Blog Archive

Tuesday, December 30, 2014

The deep Greenland Sea is warming faster than the World Ocean

Bremerhaven, September 25, 2013

Recent warming of the Greenland Sea Deep Water is about 10 times higher than warming rates estimated for the global ocean. Scientists from the Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research recently published their findings in the journal Geophysical Research Letters. For their study, they analysed  temperature data from 1950 to 2010 in the abyssal Greenland Sea, which is an ocean area located just to the south of the Arctic Ocean.
Since 1993, oceanographers from the Alfred Wegener Institute's Helmholtz Centre for Polar and Marine Research (AWI) have carried out regularly expeditions to the Greenland Sea on board the research ice breaker Polarstern to investigate the changes in this region. The program has always included extensive temperature and salinity measurements. For the present study, the AWI scientists have combined these long-term data sets with historical observations dating back to the year 1950. The result of their analysis: in the last 30 years, the water temperature between 2,000 metres depth and the sea floor has risen by 0.3 degrees centigrade.
‘This sounds like a small number, but we need to see this in relation to the large mass of water that has been warmed,’ says AWI scientist and lead author, Dr. Raquel Somavilla Cabrillo. ‘The amount of heat accumulated within the lowest 1.5 kilometres in the abyssal Greenland Sea would warm the atmosphere above Europe by 4 degrees centigrade.  The Greenland Sea is just a small part of the global ocean. However, the observed increase of 0.3 degrees in the deep Greenland Sea is 10 times higher than the temperature increase in the global ocean on average. For this reason, this area and the remaining less studied polar oceans need to be taken into consideration.’
The cause of the warming is a change in the subtle interplay of two processes in the Greenland Sea: the cooling by deep convection of very cold surface waters in winter and the warming by the import of relatively warm deep waters from the interior Arctic Ocean. 
“Until the early 1980s, the central Greenland Sea had been mixed from the top to the bottom by winter cooling at the surface making waters dense enough to reach the sea floor,” explains Somavilla. “This transfer of cold water from the top to the bottom has not occurred in the last 30 years. However, relatively warm water continues to flow from the deep Arctic Ocean into the Greenland Sea. Cooling from above and warming through inflow are no longer balanced, and thus the Greenland Sea is progressively becoming warmer and warmer.”
These changed conditions provide AWI scientists with unique research opportunities: “We use these changes as a natural experiment. The warming allows us to calculate how much water flows from the deep central Arctic into the Greenland Sea,” says Prof. Dr. Ursula Schauer, head of the Observational Oceanography Department at the Alfred Wegener Institute, about this project, and she adds, “We observe here a distinct restructuring of the Arctic Ocean. This is a very slow process, and its documentation requires long-term observations.”

To fully understand how the world’s oceans react to climate change, scientists need to investigate the Arctic Ocean in more detail. ‘Due to its large volume and its thermal inertia, the deep ocean is a powerful heat buffer for climate warming. In particular, the polar oceans are scarcely studied. If we want to understand the role of the deep ocean in the climate system, we need to expand the measurements to remote regions like the Arctic,” AWI-scientist Schauer says. For that, she has already planned further Polarstern expeditions. In 2015, Ursula Schauer and her group will go back to the Arctic.

Glossary: Why are the deep waters from the interior Arctic Ocean warm?
The mean temperature of the deep-water masses from the interior Arctic Ocean is 0.9 degrees centigrade. That is much warmer than the surface waters of the Greenland Sea, which cool down to  1.8 degrees in winter. However, where does the warmth of the deep Arctic waters come from? It is the result of a long chain reaction occurring in the shallow seas on the edge of the Arctic Ocean – right where sea ice formation takes place during the winter. When the sea ice is formed, the salt, which is present in the water, does not become enclosed. It leaves the ice instead and increases the salinity and density of the water layer below the ice. Due to their rising density, these waters become heavier and begin to sink. One can compare this sinking process with a snowball falling down a freshly snow-covered slope. The longer the snowball rolls, the more snow is attached to it. This means that, while rolling down the Arctic shelf, the salty, sinking, water masses come across a layer of warm Atlantic water. They take up part of the heat and the salt in this Atlantic layer and transport it to deeper levels in the Arctic Ocean. At the bottom of the Arctic Ocean, these sinking water masses form a body of warm deep water that eventually streams out of the Arctic Ocean into the Greenland Sea.

The study was published in Geophysical Research Letters under the following original title:
R. Somavilla, U. Schauer and G. Budéus. Increasing amount of Arctic Ocean deep waters in the Greenland Sea, Geophysical Research Letters, Vol. 40, 4361–4366, doi:10.1002/grl.50775, 2013.

Saturday, December 27, 2014

Pacific trade winds have forced heat into the ocean for decades, now set to reverse

by John Upton, Climate Central, December 22, 2014

Chemical clues in skeletons produced by coral growing at Kiribati contain a newly discovered warning. They caution of a global climate system that’s capable of drawing decades’ worth of hoarded heat out of the Pacific Ocean, and belching it back into the atmosphere.

A cryptic chemical weather log kept by Tarawa Atoll’s stony coral in the tropical Pacific archipelago has been cracked, helping scientists explain a century of peaks and troughs in global warming — and inflaming fears that a speedup will follow the recent slowdown.

Added to a growing body of research, the newly published findings indicate that all it would take to trigger what could be a historically unparalleled period of rising global temperatures would be a shift in the winds. And that type of change in the intensity of Pacific trade winds appears to happen every 20 to 30 years or so.

Kiribati. Credit: Luigi Guarino/flickr
The coral-based findings, published Monday in Nature Geoscience, provide new historical data supporting previous modeling results and observations that point to the long-term waxing and waning pattern of the trade winds in affecting worldwide temperatures.

For the past few decades, the Interdecadal Pacific Oscillation, as the influential cycle is known, has been in what’s called a negative phase, meaning trades winds have been strong.
The growing body of scientific evidence indicates that this negative phase has played a heavy role in driving an approximately 15-year old slowdown in worldwide surface warming. It suggests that a speedup in warming may follow the next switch to the oscillation’s positive phase, when trade winds weaken, and the effects of the natural cycle exacerbate those of unnaturally increasing levels of greenhouse gases in the atmosphere.

Diane Thompson, a postdoctoral fellow at the National Center for Atmospheric Research who led the study published Monday, said we’re in a surface warming slowdown right now because the Pacific trade winds are strong. But she says that apparent bout of good fortune won’t last forever.

“When winds weaken, which they inevitably will, warming will once again accelerate,” Thompson said. “The warming caused by greenhouse gases and the warming associated with this natural cycle will compound one another.”

Strong tropical Pacific trade winds serve as an air conditioner for the world, scientists are concluding. They mix warm equatorial surface water into greater depths, and help bring cooler waters to the surface. But, like the window-mounted AC unit that cools your living room during summer, all the while heating the air outside, the strong winds aren’t cooling the planet. They’re just moving heat-wielding energy to where it will bother us less.

And, just like that window-mounted unit, the strong trade winds will eventually break down. When the global air conditioner breaks down, modeling and past experience suggest that the process will start to operate in reverse.

In February 2014, Australian and American researchers who compared ocean and climate modeling results with weather observations published findings in Nature Climate Change advancing earlier studies that explored the oscillation’s global influence. They found that the effects of strong Pacific trade winds during the past two decades were “sufficient to account” for the recent slowdown in global warming.

The slowdown refers to slower-than-expected rates at which temperatures measured on the land and at sea surfaces have been rising since the turn of the century. The amount of energy being trapped on Earth continues to rise at a quickening pace, because of the effects of the thickening cloud of greenhouse gas pollution in the atmosphere, but more of that energy than usual has been ending up in the oceans. That ocean heat — while hard for many of us to notice directly — has been driving record-breaking global temperatures, with 2014 on track to be the hottest on record, and to more vicious tropical storms.

The Australian and American researchers drew a similar comparison in their paper between strong trade winds and a slight cooling in global surface temperatures from 1940 to the 1970s.

Surface air temperature (SAT) has risen fastest during the Interdecadal Pacific Oscillation's positive phases, when trade winds have been weakest. Credit: England, M. H. et al. Recent intensification of wind-driven circulation in the Pacific and the ongoing warming hiatus. Nature Clim. Change 4, 222–227 (2014).
On Monday, a team of American and British scientists led by Thompson reported on their chemical analysis of a sample core bored out of coral on the most populated atoll of Kiribati, a postcard-worthy Pacific Ocean country comprising many small islands. The sample was selected for the coral's location, growing just outside the mouth of a west-facing lagoon.

The scientists measured changes over time in the amount of manganese in the skeletons produced by coral growing since the 1890s. The waters inside the lagoon are sheltered by a ring of land from the trade winds, which blow from the east. When trade winds are weak, the lagoon’s waters are churned more frequently by gusts blowing from the west. When those gusts blow in, they kick up sediment in the lagoon, releasing manganese into the water that corals can use in place of calcium to grow their skeletons.

The team also measured strontium in a coral sample taken from Jarvis Island, an uninhabited speck of land southwest of Kiribati, to gauge historical surface water temperatures. Strontium levels in coral skeletons are affected by ocean temperatures.

The scientists found that winds blowing a century ago had a similar relationship with global weather as the more recent links that have been discovered by other scientists.

“We know that winds flip-flop between periods of strong trade winds and periods of weak trade winds,” Thompson said. “Our study shows that these winds play a role in the rate of global temperature rise.”

Thompson’s team found evidence in its Kiribati coral core of weak trade winds early in the 20th century. Those winds coincided with a period, from 1910 to 1940, when global temperatures rose faster than could have been caused by greenhouse gas pollution alone, given the still-nascent state of mass industrialization.

The group also found evidence that trade winds were stronger and surface temperatures were cooler from 1940 to 1970, providing additional evidence of the relationship between the Pacific trade winds and the rates at which global temperatures have been changing.

Coral coring at Jarvis Island. Credit: Julia Core, University of Arizona

“The paper confirms the idea that tropical Pacific trade winds play a major role in global climate variability,” Matthew England, a professor at the University of New South Wales who was not involved with the coral study, said. He said its findings support those from other recent studies, including February’s Nature Climate Change paper, which was published by a team that England led.

“What’s very much new here is the attribution of the early 20th century warming to weakened Pacific trade winds,” England said.

The use of coral cores in the study was praised by Braddock Linsley, a professor at the Lamont-Doherty Earth Observatory of Columbia University who studies ancient climatic conditions by analyzing coral skeleton samples. He was not involved with the study.

Linsley said the new results were “exciting,” suggesting that the “poorly understood, rapid rise” in surface temperature from 1910 to 1940 was, in part, “related to changes in trade wind strength and heat release from the upper water column” of the Pacific Ocean.

“The mounting evidence is coalescing around the idea that decades of stronger trade winds coincide with decades of stalls or even slight cooling of global surface temperatures, as heat is apparently transferred from the atmosphere into the upper ocean,” Linsley said.

Winds over the Atlantic Ocean also appear to modulate global surface temperatures, albeit to a lesser extent than those over the Pacific Ocean. The science isn't settled on just how much those Atlantic winds, and other potential forces, have contributed to the heaving nature of global warming. "We're still at the beginning" of this field of research, Stefan Brönnimann, a University of Bern professor who investigates climate variability, said. He also wrote a 'news and views' article for Nature Geoscience assessing and describing the new research. "Pacific and Atlantic influences are not mutually exclusive."

The new study’s findings were limited by the fact that just one coral core was analyzed to serve as a proxy wind gauge — a shortcoming that the researchers aim to address. 

“Measurements of manganese in coral skeletons are difficult and time consuming,” Thompson said. “Now that we know how important they can be, we will be making more.”

Evidence of rising temperatures deep in the Pacific Ocean, even as surface temperature rise has slowed, has come in part from measurements of the rise of expanding seas. As global temperatures continue to increase, the hastening rise of those seas as glaciers and ice sheets melt threatens the very existence of the small island nation, Kiribati, whose corals offered up these vital clues from the warming past — and of an even hotter future, shortly after the next change in the winds.

Pope Francis to issue encyclical on climate change and the environment

Pope Francis’s edict on climate change will anger deniers and US churches 

Pontiff hopes to inspire action at next year’s UN meeting in Paris in December after visits to Philippines and New York

by John Vidal, The Observer, December 27, 2014

Pope Francis was a key player in thawing relations between the US and Cuba. Photograph: Franco Origlia/Getty Images

He has been called the “Superman Pope,” and it would be hard to deny that Pope Francis has had a good December. Cited by President Barack Obama as a key player in the thawing relations between the US and Cuba, the Argentinian pontiff followed that by lecturing his cardinals on the need to clean up Vatican politics. But can Francis achieve a feat that has so far eluded secular powers and inspire decisive action on climate change?
It looks as if he will give it a go. In 2015, the pope will issue a lengthy message on the subject to the world’s 1.2 billion Catholics, give an address to the UN general assembly and call a summit of the world’s main religions.
The reason for such frenetic activity, says Bishop Marcelo Sorondo, chancellor of the Vatican’s Pontifical Academy of Sciences, is the pope’s wish to directly influence next year’s crucial UN climate meeting in Paris, when countries will try to conclude 20 years of fraught negotiations with a universal commitment to reduce emissions.
“Our academics supported the pope’s initiative to influence next year’s crucial decisions,” Sorondo told CAFOD, the Catholic development agency, at a meeting in London. “The idea is to convene a meeting with leaders of the main religions to make all people aware of the state of our climate and the tragedy of social exclusion.”
Following a visit in March to Tacloban, the Philippine city devastated in 2012 by Typhoon Haiyan, the Pope will publish a rare encyclical on climate change and human ecology. Urging all Catholics to take action on moral and scientific grounds, the document will be sent to the world’s 5,000 Catholic bishops and 400,000 priests, who will distribute it to parishioners.
According to Vatican insiders, Francis will meet other faith leaders and lobby politicians at the General Assembly in New York in September, when countries will sign up to new anti-poverty and environmental goals.
In recent months, the Pope has argued for a radical new financial and economic system to avoid human inequality and ecological devastation. In October he told a meeting of Latin American and Asian landless peasants and other social movements: “An economic system centred on the god of money needs to plunder nature to sustain the frenetic rhythm of consumption that is inherent to it.
“The system continues unchanged, since what dominates are the dynamics of an economy and a finance that are lacking in ethics. It is no longer man who commands, but money. Cash commands.
“The monopolising of lands, deforestation, the appropriation of water, inadequate agro-toxics are some of the evils that tear man from the land of his birth. Climate change, the loss of biodiversity and deforestation are already showing their devastating effects in the great cataclysms we witness,” he said.
In Lima last month, bishops from every continent expressed their frustration with the stalled climate talks and, for the first time, urged rich countries to act.
Sorondo, a fellow Argentinian who is known to be close to Pope Francis, said: “Just as humanity confronted revolutionary change in the 19th century at the time of industrialisation, today we have changed the natural environment so much. If current trends continue, the century will witness unprecedented climate change and destruction of the ecosystem with tragic consequences.”
According to Neil Thorns, head of advocacy at CAFOD, said: “The anticipation around Pope Francis’s forthcoming encyclical is unprecedented. We have seen thousands of our supporters commit to making sure their MPs know climate change is affecting the poorest communities.”
However, Francis’s environmental radicalism [huh?] is likely to attract resistance from Vatican conservatives and in rightwing church circles, particularly in the US – where Catholic climate sceptics [deniers! not skeptics!] also include John Boehner, Republican leader of the House of Representatives, and Rick Santorum, the former Republican presidential candidate.
Cardinal George Pell, a former archbishop of Sydney who has been placed in charge of the Vatican’s budget, is a climate change sceptic [no, he is a denier] who has been criticised for claiming that global warming has ceased and that if carbon dioxide in the atmosphere were doubled, then “plants would love it.”
Dan Misleh, director of the Catholic climate covenant, said: “There will always be 5-10% of people who will take offence. They are very vocal and have political clout. This encyclical will threaten some people and bring joy to others. The arguments are around economics and science rather than morality.
“A papal encyclical is rare. It is among the highest levels of a pope’s authority. It will be 50 to 60 pages long; it’s a big deal. But there is a contingent of Catholics here who say he should not be getting involved in political issues, that he is outside his expertise.”
Francis will also be opposed by the powerful US evangelical movement, said Calvin Beisner, spokesman for the conservative Cornwall Alliance for the Stewardship of Creation, which has declared the US environmental movement to be “un-biblical” and a false religion. [And the Cornwall Alliance also doesn't believe in evolution.]
“The pope should back off,” he said. “The Catholic church is correct on the ethical principles but has been misled on the science. It follows that the policies the Vatican is promoting are incorrect. Our position reflects the views of millions of evangelical Christians in the US.”

IceSat data confirm that Greenland's ice sheet melting has been underestimated, and it is accelerating

The most detailed study yet of the Greenland ice sheet illustrates the complex process that is causing billions of tonnes to melt every year

by Tim Radford, Climate News Network, December 27, 2014

LONDON − Greenland’s ice sheet shrank by an average of 243 billion tonnes a year between 2003 and 2009 – a rate of melting that is enough to raise the world’s sea levels by 0.68 mm per year.

In what is claimed as the first detailed study, geologist Beata Csatho, of the University of Buffalo in the US, and colleagues report in the Proceedings of the National Academy of Sciences that they used satellite and aerial data to reconstruct changes in the ice sheet at 100,000 places, and to confirm that the process of losing 277 cubic kilometres of ice a year is more complex than anyone had predicted.

The Greenland ice sheet is the second biggest body of ice on Earth − second only to Antarctica − and its role in the machinery of the northern hemisphere climate is profound.

Careful measurements

It has been closely studied for decades, but such are the conditions in the high Arctic that researchers have tended to make careful measurements of ice melt and glacier calving in fixed locations – in particular, at four glaciers − and then try to estimate what that might mean for the island as a whole.

“The great importance of our data is that, for the first time, we have a comprehensive picture of how all of Greenland’s glaciers have changed over the past decade,” Dr Csatho said.

The study looked at readings from NASA’s ice, cloud and land elevation satellite ICESat, and from aerial surveys of 242 glaciers wider than 1.5 km at their outlets, to get a more complete picture of melting, loss and – in some cases – thickening of the ice sheet as a whole.

Previous studies have focused on the four glaciers. One of them, Jakobshavn, has doubled its speed of flow since 2003, and closer studies have begun to reveal more about the dynamics of individual flows.

But the real strength of the study is that it establishes the pattern of ice melt in more detail, and suggests that climate models may not give a clear enough picture of the future of the ice cap. To put it crudely, Greenland could lose ice faster in the future than any of today’s predictions suggest.

Meanwhile, a team from the UK has been trying to work out what is happening on the surface of the ice sheet. Each summer, of course, some of the ice melts. Some of this gets to the sea, but some freezes again in the natural seasonal order of things.

But glaciology researcher Amber Leeson, of the University of Leeds, and colleagues report in Nature Climate Change that the “supraglacial” lakes that form each summer could also affect ice flow.

Their computer simulations suggest that these lakes will migrate further inland as the century wears on and the world continues to warm. Ice reflects heat, water absorbs it. So the process could trigger further melting. Some of this extra meltwater could slide or drain to the base of the glacier, lubricating its flow and accelerating the process yet again.

Thin pancake

“Our research shows that, by 2060, the area of Greenland covered by them will double,” Dr Leeson said. “When you pour pancake batter into a pan, if it rushes quickly to the edge of the pan, you end up with a thin pancake. It’s similar to what happens with ice sheets. The faster it flows, the thinner it will be.

“When the ice sheet is thinner, it is at a slightly lower elevation and at the mercy of warmer air temperatures than it would be if it were thicker, increasing the size of the melt zone around the edge of the ice sheet.”

In the last 40 years, the band in which such supraglacial lakes can form has crept 56 km inland. By 2060, the simulations now suggest, it could reach 110 km inland, doubling the area of coverage and delivering yet more meltwater to fuel further warming.

Once again, the research suggests that current models underestimate the rate of ice loss. 

Sunday, December 21, 2014

NASA Satellites Measure Increase of Sun’s Energy Absorbed in the Arctic

by Patrick Lynch & Mike Finneran, NASA, December 17, 2014
NASA satellite instruments have observed a marked increase in solar radiation absorbed in the Arctic since the year 2000 – a trend that aligns with the steady decrease in Arctic sea ice during the same period.
While sea ice is mostly white and reflects the sun’s rays, ocean water is dark and absorbs the sun’s energy at a higher rate. A decline in the region’s albedo – its reflectivity, in effect – has been a key concern among scientists since the summer Arctic sea ice cover began shrinking in recent decades. As more of the sun’s energy is absorbed by the climate system, it enhances ongoing warming in the region, which is more pronounced than anywhere else on the planet.
Since the year 2000, the rate of absorbed solar radiation in the Arctic in June, July and August has increased by 5%, said Norman Loeb, of NASA’s Langley Research Center, Hampton, Virginia. The measurement is made by NASA’s Clouds and the Earth’s Radiant Energy System (CERES) instruments, which fly on multiple satellites.
Arctic maps showing sea ice change (left) and absorbed solar radiation change (right)
The Arctic Ocean is absorbing more of the sun's energy in recent years as white, reflective sea ice melts and darker ocean waters are exposed. The increased darker surface area during the Arctic summer is responsible for a 5% increase in absorbed solar radiation since 2000.
Image Credit: 
NASA Goddard's Scientific Visualization Studio/Lori Perkins
While a 5% increase may not seem like much, consider that the rate globally has remained essentially flat during that same time. No other region on Earth shows a trend of potential long-term change.
When averaged over the entire Arctic Ocean, the increase in the rate of absorbed solar radiation is about 10 Watts per square meter. This is equivalent to an extra 10-watt light bulb shining continuously over every 10.76 square feet of Arctic Ocean for the entire summer.
Regionally, the increase is even greater, Loeb said. Areas such as the Beaufort Sea, which has experienced the some of the most pronounced decreases in sea-ice coverage, show a 50 watts per square meter increase in the rate of absorbed solar radiation.

“Advances in our understanding of Arctic climate change and the underlying processes that influence it will depend critically upon high quality observations like these from CERES,” Loeb said.
As a region, the Arctic is showing more dramatic signs of climate change than any other spot on the planet. These include a warming of air temperatures at a rate two to three times greater than the rest of the planet and the loss of September sea ice extent at a rate of 13% per decade.
While these CERES measurements could ultimately become another of those signs of dramatic climate change, right now scientists say they have obtained the bare minimum of a data record needed to discern what’s happening over the long term.
Getting data beyond 15 years will allow scientists to better assess if recent trend falls outside the realm of natural variability, said Jennifer Kay, an atmospheric scientist at the Cooperative Institute for Research and Environmental Science at the University of Colorado.
“We need long time series to detect climate change signals over the internal variability.  For example, observed sea ice loss over the last 30 years cannot be explained by natural variability alone.” Kay said. “Fifteen years is long, but climate is often defined as the average over 30 years – so we are only half-way there with the CERES observations.”
Kay and colleagues have also analyzed satellite observations of Arctic clouds during this same 15-year period. Kay’s research shows summer cloud amounts and vertical structure are not being affected by summer sea ice loss. While surprising, the observations show that the bright sea ice surface is not automatically replaced by bright clouds. Indeed, sea ice loss, not clouds, explain the increases in absorbed solar radiation measured by CERES.
Increasing absorbed solar radiation is causing multiple changes in the sea ice cover, said Walt Meier, a sea ice scientist from NASA’s Goddard Space Flight Center, Greenbelt, Maryland. Two of those changes include the timing of the beginning of the melt season each year and the loss of older, thicker sea ice.
The onset of the melt season in the high Arctic is now on average seven days earlier than it was in 1982, Meier said. Earlier melting can lead to increased solar radiation absorption. This is one step in a potential feedback cycle of warming leading to melting, melting leading to increased solar radiation absorption, and increased absorption leading to enhanced warming.
Since 2000, the Arctic has lost 1.4 million square kilometers (541,000 square miles) of older ice that is more than 3 meters thick, which during winter has essentially been replaced by ice that is less than 2 meters thick, according to data provided by Mark Tschudi at the University of Colorado. Once again, Meier said, this trend is a step in a feedback cycle.
“Having younger and thus thinner ice during winter makes the system more vulnerable to ice loss during the summer melt season,” Meier said.
CERES instruments are currently flying on the Terra, Aqua and Suomi-NPP satellites. The Terra satellite launched Dec. 18, 1999, and CERES first started collecting Arctic data in 2000, so 2015 will mark 15 continuous years of CERES measurements over the Arctic.
The instruments include three radiometers – one measuring solar radiation reflected by Earth (shortwave), one measuring thermal infrared radiation emitted by Earth (longwave), and one measuring all outgoing radiation, whether emitted or reflected.
For more information about NASA AGU presentations, visit:

Peter Gleick: The answer on human-caused climate change is in

by Peter Gleick, Sacramento Bee, December 20, 2014

Read more here:

As our planet warms, scientists and the general public are increasingly asking if human-caused climate change influences the extreme weather events we see all around us. Until recently, the answer was always “we don’t know yet.” Today, the answer is increasingly “yes.”

Earth is in a remarkable transition from a world in which human influence on climate has been negligible to one in which our influence is increasingly dominant. One of the most active research areas in the climate sciences is the field of detection and attribution: the effort to see and identify the fingerprint of climate change in our extremes of weather.

This is tough because the day-to-day fluctuations in weather are naturally large or “noisy.” But scientists have long known that as climate change worsens, we would eventually reach the point when the signal of human influence would rise above and become distinguishable from the noise of natural variability. The California drought is a case in point.

For the past three years, California has been experiencing a bad drought, most simply defined as the mismatch between the amounts of water nature provides and the amounts of water that humans and the environment demand. The state, like any other region of the world, experiences extreme hydrologic events naturally, including floods and droughts. 

Reconstructions of ancient climates from tree rings, ice cores, pollen records and other paleoclimatic assessments reveal extensive and persistent droughts in the past.

But the current California drought isn’t bad just because of a severe shortage of rain and snow – previous droughts have seen less precipitation. It’s so bad because the past three years also have been by far the hottest in the 119-year instrumental record. An analysis recently released by researchers from the Woods Hole Oceanographic Institute concluded these factors make the current drought the most severe in 1,200 years.

Is this a signal of climate change? Recently, there has been a growing debate about the links between climate change and the drought. The debate stems from confusion over two very different questions:

▪  Is California’s severe drought caused by climate change?
▪  Is California’s drought, no matter the cause, influenced or affected by climate change?

These questions are not the same thing. Yet the media, the public and even some scientists have mixed them up. A popular analogy is that we cannot know whether any particular home run hit by a baseball player pumped up on steroids was caused by the drugs. 

Ballplayers hit home runs naturally. But we know that these drugs influence and distort the average performance of the ballplayer over time.

The influence of climate change on extreme events works the same way: Science cannot at the moment tell us much about whether climate changes have caused any particular extreme event. But scientists from many different fields now see parallel lines of evidence from a combination of basic climate science, models and real-world observations that human-caused climate change is already influencing and worsening the risks of extremes such as heat waves, droughts and floods.

For the California drought, this evidence includes the fingerprints of higher temperatures and changes in atmospheric circulation patterns in a climate pumped up by greenhouse gases emitted by human activities. These higher temperatures have led to extra drying of soils, greater agricultural water demand, earlier and faster snowmelt, and higher evaporative losses in reservoirs.

California is not alone in experiencing the growing consequences of climate change. 

Evidence that climate change is influencing extreme events all over the world is now pouring in, including heat waves in Europe, coastal damage in the Eastern U.S. during extreme tides and storms, flooding in the United Kingdom from more intense precipitation events, drastic loss of Arctic ice, and droughts in Australia and the southwestern U.S.

The rainy season in California has started again, ironically with another set of extreme events in the form of intense storms. Many of us hope that the state will see an average or even a wet year to refill dangerously overpumped aquifers and depleted reservoirs. But if there is any lesson to be learned from the past few years, it is that California and the rest of the world must prepare for a future where the influence of human-induced climate change is ever more apparent. And costly.
Peter H. Gleick is president of the Pacific Institute, an environmental policy group based in Oakland.

Read more here:

Thursday, December 11, 2014

Warming Ocean May Be Triggering Mega Methane Leaks Off Northwest Coast

by KUOW, December 9, 2014

Sonar image of bubbles rising from the seafloor off the Washington coast. The base of the column is one-third of a mile (515 meters) deep and the top of the plume is at 1/10 of a mile (180 meters) deep. | credit: Brendan Philip / UW 
SEATTLE — As the waters of the Pacific warm, methane that was trapped in crystalline form beneath the seabed is being released. And fast.
New modeling suggests that 4 million tons of this potent greenhouse gas have escaped since 1970 from the ocean depths off Washington’s coast.
“We calculate that methane equivalent in volume to the Deepwater Horizon oil spill is released every year off the Washington coast,” said Evan Solomon, a University of Washington assistant professor of oceanography and co-author of the new paper, which was published in the journal Geophysical Research Letters. The modeling does not indicate whether the rate of release has changed as temperatures warm, but it does strengthen the connection between ocean temperature and methane behavior.
Solomon and his colleagues first learned about the methane leaks when fishermen started sending them photographs of bubbles coming up out of the deep.
“They’re really low quality phone shots of their fish finders, but every single location they gave us was 100 percent accurate,” Solomon said.
On a cruise this past summer, Solomon and his colleagues gathered core samples from the ocean floor, about one-third of a mile deep, at the spots where the fishermen reported seeing bubbles.
And sure enough, mixed in among the sediment, were crystalized methane deposits.
“It looks like slushy ice,” Solomon said. But it certainly behaves differently. “If you took it from the sediment and lit a match or put a lighter on it, it will go into flames because of all the gas.”
Methane can exist in a gas, liquid and crystalline form. The crystalline version, or methane hydrate, occurs at cold temperatures and under pressure - conditions that can be found at certain depths of the ocean. But as deep sea waters warm, scientists believe those crystals will dissolve, releasing the methane in bubbles that can change ocean chemistry and contribute to atmospheric change once they escape at the sea’s surface.
“It’s a way to contribute to ocean acidification if you have a lot of this gas coming out and being oxidized in the water column,” Solomon said.
The methane release isn’t just happening in Washington waters, Solomon says. More sampling needs to be done but the same conditions for methane hydrate release exist from Northern California to Alaska. “So it’s not a Washington central thing,” says Solomon, who is looking forward to further study of this issue. “It should be happening off of Oregon, off of British Columbia as well.”
Other research has found similar patterns of methane release in the Atlantic and off the coast of Alaska.
“It’s a hot topic,” Solomon said.