Arctic mission recovers record of surprising warmth

All cargo for the drilling operation on Lake El’gygytgyn in winter 2008/09 had to be transported to the lake from the nearest settlement, Pevek, located 360 km north across the frozen tundra with trucks supported by bulldozers. Credit: Pavel Minyuk

A warm climate with CO2 levels similar to today delayed ice sheets from forming over land in the Arctic until less than 2 million years ago. That’s the latest instalment in a climate history scientists are building using sediment from a lake created by a giant meteorite impact around 3.6 million years ago. The international team has found that 3-3.2 million years ago, summer temperatures in the region were about 8°C warmer than they are today.

Julie Brigham-Grette from the University of Massachusetts, Amherst, explained that other scientists have estimated CO2 levels in the Pliocene period from 5.3 to 2.6 million years ago. “Though the estimates are quite broad, most scientists suggest that 2-3 million years ago CO2 levels may have been similar to today,” she told me. “Our data are consistent with that – the world today could be headed toward a Pliocene-like world.” And as well as pointing to the warmer future, these findings could also help unpick climate puzzles from our past.

These insights are the prize Julie and her team-mates sought on an epic trek to North-East Russia’s frozen wilderness in 2009. She was chief scientist for the US side of the team, leading the expedition alongside Martin Melles and Pavel Minyuk, chief scientists for the German and Russian sides. Their goal lay at the bottom of Lake El’gygytgyn, or Lake E. A 13 km wide crater blasted by a meteorite up to a kilometre in diameter that filled with water, Lake E has slowly collected sediment ever since. It’s unusual because it largely escaped damage from the creep of ice sheets, meaning scientists can use its sediment to rebuild conditions further back in time.

And to get there, Julie, Martin and Pavel had to pave political, financial, logistical, and actual physical paths, Julie explained. “This lake sits in an area that has no roads,” she said. “It was an amazing logistical feat to gather the drillers and equipment and get there, without damaging the environment. It was the most difficult scientific project I’ve ever undertaken.”

The climate scientist whose world spun on through war

A young Milutin Milanković as a student in Vienna, where he became the first Serb to achieve a doctorate in technical sciences. Image via Wikimedia Commons, used under Creative Commons licence

On 6 April 1941, a world war left its mark on Milutin Milanković’s life and climate research for a second time. Nazi bombs destroyed the print works where his new book, summarising 30 years’ work, sat half-complete. As German-led forces occupied Serbia a month later, Milutin still had just one finished copy of his “Canon of Insolation and the Ice-Age Problem”.  In it, he brought together his general astronomical theory of climate, which would explain how Earth’s motion in space drives ice sheet advance and retreat over tens of thousands of years.

And when two German officers came to visit the University of Belgrade maths professor, he might have feared no-one else would ever see all his ideas in a single volume. But the officers were geology students, bringing greetings from Wolfgang Soergel at the University of Freiburg, who had previously published studies supporting Milutin’s calculations. Amid the drama unfolding around them, Milutin gave them his only copy to send to Freiburg for safe-keeping. But both Milutin and his work escaped to ultimately make strides forward in understanding what controls Earth’s temperatures.

Milutin fixed his focus on climate after joining the University of Belgrade in 1909, while reading a paper about the Sun’s heat on the Earth’s surface, whose starting equation was wrong. To study how climate could produce dramatic changes like ice ages courted controversy even then because it was unclear the puzzle could ever be solved. So little was known that when Svante Arrhenius correctly identified CO2 in the air as an important factor his findings were ruled out by flawed experiments.

Using heat from the Sun, the incoming solar radiation also known as insolation, Milutin looked at climate both on the Earth and other planets in our solar system. “A connection should be found between planets’ insolation and their atmosphere and surface temperatures,” he wrote. And thanks to the many different complex sciences such an astronomical climate theory combined, Milutin was the only one trying to make that link.

Alternate histories back unique modern warmth claims

Tree rings have a light-colored band, or earlywood, that forms in the spring and a dark-colored band, or latewood, that forms in the summer. The width of the band tells how much the tree grew during that period and therefore can be used as a proxy for the climate during that season. That approach has some uncertainties, but Martin Tingley and Peter Huybers have reduced their impact on telling if any year is the warmest. Credit: thaths via Flickr Creative Commons license

If you build a temperature record going back in time to judge modern warming against, how certain can you be of your answer? That’s a big question for scientists making such records from effects temperatures have had on the natural world. And figuring out if today’s heat is unique is too great a challenge for the methods scientists normally use to calculate uncertainty, according to Harvard University’s Martin Tingley.

But Martin and Peter Huybers have shown the precise chances that northern areas of the world are warmer than any time in rebuilt records reaching back to the year 1400. They have worked out that there’s less than one chance in 20 that 2005, 2007, 2010 and 2011’s northern summers weren’t the warmest in that time. They also find that summer 2010 has a 99% chance of being the warmest western Russia has seen. There have already been lots of claims made over the unusualness of recent warmth, Martin pointed out, but his and Peter’s are the most robust yet. “We put these estimates on a much sounder statistical footing,” he told me.

Saying one year’s summer is uniquely warm across a long period is difficult for subtle reasons that Martin explained through his height. “I’m a tall guy, 6 foot 4 inches,” he said. “I’ve never met you, but I’m going to bet I’m taller than you. What’s the intuition behind my bet? We have a sense of the distribution of heights. I’m aware I fall pretty far out on the tail, so the chances are if I meet an average person they don’t fall further out than I do. What if I’m in a room with 1,000 people I’ve never met before? Am I still likely to be the tallest in the room? Probably not.”

Temperature patterns produce perplexing Pliocene puzzle

Lafayette College’s Kira Lawrence and her teammates have used ocean bed sediment cores, like this one, to produce a 5 million year climate record. © Intergrated Ocean Drilling Program

US, UK and Hong Kong Researchers have produce a unique ‘movie’ of climate reaching back 5 million years, by bringing together data drilled from ocean beds. It reveals three important temperature patterns during the warm early part of the Pliocene period that they couldn’t recreate together in climate models using existing explanations. That’s important because scientists hope the Pliocene could help us know what the future of a warmer Earth might be like. And having uncovered another layer to the Pliocene puzzle, team member Kira Lawrence from Lafayette College in Easton, Pennsylvania, underlined the value of finding its solution.

“Our community of scientists think of the Pliocene as though it was about 3°C warmer than modern temperatures with CO2 concentration about where we are right now,” Kira told me. “But we haven’t recognised before that the pattern of temperature was a lot different. If that’s where we’re headed in the not too distant future, if the temperature and precipitation patterns change in that way, we should have some significant things to think about.”

The Pliocene period started 5.3 million years ago, during which primates made important evolutionary steps towards humanity. Since 2000, there has been a climate data explosion reaching back through this era. Around the world, international drilling expeditions have pierced ocean beds kilometres below sea level, reaching hundreds of metres into sediment to bring back ‘core’ samples. Tiny fossils within that rock and mud can tell scientists temperatures through history, which can give climate scientists real data to test their models against.

Climate change set to bring Western Europe more hurricanes

In January 2009 a cyclone called Klaus, which is shown here and boasted hurricane-force winds, hit France, Spain and Italy. Such conditions could become much more common in Europe by the end of the 21st century, according to Rein Haarsma and his KNMI team. Credit: H de C via Flickr Creative Commons license

Current once-in-a-century hurricane-force winds may become as much as 25 times as likely in parts of Western Europe at the end of the 21^st century. That’s what Rein Haarsma and a team from the Royal Netherlands Meteorological Institute (KNMI) have shown using one of the highest-resolution climate models around today. Their findings spring from a change in where hurricanes will develop that could also affect western North America, though more research is needed to study this. “The statement that the wind climate in Western Europe will not change significantly is questionable,” Rein told me. “Significant changes in wind climate will have consequences for agriculture – the increased winds are during the autumn – infrastructure and coastal defence.”

With Europe so far from the tropical regions where warmth and unstable atmosphere spawns hurricanes, it rarely sees them today. But when hurricane conditions do happen, like the ‘Great Storm’ in 1987, or Hurricane Floyd in 1993, they live long in the memory. The hurricane remnants that sometimes reach Western Europe usually bring a lot of rain, Rein noted, and only occasionally hurricane-force winds.

The warming Arctic is reducing ocean temperature differences that help create Europe’s traditional storms, meaning they pose less of a threat. But recently findings have shown that a warmer atmosphere raises hurricane risks. “Many model simulations suggest that the strength of hurricanes will increase due to climate change,” Rein explains. “The area where hurricanes develop appears to move poleward and the moisture content in a warmer atmosphere will increase. These factors might alter the possibility that these remnants of hurricanes are still strong enough to produce hurricane-force winds.”

Cave deposits reveal permafrost concern

University of Oxford’s Anton Vaks explores a cave, where he could find stalactites and stalagmites that reveal when the soil above was permafrost. Credit: University of Oxford

Stalagmite and stalactite deposits in Siberian and Mongolian caves have revealed the most accurate permafrost history yet, suggesting that a global 1.5°C temperature rise could trigger a widespread thaw. “The finding shows how vulnerable the permafrost is,” said Anton Vaks from the University of Oxford. “Russian gas facilities in north-western Siberia are located close to the boundary of the continuous permafrost and rely on it as hard ground. Thawing of the permafrost may cause damage both to Russia, as well as its gas trade partners, like the European Union. The melting permafrost may also release part of the organic carbon currently trapped in it as greenhouse gases, CO2 and methane, enhancing global warming.”

Anton first used cave deposits’ power to study climate history during his PhD to build a 350,000 year record for the northern margin of the Saharan-Arabian Desert. “Stalagmites and stalactites grow only when rain or snowmelt water seep into the cave through the ceiling,” Anton explained. “Therefore each layer of growth of stalagmites and stalactites records a humid event in the desert.” He realised that these deposits’ ability to track water flow could equally measure melting of previously permanently frozen soil known as permafrost. “Cave deposits cannot grow when the rock above the cave is frozen,” Anton said. “Thus, each growth layer in a stalagmite forms during warm periods, whereas growth breaks represent cold periods with permafrost. Past periods that were warmer than now are especially important, because they can show what may happen to the permafrost in the future warmer world.”

Altered pressure patterns bring Eurasia intense iciness

People enjoying the winter sun – typical of an anticyclone, or high pressure, weather system – on the frozen Landwehrkanal in Berlin-Kreuzberg, during February 2012, when Berlin set a record for extreme cold. Credit: onnola via Flickr

Extreme cold that has left Europe and Asia snowbound, shivering and asking, “What global warming?” in recent years has been driven by intensified high pressure patterns. That’s according to Xiangdong Zhang at the University of Alaska, Fairbanks, who has been studying how such cold snaps fit in with increasing average temperatures worldwide. “Extreme cold weather events can occur in a particular region and short time period in a warming global climate,” Xiangdong pointed out. “This may highly disrupt daily life, damage infrastructure, and impact ecosystems and environment.”

Xiangdong started thinking about extreme cold events because climate studies usually use monthly temperature averages, which overlook them. “This cannot reflect extreme cold temperatures occurring on a particular day because daily temperature changes are filtered out by the average,” he told me. “For example, the monthly averaged temperature in February 2012 was -4.9°C in Berlin. But the coldest daily temperature in the same month at the same location was -19.6°C. We don’t directly feel the monthly average temperature in our daily life. What we feel is day-by-day changes in temperature. But if we can understand mechanisms of daily temperature changes, we would be able to better understand why there is colder or warmer monthly average temperature.”

Outside of tropical areas weather patterns known as cyclones, which would be called low pressure on a weather forecast, and anticyclones, or high pressure, drive those daily temperature changes. Xiangdong had previously been part of a team that adapted an automated cyclone spotting method to look at each one separately. Last year, with researchers from Nanjing University of Information Science and Technology in China, he used that method to study records from across Europe and Asia between 1978-2012. They brought together sea level pressure data recorded every six hours by a global collection network, and daily minimum air temperatures recorded at 1337 meteorological stations.

2012’s record events put climate in mind

Extent of surface melt over Greenland’s ice sheet on July 8 (left) and July 12 (right). Measurements from three satellites showed that on July 8, about 40 percent of the ice sheet had undergone thawing at or near the surface. In just a few days, the melting had dramatically accelerated and an estimated 97 percent of the ice sheet surface had thawed by July 12. In the image, the areas classified as “probable melt” (light pink) correspond to those sites where at least one satellite detected surface melting. The areas classified as “melt” (dark pink) correspond to sites where two or three satellites detected surface melting. The satellites are measuring different physical properties at different scales and are passing over Greenland at different times. As a whole, they provide a picture of an extreme melt event about which scientists are very confident. Credit: Nicolo E. DiGirolamo, SSAI/NASA GSFC, and Jesse Allen, NASA Earth Observatory

This has been another year of striking climate events and records – but they seem to be happening so much more often today that their effect on me has weakened. That’s pretty cold-hearted, I admit. ‘Extreme weather’ is having terrible effects on peoples’ lives all around the world. But the truth is that we can only handle so many problems before becoming too numbed and overwhelmed to act. And last year, Stefan Rahmstorf and coworkers at the Potsdam Institute for Climate Impact Research showed temperature records are much more likely today than in a stable climate. “I don’t think many people appreciate how much the odds for such extremes have increased due to global warming,” he told me at the time. “I certainly didn’t until we had performed this study.” So it’s hardly surprising if we begin to get complacent when records are flowing thick and fast. But when I actually faced up to what’s happened in the climate this year, it was intriguing how well you could see global warming’s fingerprint.

Warming’s most dramatic effects have long been obvious in the Arctic, and 2012 was no different. Images from three satellites showed that almost Greenland’s entire ice sheet surface was temporarily melted by July 12. That’s the largest area in over 30 years of satellite observations. Then, on September 16, sea ice in the Arctic reached a record annual minimum area of 1.32 million square miles, approximately half the size of the average annual minimum for 1979 to 2000. Just two weeks later, Antarctic sea ice covered its highest area on record at the peak of winter, at 7.49 million square miles. In case you think that’s a natural balance that shows the planet isn’t warming, it’s worth noticing the scale of the changes. The Antarctic record is 193,000 square miles higher than its average maximum area for the last 30 years. That’s much less than the 1.32 million square miles the Arctic lost compared to its long-term average.

Space agencies pinpoint polar ice sheet damage

The midnight sun casts a golden glow on an iceberg and its reflection in Disko Bay, Greenland, where ice sheet mass loss was five times higher in 2011 than it was in 1992. Much of Greenland’s annual mass loss occurs through ‘calving’ of icebergs such as this. Credit: Ian Joughin.

47 scientists from 26 key laboratories across the world. 10 satellite missions flown over a period of 20 years, whose data adds up to 51 years’ worth. This giant effort looks to have squashed stubborn uncertainty surrounding one key climate question: How quickly are ice sheets resting on land masses at the North and South Poles shrinking? The international team has now found that Greenland’s mass loss is five times as fast as it was in 1992. Overall loss rates in Antarctica are roughly constant in this period, though the east of the continent is actually gaining ice. Over the past 20 years, the polar ice sheets have added 11 mm to sea level rise across the world, one-fifth of the total rise seen in that time.

“Our new estimates are the most reliable to date and they provide the clearest evidence yet of polar ice sheet losses,” said Andrew Shepherd from the University of Leeds, UK, co-leader of the project. “They also end 20 years of uncertainty concerning changes in the mass of the Antarctic and Greenland ice sheets and they’re intended to become the benchmark dataset for climate scientists to use from now on.”

Until the early 1990s, climate researchers expected that mass lost by ice sheets in Greenland as the planet warmed would be balanced by that gained by Antarctica. But measurements showed that both melting and ‘calving’ of icebergs could be speeding up at both poles. This meant the UN’s Intergovernmental Panel on Climate Change (IPCC) couldn’t put an upper limit on what ice sheets might add to sea levels in its last major report on global warming in 2007. And the overall picture has been confused, as efforts to measure whether ice sheets are shrinking or growing have given differing results. Since 1998, there have been 29 different estimates of changes in ice sheet mass. “Taken all of the past studies together, the recent global sea level contribution due to Antarctica and Greenland may have been anywhere between a 2 mm per year rise and a 0.4 mm per year fall,” Andrew told a press conference yesterday. At a workshop in 2010, the IPCC said it was concerned that no further progress would be made by its next report, due in 2014.

Focus on uncertain climate cliff-edge invites disaster

Scott Barrett from the Earth Institute at Columbia University says existing climate negotiation strategies have failed. Credit: Earth Institute

Countries trying to agree climate deals based on avoiding dangerous ‘cliff-edge’ limits will not work. That’s according to Scott Barrett and Astrid Dannenberg from the Earth Institute at Columbia University in New York, who’ve modelled the negotiations in a simple game. They found that uncertainty about the threshold at which their actions hurt everyone made players ignore the deals they made almost every time.  “We found that if the threshold for catastrophic climate change were certain, Mother Nature would essentially enforce an agreement to avoid the threshold,” Scott told me. “The fear of falling off of a cliff disciplined everyone to do what was needed, collectively, to avoid falling off. When the threshold was uncertain, this effect collapsed. Uncertainty about the impact made no difference at all.” And with science unable to be completely certain where the limit is, Scott and Astrid think that how climate deals are put together must change.

Scott got the idea that knowing where the cliff-edge is important because of the two different ways climate can affect the world. The first is ‘gradual’, where small emissions add a little to greenhouse gas levels in the air and raise global temperatures slightly. The second is ‘abrupt and catastrophic’, where small emissions push part of the world’s climate over a limit into a new state. “The second kinds of change are more important to welfare,” he said. “The effects tend to be uniformly negative – think of 5 meters of sea level rise, or the possibility of warm temperatures releasing methane stored in tundra, causing a rapid rise in temperature. The effects also occur quickly, meaning that adaptation will be harder. For both reasons it seemed to me that countries would have a stronger reason to prevent this kind of climate change than the gradual kind.”