News + Media

By David L. Chandler
Photo credit: Bryce Vickmark
MIT News Office

After a career that included work as a White House advisor in the Carter administration and as a partner at Goldman Sachs, Larry Linden SM ’70, PhD ’76 has turned his attention to what he says is the most critical issue facing humanity today: the threat of catastrophic global climate change.

Linden, speaking on campus Wednesday in the opening event of the MIT Climate Change Conversation, urged his audience to join him in making the issue a top priority — and in pushing elected leaders to take concrete action now, before changes to the world’s atmosphere and oceans become irreversibly damaging. And the most effective approach, he emphasized, is by putting a price on carbon emissions from fossil fuels.

That could take a number of forms: an outright tax on carbon, a cap-and-trade arrangement, or a revenue-neutral combination of fees and rebates. While the present political climate in the United States may make any such agreement an uphill battle, Linden stressed that his foundation — the Linden Trust for Conservation — and other groups are working hard to find centrist, bipartisan approaches that could lead toward the goal of limiting global climate change.

Pointing to unexpectedly rapid changes in public opinion in other areas, Linden said that while the prospects for political action on climate may now appear bleak, “We can be surprised, and I hope we will. This is an idea that could go from impossible to inevitable overnight.”

Linden, a board member of the World Wildlife Fund and former chairman of the board of directors of Resources for the Future, described the evolution of his thinking on climate change. He said his awareness of environmental issues started early: As a child in Pasadena, Calif., he personally experienced the terrible, pre-Clean Air Act smog of the Los Angeles basin. Now, he said, “I’m doing everything in my power to move our country to act [on climate change] at the scale that’s required.”

Unpredictable changes

At the current pace, Linden said, we face a rise in temperature of as much as 4 to 6 degrees Celsius by 2100 — and the carbon dioxide humans are now adding to the air will stay there for centuries or even millennia. This could lead, he said, “to abrupt, unpredictable and potentially irreversible changes” — such as the release of frozen methane, or the death of the Amazon rainforest — that could greatly amplify the impacts. If such large changes do occur, Linden said, “I don’t think it’s an overstatement to call this a planetary catastrophe.”

While Linden said the fossil fuel industry will fiercely resist any proposed regulations or fees aimed at limiting carbon emissions, he added that past experience gives reason to treat industry’s claims with some skepticism: Proposals to limit automobile pollution to deal with California’s smog problems faced similar objections, which proved unfounded.

“The financial system is an extremely complex, interrelated system — just like the climate system,” Linden said. While companies never like to be told what to do, he said, if federal rules constrain their actions, they will abide by the law.

In 2009, when federal cap-and-trade legislation was proposed in Congress and passed in the House, Linden was encouraged, thinking that this would be a be “a great start.” But when the proposed law was dropped without even being brought to a vote in the Senate, “I practically fell off my chair,” he said. In the years since, the idea has not resurfaced in Congress.

Slashing emissions

But something along those lines is exactly what is needed now, Linden said. Research has shown that to avert the most drastic climate consequences, greenhouse gas emissions must be cut by about 80 percent over the next four or five decades. In addition, massive new investment in research and development on alternative energy sources is needed, he said.

The most essential change in policy, Linden said, is a mechanism for “internalizing the externalities”: capturing the great societal costs of fossil fuel emissions in the costs of the fuels themselves. “It could be a cap-and-trade system, or a tax or a fee on carbon, or a limit on emissions,” he said.

Linden said that his foundation is supporting a revenue-neutral carbon tax as the next major national policy step. Studies have shown, he said, that an initial tax of $15 per ton of carbon emitted, with significant annual increases, could cut emissions in half by 2050.

The key, he said, lies in public action to force politicians to act. But the very nature of the issue — requiring strong action now to avoid consequences many years hence — makes action difficult: “If you designed a problem to maximize the political difficulty of addressing it, you couldn’t do much better,” Linden said. “We will therefore need extraordinary political leadership.”

“Bipartisan support is needed,” he added, noting that the Linden Trust is actively working to build support across the political spectrum. “We’re looking for centrist solutions,” he said. Like the climate itself, “our political system is an extremely complicated, interrelated system. There are possible positive feedback loops, and many nonlinear thresholds that can produce irreversible impacts. … That’s what we need to look for now.”

While the process might take years, Linden said, “We have to fight the political fight.” In the meantime, he said, state initiatives might provide useful “working examples” for national action.

Maria Zuber, MIT’s vice president for research, introduced this kickoff event of MIT's Climate Change Conversation, an effort to involve the MIT community in seeking ways in which the Institute might contribute to addressing the threat of global climate change. The proposals arising from this process, Zuber said, would be “rooted in science, would be bold, would encourage personal engagement.”

Zuber added that while this has been “a divisive issue on many campuses, of the many things that we could possibly do, there must be some things that we can all agree on that would be useful to do, and maybe we should start with doing those.”

Linden's talk was sponsored by the Committee on the MIT Climate Change Conversation, which will organize a series of events during the spring semester to engage the community in thinking about how the Institute can contribute to confronting climate change.

David L. Chandler | MIT News Office

Dara Entekhabi, an MIT professor of civil and environmental engineering and of earth, atmospheric and planetary sciences, is the science team leader of NASA’s Soil Moisture Active Passive (SMAP) satellite, scheduled to be launched from Vandenberg Air Force Base in California on Jan. 29. The satellite will provide measurements of the moisture in the top 2 inches of the soil, everywhere on Earth, over the course of its planned three-year mission, as well as specifying whether that water is liquid or frozen. Entekhabi discussed what he hopes this mission will be able to accomplish.

Q. How much of an improvement will SMAP represent over current ways of assessing soil moisture around the world? Why is it important to be able to do so?

A. Why we need soil moisture information, and what capability SMAP adds, can be explained by following a timeline of what we know about how the Earth system works, starting in the 1980s and 1990s.

Until then, the study of the water cycle — the storage and flow of water in the environment — was partitioned between meteorology and hydrology. So long as water was in the form of vapor and precipitating clouds, it was in the domain of meteorologists. Only after the precipitation hit the surface was its infiltration into soil, runoff, and stream flow in the domain of hydrologists.

Around the 1980s there was a transformative change in our thinking, with the emerging capability of fast computers and Earth system modeling. Much of that thinking, in fact, was formed at MIT: We started thinking about two-way interaction and coupling between the land and the atmospheric branches of the water cycle. In order to couple the systems, we soon realized that the key variable to track is surface soil moisture. But the ground networks to observe this variable were too few and far between to yield any meaningful insights. To make global and dynamic maps of this, we had to take on the vantage point of Earth-orbiting satellites. Starting in 2000, I became involved with NASA, and we formed a team to propose a satellite mission whose design is specifically optimized to make high-resolution and high-accuracy maps of surface soil moisture. The paired microwave-radar and radiometer instruments can sense through clouds and vegetation. The rotation of the antenna while orbiting the Earth produces a wide swath of surface measurements that can track changes in soil moisture.

Q. What would you expect to be some of the most significant findings that this mission will be able to make, and what kind of impact could these findings have?

A. With these high-quality measurements, we will have unprecedented insight into how the cycling of water weaves through its land and atmospheric branches. Because the evaporation and condensation of water also entails exchanges of energy, and because the uptake of atmospheric carbon dioxide by plants requires thawed conditions and exchange of water, soil moisture also links the three fundamental cycles of the Earth system — the water, energy, and carbon cycles — over land. These three cycles work together like gears in a clock: Perturbations in one gear will affect the others. If soil moisture were fixed everywhere, these three cycles would vary independently of one another. But with dynamic and responsive soil moisture, the three are linked over land, with synchronized variations. That is a big difference for the Earth system and its cycles. So with observations of soil moisture and improvement in links between the water, energy, and carbon cycles, our understanding of how the Earth system works will be on a new and higher level. With improved characterization and modeling, the predictions of the global and the regional environment — from short-term weather forecasts to global climate-change projections — will be impacted.

Q. How difficult is it to measure these conditions from orbit, and what kinds of tests will need to assess the accuracy of the data returned by the mission?

A. The main technological challenge has been the design of the large antenna and its rotation to make a scan of a wide swath over each orbit. Given the long microwave wavelengths (about 21 centimeters), to focus on a high-resolution spot on the surface the antenna has to be large in diameter. SMAP has a 6-meter lightweight mesh reflector that stows like an umbrella and unfurls in space. Then this large structure has to be rotating at about 15 rounds per minute to map the surface. This is pushing the technology to its limits. We have developed a calibration and validation plan where we pull data in real time from ground sensor networks, perform quality control, and compare with the SMAP data. Over the last two summers we have had two rehearsals of the end-to-end system. The calibration and validation will also include two airborne field campaigns during the summers of 2015 and 2016. Preliminary science data will be released after six months, and after one year we need to demonstrate, using ground-truth observations, that the data meet the accuracy requirements agreed upon by the project and NASA sponsors.

China Energy and Climate Project Director Professor Valerie J. Karplus appeared on Channel NewsAsia to discuss the impacts and broader significance of the Korean emissions trading system kicking off last week. Watch the interview below.


 

Anna Petherick writes for Nature Climate Change about emissions pledges from the United States and China for, including emissions projections from China Energy and Climate Project.

Read the full column here.

Amanda Peterka | E&E reporter

Bioenergy production would boom and spur steep reductions in greenhouse gas emissions if a global price is slapped on carbon, Massachusetts Institute of Technology researchers say in a report released today.

Examining bioenergy production under a $15-per-metric-ton carbon price that would rise steadily to $59 in 2050, researchers found production hitting 150 exajoules by 2050 -- compared with below 50 exajoules without a carbon price.

Global greenhouse gas emissions would plunge 16 percent under that scenario, the report says, cautioning that the carbon price studied doesn't take into account land-use changes. Taking into account emissions from land-use changes, including deforestation, it says greenhouse gas reduction would be nearly 60 percent from the no-carbon-price baseline.

"The study is one of the most in-depth evaluations to date of how bioenergy might fit into a low-carbon future," MIT said in a release. "The research team developed a cutting-edge modeling tool covering a comprehensive range of bioenergy pathways."

The MIT Joint Program on the Science and Policy of Global Change says its study goal was to see how bioenergy would compete with other low-greenhouse-gas options on a level playing field.

The researchers used the Economic Projection and Policy Analysis model to create both the carbon price scenarios and assumptions about economic, productivity and population growth without a carbon price. The model examined seven first-generation biofuel crops and two cellulosic biofuel conversion technologies -- bioelectricity and heat.

The model also accounted for international trade, ethanol blending limits, changes in land and production costs, and existing policies such as the federal renewable fuel standard, among other factors.

"Biofuels are only one channel for bioenergy," said Niven Winchester, an environmental energy economist at MIT. "If you want to study how land can be used to meet our energy needs, you have to think of all the different ways to use what grows on that land -- including food, feed and fuel."

The carbon price scenario resulted in efficiency improvements and energy use reductions, the report says. Electricity consumption in 2050 dropped 19 percent, while there was 73 percent less electricity from coal.

With a carbon price in the MIT model, bioenergy use rose from 8.5 exajoules in 2015 to 152.4 exajoules in 2050 -- or about a quarter of global energy needs.

The model found that corn ethanol would be produced in the United States until 2025, when it would become uneconomical.

After 2025, cellulosic ethanol would become the primary form of bioenergy; by 2020, cellulosic ethanol would account for about 57 percent of the globe's total bioenergy consumption.

Increased energy prices under a carbon price would make grasses -- one of the main inputs for cellulosic ethanol -- more attractive, while cellulosic producers would face lower land costs than other biofuel producers, according to the report. Rising electricity prices would also increase the revenue that cellulosic producers could receive from producing electricity as a co-product.

Africa and Brazil would become the largest bioenergy producers in a world where cellulosic ethanol is the main form of bioenergy, the MIT study found.

"Africa can become a key player in supplying global energy, if agricultural expertise can be transferred to this region," Winchester said. "It has the right climate and a large amount of land, but also the potential for deforestation if policy safeguards aren't in place."

The growth in cellulosic ethanol assumes that production costs fall over the next 35 years and that ethanol-blending constraints disappear by 2030 partly through the use of more flex-fuel cars.

MIT found that pricing greenhouse gas emissions from bioenergy land-use changes significantly increases the amount of greenhouse emission reductions that occur as a result of bioenergy expansion.

Pricing land use changes would prompt a global reforestation of 800 million hectares between 2010 and 2050, according to the study. In 2050, cumulative carbon-dioxide-equivalent emissions would be 37,381 million metric tons if land-use changes were priced, compared to 74,140 million metric tons if they were not.

"The report concludes that changes spurred by the carbon price, including bioenergy production, could cut greenhouse gas emissions by more than half, with a catch -- to achieve the cut, the carbon price must cover emissions from changing land use," MIT said. "Without this safeguard, deforestation becomes a major concern as forests are cleared to make way for farmland."

	Photo: Dara Entekhabi, courtesy of Len Rubenstein, MIT Spectrum

by Audrey Resutek | MIT Joint Program on the Science and Policy of Global Change

On January 29, 2015, a Delta II rocket launched from Vandenberg Air Force Base will carry the SMAP Observatory, the first satellite designed exclusively to monitor soil moisture, into orbit. Once there, the satellite will make a map of the Earth’s soil moisture every three days—creating a measurement with the potential to dramatically improve weather forecasts and predictions of climate change.

It’s been a long journey to get to this point, as Prof. Dara Entekhabi, the science team leader of the NASA mission and a researcher at the Joint Program on the Science and Policy of Global Change, can attest. SMAP, which stands for Soil Moisture Active Passive, was first conceived in 1999. Over the last 15 years, Entekhabi has led a team of researchers at MIT and other universities, the NASA Jet Propulsion Laboratory, and the NASA Goddard Space Flight Center working on the satellite.

“The team has stuck together,” notes Entekhabi, who holds a joint appointment in MIT’s Department of Civil and Environmental Engineering and the Department of Earth, Atmospheric and Planetary Sciences. “It’s almost the same people as when we started working on SMAP.”

Once SMAP is in orbit it will measure moisture in the first five centimeters of the soil, using two instruments—active microwave radar and a passive microwave radiometer. The data transmitted back to Earth will represent a huge leap forward for scientists studying how the Earth works.  

Unconventional Data

Entekhabi has spent his career learning about the Earth through collecting data, and the information collected by the SMAP Observatory will fill a major gap in our understanding.

“I was always into data and the environment, and reconstructing old records,” says Entekhabi. “I eventually became interested in creating new sources of data—unconventional data. Which is how I became involved with SMAP.”

SMAP is the first NASA mission dedicated to studying soil moisture and freeze/thaw data, which indicates the start and end of the growing season. Because of this, current records are spotty at best, and are based mostly on data from sparse ground stations and readings from satellites primarily designed for other uses.

Photo: Artist's rendering of the SMAP spacecraft, courtesy of NASA/JPL.

The mission is somewhat unusual, Entekhabi says, because the long development period gave the mission team time to cultivate a community of early data adopters, who have already developed applications for the data. The information produced by SMAP will be tailored to fit these users’ needs—allowing them to immediately put the data to use for forecasting and research. 

“This is a path-breaking approach for NASA, because the applications are woven into the science of the mission. So, it’s broad basic research, as well as application,” says Entekhabi.

There is an impressive range of uses for soil moisture data. These include the obvious, like improving weather and climate forecasting; estimating agricultural productivity; tracking droughts, floods and landslides; to the less obvious, such as providing early warnings of famine in areas dependent on rain-fed crops; determining soil hardness on military transportation routes, and forecasting the density of the lower atmosphere, which determines how much lift an airplane has.

The lack of information about soil moisture is also a problem for basic Earth science research, because soil moisture links the three major cycles of the Earth system—the water, energy, and carbon cycles—together. Without accurate soil moisture data it’s nearly impossible to accurately trace the movement of water through these three systems.  

“These are basically three gears that are locked together,” Entekhabi says. “If we don’t get this right in models, because we don’t know what the linkage is, it’s a problem. Measuring soil moisture is important because it’s the pivot that links these three gears.”

	Photo: SMAP lowered into place, courtesy of NASA/JPL-Caltech.

Understanding soil moisture will likely greatly improve the accuracy of weather forecasts at a fraction of the cost of other measures, like beefing up computing power to support higher resolution weather models. It will also improve how models estimate how climate change will affect precipitation, which, up until now, has been notoriously difficult to pin down.

“All the models agree on global temperature; you can’t get that wrong,” Entekhabi says. “But what’s going to happen with regional water availability, regional precipitation, the models don’t even agree in sign—some of them are positive, some of them are negative—let alone magnitude.”

Taking Extreme Weather’s Fingerprint

Entekhabi’s work on the water cycle and soil moisture spans decades, starting with his doctoral work at MIT, where he worked to improve how climate models account for land surface moisture. He joined MIT’s faculty in 1991 and has been involved with the Joint Program since its creation in the early 1990s. 

“A major question in the field today is what is climate change going to do to the water cycle?” Entekhabi says. “The real challenge is predicting the future of water availability at a regional scale.“

To address this issue, Entekhabi worked with the Joint Program to create a new way of predicting how climate change will affect the frequency and severity of extreme precipitation. The method takes advantage of the fact that climate models do a good job of simulating the large-scale atmospheric events that lead to extreme precipitation, even though they’re bad at predicting the precipitation itself. The method bypasses climate models’ built-in precipitation parameterizations, and instead looks for the large-scale conditions that have been associated with extreme weather events in the past.

“What we’re doing is basically fingerprinting,” Entekhabi says. “We use the historical record to find a fingerprint, or pattern of what’s going on in the large-scale climate that causes extreme weather.

The technique, called an “analogue” method because it does not directly simulate precipitation within the model, gives more accurate reproductions of past extreme weather events than climate models alone. Once the patterns associated with extreme weather—either very wet or very dry—are identified, the next step is to look at future changes in these patterns in a climate model.

Entekhabi is currently working to identify these patterns across several regions. In one example, he studied over 100 years of precipitation data for the region around Mumbai, where the monsoon season can cause devastating floods in densely populated areas. The monsoons that caused the worst flooding left a distinct atmospheric fingerprint, he found.

“The fingerprint of the monsoon is much larger than the local flooding in Mumbai,” Entekhabi says. “The circulation patterns extends all the way to the Arabian Sea and the coast of East Africa. Basically a long arc of vapor from the Arabian Gulf gets blocked, and it just sits there and rains a lot.”

The method can be applied to any event in any region, as long as it is associated with changes in large-scale atmospheric conditions. Working with Dr. Adam Schlosser, a senior research scientist and assistant director for science research at the Joint Program, Entekhabi is currently applying the analogue method to West Africa, a region that relies on rain-fed agriculture for most of its food. Most of the rain in the region falls during a three-month rainy season in the summer, and what happens in the rainy season can make or break the area’s food supplies.

“Models will always be uncertain once you start looking into the future,” Entekhabi says. “SMAP is one way we’re trying to improve the quality of models—by looking at how the water and carbon cycles fit together. The analogue approach is another way of attacking the challenge of regional water availability from an entirely different angle.”

For now, Entekhabi is turning his attention skyward. In the Fall, Entekhabi traveled to Southern California, where SMAP was being loaded into a rocket at the Jet Propulsion Laboratory. He’ll remain there through the spring, while SMAP is being calibrated.

“It’s been a long trek,” Entekhabi says. “But every single screw on SMAP has been reviewed and reviewed and reviewed. Right now there’s no more testing, no more touching the satellite. There’s no looking back now.”