Sorting Out India’s Soot Situation: A Conversation with Jayaraman Srinivasan

Image of Jayaraman Srinivasan, chair of the Divecha Centre for Climate Change in Bangalore. Source: Indian Institute of Science.

Jayaraman Srinivasan chairs the Divecha Centre for Climate Change in Bangalore. Source: Indian Institute of Science.

In March 2011, India announced the launch of a $45 million program of Earth observation and climate research on black carbon, better known as soot. It is a controversial topic for Indian climate science and policy. Warming caused by copious emissions of soot from heavy diesel and biomass burning may be disrupting India’s monsoons and melting Himalayan glaciers. Yet Indian policymakers oppose proposals by developed countries to regulate black carbon internationally, suspecting an effort to deflect attention from their own emissions of greenhouse gases such as carbon dioxide and methane.

The goal of India’s Black Carbon Research Initiative (BCRI) is to better define soot’s impact by developing a national inventory of black carbon sources, initiating long-term atmospheric monitoring of aerosols, and improving models to tease out soot’s role in glacial melting and climate change. The proposed collaboration by more than 100 Indian institutions and 65 observatories nationwide was advanced by Jairam Ramesh, India’s minister for environment and forests from 2009 until this summer, who earned a reputation for putting environmental science and conservation ahead of political and development interests. At the launch, Professor V. Ramanathan, the Indian-born director of the Center for Clouds, Chemistry and Climate at the Scripps Institute of Oceanography and an expert on aerosols and climate, said the “ambitious” program positioned India to be “second-to-none” on aerosols research and black carbon.

Earthzine recently spoke with Jayaraman Srinivasan, the climate modeler who Ramesh tapped to lead the BCRI. The conversation took place following the appointment of a new environment minister and, as a result, Srinivasan focused his remarks on the scientific and political context for black carbon research, rather than on the BCRI itself. He is chair of the Indian Institute of Science’s Divecha Centre for Climate Change in Bangalore and the country’s leading authority on black carbon.

Image of MOEF Proposed BC network superimposed over the existing ARFI network

India plans to enhance monitoring of black carbon and other aerosols. New monitoring sites (yellow) will reinforce an existing network of surface observatories operated by the Indian Space Research Organization (blue and red). Source: March 2011 Science Plan for India’s Black Carbon Research Initiative.

Earthzine: Why does the topic of black carbon elicit such strong reactions in India?

Srinivasan: It started with Professor Ramanathan’s 2001 report about the Asian brown cloud and the monsoons, which garnered considerable media attention in India. The way it was portrayed was that this mass of aerosol pollution over the Indian Subcontinent would cause the imminent demise of the monsoon. But the impact of aerosols on the monsoon was not so clear. It’s not like CO2, where after a century of work we have a good idea of how it controls climate. Aerosols are a comparatively new animal, and black carbon is unique. Whereas sulphate aerosols reflect sunlight back into space and thus cool Earth’s surface, soot simultaneously shades the surface and, by absorbing some light, heats the atmosphere. They were looking at the cooling that soot causes at the surface and projecting a weaker monsoon circulation and devastating droughts, but they were forgetting about the heating in the atmosphere. As subsequent research such as that by William Lau at NASA’s Goddard Space Flight Center showed, the atmospheric heating actually enhances the monsoon.

Earthzine: Today some policymakers and scientists – Ramanathan included – are raising the alarm over black carbon’s contribution to global warming and glacial melting. Are they jumping the gun again?

Srinivasan: Unfortunately, the subject has become politicized. Some are suggesting that black carbon should be controlled aggressively through international treaties to quickly arrest climate change. That to me is completely red-herring. We suspect it is a political red herring. We are surprised that people are advocating policy measures so early into the research on black carbon. One should not jump into policy issues until the science is well understood.

Earthzine: How about the connection between black carbon and climate? Could scientists such as Ramanathan be correct that black carbon’s warming impact may be greater than CO2’s in regions such as the Himalayas where soot emissions settling onto snow and ice can directly accelerate their melting?

Srinivasan: The issue of black carbon on glaciers was first studied in great depth in the Arctic region, where the surface is white and even a small amount of black carbon will greatly increase heating. In the Himalayas, however, a large number of glaciers are already brown with debris. When I first visited them I said, ‘Where is the glacier?’ because the surface was all covered with dirt and rock. That may actually insulate the glacier, so it is not clear that soot falling on top will accelerate melting. People are extrapolating from the pristine ice of the Arctic that’s as white as can be, and that’s not right. Let’s make actual measurements, gather a few year’s worth of data and carefully calculate the impacts. Let’s do some serious research before we prescribe policy options.

Earthzine: Are the Himalayan glaciers melting? There has been some doubt surrounding that since the IPCC’s 2007 statement that they would be gone by 2035 was shown to be unfounded.

Srinivasan: Because of one poor citation in the IPCC report the whole thing has become controversial. To me, it’s very clear because Indian scientists have been monitoring thousands of glaciers for the last 20 years (though some of the best data came in pretty late for the 2007 report). Most of the glaciers are retreating and it is quite clear that global warming is one of the major factors. Hundreds of small glaciers are disappearing quite rapidly and they are already affecting small communities in rural valleys. They don’t get much media coverage because they are isolated, but their water sources are dissipating all the same. The real challenge is the biggest glaciers, which are so large that the impact of global warming isn’t seen immediately. Those glaciers are currently responding to whatever forcing they received 30-40 years ago.

Earthzine: What else must be done to tighten the link between science and policy on black carbon?

Srinivasan: One thing is comprehensive data on black carbon’s origins and distribution, which exhibits large temporal and spatial variation. India’s Department of Space has organized some remote measurement and there has been a limited road campaign to observe the spatial variation in aerosols and black carbon around major cities with ground-based equipment. But we need to simultaneously make measurements in all seasons and in all regions to really understand the impacts.

An aerosol haze often hangs over the Ganges River delta. Source: NASA.

An aerosol haze often hangs over the Ganges River delta. Source: NASA.

Earthzine: What are the practical implications of that observation program?

Srinivasan: It will, for example, help determine the relative importance of diesel exhaust, burning of firewood, and power plants as black carbon sources in India. Initially, people thought the main source was diesel exhaust. Now they think firewood. As of today it’s only guesswork, and the government needs to know because the source has big implications for policy. If diesel smoke is a major source then black carbon will be fairly easy to control, analogous to lead in gasoline. If the major source is firewood, that will be much more difficult to control. To change that would require a very unusual and major campaign.

Earthzine: You have criticized calls for immediate regulation of soot as a climate actor. Are you saying that black carbon emissions are not an important target for pollution reduction?

Srinivasan: No. We know that soot is very bad for health. That’s the real reason why soot has to be reduced, both in India and elsewhere. The data is very strong. For example, a recent Canadian study that followed 20,000 women and impact of aerosols on their health found a dramatic correlation between soot exposure and the risk of heart attacks. It’s remarkable data, especially for India where aerosol exposures are considerably higher than those experienced in Canada. India has one of the highest heart attack rates in the world in a society where the meat consumption is the lowest in the world.

Unfortunately, the Indian people don’t seem to understand how bad air pollution is for health. There are still many who think that air pollution is a necessary price for progress. It’s the same thing people were saying when I was a student in the U.S. 40 years ago. The good news is that attitudes changed there, and they are changing in India. New Delhi was a pretty polluted place and because of a major campaign by the Centre for Science and Environment, an environmental NGO, the emissions were brought down. Politicians ignored their campaign and so they went to court. The court ordered emissions reductions and it was done. It’s an amazing story.

Earthzine: So why not use the climate talks as a forum for attacking those emissions? Soot lasts only days or weeks in the atmosphere and therefore emissions reductions could have immediate impact.

Srinivasan: Because it’s a diverting tactic that will tend to take the pressure off controlling CO2 emissions. That’s a serious issue. If we are going to control global warming, we need to start taking proven measures right now against those proven bad actors.