This week in Science in Action we talked to Ted Schuur, University of Florida, about the impacts of methane-producing bacteria munching their way through thawing poleward soils, Craig Baxter, a UK-playwright, about his award-winning play ‘The Alturists’, and Ian Boyd, University of St Andrews, about an open science project to decode whale song.
Science in Action is hosted by Jon Stewart, produced by me and Ania Lichtarowicz, and is a BBC World Service programme that pulls together the science issues of the week and delivers breaking science news.
Global temperatures could be less sensitive to changing atmospheric carbon dioxide (CO2) levels than previously thought, a study suggests.
The researchers said people should still expect to see “drastic changes” in climate worldwide, but that the risk was a little less imminent.
The results are published in Science.
The study is the latest to derive a value for “climate sensitivity” – the temperature rise for a doubling of CO2 concentrations – from palaeontology.
Previous studies have produced a mean value around 3C; but the new analysis concludes it is somewhat lower, around 2.3C.
More accurate analyses of climate sensitivity from historical data should allow for development of more accurate climate models that forecast the future.
The new analysis uses palaeoclimate data going back to the latter stages of the most recent Ice Age, 21,000 years ago, and a computer model.
Lead author Andreas Schmittner from Oregon State University, US, explained that by looking at how surface temperatures changed during a period when humans were having no impact on global temperatures, his team showed that it had not been as cold as previous estimates had suggested.
“This implies that the effect of CO2 on climate is less than previously thought,” he explained.
The researchers suggest that this finding can reduce uncertainty in future climate projections, though they do still give a range rather than a precise value.
The new models predict that given a doubling in CO2 levels from pre-industrial levels, the Earth’s surface temperatures will rise by 1.7C to 2.6C (3.1F to 4.7F), with a mean value of 2.3C.
That is a much tighter range than the one produced by the Intergovernmental Panel on Climate Change’s (IPCC) 2007 report, which suggested a rise of 2.0-4.5C, with a mean of about 3C.
The authors stress the results do not mean that the threat from human-induced climate change should be treated any less seriously, explained palaeoclimatologist Antoni Rosell-Mele from the Autonomous University of Barcelona, a member of the team that came up with the new estimates.
But it does mean that to induce large-scale warming of the planet, leading to widespread catastrophic consequences, we would have to increase CO2 more than we are going to do in the near future, he said.
“But we don’t want that to happen at any time, right?” he remarked
“At least, given that no one is doing very much around the planet [about] mitigating CO2 emissions, we have a bit more time.”
Whether these results mean that the global temperatures would be less responsive to falling CO2, if emissions do fall, is unclear.
“I don’t think we know that, to be honest,” remarked Dr Rosell-Mele.
Gabriele Hegerl from the University of Edinburgh is cautious about the result in her perspective piece published in the same issue of Science.
She says that this is just one particular climate model, and “future work with a range of models would serve to strengthen the result”.
Climatologist Andrey Ganopolski from the Potsdam Institute for Climate Impact Research, Germany, went further, saying he would not make such a strong conclusion based on this data.
“The results of this paper are the result of the analysis of [a] cold climate during the glacial maximum (the most recent ice age),” he told BBC News.
“There is evidence that the relationship between CO2 and surface temperatures is likely to be different [during] very cold periods than warmer [periods].”
Scientists, he said, would therefore prefer to analyse periods of the Earth’s history that are much warmer than now when making projections about future temperatures.
However, although good data exists for the last million years, temperatures during this time have been either similar to present, or colder.
“One should be very careful about using cold climates to [construct] the future,” he added.
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UK plants are flowering for a second time this year because of the unseasonably warm weather.
With temperatures soaring, plants such as foxglove and cowslip, which usually flower in the spring, are in full bloom six to eight months early.
Cold nights experienced across the UK in August are thought to have led to the early onset of autumn colours.
This warmer spell now has plants acting like it is spring.
Gardeners at the Kew’s Wakehurst Place gardens in Sussex said they are working from a “new rule book” to keep up.
“It is a very unsual year…I’ve been gardening for 30 years and have never seen anything like this,” said Wakehurst Place’s head Andy Jackson.
“We are increasingly seeing that plants are not synchronised with what the weather is doing,” he added.
In the last year, the UK experienced a severe drought, then lots of rainfall and a cold snap in the summer, all before this warm spell explained Mr Jackson.
From mid-August, gardeners were seeing trees turning yellow and orange; it is unclear what will happen now with temperatures reaching into the thirties (eighties) in parts of the South, East and the Midlands.
The BBC’s meteorologist Liam Dutton explained that the position of the jet stream north of the UK has allowed high pressure to build, bringing in the very warm air from western Europe.
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Animals and plants are shifting their natural home ranges towards the cooler poles three times faster than scientists previously thought.
In the largest study of its kind to date, researchers looked at the effects of temperature on over 2,000 species.
They report in the journal Science that species experiencing the greatest warming have moved furthest.
The results helped to “cement” the link between climate change and shifts in species’ global ranges, said the team.
Scientists have consistently told us that as the climate warms we should expect animals to head polewards in search of cooler temperatures.
Animals like the British comma butterfly, for example, has moved 220km northward from central England to southern Scotland in the last two decades.
An uphill struggle
There is also evidence that more species seem to be moving up mountains than down, explained conservation biologist Chris Thomas from the University of York, UK, who led the study.
But studies had stopped short of showing that rising temperatures are responsible for these shifts in range, he added.
Now he and his team have made this link.
Analysing the range shifts of more than 2,000 species – ranging from butterflies to birds, algae to mammals – across Europe, North and South America and Malaysia over the last four decades, they show that organisms that experience the greatest change in temperatures move the fastest.
The team found that on average organisms are shifting their home ranges at a rate of 17km per decade away from the equator; three times the speed previously thought.
Organisms also moved uphill by about 1m a year.
“Seeing that species are able to keep up with the warming is a very positive finding,” said biologist Terry Root from Stanford University in California, US.
She added that it seemed that species were able to seek out cooler habitats as long as there was not an obstacle in their way, like a highway.
Out of range
But what about the animals that already live at the poles, or at the top of mountains?
“They die,” said Dr Thomas. Take the polar bear, it does most of its hunting off the ice, and that ice is melting – this July was the lowest ever recorded Arctic ice cover – it has nowhere to go.
However, the loss of this one bear species, although eminently emblematic, seems insignificant when compared to the number of species that are threatened at the top of tropical mountains.
On Mount Kinabalu in Borneo, Dr Thomas’ graduate student, I-Ching Chen, has been following the movement of Geometrid moths uphill as temperatures increase. Their natural ranges have shifted by 59m in 42 years.
These moths “don’t have options; they are being forced up, and at some point they will run out of land,” reflected Dr Thomas.
The British scientist said that it was really too early to start generalising about the characteristics of the species that had shifted their distribution to stay within their optimal temperature range.
“But we know that the species which have expanded the most and fastest are the species that are not particularly fussy about where they live,” he told BBC News.
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As the U.S. Environmental Protection Agency (EPA) is busy girding itself for a fight over new greenhouse gas emissions rules, the U.S. Supreme Court heard arguments today in a case on whether lawsuits over climate ought to be permitted.
At stake is whether greenhouse gas pollution may be considered a “nuisance” under U.S. law. The case stems from two 2004 federal lawsuits brought by seven states and several land-trust groups alleging that emissions from five major power companies could cause harm by contributing to global warming. Rising sea levels, loss of water in the Great Lakes, and reduced hydropower were among the injuries alleged by the plaintiffs; the lawsuits have since been combined, and two states have dropped out since the original suit was filed. The district court subsequently said in its decision that the case brought up a “political” question that the other branches of government, not the judicial branch, should consider, but an appeals court reversed that ruling. When the power companies appealed, the Supreme Court took the case.
In other pollution cases, the Supreme Court has supported suits claiming that pollution caused harm as a “nuisance” under common law, most often interpreted to prohibit noise and light pollution. The 80 minutes of occasionally spirited argument at the high court this morning focused on the two main issues in the greenhouse gas litigation: For the case to go forward, the plaintiffs must prove that the case has legal standing (they must show that the court is the right venue for resolving this dispute), and that the common law definition of nuisance can support suits over greenhouse gases. On the issue of standing, the court could rule that Congress or EPA is a more appropriate body to deal with pollution control.
The Obama Administration opposed the suing states in this case largely on grounds that they lack standing, marking a rare instance in which the Administration finds itself at odds with environmentalists on a major legal issue. (Environmentalists urged the states to try this legal strategy.) U.S. attorney Neal Katyal told the justices that the complexity of the issue suggests that the executive branch, namely EPA, is a better venue for controlling such an expansive type of pollution rather than the courts. “In the 222 years that this court has been sitting, it has never heard a case with so many potential perpetrators and so many potential victims,” he said in his opening remarks. “There are billions of emitters of greenhouse gasses on the planet and billions of potential victims as well.”
The attorneys for the power companies and the Obama Administration argued that the greenhouse gases case is fundamentally different from previous nuisance cases in which pollutants have played a central role. A landmark ruling by the Supreme Court in 1907, for example, found that a judge could stop a Tennessee copper company from polluting the Georgia environment under the nuisance doctrine. Such cases, Katyal said, “are essentially: A pollutes a river or something and hurts B.” But in the case of global warming pollution, he said, “A here is the world and B is the world, and that is such a difference in scale and scope to pose enormously difficult questions” about whether such suits should go forward.
If this case is allowed to proceed, asked the justices, should subsequent cases be limited to big polluters like the five targeted in this suit? “Your briefs talk a lot about how these are the five largest [U.S.] emissions producers, but I saw nothing in your theory to limit it to those five,” Justice Elena Kagan asked New York state attorney Barbara Underwood, who spoke on behalf of the six states in the suit. “Is there something that you think limits it to large emissions producers rather than anybody in the world?”
The states have argued that the larger the greenhouse gas emitter the stronger the connection linking pollution and potential harm. “These defendants,” Underwood said, speaking of the five polluters, “produce 650 million tons a year or 10% of U.S. emissions, and individually they produce amounts ranging from 1 to 3.5% of U.S. emissions.”
Those who challenged the states also suggested that courts would be ill-equipped to make the complex judgments that big regulatory agencies staffed with scientists and other experts make on a routine basis. Judges lack “the resources, the expertise” to be a “kind of super-EPA,” said Justice Ruth Bader Ginsburg.
But Underwood said courts could make such judgments—which could include determining how “substantial” an emitter must be to be found culpable—by relying on standards set by the agencies. She pointed to a cutoff set by EPA that limits regulated greenhouse gas polluters to those that emit 100,000 tons or more per year. “According to EPA’s own technical data, there would be at most a few thousand potential defendants.”
Because Justice Sonia Sotomayor recused herself—she sat on the panel that reviewed the issue in the appeals court—only eight justices heard the arguments. A 4-4 tie would mean litigation against the polluters could go forward, because that would leave in effect the earlier decision by the appeals court. While the tone of the questioning was largely skeptical toward the idea that such suits ought to go forward, divining a final ruling from the rough-and-tumble of oral argument can be difficult, especially because justices often ask tough questions of those they’re inclined to agree with—just to test their counterarguments. Eyes were squarely focused today on Justice Anthony Kennedy, often the swing judge when decisions are split 5-4 in favor of conservative decisions. Kennedy raised a concern that federal law, and EPA’s efforts to use that law, would necessarily “preempt” the common law. The court’s three liberal members, Ginsburg, Stephen Breyer, and Kagan, seemed skeptical on this issue, too.
At least one knowledgeable observer said a 4-4 tie was unlikely. “In short, this particular lawsuit seemed doomed, with the court’s biggest task figuring out how to say so without shutting the courthouse door entirely to such claims,” said longtime Supreme Court reporter Lyle Denniston.
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Elephant seals are helping scientists study temperature and salinity changes in the Southern Ocean.
Equipped with computerised tags, the seals can reach regions of the sea impenetrable to researchers during the harsh winter months.
The data, collected during the animals’ long dives under Antarctic ice, provide the best ever estimates for the rate of sea-ice formation.
The findings appear in the Proceedings of the National Academy of Sciences.
The tags measure position, salinity, and temperature, among other things, to form a “hydrographic profile” for each of the 58 seals fitted with a device.
“By using seals, we have increased the number of hydrographic profiles 30-fold,” said Jean-Benoit Charrassin, who is based in France’s Natural History Museum.
“What we know about the Southern Ocean is very limited, which makes predicting the formation of sea-ice difficult,” Dr Charrassin told BBC News.
“These animals are filling a ‘blind spot’ in our sampling.”
Seals make excellent marine surveyors because they swim up to 100km a day and dive to depths of 2,000m (6600ft) during foraging trips.
Sea temperatures and salinity are measured by seal transmitters
Dr Charrassin told BBC News that seals returned to the surface to breathe about 60 times a day, spending three minutes, on average, bobbing there before descending again.
“Occasionally they stay long enough for the data loggers, atop their heads, to send the data via satellite,” explained the Paris-based researcher.
“On average, we can collect two profiles a day from each seal.”
Dr Charrassin said that by measuring the salinity of water beneath sea-ice, researchers could determine how quickly it formed.
“In the Antarctic, when seawater freezes to form sea-ice, the salt – usually suspended in the water – is ejected into the water beneath the ice,” he explained.
Previous measures of sea-ice – calculated by measuring the distances drifted by buoys over a three-week period – estimate that in August, it forms at a rate of 8-10cm (3-4in) per day.
Data collected by the seals allows better estimates and suggests that this rate is much lower – only 1cm (0.3 inches) per day.
Seals often drift down to the bottom, seeming to sleep on their way down.
Jean-Benoit Charrassin, SEaOS
Estimating the rate of formation of sea-ice is crucial to understanding ocean currents.
This super-salty water forms a dense layer below the ice and sinks.
The dense water then flows along the sea bottom into the ocean basins, forming part of the thermohaline circulation, a large-scale ocean current driven by global temperature and salt gradients.
This current helps redistribute energy and nutrients in the world’s oceans.
In the long-term, the researchers hope to continue using seals to help them monitor salinity levels in the Southern Ocean, and study the impact of global sea temperature changes on ocean currents.
But what about the “furry oceanographers” themselves; what can tagging seals teach scientists about seal biology?
The data loggers, as well as measuring the seals’ environment, record diving depths and time spent at the sea-bottom, giving researchers a window into the seals’ deep-sea foraging behaviour.
“We wanted to understand the foraging ecology of elephant seals and study their role in the marine food web,” said Dr Charrassin.
“We think the seals [at the bottom] try to catch deep-dwelling animals like squid and fish – at these depths, the seals’ lungs and body can be compressed to overcome the great pressures at 2,000m,” he said.
South Georgian elephant seals represent about 50% of the 740,000 breeding population in the Sub-Antarctic
Differences in foraging behaviour might explain why the island populations of elephant seals on Kerguelen and Macquarie have seen large declines, while the 400,000-strong South Georgian population has remained stable since the 1950s.
The seals’ hydrographic profiles give more weight to this idea, showing that animals from Kerguelen generally feed on the Antarctic continental shelf, while South Georgian seals tend to feed in open ocean.
Further study into prey numbers in these different environments is needed to confirm the role of foraging behaviour in the decline of two of the three seal populations.
The research is a collaborative effort involving scientists from Europe, Australia and the US. It is part of the Southern Elephant Seals as Oceanographic Samplers (SEaOS) project that has been running for four years.
The scientists stress the animals are not bothered by the data loggers carried on their heads. The boxes are glued on to the fur of the seals and stay there for one year, until the animals moult.
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