|
I have a broad range of research interests. Below I describe some of my current and past research topics. The main goal of my work is to better understand the interaction between the humans and the global environment, and how we may live more sustainably on our planet.
Earth's climate is influenced by many different systems (astronomical, atmospheric, oceanic, land, and life) interacting in often complex ways. By building a record of past climates, we can better understand how these systems work together. This allows scientists to develop an accurate picture of the current climate, to understand the current forces that are changing it, and to predict what future climates may be like. We know, for example, that throughout geological history, that the levels of CO2 in the atmosphere are highly correlated with global temperature. Some evidence suggests that during glacial periods, much of the Earth's carbon is trapped in the soil under ice sheets.
King George Island is on the Antarctic Peninsula , near the Drake Passage. During the last major ice age, about 20,000 years ago, this island was completely covered by glaciers. Now, as the Earth warms, these glaciers continue to recede, uncovering newly exposed soil. I am looking for evidence in this soil for carbon from ancient living organisms. With carbon dating, it is possible to know how long ago these organisms lived. This gives evidence on how glaciers form, and how quickly they form, and how soil stores carbon during glacial periods. This helps us better understand the role carbon plays on the Earth's climate in both glacial and interglacial periods.
We know that the global climate continually changes throughout history. We also know that the planet is currently warming and that human activities are the primary cause. When fossil fuel is burned for energy, it releases CO2 (a heat trapping gas) into the atmosphere. Fossil fuels provide 85% of the world's energy, but also account for about 80% of the total amount of CO2 humans put into the atmosphere. The level of CO2 in the atmosphere is now higher than it has been over half a million years. Data on emissions are important for climate policies that seek to stabilize the amount of heat trapping gases in the Earth's atmosphere.
My research looks at the seasonal and spatial patterns of natural gas, petroleum, and coal consumption for the leading fuel consuming nations of the world. Knowing these historic patters allows us to better approximate when, where, and how much CO2 is being emitted into the atmosphere. I also look at how these patterns evolve through time, and try to understand the relationship between other factors- such as resource availability, economic activity, and changing energy policies. Other scientists have used my work to better calibrate the measurements of CO2 coming from various natural ecosystems.
Energy consumption is closely tied to economic growth. As we try to lift more people out of poverty, we will need more energy resources, particularly in the developing world. It is therefore important to understand where these resources are located, and what the energy demand will be in the future so that we can make prudent decisions about courses of action today.
While nobody can predict the future, "Integrated Assessment" models can help us evaluate different possible human actions across a broad range of areas. These models are useful for understanding how the global energy market works, and allows us to understand how sensitive energy prices and trade patterns are to various possible technological developments and climate policies. It can also be used to forecast regional demand for agricultural land to grow food and biofuels. These models predict how sensitive the climate is to different possible human actions and allow us to understand the relationships between the energy, economic, and environmental systems- linking human behavior and the physical climate.
Currently, fossil fuels provide the majority of the world's energy supply. But as these resources become more scarce, and as concerns about global climate change lead us to limit their use, biofuels (fuels made from plants) are seen as one possible alternative. Biofuels are attractive because they store the sun's energy and are renewable (we can continue to grow plants), and the carbon they release when combusted is carbon the plants took out of the atmosphere while growing (aside from the carbon released during the harvest, transportation, and processing of the crops). However, plants do require land, water, and other resources to grow. The concern is that land for biofuels would crowd out land for other purposes, such as land for food, land for wildlife, and land for open spaces.
However, if we make biofuels out of crop residue (stalks, stems, shells, etc.) we could grow food and fuel at the same time, making much better use of our land, and making agriculture more profitable for farmers. Also, when timber is harvested from forests, the small braches, tree tops, bark, and other slash could be made into wood pellets or other fuels. I have been researching the potential for doing this, estimating how much energy we could get from this resource, and how this could compete economically with fossil energy. Using economic models, I forecast the market for agricultural products and crop residue and am able to determine the effect a climate policy has on the development of this resource. While bioenergy is not the silver bullet to our future climate and energy challenges, it does offer a way to replace a large amount of fossil fuel with a potentially clean and sustainable energy source.
Agriculture is the largest and most important way that humans have changed the surface of the Earth. Soil is one the largest carbon reservoirs on Earth. It is important to understand the impact of agriculture on soil nutrients so that we may continue to feed the global population and prevent the release of heat-trapping gases into the atmosphere.
I have been looking at how agriculture changes the composition of the soil over the long term, and what happens to the nutrients in the soil. My research has looked at the effect of agriculture on soil in China, which produces more food than any other country, and where agriculture has been occurring for thousands of years. By evaluating the differences in agricultural soils versus non-agricultural soils, we can begin to understand the effect of farming on the land and for the carbon and nitrogen cycles. Also, I am looking at how different agricultural practices (such as no-till and erosion prevention) can help preserve the soil.
If crop residues are harvested, less nutrients are available to return to the soil, and the soil is more susceptible to erosion. So I have been using computer models, satellite data, and soil surveys to estimate the threshold for the amount of residue that can be safely removed for different locations, climates, soil types, and topographies. Also, I try to see how conservation measures could increase the amount of residue that can be harvested while preserving soil nutrients and reducing erosion.
Forests have the capability to take up enormous amounts of carbon from the atmosphere and store it in a natural ecosystem. Forests are also important for the timber resources they provide, and historically, we have developed very precise management plans to maximize timber production and the economic viability of our forests. In the near future, foresters could be paid to sequester carbon from the atmosphere, changing the management practices to optimize carbon storage.
My research has looked at ways in which management plans could be optimized for both timber and carbon storage. For example, keeping a population of trees in the early stages of growth increases the amount of CO2 taken out of the atmosphere. Prudent thinning can also promote growth of larger, healthier trees and reduce the risk of forest fire (which would release the carbon back to the atmosphere). I have used computer models to compare the performance of different management plans for carbon, and based on these findings, helped establish a threshold, or "performance standard", that could be used to certify carbon emission offsets.
Almost everything we produce eventually ends up as waste or garbage. Much of this waste could be recycled, composted, or converted to energy, but most of it is currently buried. Because land is valuable near cities where more garbage is produced, and few people want to live near a landfill, finding a place for all of our waste is one of the main challenges that municipalities face. Also, biological material, such as wasted food, paper and wood products, decays in landfills and produces (along with CO2) methane, a very potent heat-trapping gas.
I am looking at the possibility of using the garbage that is not recycled or composted as a possible source for bioenergy, or waste-to-energy. This would reduce the amount of land needed for landfills and reduce methane emissions. It would also provide a non-seasonal source of energy close to urban areas where energy is needed. This source of energy could be very cost effective, because municipalities are already paid to collect garbage. In addition, with waste-to-energy, they would not have to buy more land to expand landfills, they could sell the electricity or fuel back to the community, and (with better sorting programs and technology) they could also sell recycled and recovered material and compost. Also, under a climate policy, municipalities could be paid for preventing methane emissions that would have otherwise occurred had the garbage been buried. My research has attempted to estimate how much garbage is generated in the world, country by country, and how this changes as economies develop. Also, I look at what percent of garbage that is biological, how much energy could be generated from it, and the amount of emissions that could be prevented by adopting waste-to-energy programs.
I developed a framework for trying to understand the complex relationship between energy, the environment and the economy- the 3E trilemma. Ideally, an energy system would provide a large amount of energy, be economically competitive by offering enough energy at a price where people can afford to use it, and have little impact on the environment. However, there is no ideal, perfect energy system; they all involve complex decisions about tradeoffs. This is related to the scale at which the energy source is developed. In general, as the scale is increases, more energy is available, the cost comes down, but the environmental impact grows. For example, fossil fuels have proven to be an enormous, cheap source of energy, yet it is clear that the growing environmental impact from their use at the current scale is unsustainable. The goal then is to better understand these tradeoffs, in terms of the entire life-cycle of an energy source, so that we incorporate the environmental impact (and ecosystem services) into the cost of the energy. This would allow us to find a more harmonious balance for our decisions about energy and the environment and hopefully would lead us to a more sustainable energy future.
|
