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.”

How cold hearts and ice ages kindled the science of warming

Svante Arrhenius, who won the Nobel Prize for chemistry, and also was the first to show that while water plays the largest role in the greenhouse effect, the smaller but forcing effect from CO2 can be important. Image via Wikimedia Commons, PD-US

In 1896, Swedish scientist Svante Arrhenius took off into the atmosphere. Or at least into an immense calculation about the atmosphere that might distract him from having divorced his wife Sofia, who had taken custody of their baby son Olof. He looked to the skies to settle a key argument: How can landscapes around the world show evidence of ice scraping over it?

At the time, the idea of an ice age was controversial, and the world’s great minds struggled to explain the mile-thick sheets clues suggested had existed. For months Svante laboured by hand to calculate how tiny reductions in a gas called carbon dioxide – CO2 – could team up with water vapour to cool down the world. He didn’t produce an immediate answer to the riddle of the ice age, and he may or may not have escaped the woes of his personal life. But Svante Arrhenius did lay a foundation that climate science still rests upon today.

The tools that Svante used had recently been forged in the furnace of scientific progress that was the 19^th century. Until then, even an effect as seemingly basic as heat had been poorly understood. Only slowly had the idea that it was a kind of fluid or gas been replaced by the modern understanding that it’s a flow of energy. In the 1820s French mathematician Joseph Fourier helped drive that shift. He also mused on why, when the Sun heats the Earth, doesn’t the Earth get as hot as the Sun?

Evidence rethink puts CO2 and ancient warming back in sync

A thin layer of ice from an area of the Antarctic where ancient ice records are collected, in polarized light that reveals ice crystals. Rethinking how ice crystal formation affects ancient data collection is helping to solve an outstanding climate puzzle. © Frédéric Parrenin

A different way to dig up links between past levels of CO2 in the air and temperatures could solve a troubling question over the historical climate. Previously, data collected from long cylinders drilled from Antarctica’s ice sheet seemed to show temperatures rising hundreds of years before CO2 levels did. If ancient warming came before a CO2 rise, then the greenhouse gas seemingly couldn’t have caused the warming. Climate skeptics have used this to argue  that the CO2 we produce today isn’t causing global warming.

Now, Frédéric Parrenin at the French National Centre for Scientific Research in Grenoble and his teammates have used a different method on these cylindrical ice cores. They say that their approach shows CO2 and temperature rises happened together during the last ‘deglaciation’, when ice sheets retreated during an abrupt warming period 20,000-10,000 years ago. “This makes it possible that CO2 was actually a cause of warming corresponding to the last deglaciation,” Frédéric told me.

Scientists have been using Antarctic ice cores, and bubbles of air from the time the ice formed trapped inside, to study climate history for over 30 years. The time capsule-like bubbles show what chemicals were in the air. Meanwhile, the amounts of different forms, known as isotopes, of elements like hydrogen, carbon and oxygen in the ice reveals the temperature it formed at. And finally, scientists figure out how old the ice and bubbles are from how deep they are in the core – and that’s where Frédéric found problems.

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.”

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.

Warming weakens deep freeze on Arctic islands

Pictures from William D'Andrea's August 2012 expedition to Svalbard. There are 24 slides in this series - apologies for the poor formatting. Credit: The Earth Institute/Columbia University

Normally 6°C wouldn’t be very warm – but in the Norwegian islands of Svalbard it’s a sultry modern summer, unlike anything seen for at least 1,800 years. That’s what sediments taken from an Arctic lake have told William D’Andrea from Columbia University in New York and a US team. It’s even warmer than a medieval warm period when parts of the northern half of the planet were as hot as, or hotter, than today. And while the record they’ve made reflects just this one site, it adds to the picture showing how unique today’s climate is. It’s also another step towards understanding how climate has changed through history, William told me.

Climate dynamics are extremely complex, and cooling in some locations can happen at the same time as warming in others, or increased precipitation in some places along with drought in other places,” he said. “These are the fingerprints we are trying to map and understand by generating such reconstructions.”

The fingerprints slowly become clearer as scientists collect more historical records, often as tubes of ice drilled from glaciers, or of mud and rock drilled from sea and lake beds. The tubes, or cores, cut through layers of mud or ice built up year after year. Scientists can then use fossils and chemicals to date and work out what conditions were like when they were laid down.

New models still give Arctic summer ice 30 years

A thin sheet of sea ice reflects the rising sun off the east coast of Greenland on Apr. 14, 2012, with thicker sea ice and icebergs in the background. On average, the most up to date climate models that accurately simulate recent Arctic ice melting predict a nearly ice-free September by 2035. Credit: NASA/Jefferson Beck

Predictions from a collection of the latest climate models on average say that ice will be nearly gone from the Arctic by the 2030s. But when you don’t include man-made – or ‘anthropogenic’ – CO2 emissions’ ‘forcing’ effect, those models show a much icier picture.  “This clearly shows that if you don’t consider anthropogenic forcing, the ice won’t decline that fast,” said Muyin Wang from the University of Washington. “It should be oscillating around a much higher level.”

These findings echo some that Muyin and her Seattle colleague James Overland, from the US National Oceanic and Atmospheric Administration (NOAA) Pacific Marine Environmental Laboratory, made in 2009. Then, James and Muyin used climate models that formed the basis for the Intergovernmental Panel on Climate Change’s fourth assessment report, which was published in 2007. “Because of this report’s success a lot more modelling groups around the world started doing simulations,” Muyin told me. Scientists are now bringing their improved old models together with new ones in a project to compare them. Having found the old models bad at reproducing measured shrinkage of Arctic ice at the end of the 20^th century, James and Muyin wanted to see if the new and improved ones could do any better.

It’s important to be able to reproduce real data to be confident in models’ predictions, Muyin said. “If you are interviewing someone for a job, you look at their resumé, to see if they did a good job in the past,” she explained. “Then you know that they can do the job going forward. It’s a similar idea here, if models can simulate the past climate, then they’re the models we want to use in the projection.”

In a paper published in the scientific journal Geophysical Research Letters on Tuesday, they started from 32 different models, and compared them with satellite data on sea ice coverage. Overall, their resumés were slightly better than the older models: For the period from 1981-2005, the average of all these models was near the ice coverage actually seen, whereas the older models had overestimated the values.  But the highest and lowest estimates in both groups were still very similar.

Finding nature’s part in Arctic ice loss puts spotlight on human role

University of Reading's Jonny Day talks about his studies into what's contributed to Arctic ice loss

The area of the Arctic covered by ice is set to reach a record low this year* – and much of the ongoing decline is down to man-made global warming. That’s what recent research into the role of three potential natural causes of change in ice coverage done by Jonny Day from the University of Reading, UK, and his colleagues suggests. In a paper published online in scientific journal Environmental Research Letters last month, they studied these three existing sea and wind movement patterns in five different climate models. They found that one in particular, the Atlantic multi-decadal oscillation (AMO), could be responsible for between one-twentieth and three-tenths of the decline in sea ice since the 1970s. “Our work suggests that the AMO has contributed to getting us to this low sea ice state, but does not tell the whole story,” Jonny told Simple Climate. “It is still likely that man-made global warming is the major contributor to the dramatic decline in sea ice.”

Arctic sea ice loss has surprised researchers, as it’s faster than predicted by leading climate models gathered together by the UN Intergovernmental Panel on Climate Change (IPCC). That made Jonny and his co-workers from the Yokohama Institute for Earth Sciences and University of Tokyo in Japan want to look at why this was. In particular, they wanted to see how much might be down to hard-to-predict ‘internal’ climate patterns, rather than problems with measurements of the ice or models. “The large mismatch between climate model projections of sea ice and observations in the last IPCC report was concerning,” Jonny said “My colleagues and I thought that internal or ‘natural’ climate variability may play a role.”

The possible sources of that natural variability include the Arctic Oscillation (AO), which varies between stronger and weaker winds circulating the Arctic. The other two sources come from the ocean, where the AMO is a long-term cycle of temperature change. The final source, the Atlantic meridional overturning circulation (AMOC), is a large-scale ocean flow pattern that carries warm upper waters north and returns cold, deep water south. But a limited set of measurements available for the AMO and AMOC poses researchers a problem. “The oceanic causes of variability we discuss are not well observed, making such analysis difficult,” Jonny said.