from the October 11, 2009 edition

Moscow – Mariners have dreamed for centuries of finding a commercially viable shortcut between Europe and Asia across the top of the world. Many have died trying, but none succeeded until late September, when two German freighters slipped quietly into Rotterdam Harbor after completing a historic month-long journey from Vladivostok, in Russia’s Pacific far east, through the once-impassable Arctic route.

The Bremen-based company that operates the two specially reinforced cargo ships, the Beluga Fraternity and the Beluga Foresight, that made the journey said that taking the new route saved 10 days and $300,000 per ship over the usual 11,000 nautical-mile voyage through the Indian Ocean, the Suez Canal, and the Mediterranean in order to reach the North Atlantic.

“We are all very proud and delighted to be the first Western shipping company which has successfully transited the legendary Northeast Passage,” the Beluga company said in a statement. It plans to begin using the route on a regular basis.

The bad news, scientists say, is that the feat only became possible because the Arctic icecap is retreating at an alarming rate, leaving vast swaths of open water where solid pack ice recently frustrated attempts at even summer navigation. This year saw the third-lowest amount of Arctic sea ice on record, after the record set in 2007.

“Our studies over the past 30 years show the rate of retreat by sea ice is growing very rapidly,” says Igor Mokhov, director of the official Institute of Atmospheric Physics in Moscow. “If these tendencies continue, the navigable period by the late 21st century might grow to several months” from the current six-to-eight week window the Northeast Passage offers each summer, he says.

‘Huge economic opportunity for Russia’

At least one climate-change skeptic, writing in Britain’s Daily Telegraph, has dismissed the Beluga expedition as a “warmist publicity stunt,” staged to take advantage of a statistical blip in Arctic ice formation. Other critics say that the German ships didn’t really do anything new: Large sections of the northern route had been routinely traversed by Soviet shipping in the past to service remote Arctic settlements, before falling into disuse after the collapse of the USSR. Moreover, the Beluga ships had to be accompanied by a nuclear-powered Russian icebreaker for part of their journey, though they apparently did not require any assistance.

Most Russian Arctic experts say that climate change appears undeniable, but some caution that its impact remains unpredictable.

“This phenomenon is complicated, and we can’t guarantee that the northern passage will become ice-free,” says Viktor Dmitriyev, an expert with the official Institute of the Arctic and Antarctic Regions in St. Petersburg. “But it looks very possible. And if it happens it will be a huge economic opportunity for Russia. It can mean a whole new impulse for northern development.”

A study by the US Geological Survey several years ago estimated that as much as 25 percent of the world’s remaining untapped oil deposits and 30 percent of its gas lie under the fast-receding Arctic icecap. Other resources, such as fisheries, could open up as well.

That prospect has triggered a flurry of activity at Russia’s Ministry of Transport, which regulates the country’s sea lanes. The ministry’s head of sea and river transport, Alexander Davydenko, says a new department to administer the northern sea route is being created to build infrastructure and oversee tariffs. He says the ministry is also building at least one massive new nuclear icebreaker to supplement its current fleet of six, and is establishing a new Arctic air-sea rescue unit.

“Scientists tell us that we face warming, and that the boundaries of the Arctic ice are receding,” says Mr. Davydenko. “Therefore we are taking a variety of measures … to safeguard the interests of the Russian Federation in the Arctic region.”

Greenpeace: No reason to rejoice over Arctic melting

Shipping experts say that, at least for the moment, bureaucratic obstacles remain more daunting than the threat of pack ice. The Beluga expedition was held up for nearly a month in Vladivostok while it obtained necessary permits and endured close scrutiny by the Federal Security Service. The need to be accompanied by an icebreaker is another factor that will increase costs and limit the route’s attractiveness in the near term.

“There are a lot of issues, including political ones, that remain to be worked out,” says Mr. Dmitriyev.

But if the ice disappears as predicted, the Russians say their route is the one shipping companies will likely choose. While the better-known Northwest Passage, which runs across the top of Canada, is more southerly, Russian experts say it is plagued by geographical and geopolitical problems that may prove insoluble. It runs through a maze of Arctic islands with narrow and shallow channels, they say. Moreover, Canadian sovereignty in the area is challenged by the US, which has lately begun waking up to Arctic possibilities. The Northeast Passage is Russian territory and clear water from Vladivostok to Norway.

“Look at a map, and you’ll see the Canadian route is difficult to navigate because of all the islands and fiords, while the Russian passage is wide open,” says Alexei Bezborodov, a shipping expert with Infranews, a Russian transport journal.

Amid economic optimism, Russian environmentalists are aghast.

“There is no possibility, in Russia or any other country, to develop this route in an ecologically safe mode,” says Vladimir Chuprov, head of Greenpeace-Russia’s energy program. “If this passage is opening up, it creates not only huge risks but possible disasters. That’s no reason to rejoice, but to tear our hair [out] in despair.”

David L. Chandler, MIT News Offic

Heavier rainstorms lie in our future. That’s the clear conclusion of a new MIT and Caltech study on the impact that global climate change will have on precipitation patterns.

But the increase in extreme downpours is not uniformly spread around the world, the analysis shows. While the pattern is clear and consistent outside of the tropics, climate models give conflicting results within the tropics and more research will be needed to determine the likely outcomes in tropical regions.

Overall, previous studies have shown that average annual precipitation will increase in both the deep tropics and in temperate zones, but will decrease in the subtropics. However, it’s important to know how the magnitude of extreme precipitation events will be affected, as these heavy downpours can lead to increased flooding and soil erosion.

It is the magnitude of these extreme events that was the subject of this new research, which will appear online in the Proceedings of the National Academy of Sciences during the week of Aug. 17. The report was written by Paul O’Gorman, assistant professor in the Department of Earth, Atmospheric and Planetary Sciences at MIT, and Tapio Schneider, professor of environmental science and engineering at Caltech.

Model simulations used in the study suggest that precipitation in extreme events will go up by about 5 to 6 percent for every one degree Celsius increase in temperature. Separate projections published earlier this year by MIT’s Joint Program on the Science and Policy of Global Change indicate that without rapid and massive policy changes, there is a median probability of global surface warming of 5.2 degrees Celsius by 2100, with a 90 percent probability range of 3.5 to 7.4 degrees.

Specialists in the field called the new report by O’Gorman and Schneider a significant advance. Richard Allan, a senior research fellow at the Environmental Systems Science Centre at Reading University in Britain, says, “O’Gorman’s analysis is an important step in understanding the physical basis for future increases in the most intense rainfall projected by climate models.” He adds, however, that “more work is required in reconciling these simulations with observed changes in extreme rainfall events.”

The basic underlying reason for the projected increase in precipitation is that warmer air can hold more water vapor. So as the climate heats up, “there will be more vapor in the atmosphere, which will lead to an increase in precipitation extremes,” O’Gorman says.

However, contrary to what might be expected, precipitation extremes do not increase at the same rate as the moisture capacity of the atmosphere. The extremes do go up, but not by as much as the total water vapor, he says. That is because water condenses out as rising air cools, but the rate of cooling for the rising air is less in a warmer climate, and this moderates the increase in precipitation, he says.

The reason the climate models are less consistent about what will happen to precipitation extremes in the tropics, O’Gorman explains, is that typical weather systems there fall below the size limitations of the models. While high and low pressure areas in temperate zones may span 1,000 kilometers, typical storm circulations in the tropics are too small for models to account for directly. To address that problem, O’Gorman and others are trying to run much smaller-scale, higher-resolution models for tropical areas.

The Antarctic Peninsula juts into the Southern Ocean, reaching farther north than any other part of the continent. The southernmost reach of global warming was believed to be limited to this narrow strip of land, while the rest of the continent was presumed to be cooling or stable.

Not so, according to a new analysis involving NASA data. In fact, the study has confirmed a trend suspected by some climate scientists.

“Everyone knows it has been warming on the Antarctic Peninsula, where there are lots of weather stations collecting data,” said Eric Steig, a climate researcher at the University of Washington in Seattle, and lead author of the study. “Our analysis told us that it is also warming in West Antarctica.”

Figure at right: Red represents areas where temperatures have increased the most during the last 50 years, particularly in West Antarctica, while dark blue represents areas with a lesser degree of warming. Temperature changes are measured in degrees Celsius. Credit: NASA/GSFC Scientific Visualization Studio.

The finding is the result of a novel combination of historical temperature data from ground-based weather stations and more recent data from satellites. Steig and colleagues used data from each record to fill in gaps in the other and to reconstruct a 50-year history of surface temperatures across Antarctica.

Over the years, climate research in northern latitudes led researchers to believe that the Arctic is where impacts of global climate change would be seen first. Less certain is how climate is affecting Antarctica where inland temperatures are known to plunge to -112°F, and ground-based weather stations have been sparse.

It’s this sparse data collection — from ground-stations on the Antarctic Peninsula and previous reports that much of East Antarctica has experienced cooling since 1978 — that led the International Panel on Climate Change to conclude in its most recent report that Antarctica is the one continent where we have failed to detect human-caused temperature changes.

With funding from the National Science Foundation’s Office of Polar Programs, Steig and colleagues set out to reconstruct Antarctica’s recent past. Ground-based stations have recorded temperatures since 1957, but most of those readings come from the peninsula and areas on the edges of the continent. But at the same time, scientists such as study co-author Joey Comiso of NASA’s Goddard Space Flight Center in Greenbelt, Md., have been gathering measurements from a series of Advanced Very High Resolution Radiometer (AVHRR) instruments deployed on satellites since 1981.

To construct the new 50-year temperature record, the team applied a statistical technique to estimate temperatures missing from ground-based observations. They calculated the relationship between overlapping satellite and ground-station measurements over the past 26 years. Next, they applied that correlation to ground measurements from 1957 to 1981 and calculated what the satellites would have observed.

The new analysis shows that Antarctic surface temperatures increased an average of 0.22°F (0.12°C) per decade between 1957 and 2006. That’s a rise of more than 1°F (0.5°C) in the last half century. West Antarctica warmed at a higher rate, rising 0.31°F (0.17°C) per decade. The results, published Jan. 22 in Nature, confirm earlier findings based on limited weather station data and ice cores.

While some areas of East Antarctica have been cooling in recent decades, the longer 50-year trend depicts that, on average, temperatures are rising across the continent.

Figure at right:The northern section of the Larsen B ice shelf, a large floating ice mass on the eastern side of the Antarctic Peninsula, shattered and separated from the continent on March 5, 2002, and represents a major impact that climate warming can have on the region. Credit: NASA Earth Observatory. > Larger image

West Antarctica is particularly vulnerable to climate changes because its ice sheet is grounded below sea level and surrounded by floating ice shelves. If the West Antarctic ice sheet completely melted, global sea level would rise by 16 to 20 feet (5 to 6 meters).

To identify causes of the warming, the team turned to Drew Shindell of NASA’s Goddard Institute for Space Studies in New York, who has used computer models to identify mechanisms driving Antarctica’s enigmatic temperature trends.

Previously, researchers focused on Antarctic ozone depletion, which influences large-scale atmospheric fluctuations around the continent — most notably, the Southern Annular Mode, which speeds up wind flow to isolate and cool the continent.

Shindell compared Steig’s temperature data with results from a computer model that can simulate the response of the atmospheric system to changes in land surface, ice cover, sea surface temperatures, and atmospheric composition. He found the ozone-influenced Southern Annular Mode is not necessarily the primary influence on Antarctic climate. Instead, it appears that smaller-scale, regional changes in wind circulation are bringing warmer air and more moisture-laden storms to West Antarctica.

“We still believe ozone depletion can increase wind speeds around Antarctica, further isolating the interior,” Shindell said. “But it’s clear now that it’s not such a dominant influence on temperature trends.”

Over the last several decades, large temperature increases in winter have been observed over Siberia and Alaska. Part of this effect has been associated with the prevailing west wind bringing in warmer air off the ocean. The increased west winds are related to lower sea level pressure at high latitudes, with greater sea level pressure in mid-latitudes.

Such a pressure variation is known as the “positive phase of the Northern Annular Mode” (NAM). (The negative phase is the reverse situation, higher pressure near the pole and lower pressure at mid-latitudes.) The NAM (and its North Atlantic relation, the North Atlantic Oscillation) represents the leading mode of variability of sea level pressure in the Northern Hemisphere.

As implied by the noted temperature variation, this positive phase was prevalent from the late 1970s through the 1990s. Recently the situation has been more mixed, but nevertheless, eight of the last 13 winters have still had a positive phase. Various explanations have been offered for why the positive phase has been predominant, including natural variability and greenhouse warming. Indeed, the majority of climate models suggest global warming will produce a more positive phase of the NAM during this century, although the models, and the modeling community, are not in complete agreement.

Also from the late 1970s through the 1990s, in the Southern Hemisphere the Antarctic ozone hole developed and deepened. This was caused by the release of chemicals into the atmosphere, primarily chlorine associated with CFCs. The Montreal Protocol and follow-up treaties have since succeeded in controlling the emission of the primary ozone-destroying gases, so the ozone hole is no longer growing deeper. Nevertheless, given the long residence time of chlorine in the atmosphere, the ozone hole is still with us.

These two phenomena would appear to be completely unrelated but a recent study suggests otherwise. Our modeling experiments have shown that the S.H. ozone hole appears to produce a more positive phase of the NAM. The process works like this: the ozone hole reduces the vertical stability of the S.H. troposphere, by making the air colder aloft (ozone normally absorbs radiation, and the ambient air is colder when ozone in the lower stratosphere is absent). The reduced atmospheric stability allows more storms — atmospheric waves — to develop. This wave energy propagates up into the S.H. stratosphere and intensifies the stratospheric circulation. The circulation change extends into the Northern Hemisphere, producing cooling at high northern latitudes. The N.H. cooling leads to stronger west winds that alter wave energy propagation in that hemisphere, further amplifying the effect. The result: a more positive NAM. In the model, the influence is substantial, accounting for significant portions of the observed trend.

Figure above: (Left) The modeled N.H. height/pressure pattern anomalies associated with the S.H. ozone hole. Results are shown for the lower stratosphere (100 mb), the mid-troposphere (500 mb) and the surface (sea level pressure). Lower height/pressure near the pole relative to the mid-latitudes is a sign of a more positive phase of the NAM. (Right)The same diagnostics but this time for a model experiment in which there is an ozone hole in the Northern Hemisphere as well. Under these circumstances, the reduced vertical stability in the N.H. helps generate increased wave energy that results in a very different stratospheric circulation and height/pressure response pattern.

As discussed in our paper, tropospheric and stratospheric observations, as well as the cotemporaneous nature of the two phenomena, are consistent with this interpretation. Nevertheless, there are numerous caveats. The observations are somewhat suspect, with the introduction of satellites having changed observing techniques. Various other factors likely influence the NAM, as discussed in the opening paragraph. Our own experiments show that the magnitude of the effect may very well vary with model physics. The concurrent trends may therefore still be coincidental.

However, to the extent that the relationship is as important as the modeling study suggests, it has various implications. Since the connecting link occurs in the stratosphere, it emphasizes the importance of accurate modeling of the stratosphere when attempting to predict future climate; this conclusion has been offered previously, but from different perspectives. It furthermore suggests that as chlorine and bromine in the stratosphere decrease during this century, due to their restricted emissions, the NAM may become less positive in the future; this would change the geographical pattern of warming relative to what has been observed. And it emphasizes once again that the planet we live on is interconnected; our actions in one locale or arena can well have unexpected consequences far removed from their source.

The main anthropogenic global warming culprit is carbon dioxide (CO₂), but human activity produces a host of other, shorter-lived pollutants that contribute to climate change, among them gases that react to form ozone smog and fine particles such as black carbon. Until recently, most of the attention paid to these short-lived pollutants focused on their threat to human health. But because these pollutants disappear from the atmosphere relatively quickly, global efforts to reduce their emissions can produce an immediate benefit and help avoid dangerous tipping points in the climate system over the next few decades.

Our new study offers additional insight into the climatic role of these pollutants. These findings come at a time when activity on domestic and international climate policy in general and on black carbon policy in particular is ramping up.

We calculated the overall warming effect of the transportation and power generation sectors, two of the main contributors to CO₂ emissions, for the U.S. and the world. Effective mitigation of global climate change requires action in these sectors for which technology change options exist or are being developed. We primarily used a global climate model developed at the NASA Goddard Institute for Space Studies that simulates the transport of pollutants in the atmosphere by winds and the chemical and physical reactions that transform the pollutants into smog and particles and eliminates them from the atmosphere. The model also calculates the warming or cooling effect of the different pollutants. The results are shown in Figure 1.

We found that transportation would be a particularly good sector to target for emissions controls because it emits a lot of black carbon (most notably through diesel exhaust) and ozone-producing gases in addition to CO₂. In contrast, the power generation sector emits little black carbon, but instead creates much sulfate particle pollution, which although bad for air quality and acid rain, cancels out the warming effect of the sector’s CO₂ emissions in the short-term.

We also considered a hypothetical example of switching the transportation sector to a zero-emissions or electric power source, such as in plug-in hybrid electric or pure electric technologies. The result was a hefty benefit for the climate. Such a switch would decrease the warming effect when looking just at CO₂. (Increased CO₂ emissions from the electricity generation sector would to some extent offset the decrease in emissions from vehicles.) But non-CO₂ pollutants provide an added benefit for the climate. The technology shift greatly reduces black carbon emissions. Furthermore, switching to electric power, generated predominantly with coal at present both in the U.S. and worldwide, increases emissions of cooling sulfate particles, further reducing global warming.

Of course, the power sector also needs to be cleaned up to address long-term climate damage from CO₂, as well as health problems from sulfate particles, ozone smog and other pollutants. Our results indicate that technology change options that target specific economic sectors may invoke decadal scale climate effects from the air pollutants that dominate the CO₂ effects. Assessment of the full impacts of technology and policy strategies designed to mitigate global climate change must consider the climate effects of ozone and fine aerosol particles.

Wednesday 12 August 2009 18.00 BST

Top: Aerial photograph of the Khumbu Glacier and the Everest Himalayan range
Bottom: Glacially eroded mountains in Jotunheimen in Norway. Photograph: David Lundbek Egholm (bottom) and Paula Bronstein/Getty Images

Scientists have solved the mystery of why the world’s highest mountains sit near the equator – colder climates are better at eroding peaks than had previously been realised.

Mountains are built by the collisions between continental plates that force land upwards. The fastest mountain growth is around 10mm a year in places such as New Zealand and parts of the Himalayas, but more commonly peaks grow at around 2-3mm per year.

In a study published today in Nature, David Egholm of Aarhus University in Denmark showed that mountain height depends more on ice and glacier coverage than tectonic forces. In colder climates, the snowline on mountains starts lower down, and erosion takes place at lower altitudes. At cold locations far from the equator, he found, erosion by snow and ice easily matched any growth due to the Earth’s plates crunching together.

Egholm used radar maps of the Earth’s surface, created by Nasa in 2001, to examine the height of all the world’s mountains at a single point in time. The analysis showed that mountains had a significant land area up to their snowlines, after which it dropped rapidly. In general, mountains only rise to around 1,500m above their snow lines, so it is the altitude of these lines — which depends on climate and latitude — which ultimately decides their height.

At low latitudes, the atmosphere is warm and the snowline is high. “Around the equator, the snowline is about 5,500m at its highest so mountains get up to 7,000m,” said Egholm. “There are a few exceptions [that are higher], such as Everest, but extremely few. When you then go to Canada or Chile, the snowline altitude is around 1,000m, so the mountains are around 2.5km.”

“What we show is that, once the mountain is pushed up across the snow line, a very effective erosion agent comes into play and that is represented by glaciers,” said Egholm. “It’s so effective that it can keep pace with any tectonic uplift rate that we have on the Earth today.” Below the snowline, rivers and rock falls are the main erosion agents.

Europe
1. Changes in leaf-unfolding and flowering and animal growing phases in 19
European countries: Examples are hazel, lilac, apple, linden, and birch
2. Earlier egg-laying of birds; earlier migration of birds (for example flycatchers)
3. Long-term changes within fish communities in Upper Rhone River
4. Glacier melting in the Alps
5. Rapid advance of spring arrival of long-distance migratory birds in Europe
6. Mountain birch tree-limit rise in Sweden
7. Changes in lake diatoms to warmer-adapted species in Finnish Lapland
8. Earlier pollen release in the Netherlands
9. Apple trees are leaving 35 days earlier in Spain

Asia
1. Greater growth of Siberian pines in Mongolia
2. Earlier break-up and thinning of river and lake ice in Mongolia
3. Change in freeze depth of permafrost in Russia
4. Earlier flowering of ginkgo in Japan

South America
1. Glacier wastage in Peru
2. Melting Patagonia icefields are contributing to sea-level rise

Africa
1. Decreasing aquatic ecosystem productivity of Lake Tanganyika

Australia
1. Early arrival of Australian migratory birds (examples – flycatcher, fantail)
2. Declining water levels in Western Victoria

Antarctica
1. Population of emperor penguins had declined by 50% on Antarctic Peninsula
2. Retreating glacier fronts

Ocean
1. Long-term decline in krill stock in Southern Ocean
2. Increasing abundance of tropical/subtropical species and decreasing abundances
of temperate/subpolar species in California current
3. Increasing plankton abundance in cooler reigons and decreasing plankton in
warmer regions in Northeast Atlantic