Fault lines: Earthquakes from collapsing glaciers add to sea level rise

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by Anna Bisaro
Oct 24, 2013

Icebergs the size of Manhattan’s Central Park break off of Greenland’s outlying glaciers and trigger earthquakes that can be detected thousands of miles away. About half of the mass lost from Greenland every year is due to these earthquakes.

Greenland icebergs Source/credit:   Gary Comer
Greenland icebergs
Source/credit:
Gary Comer

Seismologist Meredith Nettles of Columbia University monitors the force of the earthquakes and knows they are increasing in number.

While these earthquakes won’t knock any buildings down, they are tearing away at the ice mountains of the glaciers. And, with more recorded every year, that’s cause for alarm, Nettles said. The increasing number of quakes is adding to rising global sea levels, she told top climate scientists gathered at the annual Comber Abrupt Climate Change Conference this month in Wisconsin.

Nettles goes to Greenland year after year for stints of field research that show the increasing glacial calving in Greenland that causes glacial earthquakes.

The earthquakes themselves contribute to the collapse of the glaciers and sea level rise, according to Nettles.

“We had the same number of earthquakes that we have by now last year in early December,” she said. “So we’re more than a month ahead of schedule.”

“GLACIAL EARTHQUAKES”

Nettles said combining her study of earthquakes and climate change happened by accident. A seismologist by training, in 2003 Nettles started to notice seismic activity coming from Greenland, but the signals were not indicative of normal earthquakes.

“We didn’t’ know what they were when we first saw them,” Nettles said of the phenomena she termed glacial earthquakes. “Maybe we would have chosen a different name.”

research shows the number will be record-breaking this year. Click on graphic to enlarge. Source/credit:   Meredith Nettles
research shows the number will be record-breaking this year. Click on graphic to enlarge.
Source/credit:
Meredith Nettles

Traditional earthquakes occur with a massive release of energy as tectonic plates move past each other along a fault. This type of quake can happen in glaciers if walls of the ice move past each other along a fault, and Nettles said these quakes are aptly termed ice quakes.

Nettles described glacial earthquakes to be more like landslides except instead of large rocks falling, they are icebergs breaking off from the edge of an outlet glacier into the ocean. The seismic waves occur when the icebergs break off.

As glaciers move across a calving margin – the point at which the ice breaks– the pressure on the ice becomes too great and an iceberg breaks off. The earthquakes happen when the calving line of an iceberg is close to the grounding line. The grounding line is like a foundation for the glacier, the boundary between the rock underneath the glacier and the ocean. When the retreating glacier’s calving front is close to the grounding line, earthquakes result.

“Those calving lines have retreated closer and closer into Greenland,” Nettles said. “More and more of them are moving across grounding lines and starting to generate earthquakes.”

  Meredith Nettles presents research findings at Abrupt Climate Change Conference in Wisconsin this month. Source/credit:    Anna Bisaro/MEDILL

Meredith Nettles presents research findings at Abrupt Climate Change Conference in Wisconsin this month.
Source/credit:
Anna Bisaro/MEDILL

The icebergs that break off may be the size of a cubic kilometer, or the equivalent of the size of New York City’s Central Park, with the height of the Empire State Building.

“It’s so big that it’s really hard to visualize,” Nettles said.

Most of the icebergs that break off are about that size. A cubic kilometer equates to a giga-ton, or one billion tons of water.

Traditional earthquakes have been studied for more than 100 years and Nettles admits the limitations in making conclusions based on her research because glacial earthquakes have not been studied for very long.

“We have a basic idea of how it works, but we’re really far from having the understanding that we have of those [tectonic] earthquakes,” Nettles said.

Once Nettles and her team figured out where the seismic waves came from, their mission shifted to figuring out the effects of the quakes on the glaciers themselves, and then the greater implications for the planet.

SEA LEVELS RISING

The latest U.N. Intergovernmental Panel on Climate Change report estimates global sea levels will rise up to 3.3 feet by 2100 with high carbon fuel emission levels, more than 50 percent higher than the estimate in the previous report. That’s enough to swamp coastal regions and island countries. Sea levels could rise about 1 to 2 feet even with significant emisssions reductions, the report estimates. But the projections of sea level by the IPCC are actually very uncertain, according to Nettles. Part of the uncertainty comes from not knowing how many icebergs will break from the glaciers in Greenland, Nettles said. These icebergs make large contributions to sea level rise.

“Everything we have done in society now has really been optimized for a very particular climate and a very particular sea level,” Nettles said. “Even if you don’t live on the coasts, there will be an impact in your life from changing sea level.”

Nettles explained the importance acknowledged that a drop in sea level would present its own suite of problems as well.

“There’s a lot of ice there [Greenland]. Understanding how fast that ice can come out of the ice sheet and go into the ocean is important,” Nettles said. About half of the ice lost from Greenland is from these earthquakes. “In other ways these earthquakes are really nice. No one feels them, they don’t knock any buildings down.”

Calving of the Helheim Glacier in Greenland. Source/credit:   Comer Conference
Calving of the Helheim Glacier in Greenland.
Source/credit:
Comer Conference

SPEEDING GLACIERS

From 2003 to 2006 Nettles and her team collected data on these glacial earthquakes. By 2005, they started to notice a great increase in the number of quakes every year as well as an increase in the speed of the glaciers experiencing the quakes.

Because of the trends seen in the data, Nettles felt a great sense of urgency in finding out more about what was happening with these glacial earthquakes in Greenland and quickly applied for grants to be able to start more closely monitored research and fieldwork on the glaciers.

The five years of data collected from 2006 to 2010 has been analyzed and used to attempt to understand the affects of the glacial earthquakes on the glaciers themselves.

As the iceberg accelerates and breaks off, it triggers a reaction force on the glacier. The reaction force, in addition to causing seismic waves, also causes the glacier to accelerate in the opposite direction. That force is increasing too because ice loss from the glacier is the greatest contributor to short-term velocity, Nettles said.

To measure the change in velocity of the glaciers, Nettles uses GPS data.

Columbia University geochemist, Wallace Broecker, a climate change expert, asked Nettles during her presentation if the ice cores of the glaciers contribute to heat flow of the glaciers, thus affecting the movement. Nettles responded that she and other scientists believe ice cores do affect the heat flow, but how is beyond their level of understanding right now. The information will be integrated into the final model of the moving and quaking glaciers.

Quantifying the size of glacier that moves or the distance earthquakes is another story. From the seismic stations around the world, Nettles cannot tell if the entire glacier moves a couple meters or if a smaller mass moves a greater distance as a result of the quake.

It is clear that glaciers do speed up as a result of the earthquakes. While the speed that glacier moves as a result of the quake remains consistent there is no direct relationship between the size of the quake and how much faster the glacier will move as a result.

Right now Nettles and her team cannot predict how fast a glacier will move in response to a quake, no matter the size of it. At this point, they can only provide a range of how much faster the glacier will move given the size of the iceberg and glacier.

“It would be simple if you could say the bigger the ice loss the bigger the speed up,” she said. “It is not at all consistent.”

Nettles showed in her presentation how the biggest and smallest speed-ups that happened as a result of glacial earthquakes actually came from the two largest earthquakes, proving that there is no direct correlation between size and speed. Other factors like thickness of the glacier and melting rate.

In addition to the speed of the glacier as a result of the quake, climate scientist Klaus Lackner wanted to know the velocity of the seismic waves in the ice. You can measure velocity of seismic waves in rock, so why not ice, Lackner wondered.

Nettles said that because the ice is only a few kilometers thick – a fact they know from extensive prior research – scientists can only measure the velocity of very high frequency waves in ice.

QUAKES INCREASING

Since the 1990’s the number of glacial earthquakes in Greenland have been increasing in number according to Nettles, but it is important to keep that increasing number in perspective.

“You want to make sure you don’t have an apparent but artificial increase in the numbers that comes from being better able to detect the earthquakes,” Nettles said. Nettles said it is important to account for bias when looking at older data of the earthquakes that may come from the equipment simply not being as good as it is today.

“Presumably these kinds of earthquakes have been happening all along,” Nettles said. “But the increase in number that we see, in the sense that it is related to the retreat of the ice, and the retreat of the ice is linked to changes in the atmosphere and the oceans, whatever’s happening in the climate system affects what that ice is doing.”

Nettles said warmer ocean water and warmer temperature cause retreat of the glaciers. As the glacier melts it gets thinner and then calves faster, she said. The evidence that the number of glacial earthquakes is increasing due to climate change. But without data from further back than 1980, it is impossible to say with absolute certainty that this phenomena may have occurred anyway.

RECYCLING CO2 COULD FIGURE IN THE ZERO SUM SOLUTION TO CLIMATE CHANGE

JOI ITO/ FLICKR Scientists propose selling CO2 absorbed by carbon capture technology to the owners of greenhouses, who routinely buy CO2 that plants absorb
JOI ITO/ FLICKR
Scientists propose selling CO2 absorbed by carbon capture technology to the owners of greenhouses, who routinely buy CO2 that plants absorb

by Monika Wnuk
Oct 26, 2013

Capturing and storing the 29 billion tons of carbon dioxide the world emits annually from burning fossil fuels could help clamp a lid on climate change.

At the Comer Abrupt Climate Change Conference this month in Wisconsin, scientists shifted the focus away from capturing and storing CO2 and toward recycling it.

“If you want to store CO2, one of the problems is you end up storing a lot of CO2. I think over this next century, we are likely to produce an amount of CO2 which is comparable to the [amount of] water in Lake Michigan,” said Columbia University geophysicist Klaus Lackner said at the conference.

But the big challenge for Lackner and the planet is to capture CO2, a greenhouse gas that spread through the atmosphere, holds in heat and is forcing global warming.

Lake Michigan, which holds 5 trillion tons of water, sets a relatable scope for just how much CO2 would need to be pulled from the air to keep levels where they are now in terms of mitigating climate change. And scope is central to the feasibility of Lackner’s carbon capture technology.

At the core of the technology is what Lackner calls an “artificial tree,” a carbon scrubber that could capture one ton of CO2 a day, equivalent to the CO2 emitted by 75 cars after they burn a little more than a gallon of gas. The scrubber’s main visible feature is a carousel housing plastic filters that resemble pipe cleaners. When wind blows through the scrubber’s plastic filters, they absorb CO2 until saturated, at which point they are lowered into vacuum chambers to be cleaned before resurfacing.

Rather than storing the CO2 that’s left behind underground, scientists are coming up with various ways to recycle it. One of these is selling CO2 to greenhouses. 

“In Rotterdam, [greenhouse owners] pay 100 euros for a ton of CO2 to inject into a greenhouse,” Lackner said.

Klaus Lackner/ COLUMBIA UNIVERSITY One of Lackner's designs for an "artificial tree," the carbon scrubber he developed to absorb CO2 from the air. Each scrubber captures one ton of CO2, the amount emitted by 75 cars burning about 1.3 gallons of gasoline.
Klaus Lackner/ COLUMBIA UNIVERSITY
One of Lackner’s designs for an “artificial tree,” the carbon scrubber he developed to absorb CO2 from the air. Each scrubber captures one ton of CO2, the amount emitted by 75 cars burning about 1.3 gallons of gasoline.

 

A Johnson brand CO2 generator, which the company website states can provide up to 1,500 parts per million of CO2 per unit in a 24-by-200-foot greenhouse, sells for $50 to $600.

Although selling CO2 to greenhouses would recycle it as a gas in an inexpensive way, Lackner said that’s just one small way to recycle CO2.

Converting CO2 – an emission from gasoline back into gasoline – could have a much bigger impact even when compared to investing in battery-powered electric cars.

“I think an electric car is probably an advance over an internal combustion engine, but it’s not clear that an electric car has to run on batteries because batteries are very inefficient in storing energy” right now, Lackner said.

Converting CO2 to a liquid fuel could improve upon the overall efficiency of hybrid cars, Lackner suggested.

Klaus Lackner/COLUMBIA UNIVERSITY Thinner plastic filters than this older model are housed inside of the main carousel of a scrubber. When wind blows through the scrubber's plastic filters, they absorb CO2 unitl saturated, at which point they are lowered into vacuum chambers to be cleaned before resurfacing.
Klaus Lackner/COLUMBIA UNIVERSITY
Thinner plastic filters than this older model are housed inside of the main carousel of a scrubber. When wind blows through the scrubber’s plastic filters, they absorb CO2 unitl saturated, at which point they are lowered into vacuum chambers to be cleaned before resurfacing.

 

The process of converting CO2 emissions to a liquid fuel is nothing new. Short on resources, the Germans experimented with it in the 1920s and actually implemented the process during World War II.

In 2007, chemists at the University of California, San Diego demonstrated how sunlight could be used in the transofrmation of a greenhouse gas into a wide range of useful products, including gasoline.

Their study showed that light absorbed and converted into electricity could drive a reaction that converts carbon dioxide into carbon monoxide and oxygen. Carbon monoxide is a key ingredient in synthetic fuels, including gasoline. 

Clifford Kubiak, a chemist who worked on the study, told the university that although a much larger scale operation would be needed to implement the conversion process globally, his results show both that recycled CO2 can power machines cleanly and that it can replace fossil fiels that are being used to make plastics daily.

For Kubiak’s technology to catch on, Lackner’s carbon capture system has to first be implemented on a global scale. And this could take 20-30 years, a typical timetable for a new technology, he said.

There were practically no cars on the roads in 1900, for instance, but the horseless carriage caught on quickly after that. “If you look at a picture of New York City in 1925, the city was full of cars. That 25 years was apparently enough to get from a pre-car society to a society that had fully embraced cars,” Lackner said. “The 20-30 years is sort a typical time frame to get things going,” he added. 

Lackner has spent a decade so far working on developing his carbon scrubbing technology. In 2004, he co-founded Kilimanjaro Energy, a direct air capture company, with seed money from the late Gary Comer, the entrepreneur and philanthropist who founded Lands’ End. 

In 2006, he presented Comer with a vial of pure CO2 he had captured. Since then, Lackner has developed a prototype and a price range. He said that the initial cost of extracting a ton of CO2 from the air could be between $100 and $150, but he is optimistic that the price could drop to just $30 per ton of CO2 once things get rolling on a larger scale. 

“Solving this problem is never going to be small. If you’re talking $30 per ton of CO2, it will not break the bank. Economies can afford that,” he said.

Columbia University climate research pioneer Wallace Broecker, who helps coordinate the Comer Foundation climate change research program, said he is surprised that there’s been a delay in investment in the technology.

MEDILL photo Columbia University geophysicist Klaus Lackner is developing carbon capture technology, demonstrating viability with a prototype unit. He spoke at this month's Comer Abrupt Climate Change Conference.
MEDILL photo
Columbia University geophysicist Klaus Lackner is developing carbon capture technology, demonstrating viability with a prototype unit. He spoke at this month’s Comer Abrupt Climate Change Conference.

 

“The total amount of money that’s been spent on it in 10 years is no more than $25 million. That’s what A-Rod makes for the Yankees in one season. There’s something wrong” Broecker said.

Both Broecker and Lackner agreed that reducing the CO2 we emit daily to zero is necessary for carbon capture to make a difference. However, uncertainties in CO2 mitigation in the next few decades make it even more important to invest in carbon capture now.

“This is not an overnight fix, but it allows you to actually go backward” in terms of reducing CO2 levels and capping global warming, Lackner said.

NEW PALEOCLIMATE RESEARCH EMERGES OUT OF AFRICA

Meredith Kelly People in a boat float near the dramatic Rwenzori Mountains in Uganda, where Kelly and her team researched clues to past glaciers.
Meredith Kelly
People in a boat float near the dramatic Rwenzori Mountains in Uganda, where Kelly and her team researched clues to past glaciers.

by Jenny Draper
Oct 28, 2013

Africa—the continent for catching a glimpse of lions, zebras, elephants and glaciers.

Yes, glaciers. 

The quest for climate change clues led geologist and paleoclimatologist Meredith Kelly to Uganda last August in search of the missing puzzle piece in global warming research. 

Kelly and her team and 27 porters carried equipment up the Rwenzori Mountains, a place covered in dramatic tropical vegetation.

“It was like being in Alice in Wonderland, I mean it was just like being in a different world. It was very cool. I felt very lucky to be there,” said Kelly, an assistant professor at Dartmouth College.

Using satellite imagery, field mapping and clues left by bacteria, Kelly and her team identified “an extensive system of past glaciers.” She reported on her findings to scientists at the Comer Abrupt Climate Change Conference held in Wisconsin this month. It marked an extension of seminal climate research into Africa.

The expedition was Kelly’s second trip to the Rwenzori Mountains National Park and UNESCO World Heritage Site with James Russell, an associate professor of geological sciences at Brown University. 

Jennifer Draper/MEDILL Meredith Kelly shows the reach of glaciers into Africa, new research she presented at the Comer Abrupt Climate Change Conference in Wisconsin.
Jennifer Draper/MEDILL
Meredith Kelly shows the reach of glaciers into Africa, new research she presented at the Comer Abrupt Climate Change Conference in Wisconsin.

For two weeks, Kelly and Russell studied the evidence of long lost glaciers and sediments to figure out what the climate was like in the past to better understand how it could change in the future.

“There are two radiocarbon ages from the 1960s from those mountains and other than that there’s basically no information about the age of moraines,” the rocky ridges left as glaciers retreat, Kelly said.

Beryllium-10 surface exposure dating calculated the age of the moraines, answering a “big question” because of the past uncertainty surrounding the time frame of the glaciers. Beryllium-10 is an isotope of Beryllium created when cosmic rays strike bedrock, but it only appears when the rock is exposed to air. Predictable rates of decay tell Kelly how long ago the isotope was generated and hint that the rock was covered in ice before that date. 

Russell developed a second technique that uses organic molecules produced by bacteria that live in lakes and soils, Kelly said. Taking a sediment core reveals how the molecules changed due to different temperatures through time. 

Meredith Kelly A member of Kelly's team works in the Rwenzori Mountains in Uganda, where they studied past glacial expanses last August.
Meredith Kelly
A member of Kelly’s team works in the Rwenzori Mountains in Uganda, where they studied past glacial expanses last August.

“With these two methods together, we can work together and say were glaciers bigger or smaller when it was warm or cold.” Kelly said. “That’s important because there’s a lot of debate as to what is causing glaciers in the tropics to change.”

“I think we can really robustly say that the glaciers in the tropics reached their maximum at the same time as glaciers in the mid-latitudes during the last ice age,” Kelly said.

Scientists refer to the last ice age as the “last glacial maximum” or a time period of worldwide simultaneous cooling when the size of ice sheets peaked about 20,000 years ago. While still premature, Kelly’s initial results seem to confirm Africa cooled at the same time as other parts of the world did. 

Data collected around the world adds to the understanding of the complete glacial chronology, the end goal for most climate change research. 

For example, comparing the climate histories of Africa, New Zealand, Greenland and the Wind River Range, can reveal patterns of change around the planet, Kelly said, which help develop tools to anticipate future global conditions.

Kelly hopes to return to Uganda next summer to finish coring Lake Mahoma and a few more lakes higher in the mountains. The coring rig was too lightweight to access more than a few meters in the stiff sediment.

The hot and rainy weather also makes fieldwork challenging, Kelly said, who is more familiar with working in cold, dry conditions. 

“But in some cases it’s actually easier than working in Greenland where we worry about polar bears or have to carry rifles everywhere we work,” Kelly said. 

However, one aspect of working in Uganda is “hands down” the most dangerous thing she’s ever done in the field.

“Most people get around on these things called boda-bodas, which are motorcycles that you can pile you know one, two, three, four people on the back depending how small you are,” Kelly said. “They ride up on the sidewalk and down in the street and around and it’s so unsafe. Nobody wears a helmet.” 

She prefers walking around the Rwenzori Mountains, staying in a hostel whose profits go back to the Ibanda village for schools and healthcare. 

Yet Kelly’s African experiences and enterprising research may never have happened if not for an encounter with Russell a few years prior at an American Geophysical Union meeting in San Francisco, where he spoke about the continent’s possibilities.

“I walked up to him after the talk and I said ‘Is anybody dating those moraines?’ And he said ‘No, you want to?’ And I said, ‘Yeah!’” Kelly explained. “I had never met him before and now we have this great collaborative project together.”

Kelly said the story is a good message for students, adding, “If you have questions, ask them. You never know what will come out of them.”

MILLIONS OF YEARS OF CLIMATE CLUES BUILD MOSAIC OF GLOBAL WARMING

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by Elizabeth McCarthy and Monika Wnuk
Oct 27, 2013

Top climate scientists assessed the impact of melting glaciers, rising sea levels and lakes turning into deserts at this year’s Comer Abrupt Climate Change Conference in Wisconsin. Rising fossil fuel emissions in our era are escalating global warming, scientists said.

“The big picture, I think, was the strength of the community, the strength of the scientists doing [research], the strength of the young people doing it, and the fact that they really are now getting answers that we can rely on,” said geoscientist Richard Alley of Pennsylvania State University.

Nicolas Young Stranded icebergs dot the Tininnilik lake basin, West Greenland.
Nicolas Young
Stranded icebergs dot the Tininnilik lake basin, West Greenland.

Research presentatons looked at ancient climate shifts, from rapid warming potentially linked to a comet striking the Earth some 55 million years ago to the Little Ice Age cold spell that set in about 800 years ago, spurring the Mongol invasion of Eurasia. Scientists gathering clues to climate systems from the past provide ever more detailed data to better assess the impacts of human-forced global warming in our own times.

Peering back 55 millions years, “something happened in less than a year and possibly as fast as a few seconds” that triggered rapid escalation of carbon dioxide levels and global temperature increases of 5 degrees Celcius (9 degrees Fahrenheit), said James Wright, of Rutgers University. “Given all the the ideas, hypotheses out there, comet is the only one that can trigger a large carbon isotopic and a large carbon event as fast as – well, in less than a year.”

Lively discussions and analysis spilled over to the social hours, breakfasts, lunches and dinners held in the hilltop tent at the Comer conference retreat in Wisconsin. The late Gary Comer, the philanthropist and entrepreneurpost who founded Lands’ End, supported widespread climate research that continues to bring new findings to the conference. The Comer research legacy is ccontinued by Guy and Stephanie Comer, Gary Comer’s children, through the Comer Science and Education Foundation.

The Comer Foundation hosts the annual conference organized by Alley and veteran veteran climate scientists Wallace Broecker of Columbia University and George Denton of the Univeristy of Maine.

LITTLE ICE AGE SPURS MONGOL INVASION

David Putnam David Putnam takes samples to analyze wood and a climate of fertility in the Chinese desert.
David Putnam takes samples to analyze wood and a climate of fertility in the Chinese desert. (courtesy of David Putnam)

by Anna Bisaro
Oct 28, 2013

In a period of less than 100 years, the Mongol Empire spread across Eurasia and encompassed the greatest contiguous land empire in history under the great Khan dynasty.

Historians generally attribute rising power and domination to leadership, new inventions and military strategy. But, some climate scientists credit the Little Ice Age for the Mongol expansion and take a new look at the impact climate can deliver on the rise and fall of civilizations.

“Human societies are quite sensitive to climate change,” said David Putnam, whose multiple fields of glacial geology, anthropology and archeology professor at the University of Maine give him a unique perspective. He argues that the Little Ice Age started it all for the Mongols some 800 years ago.

TRIP TO THE DESERT’S PAST

While touring the desert of northern China, Putnam and his son Aaron, now a climate scientist at Columbia University, found sand dunes once clearly deposited by water. But there is no water in sight now and hasn’t been for centuries. Yet they also found mud cracks and mollusk burrows. The father and son partners also stumbled upon wood samples – an odd occurrence for the middle of the desert. 

Anna Bisaro/MEDILL David Putnam shows how climate change impacts culture at Comer Conference in October.
Anna Bisaro/MEDILL
David Putnam shows how climate change impacts culture at Comer Conference in October.

More curious about when the trees germinated than when they died, the Putnams took samples of the wood to be dated back in the U.S. At what time did the climate of that region allow for such growth? 

The trip to the desert actually began as a trip to the Tarim Basin in northwest China where father and son were tracking when glaciers receded from that area. The pair had wanted to collect beryllium-10 samples from boulders in moraines. These samples could be processed back in the states and used to determine at what time glaciers had last covered those moraines. Beryllium-10 is an isotope that acts like carbon-14, except that it is created when  cosmic rays strike the atmosphere, releasing showers of secondary particles that strike the rock and then start to generate the isotope. Beryllium-10 collects once ice frees the rock, a way of clocking when the glaciers of the last ice age lumbered north. 

The boulders where they tried to collect samples had been eroded by sand storms and political disputes in the region made working there difficult, though. The team decided to give up on the field mission and travel south to the desert instead. 

THE LITTLE ICE AGE

The Little Ice Age was the last period of extreme cooling prior to the climatic conditions we know today. There is some dispute among scientists as to when the Little Ice Age began – somewhere between 1100 and 1300 A.D. – but it is more widely believed to have ended by 1850 A.D. Putnam supports the earlier start, related to the Mongol expansion, while Joerg Schaefer of Columbia University offers findings to support the later onset. 

“The Little Ice Age is notoriously hard to date,” Schaefer said in a presentation at the Comer Abrupt Climate Change Conference in October. Scientists can use “historical records, in the areas where you have them, but apart from that, moraines and other Little Ice Age features are hard to date,” he said.

A famine that spread death and crisis across Europe is widely recorded in historical records of the early 1300s and linked to the start of the Little Ice Age.

The isotope beryllium-10, Schaefer argues, has helped in the dating process. The isotope can’t help date when rock is exposed to air, meaning any ice has retreated. But it is still difficult for scientists to determine exactly when the period ended. 

But Schaefer is more confident about why glaciers started retreating between 1850 and 1900: the introduction of more carbon dioxide in the atmosphere due of industrialization. Levels of CO2, a greenhouse gas released with fossil fuel emissions, is linked to rising temperatures on Earth.     

Whether the Little Ice Age was a global phenomenon is still hard to determine. Schaefer’s fieldwork suggests that while the northern and southern hemispheres appear to have responded somewhat differently, glacial retreat occurred in New Zealand, Patagonia and the Swiss Alps all around the same time. The Tropics appear to show a pattern in sync with the northern hemisphere, but more research needs to be done to confirm those findings, Schaefer said. 

Schaefer said wants to expand his research on the Little Ice Age and explore how the advancement of glaciers starting in the 14th century affected various cultures. He said he wants to compare his climate change findings with historical accounts of famine and societal struggle to see if there is any link. Climate change, Schaefer said, has always affected humans. 

THE RISE OF THE MONGOL EMPIRE

Putnam talked at the Climate Conference about the need to factor climate into the narratives of social and political change. Owen Lattimore, an American scholar of China and central Asia, hypothesized that changes in climate could account for the spread of nomadic cultures, for instance. Lattimore met resistance and his ideas were rejected by the academic world at the time. 

“People like the idea of a military innovation, a great man or other reasons,” Putnam said. “They didn’t go for this.” 

Putnam admitted during his conference talk and in an interview that many other factors contributed to the rise of the Mongol Empire. Genghis Khan, the man that unified the Mongols and led the first conquests in the 13th century, was a powerful leader, in Putnam’s eyes. 

With the rise of the Mongol Empire starting in 1206, the earth, as many scientists now believe, was experiencing a period of cooling before carbon dioxide levels began to bring global temperatures up to where they are today.  CO2 emissions, related to human use of fossil fuels, have risen steadily with the start of Industrial Revolution.

That cooling period, according to Putnam, lowered the snow line in the mountains of Asia and created a colder and wetter climate. The Mongols were oasis farmers and herders of livestock. Their crop production depended completely on irrigation systems and the change to shorter and colder growing seasons did not bode well for them. 

But, the wetter climate produced more grass where livestock could graze, particularly the Mongol’s prized horses, Putnam said. So while farming suffered, the livestock thrived, giving the Mongols a perfect storm for expanding the empire. 

Putnam argues, “The bottom line: if they didn’t’ have fuel for horses, they couldn’t go” colonize anywhere else.

DON’T BE FOOLED BY STABLE GLOBAL TEMPS – THE WORLD IS GETTING WARMER

MEDILL Oceans are temporarily absorbing heat and masking global warming. But climate change hasn't halted.
MEDILL
Oceans are temporarily absorbing heat and masking global warming. But climate change hasn’t halted.

by Monika Wnuk
Oct 23, 2013

Climate change critics are pointing to a 15-year period of stable global temperatures to suggest that global warming has stopped.

Global temperatures showed a continuous rise since 1975 before the respite set in. But climate change hasn’t halted. At the Comer Conference on abrupt climate change this month, scientists countered that oceans are temporarily absorbing heat and masking global warming. They showed how patterns from the last 200 years predict future temperature rise.

The temperature rise, forced by human use of fossil fuels, is linked to increasingly extreme weather, drought and sea level rise that threatens coastal communities. It’s the rising oceans that are providing respite from rising global temperatures, scientists said.

Scientists have mapped how natural cycles in global ocean circulation play an important role in transporting and storing heat, including the extra energy arising from the burning of fossil fuels that release carbon dioxide. The greenhouse gas gathers in the atmosphere with every bit of fossil fuel we burn.

Scientists have measured sea surface temperatures as far back as the mid-1800s. Sean Birkel, a climate modeler at the Climate Change Institute at the University of Maine, said variability in ocean surface temperatures plays a role in the temperature of Earth’s surface today.

“Since the mid-1990s, North Atlantic surface temperatures have registered in the warm phase of known natural variability. But it is important to note that this pattern of oscillating sea-surface temperature has an upward trend,” likely due to increasing CO2 levels in the atmosphere, he said at the conference. CO2, a greenhouse gas that holds heat in the atmosphere, is increasing every year with the use of fossil fuels.

As global warming and ocean acidification continue, the world’s oceans may start to absorb less CO2, which would mean even more of this greenhouse gas would accumulate in the atmosphere. Absorbed carbon dioxide could also come back into the atmosphere if it is part of an ocean warming cycle like El Niño or an ocean cooling cycle like La Niña.

Wallace Broecker/ COLUMBIA UNIVERSITY The global ocean circulatory system plays an important role in transporting and storing heat energy, including the extra energy arising from carbon dioxide emissions from fossil fuels. In the North Atlantic, surface water warms near the equator, and then loses heat as it travels north to the subpolar regions. In the far north near Iceland, the water cools and becomes dense, and then sinks to the ocean bottom where it treks towards Antarctica and eventually upwells to the surface. Wallace Broecker of Columbia University identified this circulatory system. Click graphic to enlarge.
Wallace Broecker/ COLUMBIA UNIVERSITY
The global ocean circulatory system plays an important role in transporting and storing heat energy, including the extra energy arising from carbon dioxide emissions from fossil fuels. In the North Atlantic, surface water warms near the equator, and then loses heat as it travels north to the subpolar regions. In the far north near Iceland, the water cools and becomes dense, and then sinks to the ocean bottom where it treks towards Antarctica and eventually upwells to the surface. Wallace Broecker of Columbia University identified this circulatory system. Click graphic to enlarge.

“Where we’re going, it doesn’t [matter] if you put the heat in the ocean first or in the atmosphere first. Eventually, they both get warm and we wind up in the same place,” said Richard Alley, a geoscientist at Pennsylvania State University.

“The world is getting warmer, with very high confidence. Someone who doesn’t wish to confront this can always shut up during the new record and then yell that global warming stopped again,” said Alley.

And that warming is anything but short term, scientists said.

“Half of the radiative forcing from each gigaton of CO2 you emit, stays in the atmophere for at least a thousand years,” said Raymond Pierrehumbert, professor of geophysical sciences at the University of Chicago.

Pierrehumbert’s research confirmed a consensus among climate scientists that regardless of natural variations in ocean circulation and other factors that may stall the global temperature record, CO2 emissions are central to a warming climate. Alley nodded to this conclusion.

The 2013 Intergovernmental Panel on Climate Change draft summary for policymakers projects a likely 2 degree Celsius (more than 3.5 degrees Fahrenheit) increase in global temperatures resulting from the doubling of CO2 over the next 70 years.

The Comer Conference on Abrupt Climate Change draws top scientists to the Comer Foundation retreat in Southwestern Wisconsin each year.


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