The study shows that soot is second only to carbon dioxide in contributing to global warming. But, climate models to date have mischaracterized the effects of soot in the atmosphere, said its author Mark Z. Jacobson of Stanford University in Stanford, California. Because of that, soot’s contribution to global warming has been ignored completely in national and international global warming policy legislation, he said.
"Controlling soot may be the only method of significantly slowing Arctic warming within the next two decades," said Jacobson, director of Stanford’s Atmosphere/Energy Program. “We have to start taking its effects into account in planning our mitigation efforts and the sooner we start making changes, the better.”
The study will be published this week in Journal of Geophysical Research (Atmospheres). Jacobson used a computer model of global climate, air pollution and weather that he developed over the last 20 years and updated to include additional atmospheric processes to analyze how soot can heat clouds, snow and ice.
Soot – black and brown particles that absorb solar radiation – comes from two types of sources: fossil fuels such as diesel, coal, gasoline, jet fuel; and solid biofuels ¬such as wood, manure, dung, and other solid biomass used for home heating and cooking around the world.
Jacobson found that the combination of the two types of soot is the second-leading cause of global warming after carbon dioxide. That ranks the effects of soot ahead of methane, an important greenhouse gas. He also found that soot emissions kill over 1.5 million people prematurely worldwide each year, and afflicts millions more with respiratory illness, cardiovascular disease, and asthma, mostly in the developing world where biofuels are used for home heating and cooking.
Jacobson found that eliminating soot produced by the burning of fossil fuel and solid biofuel could reduce warming above parts of the Arctic Circle in the next fifteen years by up to 1.7 degrees Celsius (3 degrees Fahrenheit). For perspective, net warming in the Arctic has been at least 2.5 degrees Celsius (4.5 degrees Fahrenheit) over the last century and is expected to warm significantly more in the future if nothing is done.
Soot lingers in the atmosphere for only a few weeks before being washed out, so a reduction in soot output would start slowing the pace of global warming almost immediately. Greenhouse gases, in contrast, typically persist in the atmosphere for decades – some up to a century or more – creating a considerable time lag between when emissions are cut and when the results become apparent.
The most immediate, effective and low-cost way to reduce soot emissions is to put particle traps on vehicles, diesel trucks, buses, and construction equipment. Particle traps filter out soot particles from exhaust fumes. Soot could be further reduced by converting vehicles to run on clean, renewable electric power.
Jacobson found that although fossil fuel soot contributed more to global warming, biofuel-derived soot caused about eight times the number of deaths. Providing electricity to rural developing areas, thereby reducing usage of solid biofuels for home heating and cooking, would have major health benefits, he said. Soot from fossil fuels contains more black carbon than soot produced by burning biofuels, which is why there is a difference in warming impact.
Black carbon is highly efficient at absorbing solar radiation in the atmosphere, just like a black shirt on a sunny day. Black carbon converts sunlight to heat and radiates it back to the air around it. This is different from greenhouse gases, which primarily trap heat that rises from the Earth’s surface. Black carbon can also absorb light reflecting from the surface, which helps make it such a potent warming agent.
Black carbon has an especially potent warming effect over the Arctic. When black carbon is present in the air over snow or ice, sunlight can hit the black carbon on its way towards Earth, and also hit it as light reflects off the ice and heads back towards space. Black carbon also lands on the snow, darkening the surface and enhancing melting.
“There is a big concern that if the Arctic melts, it will be a tipping point for the Earth’s climate because the reflective sea ice will be replaced by a much darker, heat absorbing, ocean below,” said Jacobson. “Once the sea ice is gone, it is really hard to regenerate because there is not an efficient mechanism to cool the ocean down in the short term.”
Jacobson is a senior fellow at the Woods Institute for the Environment. This work was supported by grants from the U.S. Environmental Protection Agency, NASA, the NASA high-end computing program, and the National Science Foundation.
Notes for Journalists:
As of the date of this press release, the paper by Jacobson is still “in press” (i.e. not yet published). Journalists and public information officers (PIOs) of educational and scientific institutions who have registered with AGU can download a PDF copy of this paper in press at: http://www.agu.org/journals/pip/jd/2009JD013795-pip.pdfOr, you may order a copy of the paper by emailing your request to Kathleen O'Neil at email@example.com. Please provide your name, the name of your publication, and your phone number.
Neither the paper nor this press release are under embargo.Title:
Contact information for the author: Mark Jacobson: (650) 723-6836, firstname.lastname@example.org
Kathleen O’Neil | American Geophysical Union
NASA's AIM observes early noctilucent ice clouds over Antarctica
05.12.2016 | NASA/Goddard Space Flight Center
GPM sees deadly tornadic storms moving through US Southeast
01.12.2016 | NASA/Goddard Space Flight Center
Have you ever wondered how you see the world? Vision is about photons of light, which are packets of energy, interacting with the atoms or molecules in what...
A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.
Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...
In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.
“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...
The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.
The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...
Broadband rotational spectroscopy unravels structural reshaping of isolated molecules in the gas phase to accommodate water
In two recent publications in the Journal of Chemical Physics and in the Journal of Physical Chemistry Letters, researchers around Melanie Schnell from the Max...
16.11.2016 | Event News
01.11.2016 | Event News
14.10.2016 | Event News
05.12.2016 | Power and Electrical Engineering
05.12.2016 | Materials Sciences
05.12.2016 | Power and Electrical Engineering