Wyrd - OE: that which has become; fate-shaping; destiny-unfolding

Thursday, 29 August 2013

Of monsters, methane and the burdensome sea

It's the ultimate tipping point - the so-called Methane Burp. Gigatons (Gt) of methane are released into the atmosphere by some sudden phase change in the earth's climate system.
Plumes of methane in Arctic Ocean (Westbrook et al, 2009)

With its vastly greater global warming potential - up to 100 times more powerful than CO2, over short timescales - a sudden pulse of methane would accelerate human-caused global warming. It could even cause a cascade of other knock-on effects (Amazon deforestation, collapse of the ice-sheets) so creating a runaway greenhouse effect.

It's that sort of a scenario - with 50Gt of methane gushing from a source in the Arctic over 10-20 years - that was recently modeled by economists in Nature. They put a $60 trillion price tag for the global economy from the consequences of ratcheting upwards man-made climate change. A scary monster, made even more real by describing it in the language our leaders understand most - hard cash.

But the Methane Burp is also complete fantasy - at least according to some recent detractors. Many climate scientists believe the methane locked up in frozen soils, or the curious, icy 'methane-hydrates' under the sea-floor, are a real threat - but only as a slow-burn cooker for the globe's climate. As the planet warms, the natural emissions from these sources will increase, they believe. But not at a rate that will be catastrophic. They struggle to see how anything like as large as 50,000 million tonnes of methane can erupt so quickly from Arctic permafrost, or sub-sea methane hydrates. Such sources have been thought to have been stable in the recent geological past.

Now a paper,studying one of the most vulnerable of these 'carbon time-bombs' - the methane hydrates frozen in the sub-sea sediments of the East Siberian Arctic Shelf - have found a worrying trigger for setting off the bomb. And it isn't the warming water itself that's the culprit - just the fact that there's more of it.

Figure prepared by Robert A. Rohde from published data.
Global warming has already been shown to be raising sea-levels at rates approaching 3cm (1.2 inches) per decade, much from the melting of the world's glaciers and ice-sheets. The most recent IPCC estimate sees that rate reaching 10 cm (3.6 inches) per decade, over the next century. Some reckon it could even get as high as 20cm (7.2 inches). Sea-level rises like these are a worrying problem in themselves, of course.

But such high rates aren't just potentially disastrous for those coastal cities likely to be impacted by storm surges. Higher seas from melted ice mean millions of tons of extra water sitting over the continental shelves. And that weight gain is putting areas like East Siberian Arctic Shelf under a lot more pressure. That's something the new study, published in Geology believes is a real cause for concern.

The loose sediments piled under the shallow Arctic seas fronting East Siberia are not just packed with methane hydrates. They are also riven by faults, and littered with signs of spectacular slips along the Siberian continental slope. It is looking at these old slope failures, which happened between 15,000 and 8,000 years ago, that has revealed just how vulnerable the area is to collapse. And unveiled a viable mechanism for the potential release of vast quantities of methane, fast.

This is one of the first studies to look at the reasons for these subsea landslides. The scientists involved looked at the rise in sea-level over the last 25,000 years - as the last Ice Age ended, and the ice melted - and calculated how much extra stress the rising waters would place on East Siberia's underwater fault systems. They found the additional force would be enough to trigger slips along those faults, and so produce the massive slides now seen at the foot of the continental  slope.

Given that those slides have been dated to coincide with the maximum period of sea-level rise, it seems very likely that rising seas are not good news for the stability of the East Siberian Arctic Shelf. And that's not good news for us. As well as the tsunamis that the movement of such large volumes of sediment would produce, they also 'unroof' the methane-hydrates trapped by permafrost in the area.

And the sea-level rise our global warming is causing could soon reach the same levels that were last seen 10,000 years ago. That takes the catastrophic release of multi-gigatons of methane out of the realm of pure fantasy. It seems the Methane Burp is a monster quietly biding its time in the far north - just waiting for the next tremor  to throw the gates open.

Sunday, 2 June 2013

From White to Green - Greenland's Glaciers are History


Article first published as From White to Green - Greenland's Glaciers are History on Technorati.

Greenland ice sheets (Credit: destination arctic circle/ Flickr)
Take a long hard look at Greenland's towering glacial caps - they may well already be history. That's according to a paper published in Nature Climate Change. Scientists have already noticed that the speed at which Greenland's glaciers are rushing into the sea has accelerated. And they have long-feared that, without commitments to curb our greenhouse gas emissions, much of its ice cap will eventually disappear into the sea.

But there is now research to suggest the threshold has already been passed. Previous models made some fairly simple assumptions about how the 2 mile-thick ice block, which is plastered over much of Greenland, will melt. And they gave some hope that the worst of the melting could still be avoided, if we were to pull the plug on our emissions.

Fade to green?

With this new research, however, the physics of Greenland's ice-melting process have been painted out in finer detail. And if the authors are right, the amount of global warming we have stored up, from our emissions so far, may be enough to transform Greenland. The world's biggest island could shift from an icy whiteness to a truly green land.

Ice sheet thickness (km) today (E1) and projected in future (E2/3)
The reason for the change in outlook? The simple realization that as the 2-mile high icy plateaus melt they get considerably lower. And the lower the ice surface, the warmer the air above them gets, pushing the pace of melt even faster – a positive feedback.

Positive feedbacks are the 'loaded dice' of the game of climate crap-shoot we're playing. They push the odds in favor of dangerous consequences, by accelerating the rates of change kicked off by global warming. But how dangerous would it be, if Greenland were to disgorge its entire ice sheet into the oceans, as this study suggests?

Sunday, 3 February 2013

A Book of Kells for the climate - scribe-illustrators needed?

The world of climate science sometimes seems like a swirling sea of numbers. Numbers that come, and numbers that go, like waves breaking silently on the foreshore. There's always another statistic, or table, or figure about to break, ready to erase the brief imprint of the last. But occasionally that sea tosses up a stunningly crafted piece of driftwood - and here's one I found beach-combing the wilder shores of green think-tankery:





This is one of many visual gems to be found in the World Resources Institute's report, 'Navigating the Numbers'. It tried to summarize the state of play for greenhouse gases and climate policy a few years back. I love this picture, because it takes all of those all-often-hurled statistics and beds them into a beautifully-colored context. All of the data is there, of course, showing on how each and every part of our society is contributing to our shocking of the climate.

Monday, 12 November 2012

Ten tall-tales from the skeptics – the come-backs to topple them


Photo Credit: WireWizard
First published on EarthTimes as "Ten tall-tales from the climate change skeptics

The devil has all of the best songs, so they say. And the climate-change denial camp have certainly banged out their tunes to good effect, over the last few years. It's not hard to see why the clamor of the climate skeptics has won more and more of those thronging in the stalls. But if you're caught out by one of those seductive refrains from the naysayers, what you need is counter-melody to cut them short. So what are the top-ten comebacks to the tall-tales often peddled by the denialist community?

1 Warming isn't really happening, it's all down to the 'urban heat-island effect'
The consensus that the planet is warming didn't just drop off of a graph of dodgily-placed thermometers. Yes, cities and towns are warmer than the countryside, and yes, urban areas have swallowed rural ones over the last century. But climate scientists try to correct for these when working out the globe's average temperature.

And the indicators that temperatures are rising come from a myriad of sources, not just land-based temperature records. Satellites, tree-rings, snow and ice-cores, stalactites and corals – all of these are used to piece together the global temperature record. And they confirm that the recent warming is unprecedented.

Monday, 5 November 2012

Black stain or clean climate?

First published on Earth Times as "Clean stoves could save lives and maybe the climate too"

Flecks of soot from a smoky open fire in India blacken more than just the roofs of the hut it is smoldering in. Fine particles of such smoke lodge deep in the lungs of women preparing meals, gifting them a dark scourge of ill-health and premature death. That same black soot floats higher into the air, where it helps to change the way clouds form - and so to warm the climate. Some specks may even end up coating ice in the frozen extremes of the planet, dulling their pristine surfaces, and hastening the melt of glaciers and ice-caps.

And recent reports suggest that the weakening monsoon in India, and unprecedented storms in the Arabian Sea, may owe their genesis to the smoggy brown clouds gathered over the Indian sub-continent. For such tiny little particles, soot appears to be having mammoth impacts, and in a host of different ways. But the problem of soot is not one of those tangled and knotted issues that needs an impossibly herculean effort to sort out. It may be that its dark legacy can be addressed by something as simple as a clean-burning stove.

From cooking to climate change

The problem of the gathering smoggy clouds over many parts of the developing world has been visible for decades. But only recently have all of the implications become apparent. Some of the particles making up the haze come from wildfires; some from coal-burning power stations; some from diesel-fumes, as urban traffic swells. But in many places, and especially in the Indian sub-continent, a large share comes from cooking stoves. It is thought that up to 3 billion people worldwide still cook over open fires or stoves, filling their homes, and the local atmosphere, with smoke. Maybe 800 million of these people are in India, in both cities and villages. And the sheer number of their cooking fires is helping to build up a 2 mile-thick hazy cloud over much of South Asia.

Thursday, 6 September 2012

Drying wetlands threaten a climate unraveling


Credit : Natural Resources Canada, Canadian Forest Service
Everyone knows about 'our' carbon – the thin thread of black that we spin out into the atmosphere as man-made carbon-dioxide emissions. It's the direct byproduct of all our frantic making and heating, flying and driving; the restless energy that defines our modern age. And equally well-known is its consequence -- 'our' carbon is providing much of the impetus behind the globe's rising thermometer.

But that spooling out of long-buried fossil carbon isn't the only way in which we're pulling at the threads of the planet's complex tapestry. Another thread, that scientists are just starting to understand, is that of the carbon sunk into the wetland wildernesses of peats and bogs. And a study, released last year in Nature Communications, confirms the less-than-firm grip that researchers have on the flow of carbon, for these murkier parts of the planet.

It seems that what was thought to be a carbon sink is able to transform itself into a massive carbon pump - literally in just a flash of smoke.

Carbon is pooled in many places in the complex flow of the carbon cycle. Such 'sinks' are places where carbon is not easily released from, and so is kept from boosting the atmospheric CO2 count. In that sense carbon stores are important buffers against runaway global warming. The biggest such stores are to be found in the oceans, and deeply-buried rocks. But wetlands also play a part in storing carbon, on a smaller scale.

Wednesday, 29 February 2012

When Arctic ice goes, the North wind blows..


"Global warming is now making our winters colder!"

Only the craziest of eco-doom mongerers would be foolish enough to spout such nonsense, surely? The threat from a warming planet may take many guises, but making us colder – that's plainly on the 'wing-nut' side of things, isn't it. But in fact just such a claim is now being made, not by the deep-green fringe of the environmental movement – but by respected climate scientists from Columbia University, Georgia Tech and China's Institute of Atmospheric Physics. And the tale that their research lays out, in the most recent edition of the PNAS, is anything but a madman's babblings.

Patterns all-a-flux on the climate's patchwork quilt 

Instead, their paper coolly describes how the patchwork-quilt climate of the northern hemisphere is quickly unravelling, as the world warms. And for some – including parts of North America, Europe and Asia – the new pattern has plenty of colder winters woven into the fabric. That's something that no-one living there can fail to have noticed, in recent years. Deep snows and freezing temperatures have made themselves unwelcome guests, repeatedly, over the last four winters. But the culprit for all that cold may turn out to be the very thermostat dials being turned up, to keep us snug – all thanks to the global warming being bought on by higher greenhouse gas emissions.

The story begins 30,000 feet up, with the wandering band of winds – the polar jet stream – whistling around the Arctic regions, at up to 250 mph. This high, narrow wind-belt in fact marks the boundary between the cold airs at the North pole, and the warmer moist airs of the temperate zones. The jet stream keeps all that cold where it should be, up north – and the stronger the jet stream is, the more tightly those frigid airs are locked in at the pole. It's when the jet stream weakens and slows, that the cold air has a chance to spill down below the Arctic Circle, bringing harsher winters in its wake.

The sea-ice, the cliff and the snow

The driver for the jet stream, and the wall of winds separating the cold north from the warmer south, arises precisely from that stark contrast in temperatures. The cold dense air at the pole sinks to form high pressure; while the warmer air surrounding it rises, making a ring of low pressure systems. And the frozen sea-ice over the Arctic ocean acts as an anchor,  providing a deep pool of cold that is one of the drivers for a strong jet stream. 

But something has changed of late, and changed dramatically. The Arctic's cap of sea-ice, which was slowly receding thanks to global warming, fell off a cliff in 2007. Sea-ice volumes for the last 5 years have been half, or less, what they were before 2007 – as can be seen in the plummeting graph above. With less sea-ice after each summer's melt, those waters up north are taking longer to freeze over in the autumn.

That's where the team of researchers looking for reasons for the last few winters of record snowfalls – have turned, in the search for an explanation. ′For the past four winters, for much of the northern US, east Asia and Europe, we had this persistent above-normal snow cover,'  paper co-author Dr Jiping Liu, of Georgia Tech, explained. In order see if there was a connection between less sea-ice for the Arctic, and more snow for us, the team looked afresh at the mounds of sea-ice and snow data from 1979 to 2010. They also ran computer simulations that modeled the climate, with simulated sea-ice being reduced, as has unfolded in the real-world.

Spinning top ready to topple

The conclusions drawn from these two different approaches were the same, according to Dr Liu. More open water at the start of winter means more heat is passed back into the air, when the sea freezes. That heat makes the winter Arctic air mass warmer, and so softens the contrast in air temperatures. That in turn makes the jet stream more weak and wobbly – a bit like a spinning top losing speed, and on the verge of toppling over.

′We think the recent snowy winters could be caused by the retreating Arctic ice altering atmospheric circulation patterns by weakening westerly winds, increasing the amplitude of the jet stream and increasing the amount of moisture in the atmosphere,' he said. ′These pattern changes enhance blocking patterns that favor more frequent movement of cold air masses to middle and lower latitudes, leading to increased heavy snowfall in Europe and the Northeast and Midwest regions of the United States.′

So while the world gets relentlessly warmer – on average, and over a number of years – some of us are getting slaps of rude winter cold, much more often we used to. It's almost as if the planet is pressing out its own desperate S.O.S to the world's big polluters. And the madness, maybe, is not in the planet's contradictory message, but in the perpetrators – addicted to fossil-fueled growth – who continue to ignore it, at their own peril.