UC San Diego News Center


A Hopeful Message Gets a Hearing

Scripps researcher spreads word about a potential short-term win against climate change to variety of audiences

A push to curb air pollution as a means of slowing the pace of climate change is gaining momentum as a Scripps Institution of Oceanography researcher takes his message to new audiences.

Veerabhadran Ramanathan, a distinguished professor of climate and atmospheric sciences at Scripps, published new findings April 14 that control of certain pollutants can significantly attenuate sea-level rise. Prior to that, Ramanathan framed the issue as a matter of climate justice during an event at UC San Diego on April 10 with former Irish president and human rights advocate Mary Robinson. Next week, Ramanathan will take the message to Congress, when he takes part in a hearing on the benefits of controlling emissions of methane, a key greenhouse gas.

Ramanathan’s research over the past two decades has led him to conclude that if emissions of soot, methane, and refrigerants and the formation of ozone can be controlled, the speed at which global average temperatures are rising could be cut nearly in half. In combination with efforts to control emissions of carbon dioxide, the most ubiquitous greenhouse gas produced by everyday activities, mitigation of such pollutants could help society avoid many of the dangerous consequences of climate change, according to Ramanathan.

The veteran researcher, who joined UC San Diego’s Scripps Institution of Oceanography in 1990, has sought to inform a wide range of legislative and even spiritual leaders about this solution, operating outside of common science channels to engage diplomats and religious leaders. Ramanathan made pollution control the centerpiece of his remarks during the April 2012 visit of the 14th Dalai Lama to UC San Diego. Ramanathan had previously witnessed the creation of a multilateral initiative to curb pollution launched by then-U.S. Secretary of State Hillary Clinton. The Climate and Clean Air Coalition to Reduce Short-Lived Climate Pollutants began in February 2012 with six countries and the United Nations Environment Programme as members. It has grown to 25 members in the past 14 months.

“I’ve been encouraged at the reception this concept has received,” said Ramanathan. “I think policymakers are impressed when they understand that they can achieve relatively fast results using technologies that are already available. This kind of action needn’t be delayed by the need to achieve global political consensus that has prevented action on climate before. Countries can do this now and reap the benefits themselves.”

In the latest issue of the journal Nature Climate Change, Ramanathan and colleagues concluded that the annual rate of sea-level rise could be slowed as much as 50 percent by 2100 through the curbing of soot, methane, and other substances that Ramanathan collectively terms “short-lived climate pollutants” or SLCPs. The cumulative sea-level rise from 2005 to 2100 can be reduced by as much as 22 percent to 42 percent with the mitigation of these pollutants.

Control of SLCPs provides immediate benefits because they exist in the atmosphere only for periods ranging from a few days to a decade. In comparison, carbon dioxide remains in the atmosphere for more than a century. SLCP mitigation usually takes the form of capturing methane emitted from landfills and pipelines, the retrofitting of diesel-burning vehicles with more efficient exhaust filters, and the control of accidental escapes of the gases used in refrigeration. Ramanathan has launched his own endeavor called Project Surya to replace homemade wood-burning stoves used in the developing world with cleaner-burning units.

“It is encouraging that SLCPs contribute about half of the warming reduction and about two-thirds of the sea-level rise reduction since we have technologies to reduce them,” said Ramanathan. “Without CO2 stabilization below 450 parts per million, however, both the warming and sea level can rise to dangerous levels after 2100.”

The finding of the National Science Foundation-funded study by Scripps and the National Center for Atmospheric Research (NCAR) added to a growing list of benefits obtainable in the short term through mitigation of pollutants created by everyday activities, researchers say. A previous study by Ramanathan and a follow-on study by the World Meteorological Organization and the United Nations Environment Programme noted that the pace of global warming can also be substantially slowed with such measures. Many short-lived pollutants also pose hazards to respiratory health and stunt the growth of certain crops through disruption of photosynthesis. Thus, control provides an additional societal benefit, studies suggest. The results would be measurable nearly immediately–on a scale of months to a decade–given the short-lived nature of the pollutants.

To understand the effects of mitigative actions on sea-level rise, the authors extended their previous research that found that those actions could reduce global warming by as much as 0.6º C (1.1º F) by midcentury. In this study, they extended it to the end of the century and in collaboration with NCAR included a sea-level rise model as the new dimension to the SLCP research. Key drivers of sea-level rise are the expansion of seawater as it warms and the addition of fresh water to the oceans due to glacier melting. The researchers simulated through computer models how the reduction of global warming effected by short-lived pollutant control would affect the rate of thermal expansion of seawater and empirically accounted for the effects of glacier melt.

Without mitigative action, global sea-level rise is expected to encroach upon major coastal cities, particularly on the U.S. East Coast and in Asia. In the 2010 report “Cities and Climate Change,” the Organisation for Economic Co-operation and Development estimated that $35 trillion in assets will be at risk in 20 metropolitan areas in 2070 with damage being most likely during storm events. As many as 150 million people would be exposed to harm and dislocation as a result of sea-level rise.

“It must be remembered that carbon dioxide is still the most important factor in sea-level rise over the long term,” said NCAR’s Warren Washington, a study co-author. “But we can make a real difference in the next several decades by reducing other emissions.”

During the April 10 UC San Diego event, Robinson, who now heads the Mary Robinson Foundation – Climate Justice, and Ramanathan agreed that society’s response to climate change is a matter of social justice. The world’s poorest are most likely to bear a disproportionate share of climate change consequences, ranging from drought to inadequate food supply and displacement caused by physical changes to land.

“Get angry,” Robinson exhorted the UC San Diego students in the audience. “Get active.”

Ramanathan noted that some 3 billion people don’t have access to fossil fuels and thus have contributed much less than people in developed countries. As economies emerge, however, those with new affluence may gain that access and exacerbate problems created by global warming. Prior to the tea, the researcher had spent about two months in India, living simply in remote rural areas to understand for himself the practical challenges the poor face in converting to cleaner lifestyles. With congestion still evident in his voice from air travel that had concluded only the day before, he noted that the women in the small villages he visited were eager for change despite their limited ability to effect it.

Ramanathan’s next stop will be an April 26 Congressional briefing on methane capture at the invitation of Rep. Scott Peters (D-52nd District) that is hosted by the Environmental and Energy Study Institute, a nonprofit formed by a Congressional caucus in 1984.

Ramanathan’s “cutting-edge research speaks to his abilities as a scientist and the strength of Scripps Institution of Oceanography’s research team,” said Peters. “His work to improve our air quality and to understand climate change is something that we all benefit from, and I am honored that he has accepted my invitation to speak to my colleagues and me in D.C. later this month about his work on short-lived climate pollutants.”