Matt Parker

Matt Parker, a N.C. State University associate professor, sounded almost nostalgic when he talked about the more than 700 tornadoes that were reported roaring across the South, Southeast and Midwest in April, about four times as many tornadoes as hit the U.S. during an average April.

Parker is an atmospheric scientist and has studied how tornadoes develop to help improve weather forecasts.

“This was a historic year,” Parker told science writers and educators during a Sept. 27 talk at Sigma Xi in Research Triangle Park.

A spring storm season like this year’s doesn’t come around often. That’s a good thing, considering the loss of life and the devastating destruction the tornadoes wrought.

April 2011 ranks as the most active tornado month on record, according to the National Oceanic and Atmospheric Association. A storm system that moved across Oklahoma, Arkansas, Mississippi, Alabama, Georgia, North Carolina and Virginia in mid-April killed 43 people, 22 of them in North Carolina. One of the tornadoes it spawned April 16 cut a 180-foot-long track through suburban Wake County, Parker said.

A second storm system at the end of the month was even deadlier. It caused a super outbreak of tornadoes in the South that killed more than 300 people in four days, according to NOAA.

A month later, on May 22, a powerful tornado hit Joplin, Mo., killing 157 people. According to NOAA, the Joplin tornado packed winds of more than 200 miles per hour, it was nearly a mile wide and its track lasted 6 miles.

What about climate change? Could that be a cause for the historic outbreak of tornadoes this year?

“We really don’t know,” Parker said.

A tornado is a mere blip in a 100-year data set that tracks changes in the climate, he said. The increase in the number of reported tornadoes, he added, is likely due to better forecasting and warning systems, a higher population density and the increase in the number of storm chasers.

What was devastating and deadly to the people who lived in the tornados’ way could have provided scientists like Parker with a bevy of otherwise hard-to-come-by data.

In May and June of 2009 and 2010, Parker and his team of students were among about 100 scientists who tracked storms with radar, measured wind speeds, sent up weather balloons and fed the information to a database.  The study, called VORTEX2, was one of the largest field studies to determine the origin of tornadoes and a follow-on to a more limited tornado hunt in 1994 and 1995. The teams had about $10 million worth of equipment at hand.

April 2011 was never part of VORTEX2′s data collection phase.

Working with tornadoes is often frustrating, Parker acknowledged. May and June 2009 were two very uneventful months – only two storm systems that generated tornadoes.

“Two thousand ten was much better,” Parker said. “On some days we had the pick of tornadoes.”

About 40 storm systems with the potential to generate a tornado, also known as super cells, and about 20 tornadoes occurred in May and June 2010, he said.

A super cell starts similarly to an ordinary thunderstorm. Warm, moist air rises amidst cooler surroundings and the moisture condensates. In an ordinary thunderstorm, the precipitation creates a cool downdraft that cuts off the warm, moist updraft within about 30 to 45 minutes. The storm dissipates.

A super cell thunderstorm develops when strong upper-level winds allow the warm, moist updraft to continue for up to six hours. The stage is set for the downdraft and the updraft to begin rotating.

But the process that produces a tornado in a super cell thunderstorm is not well understood, Parker said.

For example, strong super cells are not associated with tornadoes, he said. Storms with similar structures may differ in tornado production. And the relationship between near-ground wind fields and structural damage isn’t clear either.

Scientists hope that once the VORTEX2 data is crunched and analyzed and published, some of the questions will be answered, Parker said. Especially head-to-head comparisons of data collected from storms that generated tornadoes and storms that didn’t might be fruitful.

Goals of the VORTEX2 study are to extend the average lead time for tornado warnings from about 13 minutes currently to at least 35 minutes and reduce the false alarm rate, which is currently at about 70 percent.

Douglas Nychka

SAMSI, a collaboration of the RTP area’s three main universities, the RTP-based National Institute of Statistical Sciences and the National Science Foundation, picked climate change as a topic for the talk on Feb. 15 and invited Douglas Nychka, a leading statistician and climate expert at the National Center for Atmospheric Research in Boulder, Colo., as its inaugural speaker.

Nychka didn’t go into the depths of the criticism that has dogged data-driven climate change modeling for more than a decade and has left most Americans convinced they can’t do anything to change global warming.

Only 18 percent of Americans strongly believe global warming is real, harmful and caused by humans, according to the 2008 American Climate Values Survey.

“This is an argument about cause and effect,” Nychka said.

He did, however, say that it was very difficult to statistically reproduce the global warming trend without including greenhouse gases from fossil fuel consumption.

Ample data exists that temperatures worldwide have been rising over the past 50 years to 100 years, according to two reports. One was issued in 2006 by a committee the National Research Council assembled upon a Congressional request, the other followed the next year and was authored by the Intergovernmental Panel on Climate Change, an international scientific organization also known as IPCC. (Read the reports here and here.)

The Earth warmed about 1 degree Fahrenheit in the 20th century and the years from 1995 to 2006 were the 12 warmest since the instrumental record of global mean surface temperatures began in 1856. Temperatures in oceans, the top permaforst layers and the lowest part of the atmosphere have followed the warming trend.

At the same time, the amount of Arctic sea ice has shrunk (about 8 percent since 1978) and glaciers and mountain snow cover have decreased (about 7 percent since 1990). The average global sea levels have risen at least 3 inches since 1960. Heat waves, heavy downpours and extreme high sea levels have become more frequent. North of the equator, spring comes earlier, plants have increased their pollen production and the number of heat-related deaths in Europe is on the rise.

“The average northern hemisphere temperatures during the second half of the 20th century were very likely higher than during any other 50-year period in the last 500 years and likely the highest in at least the past 1,300 years,” the IPCC report read.

The conclusion is based on surface temperature reconstructions that look back 1,000 years or more. The first of these reconstructions was published in 1999. It is known as the “hockey stick” for veering up at the beginning of the 20th century and Nychka featured it in his SAMSI talk.

Source: Michael Mann, Raymond Bradley: Northern Hemisphere Temperatures During the Past Millennium; Geophysical Research Letters; March 1999

Michael Mann and Raymond Bradley, the fathers of the hockey stick, used a variety of measurements to reconstruct temperature patterns, including tree ring and ice core records. They noted that the data available was sparser for the earliest four centuries than for the period after 1400.

The centuries for which they had less data included a warm period in the North Atlantic that lasted until the 13th century and was followed by a cooler period during the 17th century and the 18th century for which more data was available.

Reconstructing temperature patterns hundreds and thousands of years ago provide climate scientists with yard sticks to assess temperature patterns during the 20th century, when an increase in fossil fuel consumption produced more and more greenhouse gases. Man-made carbon dioxide emissions increased about 80 percent from 1970 to 2004.

Global warming skeptics do not necessarily question that the Earth is getting warmer, but they do question that the warming is unprecedented in the past 1,000 years and that it is man-made.

Stephen McIntyre, a retired Canadian minerals prospector and mathematician, and Ross McKitrick, an economist at the Canadian University of Guelph, were among the first critics of the hockey stick and McIntyre has continued his critique on a blog called Climate Audit. Proponents of man-made global warming promote their views on blogs like RealClimate, which is written by climate scientists.

McIntyre and McKitrick found fault with the statistical analysis that produced the hockey stick. They also suggested that Mann and Bradley cherry-picked ring records of a tree that underwent a peculiar growth spurt in the 20th century and that the warm period more than 800 years ago – before fossil fuel consumption produced greenhouse gases – was warmer than the 20th century.

The committee put together by the National Research Council agreed with some of the points McIntyre and McKitrick made.

Then, the committee repeated the statistical analysis with the adjustments McIntyre and McKitrick suggested. The result was that the early 15th century was a fraction of a degree warmer than Mann and Bradley had figured. But the spaghetti plot, so named because of the multiple lines representing measurements from tree ring width to cave deposits, still followed the general shape of a hockey stick.

Source: National Research Council: Surface Temperature Reconstruction for the Last 2,000 years; 2006

The committee determined that the surface temperatures of the 20th century are “a well documented, globally coherent warming trend that is happening north, south, east and west; at low altitudes and high altitudes; over land and over – and into – the sea.”

McIntyre also criticized the spaghetti plot, saying it is based on similar measurements as the hockey stick. Nychka, who featured the spaghetti plot in his talk as well, acknowledged that some uncertainty remains. But he suggested that using different statistical methods to test the man-made global warming findings again and again is the best response.

As an example, he presented an unpublished Bayesian approach he and two collaborators, Caspar Ammann of the National Center for Atmospheric Research and Bo Li of Purdue University, worked on.

Sources: The Hockey Stick and the 1990s: A statistical Perspective on Reconstructing Hemispheric Temperatures; Tellus, 2007; and The Value of Multi-Proxy Reconstruction of Past Climate; Journal of the American Statistical Association, 2010.

The Bayesian approach, which measures probability based on what is known, shows a more pronounced cooling period in the 17th century followed by a warming trend that takes off at the beginning of the 20th century and is clearly unprecedented in 1,000 years.

For most climate scientists, the question whether the warming trend that started in the 20th century is man-made has been answered unequivocally. They are moving on to predicting climate trends in the 21st century based on variables gleaned from temperature patterns in the past.

Models that look ahead may not give deep detail, Nychka said, but they could provide useful information when their predictions are pooled.

Combining two climate models developed at the U.S. Geophysical Fluid Dynamics Lab near Princeton, N.J., for example, Nychka said, results in a prediction that temperatures in North Carolina are likely to warm 5 degrees to 7 degrees Fahrenheit from 2040 to 2070.

As a first-time attendee and representative of Science in the Triangle, I divided my time between chasing down interviewees and attending panels, which were organized by participants on an online wiki.

One of those interviewees, Katie Mosher of NC Sea Grant, told me that she’d observed a coming together of science blogging and science journalism in the three years since she’d started attending ScienceOnline. More journalists are using the blog form either to replace or to supplement their print or broadcast stories, she said, some of them writing in traditional journalistic objective form and some of them adopting a point of view. Some of those journalists were present at the conference, just as she sees bloggers now attending conferences hosted by organizations like the National Association of Science Writers.

But journalists appeared to be outnumbered at the conference by scientists who blog (or tweet, or both). As a professional writer who frequently covers science, I should perhaps see these scientist-bloggers as competition. Not at all. To me, they are representative of a welcome trend in academics to communicate with the public about scientific findings and (sometimes controversially) the public policy implications of these findings. A scientist-blogger who writes well (perhaps one who attended the panel by Carl Zimmer and Ed Yong on avoiding obfuscation in science writing) and who knows how to attract an audience can have an immediate impact on public understanding of breaking news, as has been the case with the scientists at Deep-Sea News who covered science surrounding the Gulf oil spill. (Bora Zivkovic explains why scientists are such good explainers.)

A scientist-blogger takes some professional risks. Although I was unable to attend “Perils of Blogging as a Woman under a Real Name,” panelist Kate Clancy provides a detailed writeup here, which alludes to the skepticism with which academic colleagues and tenure and promotion panels view blogging and similar “soft” activities.

A scientist-blogger has to deal with certain downsides of being an online presence, most notably “cranks . . . who come onto our sites and leave comments that foment dissension rather than productive commentary,” according to Rick MacPherson, interim executive director and conservation programs director at the Coral Reef Alliance. It happens wherever evolution or climate change are discussed, he said, and he is the target for negative comments every time he writes or is interviewed about the role of climate change in sea level rise and ocean acidification, both threats to coral reefs.

According to MacPherson, the negative commenters are evidence that the general public doesn’t understand the evidence-based nature of science. “People don’t understand how science works,” he said. “It’s not a democratic process. . . . not opinions.”

His sentiments were echoed in “Lessons from Climategate” by panelist Chris Mooney, coauthor of Unscientific America: How Scientific Illiteracy Threatens our Future, who listed these depressing statistics:

• only 18 percent of Americans know a scientist
• just 13 percent follow science and technology news
• 44 percent can’t name a scientific role model; those who can most frequently name Albert Einstein, Al Gore, and Bill Gates, two of whom are not scientists
• in every five hours of cable news, just one minute is devoted to science and technology

According to Mooney, the situation “is ripe for climate skeptics; they are well-trained, skilled communicators who exploit lack of public knowledge and are willing to fight hard in ways climate scientists are not.” His co-panelist Josh Rosenau, who works to defend the teaching of evolution at the National Center for Science Education, said that the language of the attacks against climate science has an eerie parallel in the attacks against evolution. “For 90 years we’ve been fighting same battle,” he said. “Public opinion has not moved. If that happens to climate change we are doomed.”

Mooney and Rosenau were joined on the panel by Thomas C. Peterson, chief scientist at NOAA’s National Climatic Data Center in Asheville. Peterson was one of the climate scientists whose emails were hacked and published just a few weeks before the 2009 Copenhagen Climate Summit. Although his role in the affair was minor, he was excoriated in blogs (Peterson reminds us that some “science” blogs are unsound scientifically), subjected to harassing calls and emails, and asked by a congressman to produce all emails on the topic (which he did, and which vindicated him). Yet he was still subsequently elected by his peers to be president of the World Meteorological Association’s Commission for Climatology. Clearly, in his professional circles, he is a rock star even if some of the public doesn’t think so.

For Peterson and his co-panelists, the implication is clearly that the public doesn’t understand scientists the way scientists do. Mooney said that the climate emails were taken out of context by people who don’t understand science or scientists. His solution: train “deadly ninjas of science communication”–people who can frame the message and convey science clearly to different constituencies. He wants good communicators to claim the vacancies created when CNN dumped its entire science reporting unit and when daily newspapers gradually reduced their science coverage.

That’s a space that good scientist-bloggers can occupy alongside professional writers: reporting on science from the trenches, bringing scientific research alive, demystifying the scientific method, and unveiling the wealth of unsound science out there.

Notes:

Read my colleague Sabine Vollmer’s post on credibility in science blogging here.

A great resource for finding science blogs is scienceblogging.org.

Higher concentrations of carbon dioxide are pumped into four of the experimental rings. Photo: Will Owen

Late in 2010, an epic ecological experiment in the Triangle will begin drawing to a close when carbon dioxide stops pumping from four massive rings of towers in the Duke Forest. Since 1996, more than 250 scientists at Duke and dozens of other institutions have measured the response of this forest ecosystem to the elevated amounts of carbon dioxide expected in the Earth’s atmosphere in the future. They’ve measured tree and plant growth, photosynthesis, leaf size, soil composition, root growth, and water use in the plots bathed in elevated carbon dioxide and in three other “ambient” control plots.

The first, prototype ring was built in 1994; six more came in 1996 (three controls and three experiments). Each ring consists of 16 metal towers in a 30-meter diameter. Computer-controlled instruments in the experimental rings bathe the interior of the plot in carbon dioxide. It’s called Free-Air CO2 Enrichment, or FACE. As opposed to “chamber studies,” in which plants are studied in carefully controlled growth chambers or greenhouses, the rings are open to nature. That means that mammals and insects can circulate freely and that natural events like hurricanes, ice storms, and droughts affect the research site.

Shannon LaDeau, who studied seed and pollen production at the site as a Ph.D. student, fondly calls it the EcoCircus, referring to both the ring-shaped sites and the riot of instruments, leaf-collection baskets, and colored flags staking out individual research groups’ claims to a particular layer of soil or stand of plants. LaDeau is one of at least 25 scientists who conducted Ph.D. research at FACE. “One of the really big bonuses of that site and others like it,” she says, “is that people are coming at it from different directions—biogeochemistry, biology, and so on.” There was an integration of ideas, she says, that “doesn’t happen naturally when scientists go out and choose their own site and do their own thing.”

Photo: Lisa M. Dellwo

I talked recently with Ram Oren, Nicholas Professor of Earth System Science at Duke and co-principal investigator for the project since 1998. He explained that the Department of Energy–funded project will enter a final phase this fall when the carbon dioxide is turned off. A scientific team will follow the trees for two more years to see how they respond to the “severe diet” that will be imposed on them when they are no longer receiving the added carbs.

Oren reminded me that when the experiment began, it was already well documented that trees grew faster under higher levels of carbon dioxide, especially when they were well nourished and watered. Retired Duke ecologist Boyd Strain and his students and colleagues had already established this in studies in which trees were isolated in growth chambers and treated with different regimes of carbon dioxide, nutrients, and water.

The FACE experiment was intended to test how entire ecosystems, not just trees, responded to additional carbon dioxide. In particular, researchers wanted to know if trees and soils would store or sequester extra carbon dioxide, keeping it from the atmosphere where it would contribute to a warmer climate.

The early major findings of the experiment were that, similar to the chamber studies, plants in the forest did indeed grow faster when exposed to extra carbon dioxide, especially in the presence of plentiful water and nutrients. And the ecosystem did store more carbon, but mostly in plant stems, not in soil as had been predicted.

Photo: Lisa M. Dellwo

A second wave of findings showed that the continuing growth response of plants to a “high-carb” diet depended on the native fertility of the site. Trees in fertile areas responded strongly to the carbon dioxide treatment and continued a higher growth rate, but trees in infertile areas didn’t retain their original growth response.

That’s important in the real world, because our most fertile soils tend to be cultivated for agriculture, leaving forests in less fertile areas. So we cannot expect trees to retain extra carbon in the forests of the future, says Oren.

While some scientists were studying tree growth and soils, others were finding that poison ivy has a remarkable response to higher CO2 conditions. Not only did it grow two times as fast as poison ivy in ambient conditions, but it produced much more toxin per leaf.

Shannon LaDeau, who conducted pollen studies, told me that the trees exposed to extra CO2 reached reproductive maturity at a younger age and smaller size. For those of us who suffer allergies, that is a bit ominous. While pine pollen—the yellow-green stuff that bathes the Triangle every spring—is not technically considered an allergen, other trees with true allergy-causing pollen may well have the same response as the pines, LaDeau says.

In 2004, when this photo was taken, the towers were still higher than the treetops. Now the trees have outgrown the towers. Photo: Lisa M. Dellwo

When the Department of Energy announced two years ago that it would cease funding the FACE project in Duke Forest—and similar projects elsewhere—Oren said that the project had not reached its true conclusion. He still believes that. But funding aside, there is a technical reason the project is drawing to a conclusion: the trees have outgrown the towers. When the experiment began, anyone who entered the site or who happened to fly over it could see the rings of towers clearly above the canopy. Now, trees that measured ten meters in 1996 are 21 meters high, and the towers have receded into the canopy.

In addition to the generation of ecological scientists trained at the site and the more than 250 papers reporting on the response of the ecosystem to elevated CO2, Oren believes that an important legacy of the FACE experiment will be the data gathered there over 17 years. Very few experiments last that long, and the accumulated data from FACE is being made available to computer modelers who will use it for years into the future to test and extrapolate responses to future climate change on a larger scope.

Cryptococcus gattii

In Africa, South America, Southeast Asia and Australia, crytococcus gattii infects eucalyptus trees and bothers people with compromised immune systems, such as HIV/AIDS patients and organ transplant recipients, who inhale its spores. But the strain that was first documented on Vancouver Island, Canada, a decade ago and has now spread to Seattle and Portland causes chest pain, fever, shortness of breath and weight loss in otherwise healthy people and has killed at least six of them.

In February 2007, the first North Carolina case, an otherwise healthy man, was treated at Duke University Medical Center, the Duke researchers reported in PLoS One. In a paper they published a week ago in PLoS Pathogen, the researchers wrote that the cryptococcus gattii strain in the Pacific Northwest was new, much more virulent and favored mammals.

The second Duke paper followed on the heels of a report on human health and climate change that was authored by a group of researchers from several federal agencies. Lead author of the report was Christopher J. Portier, the head of the environmental systems biology group at the National Institute of Environmental Health Sciences in Research Triangle Park.

“The purpose of this paper is to identify research critical for understanding the impact of climate change on human health so that we can both mitigate and adapt to the environmental effects of climate change in the healthiest and most effective way,” the report from the Interagency Working Group on Climate Change and Health read.

Filling research gaps in new diseases and well-known diseases that are coming back because of altered growing seasons, more rain in some areas and droughts in others, more violent storms and rising temperatures has been on researchers’ minds for years.

In the past decades, they have identified 30 new diseases, including hepatitis C, avian flu, HIV/AIDS and severe acute respiratory syndrome, or SARS, according to a 2004 report in Nature Medicine. Environmental changes are among the reasons for the emerging diseases. But researchers have also tracked a resurgence of previously documented diseases in new geographic areas, among them tuberculosis and cholera.

The report from the federal interagency working group zeroed in on the following research areas:

• More mold, dust, pollen and air pollution are likely to increase the prevalence of airway diseases such as asthma and respiratory allergies, which already affect about 50 million Americans.
• More information is needed on how climate change affects exposure to toxins and chemicals that might boost cancers, with about 500,000 deaths per year the second leading cause of death in the U.S.
• Heat waves and rising global temperatures could increase the number of heat-related illness and death. The 2003 heat wave in Europe, for example, caused about 35,000 deaths.
• Some birth defects linked to environmental causes have been steadily increasing.
• Exposure to biotoxins from ever more frequent, harmful algal blooms and chemicals from new batteries and compact fluorescent light bulbs could boost neurological and waterborne diseases.
• By 2050, about 200 million people are expected to be displaced by the effects of climate change. The population relocation and the changes in temperatures could cause a resurgence of diseases caused by insects, such as malaria and yellow fever, which were once rampant in parts of the U.S.

The RTI analysis is based on the “Blueprint for Legislative Action,” a plan by the U.S. Climate Action Partnership that includes mandatory  reductions of CO2 emissions. The partnership, which is a group of businesses and environmental organizations, recommended emissions reductions of 80 percent to 89 percent by 2020 and a 58 percent by 2030.

Enforcing these targets will cost U.S. households an average $89 per year in 2020 and $269 in 2030, RTI researchers figured. The projections are in 2007 dollars.

The cost increases come mostly from moderately higher electricity and natural gas bills and a 15 percent increase in petroleum prices by 2030. That means, a gallon of gas would cost $4.42 instead of $3.84, according to the RTI study. (More about the study results here.)

RTI, a research institute based in Research Triangle Park, released the study results Thursday, while negotiators from 192 countries talked about climate change in Copenhagen. Earlier in the week, the U.S. Environmental Protection Agency announced plans to regulate greenhouse gases under the Clean Air Act. And on Friday, U.S. Senators John Kerry, D-Mass., Lindsay Graham, R-S.C., and Joe Lieberman, I-Conn., will submit their legislative plan on CO2 emissions control.

UNC marine scientist Justin Ries holds two tropical pencil urchins grown under different seawater acidities. (Photo by Tom Kelindinst, WHOI)

Unlocking causes of past mass extinction events is a nifty – if not controversial – trick. But forecasting the future while also explaining the geologic past is even niftier. And that is just what a new study attempts to do by documenting experimental effects of ocean acidification upon shelled marine invertebrates.

The study, published Dec. 1 in Geology and led by a University of North Carolina scientist, reports a spectrum of positive to negative responses across seven major groups of calcifying marine organisms. It also offers supporting evidence for understanding patterns of past mass extinction — and survival — seen 251 million years ago at the Permian-Triassic boundary.

UNC marine scientist and lead author Justin Ries said that he and his team wanted to reconstruct conditions from the past to test whether carbon dioxide-induced climate change might have triggered past extinction events that removed certain shelled marine organisms from the fossil record while spurring diversification of others. Exactly why some species survive extinction events and others live or even thrive is a key question that scientists wrestle with. Ries said that an emerging body of research suggests that the Permian-Triassic extinction may have occurred because of a massive ocean acidification event. Also known as the “Great Dying,” this event resulted in an estimated 96 percent of species disappearing from the oceans.

To test the patterns of survival and extinction known from the fossil record, Ries and his colleagues from Woods Hole Oceanographic Institution in Massachusetts devised experimental tanks holding seawater and then adjusted the pH to match today’s atmospheric CO2 levels (440 parts per million), as well as elevated levels that existed 110 million years ago, during the mid-Cretaceous (2850 ppm).

“We chose the Cretaceous time point because it represents a CO2 maximum in the geologic past,” Ries said. Conditions in the Cretaceous included increased volcanic activity and rapid ocean crust production and sea floor spreading. This geologic activity pumped massive amounts of carbon dioxide into the atmosphere, spiking global concentrations which may have led to oceans being more acidic than today’s.

For 60 days, the researchers reared marine organisms representing the major invertebrate calcifying groups that inhabit the seafloor — such as urchins, algaes, clams, lobster and crabs — and then they compared the animal’s calcification rates under the modern and elevated carbon dioxide conditions. The most unexpected finding was that some crustaceans, like American lobsters, shrimp and blue crabs, grew bigger and heavier shells under the mid-Cretaceous carbon dioxide levels. The larger shells mean that the animals were increasing their rate of calcification despite the increased seawater acidity. Other species like pencil urchins and hard and soft clams grew thinner shells or suffered their hard parts dissolving under the acidified seawater conditions.

Andrew Knoll, an evolutionary biologist at Harvard University, said he thought Ries’s paper moved the field forward in important ways, toward thinking about the differential responses organisms may have to changing ocean pH. “I’m pleased, if not entirely surprised, that the responses documented in Justin’s experiments are pretty much in accord with patterns of extinction and survival at the Permian-Triassic boundary, when CO2 is thought to have reached transiently high levels,” Knoll wrote in an email. “For example, during the Permian-Triassic extinction, corals disappear completely, mollusks show a limited response, and arthropods actually increase in diversity.”

Bob Steneck, a marine biologist at the University of Maine in Orono said that the Permian-Triassic boundary was “absolutely the event to look at” to test patterns of extinction and survival in shelled marine organisms. “Of the five big extinction events, that was the biggest,” Steneck said. “And following the P-T extinction, the early Triassic was almost devoid of calcifying organisms. Theirs is the right kind of experiment to do for the right reasons; it’s just that the results are so surprising.”

Steneck said some of the organisms in the experiment responded in ways that scientists would expect. For example, many of the corals suffered eroded exoskeletons under the higher seawater acidity. “But what is harder to understand,” he said, “is why… as the oceans acidify, why is it that some organisms would calcify more robustly?”

Ries said the pattern of how the species fared in the differing CO2 scenarios was dependent upon several factors. He’d hypothesized that because organisms make different kinds of calcium carbonate shells, their vulnerability to acidified seawater would vary with their shell’s specific mineralogy. The three most common forms of calcium carbonate shells are aragonite, high-magnesium calcite and low-magnesium calcite. Because aragonite is more likely to dissolve when exposed to even slight changes in pH that increase the acidity, Ries said it made sense that animals using this form of calcium carbonate would be more vulnerable. And because low-magnesium calcite can hold up to slight changes in pH, it also made sense that animals using this form would be more resistant to acidified waters. To a large extent, they found this to be true.

“But there were some other factors at play,” Ries said. Animals that had a layer of tissue between their exoskeleton or shell — what scientists might call an epidermis, epicuticle or a periostracum — and the seawater appeared to fare better and the tissue seemed to play a powerfully protective role. And if animals were able to control pH at their calcification sites, literally buffering the acid surrounding it, they also fared much better, but with unknown energy costs. The presence of photosynthetic processes also appeared to benefit certain species and confer some protection; this even led to greater calcification in corals under the intermediate CO2 levels.

The team’s results are both forward and backward looking. They foretell a complex future of mixed responses among species to ocean acidification, and they also support the idea of preferential survival of certain species during CO2-induced climate change.

“Both biologists and paleobiologists have long predicted that ocean acidification will result in winners and losers in the oceans,” said Knoll, the evolutionary biologist at Harvard. “Justin’s research helps us to understand who the winners and losers might be.”

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MORE INFO:
Atmospheric carbon dioxide concentrations drive seawater acidity because the oceans act like a giant sponge soaking up CO2. But carbon dioxide dissolves in seawater and forms carbonic acid, lowering the ocean’s pH. Scientists have documented a 0.1 unit change in the oceans’ surface pH since the Industrial revolution, and they expect it to decline up to 0.5 units by the end of this century – leading to questions about how an acidified ocean will affect the creatures living there.

Today’s increasing concentrations of atmospheric CO2 are widely believed to be caused by humans burning of fossil fuels. But if the current trajectory of CO2 building up in the atmosphere does not change, then within 500 to 700 years our planet’s oceans could return to the acidified conditions that existed in mid-Cretaceous. This means that patterns of past mass extinctions — thought to have been triggered by spikes in atmospheric CO2 — could be repeated.

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OTHER MEDIA: ScienceNOW, USA Today