Science Special: Climate Change

  In Antarctica, the emperor penguin population has been halved as rising temperatures wipe out their prey, the shrimplike crustacean, krill.
Study links thousands of ecological changes to human-induced warming

Mainstream climate scientists have been in agreement for at least a decade: Global warming is real and it’s almost certainly caused by pollution. What exactly are its effects? That’s more difficult to say because animal populations and ocean currents, for example, are dynamic systems that respond to innumerable forces.

A new study led by Cynthia Rosenzweig, a Columbia senior research scientist, has provided the most comprehensive answer to date. Her paper is “the first to formally link” specific instances of environmental disruption to greenhouse gas emissions, wrote the editors of Nature upon publishing the findings May 15. Scientists from 10 countries worked on the project.

The researchers examined 80 previous studies that had monitored 29,000 natural systems between 1970 and 2004. Most of the studies examined the impact of climate change on plants and animals; others looked at its impact on land, water, and ice. All of the phenomena were monitored for at least 20 years.

Rosenzweig and her colleagues first counted how many of the 29,000 natural systems had changed in ways consistent with warming. Based on the conclusions of the original authors, 90 percent of the biological systems showed the effects of rising temperatures, such as penguins dying off, as did 95 percent of the physical systems, like glaciers melting. “You wouldn’t expect a 100 percent correlation across all these studies,” explains Rosenzweig, “because members of an animal species, given their genetic variations, for instance, won’t respond to warming all in the same way or at the same time.”

The next part of Rosenzweig’s study is the breakthrough: She and her collaborators plotted the location of every instance of ecological disruption and noted the local temperature trends since 1970. Her team then analyzed the average temperatures against computer models that calculate the natural climate variability for any spot on the planet, for any year.

The results are staggering. Ecological damage occurred almost exclusively in places where highly unnatural levels of warming were recorded in recent decades. Rosenzweig’s team also considered information from the original studies regarding habitat destruction, overfishing, land and water pollution, and other complications to determine if these factors might have contributed to the ecological damage. But they generally had little impact. In the end, Rosenzweig concluded that just 10 of the roughly 26,000 documented cases of ecological damage could be explained by factors other than warming.

The extreme warming in these areas could only have been caused by greenhouse gas emissions, wrote Rosenzweig and her colleagues, all of whom worked on last year’s 3000-page report of the U.N. Intergovernmental Panel on Climate Change (IPCC). That study, produced by 1000 leading climate scientists, stated with at least 90 percent certainty that the burning of fossil fuels is the primary cause of rising temperatures worldwide.

“Now we’ve closed the loop by linking the warmer temperatures to specific impacts,” says Rosenzweig. She and the other IPCC scientists shared the 2007 Nobel Peace Prize with Al Gore. “Why should we care about global warming?” she says. “Now we can answer that question very specifically.”

Among the effects of global warming, finds the Nature study, is early leafing and flowering of 89 plant species in North America, changes in bird migrations across Europe, the decline of polar bear and penguin populations, and the movement of hundreds of animal and plant species worldwide to higher altitudes and toward the earth’s poles. Other effects include the melting of glaciers, especially in Peru, Alaska, and the Alps; the thawing of permafrost in Russia, which threatens to release into the atmosphere huge concentrations of carbon now frozen underground as mulch and animal bones; and the quicker melting of mountain snowpacks on most continents every spring, which initially causes floods, and later, droughts.

The study, “Attributing physical and biological impacts to anthropogenic climate change,” can be read at

—David J. Craig

  University launches Climate Center

Columbia faculty are working on nearly every aspect of climate change, from the analysis of ice cores to the modeling of weather systems to the development of solar energy to the improvement of flood response in coastal cities.
The University recently created the Columbia Climate Center to promote collaboration among these experts. The goal is to identify research gaps and facilitate new multidisciplinary projects.

“Columbia’s greatest strength in climate research, historically, has been in paleoclimatology, which looks at geologic records to understand how climate changed in the past,” says Steve Cohen, executive director of Columbia’s Earth Institute, which oversees the new center. “But we’ve been getting into adaptation and mitigation issues more and more in recent years. So our scientists have been asking questions, like, how do you reduce carbon dioxide? And how does society adjust to global warming?”

This research requires input from engineers, social scientists, public health experts, as well as from natural scientists. “Intellectually, the climate problem is among the most complicated problems humankind has ever faced,” Cohen says. “To solve it, we have to get our best brains working on it together.”

Peter Schlosser, a professor of earth and environmental science, directs the Climate Center; Mary-Elena Carr, an oceanographer who came to Columbia last November, is the associate director.


  James Hansen recently addressed a congressional global warming committee, offering sharp words for special interests that he says have blocked the development of green energy.
Hansen to Congress: Time is running out to save environment

Twenty years ago, James Hansen made global warming a political issue almost overnight. The Columbia professor told a Senate committee he was “99 percent certain” that pollution was already warming the earth, causing droughts and heat waves. Lawmakers had to “stop waffling” and deal with the problem, he vented to reporters as he left the Senate chamber.

Never before had a prominent climate scientist argued publicly that global warming was under way. Hansen’s testimony made headlines around the world and the “greenhouse effect” a household term. Within weeks, several members of Congress had sponsored bills aimed at regulating carbon dioxide emissions and George H. W. Bush promised to mobilize the international community to fight global warming if he was elected president.

Hansen returned to Capitol Hill on June 23, the 20th anniversary of his famous testimony, to update lawmakers on the state of the planet. He spoke at a special hearing organized in his honor by Representative Edward Markey (D-MA), who called Hansen “a hero.”

What’s changed in 20 years? “The difference is that now we’ve used up all slack in the schedule for actions needed to defuse the global warming time bomb,” said Hansen, who directs NASA’s Goddard Institute for Space Studies, a Columbia affiliate. He accused Congress of having done too little to promote alternative energy or limit greenhouse gas emissions. Progress has been blocked, he said, because coal and oil companies have convinced the public that the basic science of global warming is in dispute.

“CEOs of fossil energy companies are aware of the consequences of what they are doing,” said Hansen, 67, in his calm, midwestern accent. “These people should be tried for crimes against humanity.”
What should lawmakers do? Stop construction of coal plants until technology can suck the carbon dioxide out of their smoke stacks, Hansen said, and develop a nationwide grid for alternative energy, such as from wind- and solar-powered generators.

“A path yielding energy independence and a healthier environment is, barely, still possible,” he said. “It requires a transformative change of direction in Washington in the next year.”


  Light green areas on this map depict adequate water supplies, while the dark areas show where too little fresh water exists for the local population.
Greenhouse blowback?

It could start with a drought, as shifting wind patterns blow rain clouds farther north of the Sahara each year. Or a storm could trigger a crisis, if a massive typhoon annihilates the slums of Karachi or Dhaka. Millions of refugees then would pour into countries whose governments are ill equipped to help, possibly sparking violence along ethnic lines.

Many U.S. lawmakers worry that catastrophes like these are more likely to occur as the planet warms, causing sea levels to rise, tropical storms to grow in intensity, and drinking water to dry up. The National Intelligence Council (NIC), at the request of the House and Senate intelligence committees, on June 25 issued a report about how climate change could affect U.S. security interests around the world. The report is confidential, but the NIC permitted some researchers who were involved, including Columbia geospatial data expert Marc Levy, to release findings they contributed.

Levy and several colleagues at Columbia’s Center for International Earth Science Information Network (CIESIN), which is part of the Earth Institute, were asked to assess the vulnerability of 183 nations to drought or flooding over the next 20 years. The Columbia researchers analyzed huge data sets composed of census figures, information from satellite images, and the results of previous climate studies to identify susceptible areas that are densely populated. The researchers also considered each nation’s ability to deal with such crises based on the stability of its political and economic institutions. They concluded that South Africa, Nepal, Morocco, Bangladesh, Tunisia, Paraguay, Yemen, Sudan, Côte d’Ivoire, Poland, and Iraq are potential trouble spots to watch.

Other nations that could experience internal turmoil include Iran, Sudan, Kuwait, Congo, Ethiopia, and Jordan, given the likelihood of diminished rainfall and crop failures. Some countries — the Netherlands, China, Egypt, Indonesia, and the Philippines among them — have large numbers of citizens in low-lying coastal areas but also have a reasonable capacity to deal with disasters such as floods, Levy and his colleagues concluded.

“There is clearly great interest among policy makers in knowing whether climate change will make crises, such as the conflict in Darfur, more prevalent,” Levy says. “The science of climate change does not yet give us a definitive answer to this question, but at least now we’re looking at it seriously.”

The NIC now plans to study how global warming could affect relations among the major powers and whether combating climate change could create unintended security risks.


  If a hurricane made landfall near New York Harbor today a large portion of Manhattan would be submerged, a scenario that worsens as sea levels rise, says Columbia professor Klaus Jacob.
Let’s see if it floats

Sea levels are expected to rise one to three feet this century, mainly as a result of melting ice at the earth’s poles. This threatens all coastal communities, and New York City is especially at risk: It has 578 miles of coastline among its five boroughs and many roads, railways, and airport runways are at sea level or below. To make matters worse, shifting weather patterns are expected to increase precipitation by 8 to 10 percent in New York City by 2080 and hurricanes are expected to intensify.

Columbia scientists are helping city and state officials figure out how to prepare. Seismologist Klaus Jacob, who is an expert on coastal flooding, is creating a 3-D map of the city’s subway system to identify those stations that will become more susceptible to storm surges. His research shows that at the end of this century, because of higher sea levels, storm surges that today would be considered 100-year floods could occur every 10 years. The city, he believes, should consider building floodgates and berms now. “Katrina was a preview of what is coming in many other places,” he says.

Some professors are working with the state Department of Environmental Protection to determine how storm-drainage and water-treatment systems will be affected. New York City, like many municipalities, has a combined drainage and sewer system, meaning that untreated sewage mixes with rain runoff during even minor floods. “We’re using geographic information systems to understand the vulnerability of every neighborhood,” says Cynthia Rosenzweig, a Columbia climate scientist.

Over the next two years, Columbia policy experts and climate scientists also will bring local environmental organizations together to discuss the feasibility of various adaptation strategies, from erecting flood barriers to limiting construction in low-lying areas to planting gardens atop roofs as a way to reduce water runoff. Supported by a $500,000 grant from the HSBC Foundation, the project will send Columbia graduate students to consult for the environmental groups.

“Columbia experts won’t enter this discussion with our minds made up about what is the right approach,” says Steve Cohen, who is executive director of Columbia’s Earth Institute and will lead the outreach effort. “We’re going to facilitate a discussion and go with the consensus that emerges. At the end of the project, the participants should have some hard-and-fast suggestions for the city.”


  Columbia scientists say that vast amounts of liquefied carbon dioxide could be pumped underground or underwater into caverns made of basalt — hardened lava that reacts chemically with carbon dioxide to form a solid substance similar to chalk.
CO2 may get ocean burial

To control global warming, many scientists say we need to minimize the amount of carbon dioxide that coal factories spew into the air, in addition to developing cleaner forms of energy over the long term. This requires inventing a method to vacuum carbon dioxide from factory smokestacks or straight out of the atmosphere, a challenge that Columbia geophysicist Klaus Lackner, among others, is tackling.

How could we store the captured CO2? That’s another tricky problem, and one that Columbia geophysicist David Goldberg and several colleagues think they have solved. They’ve located huge honeycombed basalt formations 9000 feet underwater off the West Coast of the United States. Liquefied CO2 could be pumped into these watery hollows and remain locked away for good, the scientists say. By analyzing data from previous deep-sea drilling experiments off California, Oregon, Washington, and British Columbia, they estimate that about 30,000 square miles of basalt caverns exist there — enough to hold 150 years’ worth of U.S. CO2 emissions.

Burying CO2 isn’t a new idea. A separate research team headed by Columbia geochemist Juerg Matter is preparing to pump liquefied CO2 into an underground basalt formation at a power plant near Reykjavik, Iceland, in the first such large-scale demonstration of the technique. Columbia scientists have previously shown that when CO2 is combined with basalt, which is hardened lava, the two naturally react to create a solid carbonate — essentially, chalk.

Undersea basalt caverns might be bigger and safer than caves beneath solid land, Goldberg says. If CO2 is buried deep below the ocean, he says, any CO2 that doesn’t react with the basalt won’t be able to rise to the surface and reenter the atmosphere, in part because it’s heavier than water. Underwater basalt formations are “immense, accessible, and well sealed—a huge prize in the search for viable options,” says Goldberg.

He and his collaborators, Taro Takahashi, a geochemist and senior scholar at Columbia’s Lamont-Doherty Research Observatory, and Angela Slagle, a marine geologist and postdoctoral student at Lamont-Doherty, hope the U.S. government will fund studies to determine whether pumping CO2 underwater is economically feasible.
The findings appeared July 14 in the Proceedings of the National Academy of Sciences.

—David J. Craig and Kevin Krajick