Black carbon larger cause of climate change than previously assessed

Jan 15, 2013
This shows black carbon processes in the climate system. Credit: American Geophysical Union 2013. Credit D. W. Fahey

Black carbon is the second largest man-made contributor to global warming and its influence on climate has been greatly underestimated, according to the first quantitative and comprehensive analysis of this issue.

The landmark study published in the Journal of Geophysical Research- today says the direct influence of , or soot, on warming the climate could be about twice previous estimates. Accounting for all of the ways it can affect climate, black carbon is believed to have a warming effect of about 1.1 Watts per square meter (W/m2), approximately two thirds of the effect of the largest man made contributor to global warming, .

Co-lead author David Fahey from the U.S. (NOAA) said, "This study confirms and goes beyond other research that suggested black carbon has a strong warming effect on climate, just ahead of ." The study, a four-year, 232-page effort, led by the International Global Atmospheric Chemistry (IGAC) Project, is likely to guide research efforts, climate modeling, and policy for years to come.

The report's best estimate of direct climate influence by black carbon is about a factor of two higher than most previous work, including the estimates in the last (IPCC) Assessment released in 2007, which were based on the best available evidence and analysis at that time.

This shows global climate forcing of black carbon and co-emitted species in the industrial era (1750-2005). Credit: American Geophysical Union 2013. Credit D. W. Fahey

Scientists have spent the years since the last IPCC assessment improving estimates, but the new assessment notes that emissions in some regions are probably higher than estimated. This is consistent with other research that also hinted at significant under-estimates in some regions' black .

The results indicate that there may be a greater potential to curb warming by reducing black carbon emissions than previously thought. "There are exciting opportunities to cool climate by reducing but it is not straightforward. Reducing emissions from diesel engines and domestic wood and coal fires is a no brainer, as there are tandem health and climate benefits. If we did everything we could to reduce these emissions we could buy ourselves up to half a degree less warming—or a couple of decades of respite," says co-author Professor Piers Forster from the University of Leeds's Faculty of Earth and Environment.

The international team urges caution because the role of black carbon in is complex. "Black carbon influences climate in many ways, both directly and indirectly, and all of these effects must be considered jointly", says co-lead author Sarah Doherty of the University of Washington, an expert in snow measurements. The dark particles absorb incoming and scattered heat from the sun (solar radiation); they can promote the formation of clouds that can have either cooling or warming impact; and black carbon can fall on the surface of snow and ice, promoting warming and increasing melting. In addition, many sources of black carbon also emit other particles whose effects counteract black carbon, providing a cooling effect.

The research team quantified all the complexities of black carbon and the impacts of co-emitted pollutants for different sources, taking into account uncertainties in measurements and calculations. The study suggests mitigation of black carbon emissions for climate benefits must consider all emissions from each source and their complex influences on climate. Based on the analysis, black carbon emission reductions targeting diesel engines followed by some types of wood and coal burning in small household burners would have an immediate cooling impact.

In addition, the report finds black carbon is a significant cause of the rapid warming in the Northern Hemisphere at mid to high latitudes, including the northern United States, Canada, northern Europe and northern Asia. Its impacts can also be felt farther south, inducing changes in rainfall patterns from the Asian Monsoon. This demonstrates that curbing black carbon emissions could have significant impact on reducing regional climate change while having a positive impact on human health.

"Policy makers, like the Climate and Clean Air Coalition, are talking about ways to slow by reducing black carbon emissions. This study shows that this is a viable option for some black carbon sources and since black carbon is short lived, the impacts would be noticed immediately. Mitigating black carbon is good for curbing short-term climate change, but to really solve the long-term problem, carbon dioxide emissions must also be reduced," says co-lead author Tami Bond from the University of Illinois at Urbana-Champaign.

Explore further: Shell files new plan to drill in Arctic

More information: onlinelibrary.wiley.com/doi/10… /jgrd.50171/abstract

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Jo01
1.8 / 5 (11) Jan 15, 2013
Now this research makes sense.
I wouldn't be surprised if black carbon is the most important part of climate 'warming'.
We will know in a few years.
Diesel is the asbestos of this time, it's time to do something about it.

J.
eachus
2.3 / 5 (6) Jan 15, 2013
Sigh! The error bars on these numbers really say that particulate carbon forcing may be negligible. However the effects of kerosene lanterns on people who have no access to electricity is huge. If you can figure out how to get solar cell powered LED lamps to these people, do it.

The problems in many areas will make you sick. If you visit many of the countries involved taking lamps with you as "house gifts" or presents will often involve a payoff to get through customs. The problem of getting the lamps to the back country is often the easy part. Why is there a problem? These countries in theory want to encourage local production, so they have extremely high tariffs on products that compete with those made locally. Of course, there are no LED, solar cells, or rechargeable batteries made locally--but there are kerosene lantern makers. ;-(

(Speaking as an economist, the extra productivity from people who use the lamps is more significant, as is the reduction in oil imports.)
packrat
3.3 / 5 (8) Jan 15, 2013
Now this research makes sense.
I wouldn't be surprised if black carbon is the most important part of climate 'warming'.
We will know in a few years.
Diesel is the asbestos of this time, it's time to do something about it.

J.


They've been doing something about it for years. The latest limits are extremely low compared to what they were 20 years ago. A modern diesel engine puts out very little pollution and is quite often less than modern gasoline engines.
that_guy
3.4 / 5 (5) Jan 15, 2013
I almost hate articles that mention the environment because then the crazies come out of the wood work. Fortunately, the response has been fairly measured so far.

There has been some knowledge about carbon black's affect on global warming for a while now. Unfortunately, anything we do about black carbon is basically a one time measure. Black carbon settles out of the atmosphere within a few decades, whereas CO2 lasts far longer, and has a more cumulative effect :/
Urgelt
5 / 5 (4) Jan 15, 2013
Agreed, That Guy.

I'll add that there is nothing static about the AGW situation we're in. It's dynamic; today's 'second-leading cause' may become tomorrow's last place. At some point, methane could surge into first place, if arctic thawing continues at its current alarming pace. It's quite possible that we'll reach a tipping point beyond which warming will be runaway until it reaches a new equilibrium. Unfortunately, we do not understand climate well enough to know where the tipping points are or where they will lead.

The good news here is that curbing soot emissions, which is much easier than getting off of fossil fuels, will mitigate. The bad news is that it probably won't be enough to stop the climate from shifting to a new equilibrium point - which we can't yet predict, owing to our incomplete understanding of Earth's climate systems.
Howhot
2.6 / 5 (5) Jan 15, 2013
Black carbon is the SECOND LARGEST man-made contributor to global warming and its influence on climate has been greatly underestimated
With CO2 being the first largest by a land slide.
Don't worry @that_guy, the crazies aren't out tonight, just the pissed of greenies like me that just want to slap you upside the head until you realize it's not Cheetos that will kill the earth, it's ignorant humans that just follow the herd like sheep that will do it.

Like coal, diesel is pretty nasty when burned and coughed into the air. The soot is just as nasty as coal.


antialias_physorg
3 / 5 (2) Jan 16, 2013
A modern diesel engine puts out very little pollution and is quite often less than modern gasoline engines.

Unfortunately car engines aren't the real problem (though it's good for local/city air quality that they have gotten better)
http://www.gizmag...n/11526/
Quote:"15 of the world's biggest ships may now emit as much pollution as all the world's 760m cars"
Quote:"The low grade bunker fuel used by the worlds 90,000 cargo ships contains up to 2,000 times the amount of sulfur compared to diesel fuel used in automobiles."

And unfortunately ship diesel engines don't get replaced/upgraded to more efficient models nearly as often as car engines do.

We can migrate to other technologies for cars. For shipping I don't see it yet (the article suggests nuclear. But that would have it's own problems. 90000 reactors floating on the world seas doesn't sound like a bright idea).
PPihkala
2.3 / 5 (3) Jan 16, 2013
Unfortunately there probably will be no real change in the use of polluting fossil fuels until something totally different will replace current engines and furnaces. What that willl be, remains to be seen. Currently, because we don't factor in cost of pollution, fossil fuels appear to be the cheapest solution as energy source. Anybody can look at www.pesn.com for possible emerging sources.
packrat
2.2 / 5 (5) Jan 16, 2013
AP, Your right in that it takes many years for some shipping companies to get the point but that's changing too. Any ship that now goes to most of the US ports has to have all kinds of anti pollution stuff on it now, California in particular. Eventually they will be cleaner too and quite a few foreign ports are changing the requirement on them also. Low grade bunker fuel is getting outlawed for use all over the place - at least in the 1st world countries. It's going to take a while for most of the 3rd world countries to get on the band wagon.
Maggnus
1 / 5 (1) Jan 17, 2013
Just to add 2 cents, this is one application where fuel cell technology might work. One of the issues with such technology is the amount of "fuel" that needs to be stored, which on a ship may not be such an impedement. I don't know if the technology would be powerful enough to work for large ships though.