black carbon


The Far-Reaching Effects of Smog: Is It a Driver of Drought?

Black carbon and tropospheric ozone, two pollutants typically associated with urban smog, may be key drivers in the advance of the northern tropics.

The northern tropics are on a march toward the pole. Over the last thirty years, the warm, moist belt around the equator has expanded by between 2-and-8 degrees northward.

When the phenomenon was first described five years ago, it was thought to be fueled primarily by carbon dioxide emissions. But a report, published recently by University of California at Riverside researchers in the journal Nature, has proposed a new driver of the expanding tropics: soot and ozone pollution generated largely by wood burning and diesel combustion in the rapidly developing nations of Southeast Asia. Continue reading

A Different Approach to Tackling Climate Change: Sweat the Small Stuff

A new study recommends cutting soot and methane emissions to curb warming and improve health.

Methane can escape from mines, power plants, farms, and landfills.

Carbon dioxide is the primary driver of climate change, but it’s not the only one. Methane also contributes to warming. In fact, a single molecule of methane causes more warming than a single molecule of carbon dioxide does. But it doesn’t stay in the atmosphere as long, so a new study from NASA affirms what others have suggested for years: that cutting methane emissions would show quicker results than cutting CO2 emissions. The same goes for soot, also known as black carbon. Plus, cutting back on soot would put a damper on the respiratory diseases it causes, and capturing more methane, which is basically natural gas, would save money.

Continue reading

Natural Carbon Storage Off the California Coast?

A new study from the University of Southern California finds that the cool waters off the coast of Los Angeles are acting as a carbon sink by sequestering more carbon than other parts of the world’s oceans.

Lisa Collins, a lecturer at the USC Dornsife College, spent four years studying samples from floating sediment traps in the San Pedro Basin as a way to determine what’s falling through the water column and how deep it’s getting.

“We have a pretty good idea of how much biomass is produced in the ocean, but we don’t have a great idea of how much of that biomass actually gets down through the water column and ultimately to the sediment,” said Collins.

One reason that matters, she says, is that phytoplankton, which make up much of the biomass, live and grow by taking up sunlight and carbon dioxide, just like plants on land do. When the phytoplankton die, they sink, taking that stored carbon down the water column with them. If they make it all the way to the mud at the bottom of the ocean, Collins says, that carbon will be sequestered there for hundreds or thousands of years or more. Continue reading

The Other Effect of CA’s Clean Air Laws

(Photo: David McNew/Getty Images)

By Andrew Freedman

Pollution reduction measures that were aimed primarily at reducing California’s notorious smog problem and improving public health, also helped cut emissions of black carbon — a key global warming agent — according to a new study published Tuesday.

Black carbon, more commonly referred to as soot, is an atmospheric particulate that scientists have shown to be a significant contributor to global warming. It is an attractive target for emissions reductions because relatively cost effective technologies to reduce it already exist, such as diesel particulate filters for trucks, and because unlike carbon dioxide (CO2), which stays in the air for decades to millennia, black carbon only remains airborne for days to weeks. Continue reading

What’s Soot Got to Do With It?

By Andrew Freedman, Climate Central

Most of the discussion regarding the highly anticipated Senate energy and climate change legislation, which Senators John Kerry (D-MA) and Joseph Lieberman (I-CT) introduced last week following months of negotiations, has focused on the bill’s provisions pertaining to offshore oil and gas drilling, incentives for renewable energy, and cap on carbon emissions for certain economic sectors.

Although the bill’s carbon dioxide (CO2) emissions reduction targets–an 80 percent emissions cut by 2050 compared to 2005 levels–would yield significant long-term climate benefits, the bill also addresses man-made climate change in the shorter term.

Stack emissions from a bulk freighter in San Francisco Bay. Photo: Craig Miller

Stack emissions from a bulk freighter in San Francisco Bay. Photo: Craig Miller

A little-noticed portion of the bill concerns short-lived air pollutants such as black carbon (otherwise known as soot) and tropospheric ozone. These pollutants disrupt the climate on far shorter timescales than CO2, which scientists consider the most important greenhouse gas and the main villain in the climate change story.

Once emitted by the burning of fossil fuels, the use of solid-fuel cooking stoves or biomass burning, among other sources, black carbon only stays aloft for days to a few weeks before being washed out of the atmosphere by precipitation. This means that once black carbon emissions are reduced, there would be almost immediate climate benefits.

The Kerry-Lieberman bill would direct the US EPA to use its existing authority under the Clean Air Act to reduce black carbon emissions from diesel engines, using devices called diesel particulate filters which trap soot emissions before they escape from a vehicle’s tailpipe.

It would also call upon the EPA to publish a report on black carbon “sources, impacts, and reduction opportunities,” including an examination of how foreign assistance programs could help reduce emissions in other nations. In addition, the bill would establish an inter-agency process to facilitate “fast mitigation strategies” that focus on non-CO2 warming agents. This process would involve agencies such as the EPA and the Energy Department (DOE).

How big a climate player is black carbon?

Black carbon is thought to be a powerful warming agent in many regions, particularly snow and ice-covered areas such as the Himalayas and the Arctic. As its name suggests, black carbon particles are dark in color, and are therefore strong absorbers of incoming solar radiation. They warm the atmosphere and alter cloud characteristics, and when they land on brightly colored snow and ice, they darken the surface, causing a large uptick in the absorption of solar radiation, which hastens melting.

In the Arctic, black carbon contributes to a feedback loop that has helped cause a rapid melting of sea ice cover and drive temperatures upward at nearly twice the rate of the rest of the world. The decade from 1999-2008 was the warmest ten-year period in the Arctic of the past 2,000 years, according to a study published in the journal Science in 2009.

In addition to Arctic warming, black carbon has been shown to alter regional climate patterns such as the Indian monsoon, and human inhalation of soot particles is known to be a major health hazard worldwide.

In recent years numerous scientists, most prominently V. (Ram) Ramanathan of the Scripps Institution of Oceanography and James Hansen of NASA have called for significant cuts in short-lived air pollutants as a way to reduce climate change in the near term, while efforts continue to address CO2 emissions in the long run. Ramanathan’s studies have shown that black carbon may be the second largest contributor to global climate change.

In March testimony before the House Select Committee for Energy Independence and Global Warming, Ramanathan stated that the current global warming effect of black carbon “may be as much as 60 percent” of the CO2 warming effect. He noted, however, that there are significant uncertainties about black carbon’s role in the climate system.

Ramanathan told House lawmakers that reducing black carbon emissions “may provide a possible mechanism for buying time to develop and implement effective steps for reducing CO2 emissions.”

Bill is aligned with recent scientific advice

The Kerry-Lieberman bill’s inclusion of rapid mitigation strategies is consistent with advice contained in a new paper from an interdisciplinary panel of scholars, published on May 11 by the University of Oxford in the UK. The paper argues that non-CO2 drivers of climate change have been overlooked “for reasons of convenience in framing policy” rather than due to scientific concerns, and it presents a vision for an overhaul of climate policy that would include a much more prominent role for addressing emissions of short-lived air pollutants.

“Since action on these non-CO2 ‘forcers’ may have quicker impact and large, immediate primary benefits, we would give them priority, now. In contrast to long and arduous tasks, these can be ‘quick hits’,” the report states.

The bill’s provisions are also consistent with the findings of a scientific panel that examined options to address rapid Arctic climate change. In a 2008 report, the panel strongly endorsed pursuing emissions reductions of black carbon and other short-lived air pollutants. “…Curbing short-lived climate forcing agents, through rapid international action and Arctic nation leadership, may prove to be the best and perhaps only viable strategy for slowing Arctic warming in the time frame of years to a decade,” the report stated.

Considering that the Kerry-Lieberman bill itself faces a highly uncertain future, with significant resistance in both political parties, it may yet take even longer to address what many experts consider to be a ripe, low hanging fruit of the climate challenge. This does not bode well, given the much more difficult work that lies ahead to reduce CO2 and other longer-lasting greenhouse gases.

In April, Molly Samuel reported on the effects of black carbon and snow albedo on the California’s water forecasting efforts.