The early part of the Cenozoic era, which started around 65.5 million years ago witnessed a series of transient global warming events called hyperthermals. The most severe of these was the PETM at the Paleocene-Eocene boundary, around 56 million years ago. Over a period of around 20,000 years, a mere blink of the eye in geological terms, ocean temperatures rose globally by approximately 5°C. There is evidence that the concentration of atmospheric carbon oxide increased, but the phenomena that triggered the event remain controversial.

One possibility is that these hyperthermals were driven by cyclic variations in the eccentricity of Earth’s orbit around the sun. At the cycle peaks, increased temperatures could have caused methane hydrate deposits in the deep sea to release large amounts of methane. Some of this potent greenhouse gas would have entered the atmosphere resulting in further intensification of the climatic warming, which would have continued as the methane was fairly rapidly converted into carbon dioxide in the atmosphere.

Alternatively, it may have been geological processes, unrelated to variation in Earth’s orbit, which could have been the culprit for the warming associated with the PETM. In this scenario, magmatism would have caused the baking of marine organic sediments, leading to the massive release of methane and/or carbon dioxide, possibly through hydrothermal vents, thus initiating the global warming which led to the methane release.

“Determining exactly what triggered the PETM requires very accurate dating of the event itself, to determine whether it occurred during a known maximum in the Earth’s orbital eccentricity” explains Adam Charles, a University of Southampton PhD student supervised by Dr Ian Harding, and first author of the newly published report.

To getter a better grip on the numerical age of the Paleocene-Eocene boundary, the researchers measured radio-isotopes of uranium and lead in the mineral zircon, found as crystals in two volcanic ash horizons deposited during the PETM. These rocks were collected from two locations in Spitsbergen, the largest island of the Svalbard Archipelago in the Arctic.

Based on their data, the researchers dated the Paleocene-Eocene boundary at between 55.728 and 55.964 million years ago, which they believe to be the most accurate estimate to date. Their analyses indicated that the onset of the PETM, unlike those of other Eocene hyperthermals, did not occur at the peak of a 400 thousand year cycle in Earth’s orbital eccentricity. Instead, it occurred on the falling limb of a cycle when warming by the sun would not have been at a maximum.

“Compared to other early Eocene hyperthermals, it appears that the PETM was triggered by a different mechanism, and thus may have involved volcanism. However, a thorough test of this hypothesis will require further detailed dating studies,” Adam concluded.

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Yet global warming may affect the capacity of trees to store carbon by altering forest nitrogen cycling, concludes a study led by Jerry Melillo of the Marine Biological Laboratory (MBL), published recently in Proceedings of the National Academy of Sciences.

The paper summarizes the results of a 7-year study at Harvard Forest in central Massachusetts, in which a section of the forest (about one-quarter of an acre) was artificially warmed about 9oF above ambient, to simulate the amount of climate warming that might be observed by the end of the century without aggressive actions to control greenhouse gas emissions from fossil-fuel burning and deforestation.

The study confirmed, as others have, that a warmer climate causes more rapid decomposition of the organic matter in soil, leading to an increase in carbon dioxide being released to the atmosphere.

But the study also showed, for the first time in a field experiment, that warmer temperatures stimulate the gain of carbon stored in trees as woody tissue, partially offsetting the soil carbon loss to the atmosphere. The carbon gains in trees, the scientists found, is due to more nitrogen being made available to the trees with warmer soil.

“Tree growth in many of the forests in the United States is limited by the lack of nitrogen,” Melillo says. “We found that warming causes nitrogen compounds locked up in soil organic matter to be released as inorganic forms of nitrogen such as ammonium, a common form of nitrogen found in garden fertilizer. When trees take up this inorganic nitrogen, they grow faster and store more carbon.”

Melillo says that the biological processes that link soil warming, increased soil organic matter decay, increased nitrogen availability to trees, and increased tree growth will likely operate together in many temperate and boreal forests — forests found in North America, Europe, Eurasia and much of the developed world. Tree growth in tropical forests is often limited by factors other than nitrogen, so lessons from this new study are not widely relevant in the tropics.

While Melillo thinks that the carbon-nitrogen interactions he is studying at Harvard Forest will help us to make predictions of carbon storage in forest over the coming decades, he adds that “the carbon balance of forest ecosystems in a changing climate will also depend on other factors that will change over the century, such as water availability, the effects of increased temperature on both plant photosynthesis and aboveground plant respiration, and the atmospheric concentration of carbon dioxide.”

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The findings of a study published in Nature Climate Change indicate negative effects on the growth of a long-lived south-east Australian and New Zealand inshore species — the banded morwong.

Scientific monitoring since 1944 by CSIRO at Maria Island, off the east coast of Tasmania, showed that surface water temperatures in the Tasman Sea have risen by nearly 2°C over the past 60 years. This warming, one of the most rapid in the southern hemisphere oceans, is due to globally increasing sea-surface temperatures and local effects caused by southward extension of the East Australian Current.

“Generally, cold-blooded animals respond to warming conditions by increasing growth rates as temperatures rise,” CSIRO marine ecologist Dr Ron Thresher, a co-author of the study with colleagues from the University of Tasmania’s Institute for Marine and Antarctic Studies, said.

“But theory and laboratory studies show that this has a limit. As temperatures get too high, we begin to see increased signs of stress, possibly eventually leading to death. We are looking at whether climate change is beginning to push fish past their physiological limits.

“By examining growth across a range that species inhabit, we found evidence of both slowing growth and increased physiological stress as higher temperatures impose a higher metabolic cost on fish at the warm edge of the range.

“In this case, off northern New Zealand, ocean warming has pushed the banded morwong — which inhabits temperate reefs in waters 10-50m deep — past the point where increasing temperatures are beneficial to growth.”

Dr Thresher said climate change can affect species directly by influencing how their bodies function, their growth and behaviour and indirectly through environmental effects on ecosystems. To assess the impacts of this temperature increase on a marine species, the research team analysed long-term changes in the growth rates of the banded morwong (Cheilodactylus spectabilis).

The bony structures fish use for orientation and detection of movement — called otoliths — have annual growth rings which were measured for changes. Similar to growth rings in trees, they can be counted to indicate a fish’s age and annual growth rate, estimated by measuring distances between each new ring.

According to a co-author of the paper, University of Tasmania (UTas) researcher Dr Jeremy Lyle, banded morwong were used in the study because they can live for almost 100 years and, as adults, they stay in essentially the same area even if the water temperature shifts. They have also been the subject of fisheries studies conducted by UTas researchers.

“Growth rates of young adult banded morwong in SE Australia have increased significantly since 1910 at four sample sites,” Dr Lyle said. “The team from CSIRO and the Institute for Marine and Antarctic Studies (UTas) compared these changes to temperature trends across the species’ distribution. They observed increased growth for populations in the middle of the species’ range in Australian waters where temperatures have increased, but are still relatively cool, but growth slowed with rising temperatures at the warmer northern edge of the species’ range in New Zealand waters.

Dr Lyle said the study showed that growth performance in banded morwong began to suffer above average annual water temperatures of about 17°C.

“Preliminary field and laboratory studies suggested that this decline in growth may be related to temperature induced physiological stress, resulting in increased oxygen consumption and reduced ability to sustain swimming activity.”

The paper’s other co-authors were: a post-doctoral fellow with CSIRO who is now with Aarhus University in Denmark, Dr Anna Neuheimer; and, Dr Jayson Semmens from UTas. The research was conducted through CSIRO’s Climate Adaptation Flagship and the Institute for Marine and Antarctic Studies, with funding from an Australian Government Endeavour Awards Fellowship and the Winnifred Violet Scott Trust.

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Rather than peer into the future, they are looking backward, exploring how species alive today survived global warming at the end of the Pleistocene and asking whether their responses provide any guidance for us today.

For his dissertation Brad Oberle, a doctoral candidate in biology in Arts & Sciences at Washington University in St. Louis, delved into the post-Pleistocene history of three species of shootingstars (Dodecatheon).

Dodecatheon is a genus of flowering plant in the Primrose family, the petals of whose nodding flowers flex upward, giving the flowers the appearance of a star falling to earth, trailing flames behind it.

Two of the species, the jeweled shootingstar (D. amethystinum), and French’s shootingstar (D. frenchii), are rare and grow only in cliff habitats.

Are the rare species glacial relicts, species adapted to the cool wet conditions during the Pleistocene that gradually retreated to smaller and smaller refuges as the climate warmed? Or were they ecotypes, local variants of a widespread species, Mead’s shootingstar (D. meadia), that had adapted to cliff microclimates but were genetically similar to Mead’s shootingstar.

“As is typical of science,” says Barbara A. Schaal, PhD, the Mary-Dell Chilton Distinguished Professor of biology in Arts & Sciences, Oberle’s dissertation advisor, and his co-author, “the result was mixed. One species is probably a relict species, and the other is probably an ecotype. Some species responded to warming by migrating but other populations apparently adapted in place.”

The article was published in the April 5th issue of the Proceedings of the National Academy of Science (PNAS).

“It’s a lovely piece of work,” Schaal says.

Why shootingstars?

“On hikes I took as a kid,” says Oberle, who grew up in Missouri, “I noticed it felt very different if you were out in a glade, an open habitat with intense sunshine and high temperatures, than if you were down in a hollow, where it’s more sheltered, cooler and tends to be a lot more moist. I also noticed that the plant communities in these two places also differed a lot.”

“When I was just getting started on my Ph, I read a book called The Terrestrial Natural Communities of Missouri by Paul Nelson.

“One species I learned about, French’s shootingstar, specializes in habitats that occur where ledges overhang the bottom of cliffs. These rock houses, as they’re called, tend to form in sandstone cliffs because of the way sandstone weathers. The cliff habitats are typically damp and shelter other interesting plants, as well.

“And then, flipping through the book, I found the jeweled shootingstar, another rare species, but one that specializes on limestone cliffs. It usually grows on slopes at the top of the cliffs right before the rock face becomes vertical.

“It also tends to grow in little patches on the rock face itself,” says Oberle, who admits both to learning technical climbing to prepare for his fieldwork and to twice falling off cliffs in the field.

“The widespread species, D. meadia, is a real mess,” he says. “It’s a beautiful plant and one that tends to catch a botanist’s eye. And almost every botanist that looks at a population of this plant feels that population is special and unique. When botanists have that reaction, they tend to slap a name on the population and call it a new species. Fifty to 100 names have been thrown onto this one species of shootingstar because it’s so beautiful, and comes up in the spring when everybody wants to go out and botanize,” he says laughing.

“The number of species in the genus is still an open question,” Oberle says, “but a revision of this genus published a few years ago named 18 species of Dodecatheon in the United States. The revision identified three species in the eastern U.S. and those are the species I worked with.”

The relict hypothesis and the ecotype hypothesis

Botanists who believe the rare species of shootingstar are distinct species explain their distribution and ecology as a response to historical climate change.

These species really like cold and moist conditions. They throve throughout the last glacial period.

“If you roll the clock back to 20,000 years ago, St. Louis was 50 to 100 miles from a glacier that was about a mile thick,” Oberle says.

These species were widespread at the last glacial maximum when conditions were cooler, but when the climate started to warm up, they couldn’t adapt, so their ranges shrank and they became stuck — i solated in these cliff habitats.

Other botanists, however, think that the shootingstars are just one big jumbled species. If you find an odd-looking shootingstar in a cliff habitat, it isn’t because it had some special history, but instead because the cliff habitat has unusual characteristics and the process of natural selection produces local variants that are adapted to those characteristics. So the rare species are ecotypes, plants specialized for a particular habitat, not relicts.

What the hypotheses predict

As Oberle realized, these hypotheses make specific predictions that could be falsified by research.

The relict hypothesis predicts that the relict species will be genetically distinct from any other species in the area. It’s doing its own thing and it has its own history and it should be possible to detect that history by looking at patterns of genetic variation.

The relict hypothesis also predicts that far flung populations of the relict species will occur in the same kind of habitat and be genetically more similar to one another than to plants that occur in different habitats, even if those plants are nearby.

The ecotype hypothesis makes a contrasting set of predictions. If the rare species are ecotypes, just local variants of the widespread species, their genomes should not vary markedly from that of another random population of the widespread species.

Further, if the rare populations are ecotypes, they should be more similar genetically to nearby ecotypes than they are to distant ones.

The fieldwork

To distinguish between these hypothesesm Oberle collected shootingstars across the eadtern United States, from Pennsylvania to Texas, and from Georgia up to Minnesota.

“One of the ironies of this project,” he says ruefully, “was that I was doing this research about global warming and I was driving all over the country to do it. But it was a fantastic trip, and I got to see amazing places and meet very generous people.

“At every location, I’d take GPS coordinates, try to get a sense for how big the population of plants was, and then sample the plants in a consistent way.

“I measured a trait called specific leaf area, or the fresh leaf area per unit mass, because it gave me insight into how well the plants were adapted to the habitats where I found them.

“I also grabbed leaves for genetic analysis. I sequenced some DNA from all of the plants, but because DNA sequences don’t vary much between plants, I turned to a technique called amplified fragment-length polymorphism (AFLP). That technique tends to be very sensitive; closely related individuals often have very different AFLP banding patterns.

“And finally, I collected a voucher specimen from every population for the herbarium at the Missouri Botanical Garden,” Oberle says.

Some relicts, some ecotypes

The results, which ultimately emerged from the genetic work, depended on the species.

“Populations of jeweled shootingstar from Wisconsin and from Pennsylvania are genetically distinct from all other shootingstars in North America and very similar to one another even though they are so far apart,” Oberle says.

This suggests the jeweled shootingstar is a relict, a plant that was widespread in the past but whose range has become fragmented and that that now survives only in refuge habitats.

French’s shootingstar, on the other hand, is not genetically distinct from D. meadia at all, even though these plants look different and grow in different habitats. Although earlier work has showed they were genetically adapted to different circumstances, overall their genomes are very much alike. So French’s shootingstar is probably just a simple ecotype of D. meadia.

Conservation recommendations

The results suggest that the two rare “species” of shootingstar in the eastern United States should be managed quite differently. Because the jeweled shootingstar is a relict, it’s probably hanging on by a thread. If climate continues to warm, it is likely to go extinct.

“Because we know this species is genetically distinctive, the jeweled shootingstar should be a priority for conservation as climate continues to warm,” Oberle says.

On the other hand, since French’s shootingstar is an ecotype, that suggests that it’s capable of adapting to changing climate.

And, because it isn’t genetically distinctive, a population of French’s shootingstar has the same conservation value as any other random population of D. meadia.

But, Oberle cautions, shootingstars may not respond to human-caused global warming as they did to the warming at the end of the last ice age, both because the warming is more rapid and because the habitat is now fragmented.

The sad part

“I was sad to come to the conclusion that D. frenchii wasn’t really a distinct species, because it is a beautiful plant and it grows in a beautiful habitat, so part of me wanted to recognize the beautiful distinction of it, too.

“My family has owned a farm since the 1860s that is near one of these sandstone cliff habitats. My grandparents and my great-grandparents used to go there in the summertime to rest under the waterfall after working in the fields. And this cliff has a population of D. frenchii, one of the few populations in Missouri. So I have a family connection to this beautiful rare plant, and my research showed it is not as special as we thought it was.

“I felt almost as though I had caused an extinction, although the extinction was just an extinction on paper.”

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“It appears as if farmers in North America got a pass on the first round of global warming,” said David Lobell, an assistant professor of environmental Earth system science at Stanford University. “That was surprising, given how fast we see weather has been changing in agricultural areas around the world as a whole.”

Lobell and his colleagues examined temperature and precipitation records since 1980 for major crop-growing countries in the places and times of year when crops are grown. They then used crop models to estimate what worldwide crop yields would have been had temperature and precipitation had typical fluctuations around 1980 levels.

The researchers found that global wheat production was 5.5 percent lower than it would have been had the climate remained stable, and global corn production was lower by almost 4 percent. Global rice and soybean production were not significantly affected.

The United States, which is the world’s largest producer of soybeans and corn, accounting for roughly 40 percent of global production, experienced a very slight cooling trend and no significant production impacts.

Outside of North America, most major producing countries were found to have experienced some decline in wheat and corn (or maize) yields related to the rise in global temperature. “Yields in most countries are still going up, but not as fast as we estimate they would be without climate trends,” Lobell said.

Lobell is the lead author of a paper about the research to be published May 5 online in Science Express.

Russia, India and France suffered the greatest drops in wheat production relative to what might have been with no global warming. The largest comparative losses in corn production were seen in China and Brazil.

Total worldwide relative losses of the two crops equal the annual production of corn in Mexico and wheat in France. Together, the four crops in the study constitute approximately 75 percent of the calories that humans worldwide consume, directly or indirectly through livestock, according to research cited in the study.

“Given the relatively small temperature trends in the U.S. Corn Belt, it shouldn’t be surprising if complacency or even skepticism about global warming has set in, but this study suggests that would be misguided,” Lobell said.

Since 1950, the average global temperature has increased at a rate of roughly 0.13 degrees Celsius per decade. But over the next two to three decades average global temperature is expected to rise approximately 50 percent faster than that, according to the report of the Intergovernmental Panel on Climate Change. With that rate of temperature change, it is unlikely that the crop-growing regions of the United States will continue to escape the rising temperatures, Lobell said.

“The climate science is still unclear about why summers in the Corn Belt haven’t been warming. But most explanations suggest that warming in the future is just as likely there as elsewhere in the world,” Lobell said.

“In other words, farmers in the Corn Belt seem to have been lucky so far.”

This is the first study to come up with a global estimate for the past 30 years of what has been happening, Lobell said.

To develop their estimates, the researchers used publicly available global data sets from the United Nations Food and Agriculture Organization and from the University of Delaware, University of Wisconsin, and McGill University.

The researchers also estimated the economic effects of the changes in crop yield using models of commodity markets.

“We found that since 1980, the effects of climate change on crop yields have caused an increase of approximately 20 percent in global market prices,” said Wolfram Schlenker, an economist at Columbia University and a coauthor of the paper in Science.

He said if the beneficial effects of higher carbon dioxide levels on crop growth are factored into the calculation, the increase drops down to 5 percent.

“Five percent sounds small until you realize that at current prices world production of these four crops are together worth nearly $1 trillion per year,” Schlenker said. “So a price increase of 5 percent implies roughly $50 billion per year more spent on food.”

Rising commodity prices have so far benefited American farmers, Lobell and Schlenker said, because they haven’t suffered the relative declines in crop yield that the rest of the world has been experiencing.

“It will be interesting to see what happens over the next decade in North America,” Lobell said. “But to me the key message is not necessarily the specifics of each country. I think the real take-home message is that climate change is not just about the future, but that it is affecting agriculture now. Accordingly, efforts to adapt agriculture such as by developing more heat- and drought-tolerant crops will have big payoffs, even today. “

Justin Costa-Roberts, an undergraduate student at Stanford, is also a coauthor of the Science paper. David Lobell is a researcher in Stanford’s Program on Food Security and the Environment, a joint program of Stanford’s Woods Institute for the Environment and Freeman Spogli Institute for International Studies. Schlenker is an assistant professor at the School of International and Public Affairs and at the Department of Economics at Columbia.

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When faced with high levels of atmospheric carbon dioxide and rising temperatures 56 million years ago, Earth increased its ability to pull carbon from the air. This led to a recovery that was quicker than anticipated by many models of the carbon cycle — though still on the order of tens of thousands of years, said Gabriel Bowen, the associate professor of earth and atmospheric sciences who led the study.

“We found that more than half of the added carbon dioxide was pulled from the atmosphere within 30,000 to 40,000 years, which is one-third of the time span previously thought,” said Bowen, who also is a member of the Purdue Climate Change Research Center. “We still don’t know exactly where this carbon went, but the evidence suggests it was a much more dynamic response than traditional models represent.”

Bowen worked with James Zachos, a professor of earth and planetary sciences at the University of California, Santa Cruz, to study the end of the Palaeocene-Eocene Thermal Maximum, an approximately 170,000-year-long period of global warming that has many features in common with the world’s current situation, he said.

“During this prehistoric event billions of tons of carbon was released into the ocean, atmosphere and biosphere, causing warming of about 5 degrees Celsius,” Bowen said. “This is a good analog for the carbon being released from fossil fuels today.”

Scientists have known of this prehistoric event for 20 years, but how the system recovered and returned to normal atmospheric levels has remained a mystery.

Bowen and Zachos examined samples of marine and terrestrial sediments deposited throughout the event. The team measured the levels of two different types of carbon atoms, the isotopes carbon-12 and carbon-13. The ratio of these isotopes changes as carbon dioxide is drawn from or added to the atmosphere during the growth or decay of organic matter.

Plants prefer carbon-12 during photosynthesis, and when they accelerate their uptake of carbon dioxide it shifts the carbon isotope ratio in the atmosphere. This shift is then reflected in the carbon isotopes present in rock minerals formed by reactions involving atmospheric carbon dioxide, Bowen said.

“The rate of the carbon isotope change in rock minerals tells us how rapidly the carbon dioxide was pulled from the atmosphere,” he said. “We can see the fluxes of carbon dioxide in to and out of the atmosphere. At the beginning of the event we see a shift indicating that a lot of organic-derived carbon dioxide had been added to the atmosphere, and at the end of the event we see a shift indicating that a lot of carbon dioxide was taken up as organic carbon and thus removed from the atmosphere.”

A paper detailing the team’s National Science Foundation-funded work was published in Nature Geoscience.

It had been thought that a slow and fairly constant recovery began soon after excess carbon entered the atmosphere and that the weathering of rocks, called silicate weathering, dictated the timing of the response.

Atmospheric carbon dioxide that reacts with silicon-based minerals in rocks is pulled from the air and captured in the end product of the reaction. This mechanism has a fairly direct correlation with the amount of carbon dioxide in the atmosphere and occurs relatively slowly, Bowen said.

The changes Bowen and Zachos found during the Palaeocene-Eocene Thermal Maximum went beyond the effects expected from silicate weathering, he said.

“It seems there was actually a long period of higher levels of atmospheric carbon dioxide followed by a short and rapid recovery to normal levels,” he said. “During the recovery, the rate at which carbon was pulled from the atmosphere was an order of magnitude greater than the slow drawdown of carbon expected from silicate weathering alone.”

A rapid growth of the biosphere, with a spread of forests, plants and carbon-rich soils to take in the excess carbon dioxide, could explain the quick recovery, Bowen said.

“Expansion of the biosphere is one plausible mechanism for the rapid recovery, but in order to take up this much carbon in forests and soils there must have first been a massive depletion of these carbon stocks,” he said. “We don’t currently know where all the carbon that caused this event came from, and our results suggest the troubling possibility that widespread decay or burning of large parts of the continental biosphere may have been involved.”

Release from a different source, such as volcanoes or sea floor sediments, may have started the event, he said.

“The release of carbon from the biosphere may have occurred as a positive feedback to the warming,” Bowen said. “The forests may have dried out, which can lead to die off and forest fires. If we take the Earth’s future climate to a place where that feedback starts to happen we could see accelerated rates of climate change.”

The team continues to work on new models of the carbon cycle and is also investigating changes in the water cycle during the Palaeocene-Eocene Thermal Maximum.

“We need to figure out where the carbon went all those years ago to know where it could go in the future,” he said. “These findings show that the Earth’s response is much more dynamic than we thought and highlight the importance of feedback loops in the carbon cycle.”

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The Agulhas Current transports warm and salty waters from the tropical Indian Ocean to the southern tip of Africa, where most of the water loops around to remain in the Indian Ocean (the Agulhas Retroflection), while some waters leak into the fresher Atlantic Ocean via giant Agulhas rings. Once in the Atlantic, the salty Agulhas leakage waters eventually flow into the Northern Hemisphere and act to strengthen the Atlantic overturning circulation by enhancing deep water formation.

Recent research points to an increase in Agulhas leakage over the last few decades caused primarily by human-induced climate change. This finding is profound, because it suggests that increased Agulhas leakage could trigger a strengthening in the Atlantic overturning circulation, at a time when warming and accelerated meltwater input in the North Atlantic has been predicted to weaken it.

“This could mean that current IPCC model predictions for the next century are wrong and there will be no cooling in the North Atlantic to partially offset the effects of global climate change over North America and Europe,” said Beal, “Instead, increasing Agulhas leakage could stabilize the oceanic heat transport carried by the Atlantic overturning circulation.”

There is also paleoceanographic data to suggest that dramatic peaks in Agulhas leakage over the past 500,000 years may have triggered the end of glacial cycles. This serves as further evidence that the Agulhas system and its leakage play an important role in the planet’s climate.

“This study shows that local changes in atmospheric and oceanic conditions in the Southern Hemisphere can affect the strength of the ocean circulation in unexpected ways. Under a warming climate, the Agulhas Current system near the tip of South Africa could bring more warm salty water from the Indian to the Atlantic Ocean and counteract opposing effects from the Arctic Ocean,” said Eric Itsweire, director of the National Science Foundation (NSF)’s physical oceanography program, which funded the research.

The study establishes the need for additional research in the region that focuses on Agulhas rings, as well as the leakage. Climate modeling experiments are critical, and need to be supported by paleoceanographic data and sustained observations to firmly establish the role of this system in a warming climate.

“Our goal now is to get more of the scientific community involved in research of the Agulhas system and its global effects. The emphasis has been too long in the North Atlantic,” said Beal.

The scientific review team included UM’s Lisa Beal, Wilhelmus P.M. de Ruijter of Utrecht University in the Netherlands, Arne Biastoch of Leibniz- Institut für Meereswissenschaften (IFM-GEOMAR) in Germany, and Rainer Zahn of the Universitat Autònoma de Barcelona in Spain, as well as members of SCOR Working Group 136 on the Climatic Importance of the Agulhas System, sponsored by the Scientific Committee for Oceanic Research, the International Association for the Physical Sciences of the Oceans, and the World Climate Research Program. The Scientific Committee on Oceanic Research is supported by the National Science Foundation, award no. OCE-0938349. Beal is funded by the National Science Foundation through the ACT (Agulhas Current Time-series) project, award no. OCE-0850891.

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The gap between Democrats and Republicans who believe global warming is happening increased 30 percent between 2001 and 2010 — a “depressing” trend that’s essentially keeping meaningful national energy policies from being considered, argues sociologist Aaron M. McCright.

“Instead of a public debate about different policies to deal with global warming, a significant percentage of the American public is still debating the science,” said McCright, MSU associate professor and primary investigator on the study. “As a result, we’re failing to significantly address one of the most serious problems of our time.”

The study is featured in the spring issue of the research journal Sociological Quarterly, online now.

McCright and Riley E. Dunlap of Oklahoma State University analyzed 10 years of data from Gallup’s environmental poll, making the study the first of its kind to use multiple years of data. The Gallup poll, conducted annually, consists of a nationally representative telephone survey of at least 1,000 people.

According to the MSU-led study, people on the right of the political spectrum increasingly deny the existence of global warming, while people on the left generally believe in global warming more now than they did 10 years ago. Among other things, the study found:

According to McCright, these results are consistent with the prevailing theory that explains how political polarization occurs in the general public. “In the last few decades political elites have become polarized on climate change. This has driven the political divide on this topic within the American public, as regular citizens have taken cues from ideological and party leaders they trust.”

McCright said the process has been magnified over the past decade by the emergence of media outlets where citizens can seek out news and ideas that reinforce their values and beliefs. He said citizens at either end of the political spectrum can get daily information — albeit very different information — on global warming that further strengthens their opposing beliefs about what is real.

“Unfortunately, this is not a recipe for promoting a civil, science-based discussion on this very serious environmental problem,” McCright said. “Like with the national discussion on health care, we don’t even agree on what the basic facts are.”

This political polarization on climate change is not likely to go away in the near future, he added.

“Many Republican Party leaders have moved further to the right since the 2008 presidential election. We’ve also seen attacks on climate science by Tea Party activists. It seems like climate change denial has become something of a litmus test for Republican candidates,” McCright said.

“This continued elite polarization on climate change means that the general public will likely remain politically divided on climate change for a while.”

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Their report — the first analysis of long-term stability of wind over the U.S. — appears in the Proceedings of the National Academy of Sciences Early Edition.

“The greatest consistencies in wind density we found were over the Great Plains, which are already being used to harness wind, and over the Great Lakes, which the U.S. and Canada are looking at right now,” said Provost’s Professor of Atmospheric Science Sara Pryor, the project’s principal investigator. “Areas where the model predicts decreases in wind density are quite limited, and many of the areas where wind density is predicted to decrease are off limits for wind farms anyway.”

Coauthor Rebecca Barthelmie, also a professor of atmospheric science, said the present study begins to address a major dearth of information about the long-term stability of wind as an energy resource. Questions have lingered about whether a warmer atmosphere might lead to decreases in wind density or changes in wind patterns.

“We decided it was time someone did a thorough analysis of long term-patterns in wind density,” Barthelmie said. “There are a lot of myths out there about the stability of wind patterns, and industry and government also want more information before making decisions to expand it.”

Pryor and Barthelmie examined three different regional climate models in terms of wind density changes in a future U.S. experiencing modest but noticeable climate change (warming of about 2 degrees Celsius relative to the end of the last century).

The scientists found the Canadian Regional Climate Model (CRCM) did the best job modeling the current wind climate, but included results from Regional Climate Model 3 (created in Italy but now developed in the U.S.) and the Hadley Centre Model (developed in the U.K.) for the sake of academic robustness and to see whether the different models agreed or disagreed when seeded with the same parameters.

All three state-of-the-art regional climate models were chained to output from one of four atmospheric-ocean general circulation models to derive a complete picture of wind density changes throughout the study area — the lower 48 United States and a portion of northern Mexico.

Comparing model predictions for 2041-2062 to past observations of wind density (1979-2000), most areas were predicted to see little or no change. The areas expected to see continuing high wind density — and therefore greater opportunities for wind energy production — are atop the Great Lakes, eastern New Mexico, southwestern Ohio, southern Texas, and large swaths of several Mexican states, including Nuevo Leon, Tamaulipas, Chihuahua, and Durango.

“There was quite a bit of variability in predicted wind densities, but interestingly, that variability was very similar to the variability we observe in current wind patterns,” Pryor said.

The Great Lakes — Lakes Michigan, Superior, and Erie in particular — consistently showed high wind density no matter what model was used.

Such predictions should prove crucial to American policymakers and energy producers, many of whom have pledged to make wind energy 20 percent of America’s total energy production by 2030. Currently only about 2 percent of American energy comes from wind.

“There have been questions about the stability of wind energy over the long term, ” Barthelmie said. “So we are focusing on providing the best science available to help decision makers.” Pryor added that ‘this is the first assessment of its type, so the results have to be considered preliminary. Climate models are evolving and improving all the time, so we intend to continue this assessment as new models become available.”

Wind farms are nearly carbon neutral, and studies show that a turbine pays for itself after only three months of energy production. A typical turbine lasts about 30 years, Pryor says, not because parts break, but because advances in technology make it desirable to replace turbines with newer versions.

“Wind speed increases with height, so turbines are also getting taller,” Pryor said. “One of our future projects will be to assess the benefit of deploying bigger turbines that extend farther from the ground.”

This is also the week of the annual Offshore Technology Conference in Houston, the largest such energy conference in the world, which has increasingly focused on offshore wind energy production in recent years.

Last month, Pryor was appointed to the National Climate Assessment and Development Committee, convened by the U.S. Department of Commerce’s National Oceanic and Atmospheric Administration to help the U.S. government prepare for and deal with climate change. She also contributed to a special report used by the Intergovernmental Panel on Climate Change (IPCC). Barthelmie is a widely respected expert on wind energy, particularly in northern Europe, whose wind farms she has studied for years. She was the winner of the European Academy of Wind Energy’s 2009 Academy Science Award. Both Pryor and Barthelmie are faculty in the IU Bloomington Department of Geography, a division of the College of Arts and Sciences, and the Center for Research in Environmental Science.

Pryor and Barthelmie’s work was supported by grants from the National Science Foundation (BCS 1019603), the International Atomic Energy Authority, and the IU Center for Research in Environmental Sciences. The model output they analyzed were provided by the North American Regional Climate Change Assessment Program (NARCCAP). NARCCAP is funded by the National Science Foundation, the U.S. Department of Energy, the National Oceanic and Atmospheric Administration, and the U.S. Environmental Protection Agency Office of Research and Development.

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The two penguin species of focus in the study rely on small shrimp-like creatures known as krill for their survival. A previous assessment in Nature of krill in the Southern Ocean suggests that their abundance has declined as much as 80 percent since the 1970s.

“For penguins and other species, krill is the linchpin in the food web. Regardless of their environmental preferences, we see a connection between climate change and penguin populations through the loss of habitat for their main food source,” said Dr. Wayne Trivelpiece, lead author and seabird researcher of the National Oceanic and Atmospheric Administration’s Antarctic Ecosystem Research Division. “As warming continues, the loss of krill will have a profound effect throughout the Antarctic ecosystem.”

A 30-year field study of Adélie (ice-loving) and chinstrap (ice-avoiding) penguins shows that populations of both species in the West Antarctic Peninsula and Scotia Sea have declined by respective averages of 2.9 and 4.3 percent per year for at least the last 10 years. Some colonies have decreased by more than 50 percent. Lack of an abundant supply of krill has been particularly hard on fledgling penguins that must learn where to locate and how to catch the prey on their own, having never been at sea before. Data from the study suggest that fewer young penguins are surviving this transition to independence today than in previous years when these crustaceans were much more abundant.

Although chinstrap penguins avoid feeding in icy habitats, sea ice provides the necessary environment for krill to reproduce. Increasing temperatures and reductions in sea ice have made conditions unfavorable to sustain ample populations of this food source. The authors suggest that fishing for krill and increased competition among other predators also have made them less available to penguins.

“Penguins are excellent indicators of changes to the biological and environmental health of the broader ecosystem because they are easily accessible while breeding on land, yet they depend entirely on food resources from the sea. In addition, unlike many other krill-eating top predators in the Antarctic, such as whales and fur seals, they were not hunted by humans,” said Dr. Trivelpiece. “When we see steep declines in populations, as we have been documenting with both chinstrap and Adélie penguins, we know there’s a much larger ecological problem.”

Adélie penguins, which feed in icy habitats, are also declining due to food shortages and shrinking habitat. They differ from chinstrap penguins, however, in that they have breeding populations outside of the western Antarctic, which makes them less vulnerable to the rapid warming in the Antarctic Peninsula region by comparison.

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