Danger Ahead

Rising sea levels, catastrophic weather patterns, species disappearing. It could really happen, say Stanford scientists, who are working on a better way forward.

September/October 2005

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Danger Ahead

Photo: Anne Dowie

Some of them wade in the brackish wetlands that swirl around mangrove forests. Some chug through Antarctic ice fields, or check rodent traps in a Montana meadow. Others fiddle with spindly contraptions emitting a faint hissing sound in the grassy hills just west of Stanford, or peer through a microscope at nanoscale solar cells. Another group works in comfortable, air-conditioned offices poring over stacks of studies or printouts of numbers from computer simulations that can take a full year to crunch. But wherever they happen to be, these Stanford scientists operate with a palpable sense of urgency. That’s because they are tackling what may be the most complex and highly charged big science arena today: the quest to understand and mitigate global warming.

The science is complicated because the earth is a living, breathing system whose parts interact in ways not fully understood or easily predicted. Seemingly slight changes in temperature or the atmosphere’s composition can cause repercussions all over the world—and in different, even opposite, ways depending on a host of factors. Grappling with climate change takes the expertise of an alphabet of disciplines, from anthropology to zoology.

The issue has become pressing in the face of more and more observable effects of global warming—on plants, animals, water, air and land—and the widely accepted prediction that the earth’s temperature will keep rising, somewhere between 1.5 and nearly 6 degrees C by 2100. If that seems modest, consider this: a global shift of 6 degrees C downward would make the difference between our current climate and an ice age. Global warming’s effect on sea levels alone will impact half or more of the world’s population who live in coastal areas. Among the possible consequences: entire communities could disappear in Asia, the South Pacific and the Far North and more than a third of U.S. coastal wetlands could be lost.

Although Stanford does not have a department of meteorology or atmospheric science, it nonetheless is home to advanced research aimed at fundamental questions about the impact of climate change on planet Earth. In earth sciences, engineering, economics and biological sciences, as well as several interdisciplinary programs and centers, faculty and students are adding vital evidence for the growing consensus that anthropogenic, or human-caused, factors are shortening winters, melting ice fields and glaciers, and changing animal behaviors and plant life cycles that affect entire ecosystems.

As early as the 19th century, scientists believed they were witnessing warming trends that some speculated could be caused by human activity. Much of the modern concern about the contribution of carbon dioxide and other greenhouse gases to climate change began with the work of the late Charles D. Keeling, of UC-San Diego. Starting in 1955, he collected air samples to measure their COcontent; over the years he showed that levels were steadily rising.

For some time, global warming has been described as a debate, a characterization most Stanford faculty consider inaccurate. In fact, there is no argument among climatologists that the average global temperature has risen since the mid-19th century, by 0.6 degree C (roughly 1 degree F), and that the amount of carbon dioxide in the atmosphere has increased about 30 percent from preindustrial times. The friction comes from a minority of outspoken scientists and social scientists who are not climatologists. They question whether human-generated CO caused this temperature increase, how much warmer it will get and what the results will be, and what we can or should do about it.

Stated broadly, the prevailing thinking is expressed by the United Nations’ 17-year-old Intergovernmental Panel on Climate Change, made up of the world’s leading climatologists and other scientists. The IPCC periodically reviews climate-change research and tries to make projections based upon it. Stanford climatologist Stephen H. Schneider is a professor of biological sciences, a senior fellow at the center for environmental science and policy, and editor and founder of the 30-year-old journal Climatic Change. He is one of half a dozen Stanford researchers who contributed to the IPCC’s most recent report in 2001.

“We know from quite literally thousands of laboratory experiments and direct measurements, millions of balloon observations, and trillions of satellite data bits, that the basic structure of the energy [heat] flows in and out of the earth’s atmosphere is relatively well understood,” Schneider says. He describes the so-called greenhouse effect whereby some of the sun’s heat is trapped instead of radiating back into space: “We know that water vapor, carbon dioxide and methane trap enough energy on earth to warm the surface up about 33 degrees C” higher than it would be in their absence.

The problem is maintaining an optimum concentration of these gases. The IPCC report predicted CO levels could more than double from present levels by 2100, and that the temperature would likely increase between 1.4 degrees and 5.8 degrees C. The panel identified impacts that include sea levels rising as much as 34 inches; increased precipitation; threats to human health from heat stress and the expanded ranges of disease-carrying insects; and loss of life from floods and storms.

Behind the big scary numbers of global warming is a world of field research on earth’s systems and life forms. Adina Paytan, assistant professor of geological and environmental sciences, asserts, “The oceans will dictate where the climate will end up.” She and her colleagues are using biogeochemistry to reach back millions of years, analyzing marine sediments to unearth how oceans responded in the past to fluctuating levels of various gases as well as temperature changes in the atmosphere. For example, they are studying how marine productivity affects atmospheric CO concentrations, since plant organisms in the oceans absorb CO, keeping it out of the atmosphere.

Her lab also studies mangrove forests, which cover large areas of tropical wetlands and are known to be a substantial natural source of methane, another potent greenhouse gas. Paytan and her group have shown that rising sea levels and pollution “will induce changes in the mangrove ecosystems [that] will result in increased methane emissions.” This will amplify the greenhouse effect and may contribute to global warming.

Oceanographer Rob Dunbar, professor of geological and environmental sciences, is exploring far-flung areas from Antarctica to Lake Titicaca. He probes ancient ice cores and sediment for climatic data to help researchers analyze, for example, the impact of a few degrees’ change in climate on vast expanses of sea ice or glacial activity, or the effect of carbon dioxide on coral reefs. Two years ago, Dunbar observed that air temperatures at one of his research sites in Antarctica were 3 to 5 degrees F higher than they had been in 1960. A year earlier, the 1,250-square-mile Larsen Ice Shelf had broken from the mainland and split into thousands of icebergs. Dunbar is outfitting coral near Israel, as well as the Great Barrier Reef in Australia, with instruments designed to monitor their health, because as oceans warm, coral shed the algae that cling to their surface, then “bleach” and die. Coral reefs are a vital fish and marine habitat.

On land, there’s plenty of fieldwork that does not require a passport. Biological sciences professor Chris Field, PhD ’81, commutes to one of the world’s most carefully tended and well-controlled climate change experiments—an easy two-mile drive up Sand Hill Road. On a beautiful spring day, Field, in shorts and hiking boots, strolls up a small hill at Jasper Ridge, the University’s 1,189-acre biological preserve. The hill is covered with grasses, wild oats and dandelions. “This is just a spectacular set of ecosystems,” he says.

Field, who is director of the department of global ecology at the Carnegie Institution of Washington at Stanford, walks to a spindly-armed machine, one of dozens dotting this hillside. What look like desk lamp heads sit at the end of several foot-long arms; black tubing regulates the amount of water this 6-foot grass patch gets, while another device sprays CO into the air above the plants, mimicking CO levels predicted for coming decades.

The Jasper Ridge experiments are designed to study four key elements of global change: a warming in temperature, increased CO, additional nitrogen released into the atmosphere from fossil fuel consumption, and more precipitation. Each input can be adjusted on each plot. “Half of CO is stored in the ocean and the ecosystem on land. We’re interested in whether that free service will continue, increase or decrease,” he explains. Some forecasters have suggested that additional CO levels in the environment will serve to fertilize plants, thus equipping them to trap more CO. Field’s work sheds some doubt on that.

“Ecosystems are not going to solve climate problems,” by absorbing significantly more CO, he says. In 2002, Field’s team found that too much atmospheric CO can retard plant growth instead of increasing it; in 2003, they observed that excess CO combined with a surfeit of water and nitrogen can reduce the diversity of plant species. The same year, in one of their most dramatic findings, Field’s team contradicted many models of global warming by showing it may make some soils wetter, not drier. Jasper Ridge’s grasses and wildflowers normally pull water up out of the soil in a process called evapotranspiration, but when warmer temperatures killed them prematurely, more moisture stayed in the ground.

Conservation biologist Terry Root, a senior fellow at the center for environmental science and policy, has conducted several landmark studies of significant responses by plants and animals to warming temperatures. Root’s research involves what are called meta-analyses: she sits down with massive data from individual studies worldwide and draws larger conclusions from the overall trends. In 2002, she published a paper in Nature showing that global warming was forcing the world’s flora and fauna to shift their ranges and was affecting the timing of spring-related events such as egg-laying and migration. At higher latitudes, she found, these activities were generally happening 5.2 days earlier each decade. And there were extreme reactions: the tree swallow, common in the mid-to-northern United States and Canada, was nesting 20 days earlier than it did 24 years ago.

Root has no doubts about anthropogenic factors. “The temperature in your backyard is being affected by the emissions of people,” she says. In May, she and her colleagues reported in the Proceedings of the National Academy of Sciences that atmospheric greenhouse gases and aerosols cause regional climate change that in turn alters the springtime activity of many animals and plants. In the Northern Hemisphere, for example, plants bloom an average 10 days earlier than they did three decades ago.

What these phenomena may portend is uncertain, but the possibilities are disturbing. While humans have mobility, animals and plants can be hemmed in by mountain ranges, bodies of water or human development. Crops sensitive to higher temperatures may be lost. If insects needed for pollination disappear from a region, that could spell ruin for fruit trees and other crops. Large numbers of birds could die if they hatch earlier than insect food sources arrive. And so on.

One of Field’s students, Kim Nicholas Cahill, ’99, is looking at the impact of climate change on California’s wine industry. “Under warming, grapes ripen earlier and at higher temperatures, which threatens quality,” she explains. Models created to simulate predicted warming suggest that these factors will degrade the quality and conditions for wine grapes in all but California’s cooler coastal regions by the end of the century.

In associate professor of biological sciences Elizabeth Hadly’s lab, graduate students fan out into the field to examine how climate affects the behavior of specific animal populations (see page 50). Hadly published a key paper in 2004 presenting evidence that climate change shifted genetic diversity in two rodent populations in the Yellowstone area. Her analysis of fossilized DNA showed that the rodent populations thinned out considerably during a warming period after a prolonged cool period. In one population of gophers, the fact that they didn’t migrate widely shrank their gene pool. Species cannot withstand diseases and other onslaughts if they become genetically limited.

Questions remain about global warming’s effects and what can and should be done about them. Some climate skeptics say that fluctuations in the earth’s temperatures occur naturally and that there’s no reason to believe we can mitigate the warming. Others think that while humankind may have caused this warming, there are sufficient benefits to it—and such expense associated with trying to stop it—that we should focus on dealing with its impacts rather than mitigation.

“I don’t argue that we’re having global warming, but I find the effects are going to be small,” contends Thomas Gale Moore, an economist and senior fellow at the Hoover Institution. He insists that Americans in particular will benefit from a warmer climate in many ways, including longer growing seasons and reduced heating costs.

For its part, the Bush administration maintains that the science is still too uncertain a basis for far-reaching and potentially expensive policy decisions. It used that position to justify rejecting the Kyoto Protocol, an international treaty in which more than 140 nations committed to reduce their emissions of carbon dioxide and five other greenhouse gases, or engage in emissions trading if they maintained or increased emissions.

Schneider, who drives a hybrid vehicle with the license plate LES CO, is an outspoken critic of the Bush administration’s Kyoto decision, though he acknowledges the field is characterized by many uncertainties. But he argues that the commercial world, for example, copes with unknowns all the time—businesses don’t have the luxury of doing nothing in the face of unpredictable weather, liability or inflation. Delaying action until we have greater certainty could be disastrous, Schneider warns.

Moreover, attacking uncertainty bit by bit is the essence of a university’s research mission. “We can’t predict the future, so how do we get on it? We apply decision analysis,” Schneider says, referring to complex mathematical models that evaluate the different, often contradictory, factors that policy makers must take into account. Computer models and forecasting tools are getting better and better, Schneider points out, noting that Stanford’s “specialty is integration. No place in the country comes close to what we do in integrated assessment.”

Indeed, the University is turning up its own thermostat on integrated global warming research. Last year, Stanford began a fund-raising effort to establish the Stanford Institute for the Environment (see page 55). Scientists from around the world gathered on campus in June for Stanford’s Global Climate and Energy Project symposium. GCEP is a project underwritten largely by several major corporations; it is aimed at researching new technologies that store, reduce or eliminate greenhouse gas emissions. Director Franklin M. Orr Jr., ’69, professor of petroleum engineering, called supplying and transferring energy in a way that will let us reduce greenhouse gases “one of the great challenges humans have to face in this century.”

GCEP-funded projects range from storing CO in deep underground caverns to developing hydrogen-powered vehicles. Assistant professor of materials science and engineering Michael McGehee is trying to reduce the cost of solar power by using nanoscale photovoltaic cells that capture energy in polymer film. The idea is to create flexible strips that could, for example, be mass-manufactured and integrated into roofing material. There, solar power could generate energy for a given structure or even feed back into a larger grid. Doing this requires the input of electrical engineers, chemical engineers, material scientists and more. “I’ve cared about the energy problem since I was in high school,” McGehee says.

The degree to which diverse disciplines play into virtually every aspect of the climate change issue is striking. Schneider’s journal, for example, solicits papers from “meteorology, anthropology, agricultural science, astronomy, biology, chemistry, physics, geography, policy analysis, economics, engineering, geology, ecology, or history of climate.” His own specialty is modeling the atmosphere and climate change and collaborating with economists trying to develop reasonable policy for limiting emissions. He also works with other scholars—including Root, his wife—who integrate global temperature models and other climate-based analysis into their research.

Another researcher who assimilates a complex array of inputs is Mark Jacobson, associate professor of civil and environmental engineering. He has spent the past 15 years expanding a complex computer simulation of climate, air pollution and weather that includes more than 350 different chemical and physical processes—130 are not included in other models—covering everything from the role of winds in climate, to the reflection of radiation off clouds and ice, to ocean chemistry. Until the 1990s, weather prediction modeling and air pollution modeling were independent activities; Jacobson, ’87, MS ’88, put them together and uncovered some important findings, particularly about the contribution of particulate matter such as black soot to warming. (In the short term soot blocks sunlight and cools the temperature, but over time it absorbs heat and radiates it, and also makes snow and ice melt more rapidly when it falls on them.) His models also suggest that air pollution may be reducing rainfall in California: suspended pollutants can cut Sierra snowfall by disturbing air pressure systems, and by limiting the number of cloud droplets that fall as rain.

“The [global warming] problem is urgent and it’s important to keep firming up areas of the research,” to provide accurate assessment of developing phenomena and potential solutions, Jacobson says. He is perplexed, for example, that the Bush administration’s current energy bill provides a tax credit for buying a diesel vehicle. His work has shown that the highest mileage diesel vehicles today offer no advantage over the highest mileage pure gasoline cars in terms of emitting carbon, and they are more dangerous because of the particulate pollution they release into the environment.

Just as scientists from multiple disciplines are working together to understand global warming, they are joining forces to make their findings heard outside the academy. In advance of June’s meeting of the leaders of the major industrial democracies (G8), a statement representing the national science academies of 11 countries, including the United States and China, urged world leaders to take prompt action to curb greenhouse gas emissions. “The scientific understanding of climate change is now sufficiently clear to justify nations taking prompt action,” the statement said.

Also in June, California Gov. Arnold Schwarzenegger broke with the White House and announced a set of targets for California to reduce its greenhouse emissions. “I say, ‘the debate is over.’ We know the science. We see the threat, and we know the time for action is now.” Schneider and Field were on hand, having advised the governor’s staff on climate change. Getting to those targets and other policy implications of the changing climate will be another huge challenge. And the subject of part two of this report.

JOAN HAMILTON, ’83, is a frequent contributor to Stanford.

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