Tuesday, October 13, 2009

If all nations burned gasoline for transportation at the same rate as the United States, world gasoline consumption would rise nearly ten-fold, with a corresponding hike in the concentration of greenhouse gases.

That’s just one reason why it is imperative that nations work to create a more sustainable transportation system, says John Heywood, director of MIT’s Sloan Automotive Lab and the Sun Jae Professor of Mechanical Engineering.

“As the countries in the developing world rapidly motorize, the increasing global demand for fuel will pose one of the biggest challenges to controlling the concentration of greenhouse gases in the atmosphere,” Heywood writes in “Fueling Our Transportation Future,” an article he wrote for the September issue of Scientific American.

Heywood is one of three MIT professors who tackle energy in the magazine’s September issue, whose cover proclaims the theme “Energy’s Future: Beyond Carbon.”

While Heywood’s article focuses on improving transportation efficiency, MIT Professors John Deutch and Ernest Moniz explore the possibilities of expanding nuclear power to reduce emissions of greenhouse gases.

All three professors are members of MIT’s Energy Research Council, which issued a report in May exploring how MIT can help solve the global energy crisis.

Improving transportation efficiency will be a critical part of any energy strategy, says Heywood, because transportation accounts for 25 percent of worldwide greenhouse gas emissions. Greenhouse gases such as carbon dioxide are emitted when fossil fuels like gasoline and coal are burned. The gases trap heat within Earth’s atmosphere, raising global temperatures and altering weather patterns.

In his piece, Heywood outlines four options for improving transportation sustainability: “We could improve or change vehicle technology; we could change how we use our vehicles; we could reduce the size of our vehicles; we could use different fuels. We will likely have to do all of these to drastically reduce energy consumption and greenhouse gas emissions.”

U.S. petroleum consumption has been steadily growing by about two percent per year. It will take quite some time to reverse that trend, according to Heywood. By reducing the weight and size of vehicles and “step(ping) off the ever increasing horsepower/performance path,” developed nations may be able to level off petroleum demand in 15 to 20 years and start a slow downward path, he writes.

In the longer term, new technologies could further reduce fuel consumption. Heywood estimates that within five years, new technologies such as gasoline hybrids, turbocharged gasoline engines and low-emissions diesel could produce market-competitive vehicles. Hydrogen fuel cell technology will take longer to reach consumers.

However, it will take 20 to 30 years for any of these engine technologies to reach “major fleet penetration,” meaning, the point at which they account for more than one-third of mileage driven, according to Heywood. It may take some 50 years for fuel cells and hydrogen to reach that state, he noted.

Other alternative fuels, including biomass-based fuels such as ethanol and biodiesel, are already being produced but have not made much of an impact in the United States yet.

“It is likely that the use of biomass-based fuels will steadily grow,” Heywood writes. “But given the uncertainty about the environmental impacts of large-scale conversion of biomass crops to fuel (on soil quality, water resources and overall greenhouse gas emissions), this source will contribute but is unlikely to dominate the future fuel supply anytime soon.”

Heywood suggests that new regulatory and tax policies will be needed to realize the fuel-reduction benefits as new technologies come into the market. Raising fuel-efficiency requirements, charging a fee to consumers who purchase high-fuel-consumption cars and offering rebates to those who buy efficient models could all help achieve a more sustainable transportation system.

Another promising way to cut carbon emissions is to rely more heavily on nuclear power, according to Moniz and Deutch.

Moniz, co-director of MIT’s Laboratory for Energy and the Environment and Cecil and Ida Green Professor of Physics, co-chairs MIT’s Energy Research Council. Deutch, also a member of the energy council, is an Institute Professor at MIT.

Nuclear power now supplies about one-sixth of the world’s electricity, making it the largest “carbon-free” energy source in the world. Only a handful of new plants are now planned in the United States, but nuclear power is drawing renewed attention, spurred by concerns over global warming and new advances in nuclear plant technology and safety.

“With growing worries about global warming and the associated likelihood that greenhouse gas emissions will be regulated in some fashion, it is not surprising that governments and power providers in the U.S. and elsewhere are increasingly considering building a substantial number of additional nuclear power plants,” Deutch and Moniz write in their Scientific American article, titled “The Nuclear Option.”

Global electricity consumption is expected to grow 160 percent by 2050. A tripling of the world’s nuclear capacity by that year could help meet that electricity need without large new emissions of carbon, according to a 2003 MIT study, “The Future of Nuclear Power,” which Deutch and Moniz co-chaired.

That study proposed that if worldwide nuclear power generation tripled to one million megawatts by the year 2050, it would save between 0.8 billion and 1.8 billion tons of carbon emissions per year, depending on whether gas- or coal-powered plants were displaced.

“At this scale, nuclear power would significantly contribute to the stabilization of greenhouse gas emissions, which requires about seven billion tons of carbon to be averted annually by 2050,” Deutch and Moniz wrote.

To reach that level of nuclear energy production, a few obstacles must be overcome, according to Deutch and Moniz. Major obstacles are the high costs of nuclear power plant construction, uncertainty over nuclear waste management and concerns about nuclear proliferation.

Deutch and Moniz suggest that a government-imposed “carbon tax” could raise the cost of generating electricity from coal or natural gas, making nuclear energy more attractive to power companies. Reducing construction costs and time would also make nuclear power more economical.

They also propose that the federal government establish consolidated interim storage as part of the nation’s nuclear waste management strategy.

Threats of nuclear proliferation could be countered by establishing relationships in which countries such as the United States, Russia and France would lease nuclear fuel to countries that want to develop nuclear power plants. The United States would then reclaim the spent fuel and dispose of it, eliminating the risk that countries could secretly develop weapons programs under the guise of generating nuclear power.

Although the challenge is great, Deutch and Moniz believe success is attainable. Since 2000, more than 20,000 megawatts of nuclear capacity have come online, mostly in the Far East.

“Reaching a terawatt of nuclear power by 2050 is certainly challenging, requiring deployment of about 2,000 megawatts a month,” they write. “A capital investment of $2 trillion over several decades is called for, and power plant cost reduction, nuclear waste management and a proliferation-resistant international fuel cycle regime must all be addressed aggressively over the next decade or so.”

The Scientific American issue on energy can be found at www.sciam.com/issue.cfm.

Today’s release of a widely anticipated international report on global warming coincides with a growing clamor within the United States to reduce greenhouse gas emissions and prevent the potentially devastating consequences of global climate change.

“There’s more interest in this now than at any time in the last 20 years,” says Ronald Prinn, TEPCO Professor of Atmospheric Sciences at MIT, who was a lead author of the report issued by the Intergovernmental Panel on Climate Change (IPCC).

The report issued today in Paris, a 21-page summary of a much longer study on the science behind climate change, concludes there is a greater than 90 percent chance that greenhouse gases from human activity are responsible for most of the steadily rising average global temperatures observed in the past 50 years.

“There’s clear evidence that greenhouse gases have been increasing by very large amounts since preindustrial times, and the vast majority of these increases are due to human activity,” said Prinn, whose specific task on the panel was to assess this issue.

This is the fourth climate report issued by the IPCC since it was established by the U.N. in 1988. Prinn, who is the director of MIT’s Center for Global Change Science, was one of more than 100 lead authors for the three-year study, which involved climate researchers from around the world.

For the first time, the IPCC provides extensive evidence of the regional signals of climate change, including rising continental-scale temperatures, rising sea levels, shrinking of Arctic summer sea ice and decrease in snow cover in the Northern Hemisphere. It also offers predictions for how rising temperatures will affect the planet in decades to come.

Taken as a whole, the report presents a strong case that the United States, which is responsible for about 25 percent of global greenhouse gas emissions, should take much more vigorous steps to curb its emissions along with the other major emitters around the world, Prinn said.

“Overall, the scientific evidence for human influence on climate has strengthened significantly in the past half dozen years, and the case for decreasing greenhouse gas emissions is significantly more compelling than it was six years ago,” he said.

Greenhouse gases, which include methane, nitrous oxide, ozone, chlorofluorocarbons and their replacements (hydrofluorocarbons) as well as the better-known carbon dioxide, trap infrared radiation in the Earth’s atmosphere, inhibiting the planet’s cooling capability. Burning of fossil fuels is a major contributor to greenhouse gas emissions, but agricultural activities and deforestation also contribute.

“It’s not just the highly industrialized nations that are involved here,” Prinn said. “To some degree, every person on the planet is responsible, but some are much more responsible than others.”

There is now a near-universal scientific consensus that human activity is driving climate change, but 10 years ago, Prinn himself was not convinced that that was the case. But, as the evidence mounted, Prinn concluded that the changes were too great to be explained by natural climate variations.

Other highlights of the report include:

• While global temperatures have risen significantly, the rise is less than expected from the greenhouse gases alone, because of the cooling effect of sulfate aerosols, another type of pollutant caused by fossil fuel combustion. Efforts already underway to reduce those aerosols, which cause acid rain and are harmful to human health, could lead to greater future warming.
• For the first time, the IPCC has placed odds on the accuracy of its climate predictions: The report offers several different greenhouse gas emissions scenarios and, for each one, predicts the likelihood of a certain temperature increase–for example, a two-thirds chance that global temperatures will rise 2.4 to 6.4 degrees Celsius for one high-emissions scenario.

Those odds will help policy-makers decide how much effort is needed to lessen or adapt to the potential impacts of climate change, according to Prinn.

“I’m very pleased because this has been a quest by the climate researchers at the Center for Global Change Science and the Joint Program on the Science and Policy of Global Change at MIT for more than a decade,” he said. “In order to help make policy decisions, scientists have got to provide the uncertainties on their key numbers.”

In recent weeks, several climate change bills have been introduced in Congress, and Prinn anticipates that he and other MIT researchers will be asked to testify on the scientific, technological and economic aspects of the proposed legislation.

In late November, Prinn spoke to a group of 36 newly elected members of Congress at Harvard’s Kennedy School of Government. The representatives were very interested in the topic of global warming, he said.

“It was very clear that this is something they are hearing from the people that elected them,” whose attention to climate issues has been drawn in part by destructive storms like Hurricane Katrina and decidedly un-winter-like temperatures in the Northeast, said Prinn.

“Many of the newly elected members were beginning to ask whether the United States is doing what it should be doing on this issue,” he said.

In addition to reducing emissions, the world should also be thinking about the need to prepare for and adapt to the effects of climate change, Prinn said. For example, it may not be wise to build new infrastructure in coastal areas that may be inundated with rising waters, he said. The IPCC report emphasizes that we are already committed to future warming due simply to the greenhouse gases already in the atmosphere.

Later this year, the IPCC will issue two more reports. One focuses on possible mitigation strategies, while the other will address the impact of climate change on global ecosystems and economies.