NASA GISS Study Finds That Methane Has an Elevated Warming Effect Due to Interactions With Aerosols
30 October 2009
| The 100-year global warming potentials (GWPs) for methane, CO, and NOx (per Tg N) as given in the AR4 and in this study when including no aerosol response; the direct radiative effect of aerosol responses; and the direct+indirect radiative effects of aerosol responses. Source: Shindell at al. Click to enlarge. |
New research by a team at the NASA Goddard Institute for Space Studies (GISS) in New York suggests that gas-aerosol interactions can amplify the global warming impact of some greenhouse gases. In particular, the study led by Drew Shindell found that methane emissions have a larger warming impact due to those interactions than accounted for in current carbon-trading schemes or in the Kyoto Protocol.
Among other conclusions, they found that the 100-year global warming potential (GWP) of methane is ~10% greater (~20 to 40%, including aerosol indirect effects AIE) than earlier estimates that neglected interactions between oxidants and aerosols. Calculations for the shorter 20-year GWP, including aerosol responses, yielded values of 79 and 105 for methane, including direct and direct+indirect radiative effects of aerosols, respectively. The UNIPCC AR4 estimates the 100-year GWP for methane at 25, with a value of 72 for the 20-year GWP.
As a result of their findings, published in the 30 October issue of the journal Science, the authors argue that assessments of multigas mitigation policies, as well as any separate efforts to mitigate warming from short-lived pollutants, should include gas-aerosol interactions.
Despite their limitations, GWPs are widely used for comparison among long-lived gases, forming the basis for worldwide political agreements on climate and carbon trading. Because the latter was a $126 billion/year market in 2008, even small differences in GWPs can have large economic consequences. Our results suggest that gas-aerosol interactions play an important role in methane’s GWP, and hence our larger value would allow better optimization of climate change mitigation policies. Methane’s GWP may also change with time as air quality regulations alter the background state of tropospheric chemistry. Finally, our results demonstrate that improving our knowledge of aerosol-climate interactions is important not only for better understanding the aerosol contribution to past and future climate change, but even for correctly evaluating the effects of long-lived greenhouse gas emissions from methane-oxidant-aerosol interactions.
—Shindell et al.
When vehicles, factories, landfills, and livestock emit methane and carbon monoxide into the atmosphere, they are doing more than just increasing their atmospheric concentrations. The release of these gases also have indirect effects on a variety of other atmospheric constituents, including reducing the production of particles called aerosols that can influence both the climate and the air quality. These two gases, as well as others, are part of a complicated cascade of chemical reactions that features competition with aerosols for highly reactive molecules that cleanse the air of pollutants.
Aerosols can have either a warming or cooling effect, depending on their composition, but the two aerosol types that Shindell modeled—sulfates and nitrates—scatter incoming light and affect clouds in ways that cool Earth. They are also related to the formation of acid rain and can cause respiratory distress and other health problems for those who breathe them.
| “We’ve known for years that methane and carbon monoxide have a warming effect, but our new findings suggest these gases have a significantly more powerful warming impact than previously thought.” —Drew Shindell |
Human activity is a major source of sulfate aerosols, but smokestacks don’t emit sulfate particles directly. Rather, coal power production and other industrial processes release sulfur dioxide—the same gas that billows from volcanoes—that later reacts with atmospheric molecules called hydroxyl radicals to produce sulfates as a byproduct. Hydroxyl is so reactive scientists consider it an atmospheric detergent or scrubber because it cleanses the atmosphere of many types of pollution.
In the chemical soup of the lower atmosphere, however, sulfur dioxide isn’t the only substance interacting with hydroxyl. Similar reactions influence the creation of nitrate aerosols. And hydroxyls drive long chains of reactions involving other common gases, including ozone.
Methane and carbon monoxide use up hydroxyl that would otherwise produce sulfate, thereby reducing the concentration of sulfate aerosols. It’s a seemingly minor change, but it makes a difference to the climate.
More methane means less hydroxyl, less sulfate, and more warming.
—Drew Shindell
The team’s modeling experiment, one of the first to rigorously quantify the impact of gas-aerosol interactions on both climate and air quality, showed that increases in global methane emissions have caused a 26% decrease in hydroxyl and an 11% decrease in the number concentration of sulfate particles. Reducing sulfate unmasks methane’s warming by 20 to 40% over current estimates, but also helps reduce negative health effects from sulfate aerosols.
| “The bottom line is that the chemistry of the atmosphere can get hideously complicated. Sorting out what affects climate and what affects air quality isn’t simple, but we’re making progress.” —Drew Shindell |
In comparison, the model calculated that global carbon monoxide emissions have caused a 13% reduction in hydroxyl and 9% reduction in sulfate aerosols.
Nitrogen oxides—pollutants produced largely by power plants, trucks, and cars—led to overall cooling when their effects on aerosol particles are included, said Nadine Unger, another coauthor on the paper and a climate scientist at GISS. That’s noteworthy because nitrogen oxides have primarily been associated with ozone formation and warming in the past.
Although our calculations are more complete than previous studies, additional processes should be included as they become better understood. These include mixing between aerosol types, formation of secondary organic aerosols, which are sensitive to both organic aerosol emissions and oxidant levels, and interactions between pollutants and ecosystems. The latter includes suppression of CO2 uptake by increased surface ozone concentrations, aerosols enhancing the ratio of diffuse to direct radiation reaching the biosphere leading to increased CO2 uptake (at least for some plant types when aerosol loading is not so large as to dramatically reduce total surface irradiance), and the effects of nitrogen and sulfur deposition on ecosystems. These effects may be important but are highly uncertain at present.
Ecosystem-chemistry interactions add both positive and negative forcing terms to the GWP of NOx (NOx leads to increased ozone, causing increased CO2, but also leads to increased aerosol, causing decreased CO2), adding to an already complex set of multiple, sometimes opposing, forcings. For CO and methane, however, increased emissions lead to increased CO2 from both the ozone-ecosystem interactions and the aerosol-ecosystem interactions, so would simply increase their positive GWPs still further. Hence, the uncertainty in quantifying these processes implies only that the larger estimates of CO and methane GWPs presented here may still be too low.
—Shindell et al.
| Radiative forcing by greenhouse gases from 1750 to 2000. The “abundance-based” values reflect the conventional approach without consideration of gas-aerosol interactions. The “emissions-based” values factor in gas-aerosol interactions. Source: Shindell et al. Click to enlarge. |
Abundance-based vs. Emissions-based modeling. To determine the climate impact of particular greenhouse gases, scientists have traditionally relied on surface stations and satellites to measure the concentration of each gas in the air. Then, they have extrapolated such measurements to arrive at a global estimate.
The drawback to that “abundance-based approach,” explained Gavin Schmidt, another GISS climate scientist and coauthor of the study, is that it doesn’t account for the constant interactions that occur between various atmospheric constituents. Nor is it easy to parse out whether pollutants have human or natural origins.
You get a much more accurate picture of how human emissions are impacting the climate—and how policy makers might effectively counteract climate change—if you look at what’s emitted at the surface rather than what ends up in the atmosphere.
—Drew Shindell
The GISS team used the emissions-based approach as the groundwork for their modeling project.
However, the abundance-based approach serves as the foundation of key international climate treaties, such as the Kyoto Protocol or the carbon dioxide cap-and-trade plans being discussed among policymakers. Such treaties underestimate the contributions of methane and carbon monoxide to global warming, Shindell said.
Implications. According to Shindell, the new findings underscore the importance of devising multi-pronged strategies to address climate change rather than focusing exclusively on carbon dioxide.Our calculations suggest that all the non-carbon dioxide greenhouse gases together have a net impact that rivals the warming caused by carbon dioxide.
—Drew Shindell
In particular, the study reinforces the idea that proposals to reduce methane may be an easier place for policy makers to start climate change agreements. “Since we already know how to capture methane from animals, landfills, and sewage treatment plants at fairly low cost, targeting methane makes sense,” said Michael MacCracken, chief scientist for the Climate Institute in Washington, DC
This research also provides regulators insight into how certain pollution mitigation strategies might simultaneously affect climate and air quality. Reductions of carbon monoxide, for example, would have positive effects for both climate and the public’s health, while reducing nitrogen oxide could have a positive impact on health but a negative impact on the climate.
Resources
Shindell, D.T., G. Faluvegi, D.M. Koch, G.A. Schmidt, N. Unger, and S.E. Bauer (2009) Improved Attribution of Climate Forcing to Emissions. Science 326, 716 - 718 doi: 10.1126/science.1174760
Arneth, A., N. Unger, M. Kulmala, and M.O. Andreae (2009) Perspectives: Clean the air, heat the planet? Science, 326, 672-673, doi: 10.1126/science.1181568
Quote:
“Since we already know how to capture methane from animals, landfills, and sewage treatment plants at fairly low cost, targeting methane makes sense,”
That animal bit sounds surprising.
I've heard of successful attempts at a 'vaccination' that drastically reduces methane from sheep and cows.
Also some animal methane emissions are well quantified.
Posted by: arnold | 30 October 2009 at 03:49 PM
Who else but siro.
25 Feb 2009 ... The impacts on enteric methane emissions and animal productivity over ... It will also analyse how the reduction occurs within rumen. ... Mitigation of methane emissions from the northern Australian beef herd – CSIRO ...
www.daff.gov.au/.../research_to_cut_greenhouse_gas_emissions_in_livestock -
Posted by: arnold | 30 October 2009 at 03:52 PM
Headline: "NASA GISS Study Finds That Methane Has an Elevated Warming Effect Due to Interactions With Aerosols" First Sentence: "New research by a team at the NASA Goddard Institute for Space Studies (GISS) in New York suggests that gas-aerosol interactions can amplify the global warming impact of some greenhouse gases." ...we went from "has an elevated warming effect" to "suggests"...and these guys are working with "100 year potential" and "estimates"...I suggest we throw the potential estimates where they belong - in the trash.
Posted by: ejj | 30 October 2009 at 05:20 PM
"Unfortunately, "likely", "evidence suggests" and "probability" is the language of science. There is no proof, there are no absolute certainties. Scientists are always aware that new data may overturn old theories and that human knowledge is constantly evolving. Consequently, it is viewed as unjustifiable hubris to ever claim one's findings as unassailable."
http://scienceblogs.com/illconsidered/2006/04/scientists-arent-even-sure.php
You will never ever get a purely scientific source saying "the future is certain." Even gravity is still referred to as 'a theory,'
Posted by: ai_vin | 30 October 2009 at 10:56 PM
"Unfortunately, "likely", "evidence suggests" and "probability" is the language of speculation & theorization about global warming, climate science and virtually all social science. In other areas of real science (physical sciences) there IS proof; there ARE absolute certainties....look around you - you can be absolutely certain that the objects around you exist (unless you're hallucinating and/or have psychiatric issues), absolutely certain that gravity exists. These things can be measured & experiments can be run over and over again to get the same result - ie. their existence is proven, and the degree to which they exist measured & verified. There have been no experiments to prove global warming, nothing that can be set up to demonstrate how it works - just a bunch of "likely", "probability", "potential", "suggests". Some of our elected representatives want to radically expand government (including taxes, penalties & potential prison time) for a bunch of "likely", "probability", "potential", "suggests" cap & trade schemes without any real cause & effect verifiable through experimentation & its sickening.
Posted by: ejj | 31 October 2009 at 11:26 AM
Looks like GISS and Gavin are setting the groundwork for a bit of face-saving. By redirecting attention to methane as the "real global warming culprit" - he can duck away from CO2 as the villain.
This makes sense for the warmists and is already being accepted by some of the skeptics. It will focus on the heavy consumption of meat in the west and emerging middle classes. It is doubtful that half the population can sustainably eat meat regularly. Nary the twain shall meet?
Posted by: sulleny | 31 October 2009 at 01:16 PM
As has so often pointed out ejj, we don't have a "real world to conduct experiments on? O.K. I'll rephrase that.
The only world we have available currently is otherwise occupied by inhabitants that are not inclined to take outrageous risks - 95% plus probability on the basis of satisfying some recalcitrant school dropouts.
Go find another planet to 'experiment' on
When you find out you are right, drop us a line will you?
sulleny,
Methane you real culprit, when it isn't water vapour is rated as CO2 equivalent for the purposes of GWPotential. Like that word potential? no ?
Methane with its ~20 ~ 100 ~ 130? * CO2 warming potential breaks down eventually to CO2 yes?
It's one thing to back up your mates, but talking gibberish and delusional thinking will not make this world work any better for you.
That is to say according to the Phsycs, one thing to lie but (very) dangerous to believe it yourself.
Posted by: arnold | 31 October 2009 at 04:15 PM
Methane is not being touted as an alternative culprit.
We do have an increasing warm arctic with massive stores of methane. By not accurately trying to assess the future warmming we've already committed to, we cannot assess the impact of what will happen. ie. we've underestimated a positive feedback loop, which is no surprise since science is usually conservative
Ejj's comments on scientific language shows that he has no concept of science. There is no proof as such. All we have are theories that are supported by empircal evidence and even our oldest ideas are subject to change. Think of Newton and Einstein ideas of gravity. Theories are stronger than laws. Black holes were a consequence of Einsteinian ideas of gravity, before they were discovered. You can't do that with a law. I believe I've had this arguement before with him and it seems that he hasn't changed at all, still clinging to his worldview.
The descriptive language used is commonplace. For all intents, science supports AGW. No recognized scientific organization doesn't support AGW as the main view on the workings of climate.
Posted by: aym | 31 October 2009 at 09:50 PM
Aym needs to back to school..."Theories are stronger than laws"....What? Actually it's vice versa:
Scientific Law
http://dictionary.reference.com/browse/scientific%20law
Scientific Theory
http://ask.reference.com/web?q=scientific%20theory&o=10616&l=dir&qsrc=2891
Again...."unfortunately, "likely", "evidence suggests" and "probability" is the language of speculation & theorization about global warming, climate science and virtually all social science. In other areas of real science (physical sciences) there IS proof; there ARE absolute certainties....look around you - you can be absolutely certain that the objects around you exist (unless you're hallucinating and/or have psychiatric issues), absolutely certain that gravity exists. These things can be measured & experiments can be run over and over again to get the same result - ie. their existence is proven, and the degree to which they exist measured & verified. There have been no experiments to prove global warming, nothing that can be set up to demonstrate how it works - just a bunch of "likely", "probability", "potential", "suggests".
There haven't been ANY global warming experiments, and data collected to support the theory (sediment & ice cores) is from ~200,000 years out of ~4.5 BILLION years of earth history. 4.5 Billion minus 200,000 equals 4,499,800,000 years where this is NO DATA. Yet, some of our elected representatives want to radically expand government (including taxes, penalties & potential prison time) for a bunch of "likely", "probability", "potential", "suggests" cap & trade schemes, that many here are accepting blindly, without any real cause & effect, verifiable through experimentation....and its sickening.
Posted by: ejj | 01 November 2009 at 07:55 AM
...Aym needs to GO back to school... Go back to school Aym! Take some science courses (chemistry and physics) and philosophy (logic, reasoning).
Posted by: ejj | 01 November 2009 at 08:00 AM
A theory is not something that is proved correct in any fashion. It is an operational idea of how the system works. As such it has consequences.
In modern gravitational theory, black holes were postulated to exist from the basis of the theory. You cannot have guessed this from gravitational law. The postulated bodies had theorized secondary effects which were looked for and it strengthened the case that the theory was correct when they were found. This does not mean that a different theory could not take its place. But it must be able to incorporate the data in a unbiased fashion.
It encompasses so called laws and creates understanding on how it fits. In terms of a simple Venn diagram, in science, theory encompasses law.
Absolute certainties? Newtonian law of gravity. Whoops, failed. Just showed how wrong you were.
Around high gravity wells, Newtonian laws don't work. Einsteins' theories were shown to be more correct with the discovery of black holes.
And even his work is being reworked to try to meld it with quantum mechanics. Einstein tried to do it himself during the last years of his life and it still remains an objective to physicists today.
Theories encompass laws. They explain the why, which is what science basically is about and is far more than any straight mathematical relationships encompassed by the laws.
No, ejj. You need to learn some actual history of science and general science. You pretty much still have the narrow views and lack of depth I first encountered in your posts.
The use of scientific language, which you seem to deride is your own limiting baggage. It exists to put certaintainty levels into their specialist dialogue. I have gotten marks taken off for using "I" instead of "we" and present tense instead of past tense on reports so if you don't like, tough for you.
Yet, some of our elected representatives want to radically expand government (including taxes, penalties & potential prison time) for a bunch...
And here's the real reason. At it's heart not about science at all. If you cannot seperate your ideology and emotional baggage from the question of science then you obviously cannot deal with it rationally.
Posted by: aym | 01 November 2009 at 09:27 AM
Ah yes... here we have yet another dodge by the alarmists who have lost so much mind share in the past year as to put AGW into the dust bin of disbelief. Alarmists have tried to move the goal posts each time their latest "theory" gets falsified.
It is plain that alarmists will try this last gasp attempt to indict methane as the next man-made problem. After having been caught fabricating data, hiding research, stonewalling open release of data, calling PR stunts (Catlin Arctic Expedition)"research" - the whole alarmist myth looks pathetic.
aym and fellow marxists should suck it up and admit their failed AGW campaign to de-industrialize the west was meant to serve... themselves. Fat fees from carbon taxes, cap an trade commissions, fuel taxes etc. Their mantra is "I...er, WE want what you have!"
Meanwhile a certain popular skeptic site rates 2M hits per month - annihilating the competition.
Posted by: Reel$$ | 01 November 2009 at 03:16 PM
There are no absolute certainties Aym? Try 1 + 1 = 2. "And here's the real reason. At it's heart not about science at all." - EXACTLY AYM...EXACTLY and that is the main problem here. A bunch of PhD's in academia kicking around unproven theories is fine...but throw government policies, laws & penalties into the mix and that is where there is a major problem. Unproven theories + government = erosion of liberty, crimes against humanity. Look at what the nazis tried to do.
Posted by: ejj | 02 November 2009 at 05:20 AM
Nice try but that is a part of number theory. It lies in the proof of the addition of natural numbers. It doesn't just arise from nothing. It may be intuitive to do it like you wrote but the truth is, mathematicians derived that in classical Greek times I believe. It's that old a proof. It certainly isn't taken for granted.
As for the rest of your dialogue. Science doesn't care about your ideological bias about gov't policies. It is extraneous to the question of the scientific validity of AGW, which has passed peer review unlike many denialist claims of their reasons.
Unreasonable, fantastical claims like nazis and crimes against humanity? Pure historonics. Nothing to do with the science.
The response to AGW is similar to the response to evolution. It too was attacked, not because of it's validity, but it's societal implications.
Evolution is germaine because, in essence, my arguement for theory arises from my exposure to Dawkins and his defense of evolution vs intelligent design and creationism. Ejj your position is essentially that of the intelligent design crowd.
There are no declarations of scientific law these days because it is essentially an outmoded concept. You do not have infinite experience and access to observations. People are not onmiscient. The support of views of how the universe works arises from experimental/observational evidence.
The scientific rigour applied to AGW is the same scientific methodology applied to all modern science.
Posted by: aym | 04 November 2009 at 07:06 AM
$Reel, your acusations of what my or any others' societal leanings or motivations and goals are, are truly out of this world and the truly the product of a mind full of propaganda and trying to sell it.
Full of soundbites that express bias but no basis for such generalizations. Also the need to paint those who hold differnet opinions as evil. That is what the denialist sites and you sell Reel.
Skeptic sites are not science. They are sensationalist dribble for the drooling masses. Science isn't decided by the mob, though public policy may be.
AGW isn't falsified in any way. A quantification of an aspect that may become an important factor is part of the refinement that occurs all the time in all aspects of our knowledge. Your bias is showing when you see that refinement as some sort of questioning. We see refinements to carcinogens all the time. In none of them do we lessen the impact of the carcinogens' impact on human health.
Your appeal to unreason and emotion to attack a scientific discipline which has empirical experimental backing and ascribing your own interpretions is unwarrented and manipulative.
You're selling fear. And then you're providing reasons to leverage that fear into inaction. Marshall Mcluhan correctly deduced that media doesn't teach as much as it reinforces the views and bias of the watcher. There's nothing easier than a call for inaction and passivity in a time where change is called for.
When that happens it is a failure of reason. Another dumbing down of society. Nothing to be proud of.
Posted by: aym | 04 November 2009 at 07:48 AM
"When you find out you are right, drop us a line will you?" - Arnold.
There isn't enough evidence to prove global warming either. Again - there haven't been ANY experiments to prove global warming (using the scientific method anyway), and data collected to support the theory (sediment & ice cores) is from ~200,000 years out of ~4.5 BILLION years of earth history. 4.5 Billion minus 200,000 equals 4,499,800,000 years where this is NO DATA. Yet, some of our elected representatives want to radically expand government (including taxes, penalties & potential prison time) for a bunch of "likely", "probability", "potential", "suggests" cap & trade schemes, that many here are accepting blindly, without any real cause & effect, verifiable through experimentation....and its scary - sounds similar to other regimes that have warped science for deviant reasons....
Posted by: ejj | 07 November 2009 at 11:46 AM