CS3 In the News

In climate change, science and policy are inextricably linked—more so than in most contemporary social phenomena. The complexity of understanding earth’s systems generates uncertainty, which feeds into an imperfect policy process that often warps ideal economic instruments beyond recognition. Without clear recognition of this linkage, the resulting mixture is frequently less than appetizing. ­­This January, we continued an MIT Joint Program on the Science and Policy of Global Change tradition of presenting to the MIT community the basics (and some of the nuance) of this complex issue over a two-session Independent Activities Period (IAP) course.

While the minutiae of a 3-dimensional atmosphere and ocean model may be daunting (and require clusters of networked high-performance computers to complete a run), it turns out we can understand a lot about climate change from simplified models that build on basic physics accessible to any first-year undergraduate. Fundamental principles, such as energy balance, yield straightforward arguments about why the Earth should warm as we add greenhouse gases to its atmosphere. Those same principles can also be used to frame simple predictions about how future warming might proceed—information that policymakers and analysts can use to help plan for the future.

Considering climate change as an “externality” (a cost imposed on society by individuals and companies without compensation), economists have developed theories of how to reduce environmental impacts by appealing to pocketbooks. Putting a price on pollution (e.g., carbon tax) or selling and trading “rights” to pollute (e.g., cap-and-trade) are two common policy levers to encourage polluters to cut back while lessening the overall economic impact. When we couple our global climate models with global economic models (collectively, the Integrated Global System Modeling framework – IGSM), we can better understand the complex interactions between human activities and earth system changes.

We are invariably asked: Do we prefer to tax or to trade? Strictly economically speaking, if we have perfect information on the damages from climate change and the costs required to mitigate, the two should be equivalent. However, accounting for uncertainties on both ends of the human-earth interaction, we find that our answer from a strictly modeling perspective depends on which we can estimate better: the social cost of carbon (the total cost to society of the externality) or the “tipping point” thresholds of irreversible climate change? This is an area of ongoing research.

Policy-makers tend to respond to what they can see, an important part of the policy-science nexus of climate change. Typhoon Haiyan, which devastated the Philippines last November, stood as a stark reminder of the human suffering from extreme weather events—as did Hurricanes Sandy and Katrina on the domestic front. Hitting land just as the annual UN climate talks opened in Poland, Haiyan (or Yolanda, in the Philippines) became an impetus for international efforts there to create the beginnings of a “Warsaw Mechanism”, an international compensation scheme for loss and damage resulting from climate change. Predicting how the frequency and severity of such storms will change in a warming world is a crucial research focus, particularly as society builds more densely along coasts and in floodplains and exposes itself to more potential economic and personal loss.

Ultimately—unlike the Earth’s orbit—no policy issue exists in a vacuum. As we described examples of current efforts in the US, China and the EU to reduce greenhouse gas emissions, it is rare that the best of both science and economics are captured by policies in practice. The prevailing politics have a large impact on where the needle lands—tax, trade or other—and indicate an even bigger challenge that lay before us, not as scientists but as citizens.

Daniel Rothenberg and Daniel Gilford are graduate students in MIT’s Department of Earth and Planetary Sciences. Michael Davidson and Arthur Yip are graduate students in MIT’s Engineering Systems Division.

Genevieve Wanucha
Program in Atmospheres, Oceans and Climate

IAP 2014 was bone-chilling, and thanks to 12.310, An Introduction to Weather Forecasting, 20 new amateur forecasters can tell you why.

Always offered between semesters, 12.310 reveals the principles of fluid dynamics that govern the atmosphere’s movement. In lectures, real forecasting exercises, and a trip to WBZ TV’s on-air weather center, students learn where newsrooms get their daily weather predictions — and how they can make their own.

“Our aim is that students come to understand that weather forecasting is not guessing and is based on real science,” says Lodovica Illari, senior lecturer in synoptic meteorology in MIT’s Program for Atmospheres, Oceans, and Climate (PAOC), who has taught the course for 20 years. “We hope the students get interested in fluid dynamics and come back and do some more.”

To reveal the laws governing the atmosphere’s motion “in action,” Illari used demonstrations with MIT’s Weather in the Tank materials. In one class, Illari rotated a cylindrical tank of water on a turntable to emulate the dynamics of Earth’s atmosphere. A bucket of ice at the tank’s center created a temperature gradient. As students peered in, Illari dropped ink into the water to make visible the small currents forming in the water, demonstrating the conditions that create weather systems.

12.310 stands as a yearly reminder of MIT’s distinguished history in weather forecasting. In fact, Carl-Gustaf Rossby, who transformed weather forecasting into an atmospheric science, founded the country’s first meteorology program at MIT in 1928. A line of prominent MIT faculty meteorologists followed, including Jule Charney, Norman Phillips, Victor Starr, and Edward Lorenz. The fundamental contributions to fluid dynamics made by these past professors resonate in MIT’s modern-day research into much longer-time-scale atmospheric phenomena such as climate.

As the students of 12.310 learned the basics of weather forecasting, they came to appreciate an insight of Professor Lorenz’s that changed meteorology forever. At MIT in 1961, Lorenz found that rounding a few digits off one decimal number in a computer weather simulation changed its projected long-term pattern. He had discovered the big implications of the chaos theory principle of “sensitive dependence on initial conditions” for weather prediction. Slightly imprecise measurements, even single-digit differences in dew point, can skew long-term forecasts. The chaotic nature of short-term weather places a limit of less than 10 days on accurate forecasts.

To make their own forecasts, the students used raw data spit out of weather prediction models run at the National Weather Service, which are read out in maps of the temperature, air pressure, dew point, wind, and moisture across the country. With that information, the students anticipated the likely passage of warm or cold weather fronts by searching for regions of strong gradients in temperature or moisture and shifts in wind direction. The class ended with a TV-style presentation of the day’s weather and a Boston weather forecasting competition. This year, Fiona Paine ’17 took home the prize of a digital indoor/outdoor thermometer.



The course was organized and taught by Illari and co-instructor Jeff Scott, a research scientist at PAOC and the Center for Global Change Science, along with teaching assistants Casey Hilgenbrink ’15 and PAOC graduate student Vince Agard ’11, who are both members of the MIT Weather Forecasting Team.



Many of the undergraduates signed up for 12.310 to get a taste of the kind of science they could pursue in PAOC. Others said that knowing how to predict the weather is just plain useful. And everyone found the class eye-opening. “It was surprising to me just how difficult it can be to predict tomorrow's weather, even when using the newest technology,” says Oren Katzen ’16. “I will be certain to be more forgiving to the weatherman in the future.”

By Michael Davidson

It is quite a challenge to pin down an electricity system that has grown 10.8 percent annually over the last decade, doubled power generation in just 7 years and added 80-90 gigawatts (GW) – the equivalent of the United Kingdom’s entire generating capacity –every year.

Nevertheless, some preliminary year-end statistics recently published by central agencies (NEA, NBS,CNREC) offer an interesting, though imperfect, snapshot of China’s power sector in 2013.

Notably, after a lull in 2012, electricity demand growth recovered last year owing to resurgent industrial demand. Coal retained its share in terms of capacity factor, while wind saw a rise in capacity factors indicating that some measures to improvement integration have had an impact. The “Big Five” state-owned generating companies – which collectively own 47 percent of Chinese generating capacity – made record profits in 2013, and the top electricity regulator was rolled into the top energy policy body in an attempt to streamline oversight.

Let’s take a spin through the 1,250 GW Chinese electricity system…

Electricity demand rebounds with heavy industry-led growth

In 2012, electricity demand growth fell to 5.6 percent, its lowest rate since 1998. In contrast, 2013 saw electricity growth regain 1.6 percentage points, to 7.2 percent growth for the year. While GDP grew at the same 7.7-7.8 percent rate in both years, last year’s surge in electricity demand was driven by anuptick in heavy industry-led growth. Crude steel production grew 7.5 percent compared to 3.1 percent in 2012, while the automobile production sector grew 18.4 percent, almost three times faster than in 2012. As over 70 percent of electricity production in China goes to satisfy industry demands, this readjustment drove national power sector demand (see figure, throughout, historic data is from the CEC– China Electricity Council.) More...

The Global Young Academy (GYA) is an international group of two hundred young (up to ten years post PhD) scientists selected based on research excellence and commitment to impact. Through GYA, members are linked to the senior international academy network IAP, meet outstanding leaders of the international science community and may be nominated to contribute to international policy statements and working groups. Appointments are for a period of four years.

Selin's research focuses on using atmospheric chemistry modeling to inform decision-­â€making strategies on air pollution, climate change and toxic substances including mercury and persistent organic pollutants. She has also published articles and book chapters on the interactions between science and policy in international environmental negotiations, in particular focusing on global efforts to regulate hazardous chemicals and persistent organic pollutants. 

Selin, who will be formally appointed at a GYA symposium on May 21st, says she is very much looking forward to leveraging her new appointment to expand the reach of her science-policy work and educational initiatives.

By Michael Craig, Amanda Giang, Colin Thackrayʉ۬

What’s the difference between climate change, the Northern spotted owl, and acid rain?

That question is not the beginning of a bad joke. Rather, it was the type of question that lay at the heart of the class ‘Science, Politics, and Environmental Policy’ offered this past fall at the Massachusetts Institute of Technology. For the first time, the class was co-taught by Professors Susan Solomon of Earth, Atmospheric and Planetary Sciences and Judy Layzer of Urban Studies and Planning – an interdisciplinary team that drew students from diverse backgrounds across MIT’s schools and departments. Through weekly case studies, the class aimed to better understand how the United States has dealt with environmental problems and the multifaceted role of science in that process.

Each week, students focused on a different environmental issue, ranging from historical examples like the use of lead in gasoline, to currently unfolding debates, like the environmental impacts of unconventional shale gas production. Through reading, writing, and discussion, students explored how and why these issues entered the policy agenda (or didn’t), evolving policy responses, and how science fit into the picture. While fast and hard conclusions were elusive, as the class drew to a close students reflected on several themes that emerged over the course of the semester: the complexity of the policy-making process, the convoluted path that science takes from its origin to its use in policy, and the importance of storytelling for communicating science effectively.

Opening the black box of policy-making

Many of us initially saw the policy process as a black box – we could see the inputs (mainly science) and outputs (environmental policy), but did not fully grasp how one led to the other. Over the course of the semester, we came to a far better understanding of what levers exist to influence the policy-making process.

Some of those levers are litigation, direct involvement in the political process, and communication to the public. Each can influence the conversion of inputs to outputs, but vary in effectiveness under different circumstances. In part, such circumstances emerge from existing economic and political institutions, which can constrain policymaking and create path dependency. Recognizing these realities through case studies demonstrated the importance of looking at policy issues from different angles and thinking carefully about the best strategy for effecting change.

The path from science to policy

As we peeled the lid off the black box of policymaking, we also began to recognize how convoluted the path science travels from generation to use in policymaking can be. Science does not pass directly from academics to policymakers, but rather is filtered and translated by many individuals. These individuals – and even scientists themselves – have differing values, biases, and goals that can lead them to different interpretations of, and conclusions from, science. What role, if any, should scientists play along science’s path from lab to policy? Do scientists who act as advocates harm the credibility of science as a whole, and if so, does this harm outweigh the potential benefits? For scientists who act as the ‘experts’ that communicate the scientific basis of environmental issues to non-scientists, how do their biases and values shape their actions and their interpretation of science? If science is being filtered and reinterpreted, how can we ensure the veracity of information we receive that is purportedly "based on science”?

Stories matter

Over the course of the semester, the importance of storytelling also emerged as a major theme. In many of the cases we studied, public engagement was a key driver for policy action, so effectively communicating with and reaching the public is crucial. Doing so requires the ability to tell a clear story – to communicate information (scientific or otherwise) clearly, concisely, and in a way that is relevant to the audience. Focusing on what you know can help in putting forth a clear narrative, and while uncertainties are important to convey, they do not need to be the focus of communication.

There is no easy formula for developing strong environmental policies, nor are there simple rules for how science should be involved. That said, 'Science, Politics, and Environmental Policy' helped us develop a more nuanced understanding of the complex policy-making process, and gave us tools to engage in it strategically, and with self-awareness. Rarely is there an opportunity to discuss the many-layered environmental policy system with students with such diverse expertise. The confluence of ideas and points of view from the varied backgrounds of both the students and professors resulted in a unique learning experience for this collection of young environmental scholars.

Colin Thackray is a graduate student in MIT's Department of Earth, Atmospheric and Planetary Sciences working with Noelle Selin. Amanda Giang and Michael Craig are graduate students in MIT's Engineering Systems Division.

Sergey Paltsev, assistant director for economic research at the MIT Joint Program on the Science and Policy of Global Change, presented at the 2014 Gaidar Forum entitled "Russia and the World: Sustainable Development."

The expert discussion “Green growth” and sustainable development” was dedicated to such topics as energy efficiency and renewable energy as the drivers of economic growthas economic growth drivers. Besides it focused on the perspectives of “the third industrial revolution”, which is not a new idea, however it opens the prospects for efficient energy use.

Oleg Lugovoy, Research Advisor, Center for Economic Modeling of Energy and Environment, RANEPA, Jeffrey Sachs, Director of the Earth Institute and Professor of Columbia University, Hillard Huntington, Executive Director of Energy Modeling Forum, Stanford University, Emmanuel Guérin, Associate Director of Sustainable Development Solutions Network (SDSN), Frederic Vidal, President of Université de Nice Sophia-Antipolis, Sergey Paltsev, Assistant Director for Economic Research of MIT Joint Program on the Science and Policy of Global Change of the Massachusetts Institute of Technology, John Laitner, Resource Economist and Independent Consultant of Economic and Human Dimensions Research Associates and Glen Peters, Senior Research Fellow of the Center for International Climate and Environmental Research of Norway, took part in the discussion.

In his opening remarks, the moderator Oleg Lugovoy defined the vector of the discussion: “It’s a discussion on how to achieve high growth rates and improve life quality without causing harm to the environment.” He also noted that the problem could not be solved by the efforts of business and public organizations alone, but depends on economic regulation.

John Laitner turned the participants’ attention to the task of increasing the quality of energy efficiency giving USA as an example, where 86% of all energy is spent to no purpose. Inefficient use of energy leads to huge costs and is a factor limiting, in Russia as well, the potential for economic development. The expert underlined that the idea of the third industrial revolution which consists of combination of interactive communications and new green technologies is getting more important.

Jeffrey Sachs reminded the participants of the discussion about the idea of a prominent Russian economist Nikolai Kondratyev on periodic economic cycles (waves) linking it to the concept of a shift in technological modes. Each of them had limited resources, but never before has the scale of economic activity been so impressive and the number of population so huge (7.2 billion people). “90 trillion dollars – this is the volume of the annual economic output,” Jeffrey Sachs noted, “and this figure tends to grow progressively. So do the CO2 emissions as well. Already today 38 billion tons of СО2 are annually emitted into the Earth’s atmosphere,” the expert noted.

However, changing the energy system profoundly and substantially over 40-50 years is quite a challenge. One of the possible solutions is to switch to alternative types of fuel or renewable energy sources. Nuclear energy, if it is safe, also has a high potential. But the most important thing, according to the expert, is to reduce coal consumption, in particular, “convince China, the country which consumes this fuel in huge volumes, to do so.”

The report by Hillard Huntington marked a turn in the discussion to the subject of shale gas. The expert noted numerous uncertainties pertaining to shale gas extraction. It is still difficult to evaluate the outlook for price policy in this field unambiguously, which is caused not only by the way it is extracted, but also the volumes of gas supply.

Sergey Paltsev agreed with his colleague. He immediately dotted the i’s noting the “platitude” of shale gas: “It does not differ from the common methane, the difference lies in the method of extraction which consists in subsurface fracture.” Answering the question “whether Gazprom has overslept shale gas revolution or not”, the expert agreed with the estimation given by the Prime Minister of the Russian Federation Dmitry Medvedev who said that “this question is quite complicated.” “Gazprom has enough gas and it can go without shale gas, given proper investment and price policy,” Mr. Paltsev summarized. He also noted that the consequences of fraction are difficult to predict. Besides, the use of huge amount of water during extraction makes its benefits ambiguous, at the same time CO2 emissions from the use of natural gas are far from zero, therefore it is impossible to say that its production can address the problem of emissions globally.

Channel News Asia interviews Michael Davidson on the Business Central show. Michael Davidson is Research Assistant for the China Energy and Climate Project and a doctoral student in the Engineering Systems Division.

In many public discussions of climate change, science takes a back seat to political agendas and rhetoric. But 12.340x (Global Warming Science), a new massive open online course from MITx now open for enrollment on the edX platform, aims to change that dynamic by providing a solid scientific view of what is really happening with global warming.

“We are trying to bring back some of the intellectual excitement that belongs to the field,” says Professor Kerry Emanuel, a co-teacher of the course whose research focuses on hurricanes. “This is a serious science course.”

The MITx course will use many of the lecture materials developed for the on-campus version of the course, along with new videos and visuals. The course will also include new exercises, problem sets, and a final exam, all tailored to the assessment tools available on the edX platform and developed with an eye on preserving the rigor of the course. “You have to have a background in mathematics up through differential equations, and a background in physics,” says Emanuel, the Cecil and Ida Green Professor of Atmospheric Science. “Our intent is that it will be as challenging as the classroom course.”

12.340x will also bring simulations used in the MIT residential course to a wider audience, including the single-column model simulation. Emanuel describes this unique tool as “a computer climate model that takes inputs such as solar radiation and atmospheric greenhouse gas content and calculates the temperatures of the surface and atmosphere, and the moisture and cloud distributions in the atmosphere. Students can change the intensity of sunlight, the time of year, the greenhouse gas concentrations, and other inputs to see how they affect climate change.”

Emanuel expects a wide range of people to take 12.340x. “You’re going to find a lot of students in climate and energy. They will want to know the physics, chemistry, and biology (of climate change).” He also expects professionals working in energy and public policy to be interested in the course. Even a politician has expressed interest in 12.340x, but Emanuel is keeping the individual’s name confidential.

Emanuel and the Department of Earth, Atmospheric and Planetary Sciences also hope to change the dynamic around the study of climate change on the MIT campus. In part because the course is not a requirement, and in part because of the perception among students that climate-change study is mostly about politics and not hard science, the on-campus course has not seen the enrollment levels Emanuel would like to see. “Part of the problem is all the publicity of global warming has sent out a message that global warming is highly politicized, and has nothing to do with science,” he says. “Nothing could be further from the truth.”

By Laura Barron-Lopez

Global warming may be contributing to the "polar vortex" causing frigid temperatures across most of the nation on Monday, according to some climate change researchers.

While it seems counter-intuitive, the research argues that plunging temperatures could come from changes in the jet stream caused by climate change.

Rutgers University climate scientist Jennifer A Francis has released a number of papers about changes in the jet stream brought about by warming Arctic temperatures.

Her conclusions suggest that warming Arctic air caused by greenhouse gas emissions has caused changing to the jet stream that is pushing colder Arctic air further south, causing temperatures to plunge from the High Plains to the Deep South.

The jet stream shift has sent frigid air across the central part of the country, and deeper into the south than normal.

Alaska, meanwhile, is being hit by unusually warm conditions and California is facing record-breaking drought, Francis said.

She said the strange weather is becoming more likely because of climate change.

"We can't say that these are extremes are because of climate change but we can say that this kind of pattern is becoming more likely because of climate change," Francis said.

NASA analysis has also drawn a link between the jet stream, climate change and colder temperatures.

A 2010 NASA analysis tied colder temperatures over the course of 2009 to an event similar to the wavy jet stream, called "Arctic oscillation" — a see-sawing pressure system over the North Pole. That oscillation pushed cold air to teh south.

The NASA analysis also said that despite cold snaps, and other weather changes being a part of naturally occurring patterns, they are still in line with a "globally warming world."

According to Francis, big fluctuations in the jet stream cause extreme weather conditions to hang around longer.

She argues greenhouse gas emissions are a key factor.

"The process of warming the Arctic is intensified due to greenhouse gas emissions," Francis said. "The Arctic is warming two to three times faster than the rest of the Northern Hemisphere."

MIT atmospheric scientist Kerry Emanuel said long-term climate change can only be seen by looking at detailed statistics.

“It's certainly plausible, at lease for awhile that a changing jet stream, may cause colder winters,” Emanuel said.

But he added that it is difficult to tie a direct link between individual events like the cold snap occurring in the Midwest and East Coast to global warming.

Emanuel added that that doesn't mean you can disregard global warming.

“If you cherry pick you can always find an excuse to go against [global warming,” Emanuel said.

Image Credit: Satellite Image Shows Entry of the Polar Vortex into the Northern U.S.

Oceans cover 97 percent of the Earth’s surface, and act as an important carbon sink. However, each part of the ocean works in different ways to take up carbon from the atmosphere and store it. Two new studies shed light on the nuances how these processes work in the Arctic Ocean and coastal zones.

The findings about the Arctic Ocean were published recently in the journal Global Biogeochemical Cycles. Stephanie Dutkiewicz, a research scientist at the Massachusetts Institute for Technology, worked with colleagues to figure out how decreasing sea ice in the summer is affecting the carbon cycle in that ocean basin from 1997-2006.

That period is in the middle a timeframe when the Arctic has been warming twice as fast as the rest of the globe, leading to major losses in sea ice, which hit a record low in 2012. Over that time, the Arctic Ocean has become a greater repository for carbon.

That’s because more open water provides more suitable habitat for phytoplankton, or algae, to grow and suck carbon dioxide out of the air. As days get shorter, the algae dies and sinks, sequestering the carbon at the bottom of the ocean.
With summer loss of sea ice and warming in the Arctic projected to continue, phytoplankton blooms are likely to be a more common occurance across the region. However, the warming trend encouraging algae growth could also have negative consequences on another ocean mechanism that removes carbon from the atmosphere.

Sunlight not only increases plant life but it also warms the surface waters of the Arctic. Dutkiewicz’s findings show that warming could eventually reduce the Arctic Ocean’s ability to absorb carbon dioxide because cold water dissolves it better than warm water.

Of course water is warming in a relative sense in the Arctic. Sea surface temperatures in the region have risen since 1965 but are still near freezing for most of the region during the summer. However, if the trend continues it could still reduce the region’s ability to take up carbon. Dutkiewicz also said the study’s findings have applications beyond the Arctic’s borders.

“The processes we’re looking at are happening everywhere,” Dutkiewicz said. “We need to be studying it (in the Arctic) and understanding the changes. That will help us understand what will happen in 20 or 50 years in other parts of other oceans.”
The other study, a review published in Nature, found that coastal oceans are also helping store carbon. Coastals oceans account for only 7 percent of the overall area of oceans, but the new study finds they play an outsize role when it comes to carbon storage.

Coastal zones weren’t always carbon sinks. Prior to the Industrial Revolution, oceans acted as net emitters of carbon. However, in the ensuing 50-100 years, a shift occurred and these areas now take up more carbon than they emit.

The new research estimates that in pre-industrial times, coastal areas emitted about 150 million metric tons of carbon a year. Presently they take up 250 million metric tons annually. That’s about equivalent to Turkey’s carbon emissions in 2008.
“Traditionally, most thinking has been that there’s a shift in biological production in recent decades, that the ocean has become more productive,” said Wei-Jun Cai, an oceanographer at the University of Delaware and author of the report. The reason, he said, is because increased runoff from agriculture finds it way down rivers and into the coastal zone, which in turn increases plant life.

However, Cai believes there’s another mechanism at play. Measurements in the open ocean of carbon dioxide in the water and the atmosphere tend to show the two stay pretty close to equilibrium. In other words, if there’s 400 parts per million of carbon dioxide in the atmosphere, a similar ratio is likely to exist in the ocean waters.

That relationship doesn’t exist in coastal areas, though. Cai recalled a trip to measure carbon dioxide in the water off the Georgia coast in 2005.

“It was very similar to what someone else measured in 1995,” he said about his measurements. “I was shocked as there was very little increase. The reason is the water doesn’t stay there for a long enough time so it doesn’t really accumulate the anthropogenic signal.”

Instead, water in coastal zones is constantly on the move thanks to the conveyor belt of ocean currents. Those currents eventually dive to the depth of the ocean, and could be storing the carbon down there according to Cai’s theory.

Both studies point to the need for better monitoring in both those regions. They offer tantalizing results that suggest revisiting our understanding of the globe’s carbon budget, but more data is needed to reinforce their results.

That data would not only inform a better understanding of the planet’s carbon budget, but also paint a clearer picture of how regions that have great economic and environmental importance are changing.

The Arctic Ocean has has long been known as a carbon sink, but a new study suggests that while the frigid waters do store large quantities of carbon, parts of the ocean also emit atmospheric carbon dioxide.

Researchers from MIT constructed a model to simulate the effect of sea ice loss in the Arctic, finding that as the region loses its ice, it is becoming more of a carbon sink, taking on about one additional megaton of carbon each year between 1996 and 2007. But while the Arctic is taking on more carbon, the researchers found, paradoxically, the regions where the water is warmest are actually able to store less carbon and are instead emitting carbon dioxide into the atmosphere.

While the Arctic region as a whole remains a large carbon sink, the realization that parts of the Arctic are carbon emitters paints a more complex picture of how the region is responding to global warming.

"People have suggested that the Arctic is having higher productivity, and therefore higher uptake of carbon," said Stephanie Dutkiewicz, an MIT research scientist. "What's nice about this study is, it says that's not the whole story. We've begun to pull apart the actual bits and pieces that are going on."

Dutkiewicz and her colleagues, including Mick Follows and Christopher Hill of MIT, Manfredi Manizza of the Scripps Institute of Oceanography and Dimitris Menemenlis of NASA's Jet Propulsion Laboratory, published their work in the journal Global Biogeochemical Cycles.

To model the Arctic's carbon cycle, the research team developed a model that traces the flow of carbon in the Arctic, looking for conditions that led to the ocean's storage or release of carbon. To accomplish this, the team incorporated three models, which MIT detailed in a news release:

"A physical model that integrates temperature and salinity data, along with the direction of currents in a region; a sea ice model that estimates ice growth and shrinkage from year to year; and a biogeochemistry model, which simulates the flow of nutrients and carbon, given the parameters of the other two models."

The model showed the Arctic taking on an average of 58 megatons of carbon each year, with an average increase of 1 megaton each year between 1996 and 2007. One megaton is 1 million tons.

The model confirms a long held theory: as sea ice melts, more organisms grow, leading to a larger carbon sink as the organisms store carbon.

But there was the anomaly of 2005-2007 where portions of the Arctic released more carbon than they stored. These years saw significant sea ice shrinkage, yet in certain regions, more carbon was emitted than stored. The researchers accounted for the anomaly by factoring in water temperature along with the levels of sea ice loss.

"The Arctic is special in that it's certainly a place where we see changes happening faster than anywhere else," Dutkiewicz said. "Because of that, there are bigger changes in the sea ice and biology, and therefore possibly to the carbon sink."

Jennifer Chu, MIT News Office

For the past three decades, as the climate has warmed, the massive plates of sea ice in the Arctic Ocean have shrunk: In 2007, scientists observed nearly 50 percent less summer ice than had been seen in 1980.

Dramatic changes in ice cover have, in turn, altered the Arctic ecosystem — particularly in summer months, when ice recedes and sunlight penetrates surface waters, spurring life to grow. Satellite images have captured large blooms of phytoplankton in Arctic regions that were once relatively unproductive. When these organisms die, a small portion of their carbon sinks to the deep ocean, creating a sink, or reservoir, of carbon.

Now researchers at MIT have found that with the loss of sea ice, the Arctic Ocean is becoming more of a carbon sink. The team modeled changes in Arctic sea ice, temperatures, currents, and flow of carbon from 1996 to 2007, and found that the amount of carbon taken up by the Arctic increased by 1 megaton each year.

But the group also observed a somewhat paradoxical effect: A few Arctic regions where waters were warmest were actually less able to store carbon. Instead, these regions — such as the Barents Sea, near Greenland — were a carbon source, emitting carbon dioxide to the atmosphere. 

While the Arctic Ocean as a whole remains a carbon sink, MIT principal research scientist Stephanie Dutkiewicz says places like the Barents Sea paint a more complex picture of how the Arctic is changing with global warming.

“People have suggested that the Arctic is having higher productivity, and therefore higher uptake of carbon,” Dutkiewicz says. “What’s nice about this study is, it says that’s not the whole story. We’ve begun to pull apart the actual bits and pieces that are going on.”

A paper by Dutkiewicz and co-authors Mick Follows and Christopher Hill of MIT, Manfredi Manizza of the Scripps Institute of Oceanography, and Dimitris Menemenlis of NASA’s Jet Propulsion Laboratory is published in the journal Global Biogeochemical Cycles.

The ocean’s carbon cycle

The cycling of carbon in the oceans is relatively straightforward: As organisms like phytoplankton grow in surface waters, they absorb sunlight and carbon dioxide from the atmosphere. Through photosynthesis, carbon dioxide builds cell walls and other structures; when organisms die, some portion of the plankton sink as organic carbon to the deep ocean. Over time, bacteria eat away at the detritus, converting it back into carbon dioxide that, when stirred up by ocean currents, can escape into the atmosphere.

The MIT group developed a model to trace the flow of carbon in the Arctic, looking at conditions in which carbon was either stored or released from the ocean. To do this, the researchers combined three models: a physical model that integrates temperature and salinity data, along with the direction of currents in a region; a sea ice model that estimates ice growth and shrinkage from year to year; and a biogeochemistry model, which simulates the flow of nutrients and carbon, given the parameters of the other two models.

The researchers modeled the changing Arctic between 1996 and 2007 and found that the ocean stored, on average, about 58 megatons of carbon each year — a figure that increased by an average of 1 megaton annually over this time period.

These numbers, Dutkiewicz says, are not surprising, as the Arctic has long been known to be a carbon sink. The group’s results confirm a widely held theory: With less sea ice, more organisms grow, eventually creating a bigger carbon sink.

A new counterbalance

However, one finding from the group muddies this seemingly linear relationship. Manizza found a discrepancy between 2005 and 2007, the most severe periods of sea ice shrinkage. While the Arctic lost more ice cover in 2007 than in 2005, less carbon was taken up by the ocean in 2007 — an unexpected finding, in light of the theory that less sea ice leads to more carbon stored.

Manizza traced the discrepancy to the Greenland and Barents seas, regions of the Arctic Ocean that take in warmer waters from the Atlantic. (In warmer environments, carbon is less soluble in seawater.) Manizza observed this scenario in the Barents Sea in 2007, when warmer temperatures caused more carbon dioxide to be released than stored.

The results point to a subtle balance: An ocean’s carbon flow depends on both water temperature and biological activity. In warmer waters, carbon is more likely to be expelled into the atmosphere; in waters with more biological growth — for example, due to less sea ice — carbon is more likely to be stored in ocean organisms.

In short, while the Arctic Ocean as a whole seems to be storing more carbon than in previous years, the increase in the carbon sink may not be as large as scientists had previously thought.

“The Arctic is special in that it’s certainly a place where we see changes happening faster than anywhere else,” Dutkiewicz says. “Because of that, there are bigger changes in the sea ice and biology, and therefore possibly to the carbon sink.”

Manizza adds that while the remoteness of the Arctic makes it difficult for scientists to obtain accurate measurements, more data from this region “can both inform us about the change 
in the polar area and make our models highly reliable
for policymaking decisions.”

This research was supported by the National Science Foundation and the National Oceanic and Atmospheric Administration.