1 °F), on May 17, 2006 in Andujar, Spain. What's really remarkable about the two European all-time May heat records set this month is that they have occurred in the first half of the month. We would expect all-time monthly heat records to fall near the end of the month, as summer's heat begins to really ramp up. Note that the World Meteorological Organization (WMO) does not maintain official monthly all-time extreme temperature records for the continents, so the records quoted here are from Maximiliano Herrera.

Thanks go to Maximiliano Herrera and Michael Theusner for the temperature records provided in this post.

http://www.wunderground.com/blog/JeffMasters/comment.html?entrynum=2987

When nutcases and idiots are elected to Congress, this is what we get

While these damned fool Republicans are busy talking about farts and listening to a quack like John Christy, Spain is experiencing off-the-charts, record-breaking temperatures


On May 13, 2015, the Committee held a hearing on a proposed guidance to federal agencies on implementing the National Environmental Policy Act. Republicans on the Committee spent the hearing denying the science and risks of climate change. These are the highlights.

https://www.youtube.com/watch?v=xIPeOKNlHZU

Stefan Rahmstorf: What's going on in the North Atlantic?

by Stefan Rahmstorf, RealClimate, March 23, 2015

The North Atlantic between Newfoundland and Ireland is practically the only region of the world that has defied global warming and even cooled. Last winter there even was the coldest on record – while globally it was the hottest on record. Our recent study (Rahmstorf et al., 2015) attributes this to a weakening of the Gulf Stream System, which is apparently unique in the last thousand years.

The whole world is warming. The whole world? No! A region in the subpolar Atlantic has cooled over the past century – unique in the world for an area with reasonable data coverage (Fig. 1). So what’s so special about this region between Newfoundland and Ireland?

Figure 1. Linear temperature trend from 1900 to 2013. The cooling in the subpolar North Atlantic is remarkable and well documented by numerous measurements – unlike the cold spot in central Africa, which on closer inspection apparently is an artifact of incomplete and inhomogeneous weather station data.

It happens to be just that area for which climate models predict a cooling when the Gulf Stream System weakens (experts speak of the Atlantic meridional overturning circulation or AMOC, as part of the global thermohaline circulation). That this might happen as a result of global warming is discussed in the scientific community since the 1980s – since Wally Broecker’s classical Nature article “Unpleasant surprises in the greenhouse?” Meanwhile evidence is mounting that the long-feared circulation decline is already well underway.

The Atlantic circulation (AMOC) as part of the global overturning circulation of the oceans in an animation from NASA.

Difficult to measure

Climate models have long predicted such a slowdown – both the current 5th and the previous 4th IPCC report call a slowdown in this century “very likely,” which means at least 90% probability. When emissions continue unabated (RCP8.5 scenario), the IPCC expects 12% to 54% decline by 2100 (see also the current probabilistic projections of Schleussner et al., 2014). But the actual past evolution of the flow is difficult to reconstruct owing to the scarcity of direct measurements. Therefore, in our study we use data on sea surface temperatures in order to infer the strength of the flow: we use the temperature difference between the region most strongly influenced by the AMOC and the rest of the Northern Hemisphere.

Figure 2. Schematic of the Atlantic circulation. Surface currents in red, deep currents in blue, sea-ice cover in winter in white. (Source: Rahmstorf, Nature 1997)

Now we are not the first to have inferred from temperature data that the flow must have weakened.  Evidence for this was already presented by Dima and Lohmann (2010) or Drijfhout et al. (2012), among others (for further references see the introduction of our paper).

What is new is that we have used proxy reconstructions of large-scale surface temperature (Mann et al., 2009) previously published by one of us (study co-author and RealClimate co-founder Mike Mann) that extend back to 900 AD (see “What we can learn from studying the last millennium (or so)”) to estimate the circulation (AMOC) intensity over the entire last 1,100 years (Fig. 3). This shows that despite the substantial uncertainties in the proxy reconstruction, the weakness of the flow after 1975 is unique in more than a thousand years, with at least 99% probability. This strongly suggests that the weak overturning is not due to natural variability but rather a result of global warming.

Figure 3. Time series of the temperature difference between the subpolar North Atlantic and the entire Northern Hemisphere, which can be interpreted as an indicator of the strength of the Atlantic circulation.

Also in 2014 we again find a remarkable cold bubble over the northern Atlantic – as a look at the NASA website shows. 2014 was globally the warmest year on record, 1 °C warmer than the average for 1880-1920. But the subpolar Atlantic was 1-2 °C colder than that baseline. 

And even more recently, NOAA last week released the stunning temperature analysis for the past winter shown in Figure 4. That winter was globally the warmest since records began in 1880. But in the subpolar North Atlantic, it was the coldest on record! That suggests the decline of the circulation has progressed even further now than we documented in the paper.

Figure 4. Temperature anomaly map for the past December-January-February, from NOAA.

The role of Greenland

Another new aspect is the importance of the increasing mass loss of the Greenland ice sheet, which causes extra freshwater to enter the North Atlantic that dilutes the sea water. We have joined forces with Greenland expert Jason Box who has reconstructed the mass balance of the Greenland ice sheet since 1840 (Figure 6 of our paper, see also his blog). The ice loss amounts to a freshwater volume which should have made an important contribution to the observed decrease in salinity in the northern Atlantic – probably including the “great salinity anomaly” of the 1970s, famous amongst oceanographers.

Meltwater on the Greenland ice sheet. Photo: Ian Joughin.

What are the impacts of a slowdown?

The consequences of a large reduction in ocean overturning would look nothing like the Hollywood film The Day After Tomorrow. But they would not be harmless either – e.g., for sea level (Levermann et al., 2005) particularly along the US east coast (Yin et al., 2009), marine ecosystems, fisheries and possibly even storminess in Europe (Woollings et al., 2012). We have studied these consequences some years ago in an interdisciplinary project with colleagues from Bremerhaven, Hamburg and Norway – the results are summarized in Kuhlbrodt et al. (2009).

If our analysis is correct, then this indicates that climate models underestimate the weakening of the Atlantic circulation in response to global warming – probably because the flow in these models is too stable (see Hofmann and Rahmstorf, 2009). Although these models predict a significant weakening for the future, they do not suggest this as early as the observations show it (see Figure 2 of our paper). That the real flow may be more unstable than previously thought would be bad news for the future.

If the circulation weakens too much it can even completely break down – the AMOC has a well-known “tipping point” (Lenton et al., 2008). The latest IPCC report (just like the previous one) estimates a probability of up to 10% that this could happen as early as this century. However, this assessment is based on models that may underestimate the risk, as mentioned above. Expert surveys indicate that many researchers assess the risk higher than the (generally conservative) IPCC, as is the case for sea level. In a detailed survey (Kriegler et al., 2009), the 16 experts interviewed saw already at moderate global warming (2-4 °C) a probability of a ‘tipping’ (major reorganisation) of the flow between 5 and 40 percent. With strong global warming (4-8 °C) this probability was even estimated as between 20 and 65 percent.

Figure 5. Sea surface temperature anomaly on 20 March 2015. Note that this is relative to a baseline 1979-2000, which is already a cold period in the subpolar Atlantic. Source: Climate Reanalyzer.

Links

Thermohaline Ocean Circulation (Encyclopedia of Quaternary Sciences)

The Washington Post on our paper

And The Independent

Vox includes comments by some colleagues: Tom Delworth and Gerald Meehl

Peter Sinclair has posted a short video on our paper with interview clips with Mike Mann, Jason Box and myself

Climate Central weighs in with more comments from other scientists on our paper

And here a brand new paper on the impacts of an AMOC shutdown (hat tip to our reader Yvan Dutil)

By coincidence, this came out the same day as our paper: Ten years of ocean monitoring uncovers secrets of changing UK winters

References

Rahmstorf, S., Box, J., Feulner, G., Mann, M., Robinson, A., Rutherford, S., Schaffernicht, E. (2015). Exceptional twentieth-century slowdown in Atlantic Ocean Overturning Circulation, Nature Climate Change (online)

W.S. Broecker (1987). Unpleasant surprises in the greenhouse? Nature, vol. 328, pp. 123-126. http://dx.doi.org/10.1038/328123a0

C. Schleussner, A. Levermann, and M. Meinshausen (2015). Probabilistic projections of the Atlantic overturning, Climatic Change, vol. 127, pp. 579-586. http://dx.doi.org/10.1007/s10584-014-1265-2

M. Dima, and G. Lohmann (2010). Evidence for two distinct modes of large-scale ocean circulation changes over the last century, Journal of Climate, vol. 23, pp. 5-16. http://dx.doi.org/10.1175/2009jcli2867.1

S. Drijfhout, G.J. van Oldenborgh, and A. Cimatoribus (2012). Is a decline of AMOC causing the warming hole above the North Atlantic in observed and modeled warming patterns? Journal of Climate, vol. 25, pp. 8373-8379. http://dx.doi.org/10.1175/jcli-d-12-00490.1

M.E. Mann, Z. Zhang, S. Rutherford, R.S. Bradley, M.K. Hughes, D. Shindell, C. Ammann, G. Faluvegi, F. Ni (2009). Global signatures and dynamical origins of the Little Ice Age and Medieval Climate Anomaly, Science, 326, 1256-1260. http://dx.doi.org/10.1126/science.1177303

A. Levermann, A. Griesel, M. Hofmann, M. Montoya, and S. Rahmstorf (2005). Dynamic sea level changes following changes in the thermohaline circulation, Climate Dynamics, vol. 24, pp. 347-354, 2005. http://dx.doi.org/10.1007/s00382-004-0505-y

J. Yin, M.E. Schlesinger, and R.J. Stouffer (2009). Model projections of rapid sea-level rise on the northeast coast of the United States, Nature Geoscience, vol. 2, pp. 262-266. http://dx.doi.org/10.1038/ngeo462

T. Woollings, J.M. Gregory, J.G. Pinto, M. Reyers, and D.J. Brayshaw (2012). Response of the North Atlantic storm track to climate change shaped by ocean–atmosphere coupling, Nature Geoscience, vol. 5, pp. 313-317. http://dx.doi.org/10.1038/NGEO1438

T. Kuhlbrodt, S. Rahmstorf, K. Zickfeld, F.B. Vikebø, S. Sundby, M. Hofmann, P.M. Link, A. Bondeau, W. Cramer, and C. Jaeger (2009). An integrated assessment of changes in the thermohaline circulation, Climatic Change, vol. 96, pp. 489-537. http://dx.doi.org/10.1007/s10584-009-9561-y

M. Hofmann, and S. Rahmstorf (2009). On the stability of the Atlantic meridional overturning circulation, Proceedings of the National Academy of Sciences, vol. 106, pp. 20584-20589. http://dx.doi.org/10.1073/pnas.0909146106

T.M. Lenton, H. Held, E. Kriegler, J.W. Hall, W. Lucht, S. Rahmstorf, and H.J. Schellnhuber (2008). Tipping elements in the Earth’s climate system, Proceedings of the National Academy of Sciences, vol. 105, pp. 1786-1793. http://dx.doi.org/10.1073/pnas.0705414105

E. Kriegler, J.W. Hall, H. Held, R. Dawson, and H.J. Schellnhuber (2009). Imprecise probability assessment of tipping points in the climate system, Proceedings of the National Academy of Sciences, vol. 106, pp. 5041-5046. http://dx.doi.org/10.1073/pnas.0809117106

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