The Habitable Planet: A Systems Approach to Environmental Science
Earth’s Changing Climate Scientists
Daniel P. Schrag
Daniel Schrag is a professor of Earth and planetary sciences and environmental engineering at Harvard University and the director of the Harvard University Center for the Environment. Schrag studies climate and climate change over the broadest range of Earth history. Schrag received a B.S. from Yale in 1988. He majored in political science and geology, beginning an interest in science and policy that continues to this day. As a graduate student at Berkeley, Schrag was introduced to geochemistry and paleoclimatology through his work developing new methods for reconstructing ancient climates. After receiving his Ph.D. in 1993, Schrag taught at Princeton until 1997, when he moved to Harvard’s Department of Earth and Planetary Sciences. In his research, Schrag applies a variety of techniques from analytical chemistry to a wide range of Earth materials including trees, corals, and deep-sea sediments, using the data to understand the chemical and physical evolution of the atmosphere and ocean and the relationship to the evolution of life. He has studied the physical circulation of the modern ocean, focusing on El Niño and the tropical Pacific. He has worked on theories for Pleistocene ice-age cycles over the last few hundred thousand years. He helped develop the Snowball Earth hypothesis, proposing that a series of global glaciations occurred between 750 and 580 million years ago that may have contributed to the evolution of multicellular animals. He has also worked on the early climates of Earth and Mars nearly 4 billion years ago. He is currently working with economists and engineers on technological approaches to mitigating future climate change. Among various honors, Schrag was awarded a MacArthur Fellowship in 2000.
Chris Field is the founding director of the Carnegie Institution’s Department of Global Ecology, professor of biological sciences at Stanford University, and faculty director of Stanford’s Jasper Ridge Biological Preserve. His research emphasizes ecological contributions across the range of earth-science disciplines. Field and his colleagues have developed diverse approaches to quantifying large-scale ecosystem processes, using satellites, atmospheric data, models, and census data. They have explored global-scale patterns of vegetation-climate feedbacks, carbon cycle dynamics, primary production, forest management, and fire. At the ecosystem-scale, Field has, for more than a decade, led major experiments on grassland responses to global change, experiments that integrate approaches from molecular biology to remote sensing. Field’s activities in building the culture of global ecology include chairing the US National Committee for SCOPE (Scientific Committee on Problems of the Environment) and U.S. Interagency Science Steering Group on Carbon Cycle Science, plus service on many committees of the National Research Council and the International Geosphere-Biosphere Programme. Field was the lead author on the first Ecological Society of America (ESA)-Union of Concerned Scientists assessment of regional impacts of climate change on ecosystems (1999), which was a foundation for California’s first-in-the-nation law to regulate vehicle greenhouse gas emissions. He is currently a convening lead author for the fourth assessment report of the Intergovernmental Panel on Climate Change. Field is a fellow of the ESA Aldo Leopold Leadership Program and a member of the US National Academy of Sciences. He has served on the editorial boards of Ecology, Ecological Applications, Ecosystems, Global Change Biology, and the Proceedings of the National Academy of Science (PNAS). Field received his Ph.D. from Stanford in 1981 and has been at the Carnegie Institution since 1984. His recent priorities include high performance “green” laboratories, integrity in the use of science by governments, local efforts to reduce carbon emissions, and the future of scientific publishing. //Read Interview Transcript
Lonnie G. Thompson
Lonnie Thompson, a distinguished professor of geologic sciences at The Ohio State University and senior research scientist with the Byrd Polar Research Center, has become one of the world’s authorities on the melting of glaciers and ice caps as a warning of rising global temperatures. For the past three decades, Thompson, along with his wife and research partner Ellen Mosely-Thompson, has led an effort to first recognize that the shrinking of tropical glaciers and ice fields is an early warning of the impact of global climate change, and second, to rescue the remaining archives of ancient climate trapped in ice cores from those locations for future research. To rescue those records, Thompson and his team have conducted nearly 50 expeditions to some of the Earth’s most remote places, to drill ice cores and bring them back to Ohio State to extract those climate records. The expeditions, dating back to 1973, have taken him to Antarctica and numerous ice caps on five continents, some as high as 23,600 feet (7,200 meters). He is believed to have spent more time at altitudes above 18,000 feet (5,500 meters) than any other human. Thompson was elected to the National Academy of Science in 2005. In November 2005, he was featured in a Rolling Stone article on those fighting global climate change. Also in 2005, he was awarded the prestigious Tyler Prize for Environmental Achievement, an honor often regarded as the environmental science equivalent to the Nobel Prize. Through his research endeavors, Thompson is a leading national spokesman on the subject of global climate change and is considered one of the most respected voices in the world on related policy issues. Thompson obtained his undergraduate degree from Marshall University, where he majored in geology. He subsequently attended The Ohio State University where he received his M.S. and Ph.D. degrees. //Read Interview Transcript
12.1 Earth’s Changing Climate (video)
Tropical glaciers are the world's thermometers; their melting is a signal that human activities are warming the planet. A California project tries to predict whether natural ecosystems will be able to absorb enough additional carbon dioxide from the atmosphere in the next 50 years to mitigate the full impact of human-induced greenhouse gas emissions.
Unit 1 Many Planets, One Earth
Astronomers have discovered dozens of planets orbiting other stars, and space probes have explored many parts of our solar system, but so far scientists have only discovered one place in the universe where conditions are suitable for complex life forms: Earth. In this unit, examine the unique characteristics that make our planet habitable and learn how these conditions were created.
unit 2 Atmosphere
The atmosphere is what makes the Earth habitable. Heat-trapping gases allow ecosystems to flourish. While the NOAA Global Monitoring Project documents the fluctuations in greenhouse gases worldwide, MIT's Kerry Emanuel looks at the role of hurricanes in regulating global climate.
Unit 3 Oceans
Oceans cover three-quarters of the Earth's surface, but many parts of the deep oceans have yet to be explored. Learn about the large-scale ocean circulation patterns that help to regulate temperatures and weather patterns on land, and the microscopic marine organisms that form the base of marine food webs.
Unit 4 Ecosystems
Why are there so many living organisms on Earth, and so many different species? How do the characteristics of the nonliving environment, such as soil quality and water salinity, help determine which organisms thrive in particular areas? These questions are central to the study of ecosystems—communities of living organisms in particular places and the chemical and physical factors that influence them. Learn how scientists study ecosystems to predict how they may change over time and respond to human impacts.
Unit 5 Human Population Dynamics
What factors influence human population growth trends most strongly, and how does population growth or decline impact the environment? Does urbanization threaten our quality of life or offer a pathway to better living conditions? What are the social implications of an aging world population? Discover how demographers approach these questions through the study of human population dynamics.
Unit 6 Risk, Exposure, and Health
We are exposed to numerous chemicals every day from environmental sources such as air and water pollution, pesticides, cleaning products, and food additives. Some of these chemicals are threats to human health, but tracing exposures and determining what levels of risk they pose is a painstaking process. How do harmful substances enter the body, and how do they damage cells? Learn how dangers are assessed, what kind of regulations we use to reduce exposures, and how we manage associated human health risks.
Unit 7 Agriculture
Demographers project that Earth's population will peak during the 21st century at approximately ten billion people. But the amount of new cultivable land that can be brought under production is limited. In many nations, the need to feed a growing population is spurring an intensification of agriculture—finding ways to grow higher yields of food, fuel, and fiber from a given amount of land, water, and labor. This unit describes the physical and environmental factors that limit crop growth and discusses ways of minimizing agriculture's extensive environmental impacts.
unit 8 Water Resources
Earth's water resources, including rivers, lakes, oceans, and underground aquifers, are under stress in many regions. Humans need water for drinking, sanitation, agriculture, and industry; and contaminated water can spread illnesses and disease vectors, so clean water is both an environmental and a public health issue. In this unit, learn how water is distributed around the globe; how it cycles among the oceans, atmosphere, and land; and how human activities are affecting our finite supply of usable water.
unit 9 Biodiversity Decline
Living species on Earth may number anywhere from 5 million to 50 million or more. Although we have yet to identify and describe most of these life forms, we know that many are endangered today by development, pollution, over-harvesting, and other threats. Earth has experienced mass extinctions in the past due to natural causes, but the factors reducing biodiversity today increasingly stem from human activities. In this unit we see how scientists measure biodiversity, how it benefits our species, and what trends might cause Earth's next mass extinction.
unit 10 Energy Challenges
Global energy use increases by the day. Polluting the atmosphere with ever more carbon dioxide is not a viable solution for our future energy needs. Can new technologies such as carbon sequestration and ethanol production help provide the energy we need without pushing the concentrations of CO2 to dangerous levels?
Unit 11 Atmospheric Pollution
Many forms of atmospheric pollution affect human health and the environment at levels from local to global. These contaminants are emitted from diverse sources, and some of them react together to form new compounds in the air. Industrialized nations have made important progress toward controlling some pollutants in recent decades, but air quality is much worse in many developing countries, and global circulation patterns can transport some types of pollution rapidly around the world. In this unit, discover the basic chemistry of atmospheric pollution and learn which human activities have the greatest impacts on air quality.
Unit 12 Earth’s Changing Climate
Earth's climate is a sensitive system that is subject to dramatic shifts over varying time scales. Today human activities are altering the climate system by increasing concentrations of heat-trapping greenhouse gases in the atmosphere, which raises global temperatures. In this unit, examine the science behind global climate change and explore its potential impacts on natural ecosystems and human societies.
Unit 13 Looking Forward: Our Global Experiment
Emerging technologies offer potential solutions to environmental problems. Over the long-term, human ingenuity may ensure the survival not only of our own species but of the complex ecosystems that enhance the quality of human life. In this unit, examine the wide range of efforts now underway to mitigate the worst effects of man-made environmental change, looking toward those that will have a positive impact on the future of our habitable planet.