Some interesting work, but realistically, reducing soot and tropospheric ozone are easier said than done and will require about the same number of decades as it will take for the sources of tropospheric sulfate aerosols to become insignificant. To make all of them go away for good, we have to stop using fossil fuels and burning trees. MacCracken also suggested recently that an emphasis on non CO2 sources of greenhouse forcing such as methane and ozone would be beneficial, especially with regard to the developing world.
So while it may be true that 45% of recent Arctic warming may be due to non GHG forcing, that still means that 55% is due to these gases, a percentage that is bound to increase significantly as the atmospheric CO2 levels increase. The articles imply that Shindell is suggesting we go slow on reducing CO2 emissions in order to focus attention on these other sources. I believe that would be a serious mistake. Also part of the reason for the slower warming of the Antarctic also has to do with its isolation. Unlike the Arctic, where warmer air is regularly transported north, that doesn't happen as frequently in the south polar region. ----- Original Message ----- From: "DW" <[email protected]> To: "geoengineering" <[email protected]> Sent: Saturday, April 11, 2009 9:57 PM Subject: [geo] Re: More on that global aerosol experiment we just ran ... This one specifically catches the implications to geoengineering in the context of Holdren's recent remarks... Also interesting that Shindell works under Hansen. Original URL: http://www.theregister.co.uk/2009/04/09/arctic_aerosols_goddard_institute/ NASA: Clean-air regs, not CO2, are melting the ice cap Acid-rain countermeasures could drown London By Lewis Page Posted in Environment, 9th April 2009 12:10 GMT Join the Intel seminar. IT has companies talking New research from NASA suggests that the Arctic warming trend seen in recent decades has indeed resulted from human activities: but not, as is widely assumed at present, those leading to carbon dioxide emissions. Rather, Arctic warming has been caused in large part by laws introduced to improve air quality and fight acid rain. Dr Drew Shindell of NASA's Goddard Institute of Space Studies has led a new study which indicates that much of the general upward trend in temperatures since the 1970s - particularly in the Arctic - may have resulted from changes in levels of solid "aerosol" particles in the atmosphere, rather than elevated CO2. Arctic temperatures are of particular concern to those worried about the effects of global warming, as a melting of the ice cap could lead to disastrous rises in sea level - of a sort which might burst the Thames Barrier and flood London, for instance. NASA graphic showing temperature trends vis-a-vis clean air rules Acid rain fixed, woo! Hey, what's that gurgling sound? Shindell's research indicates that, ironically, much of the rise in polar temperature seen over the last few decades may have resulted from US and European restrictions on sulphur emissions. According to NASA: Sulfates, which come primarily from the burning of coal and oil, scatter incoming solar radiation and have a net cooling effect on climate. Over the past three decades, the United States and European countries have passed a series of laws that have reduced sulfate emissions by 50 percent. While improving air quality and aiding public health, the result has been less atmospheric cooling from sulfates. Meanwhile, levels of black-carbon aerosols (soot, in other words) have been rising, largely driven by greater industrialisation in Asia. Soot, rather than reflecting heat as sulphates do, traps solar energy in the atmosphere and warms things up. The Arctic is especially subject to aerosol effects, says Shindell, because the planet's main industrialised areas are all in the northern hemisphere and because there's not much precipitation to wash the air clean. "Right now, in the mid-latitudes of the Northern Hemisphere and in the Arctic, the impact of aerosols is just as strong as that of the greenhouse gases," says Shindell. Dirty Chinese coal to save us all? Other scientists have recently suggested that it's not just the Arctic which is subject to aerosol effects. Boffins from the US National Oceanic and Atmospheric Administration have said (http:// www.theregister.co.uk/2009/03/27/atlantic_dust_temp_hurricane_study/) that aerosol levels from dust storms and volcanoes alone would account for as much as 70 per cent of the temperature rise seen in the Atlantic ocean during the past 26 years, leaving carbon simply nowhere. Shindell's new NASA study is particularly topical, as President Obama's new science advisor has just suggested that the subject of "geoengineering" - artificially modifying the climate - must be considered as a countermeasure to global warming. One measure put forward by geoengineering advocates is the deliberate injection of sulphur particulates into the atmosphere. There might not even be any need for action on the part of the West, with China building sulphur-belching coal power stations and diesel vehicles at a furious rate in recent times. Dr Shindell doesn't say so, but it's at least possible that this has something to do with the fact that global temperatures have actually dipped slightly (http:// www.theregister.co.uk/2008/09/23/met_office_denies_deniers/) over the last couple of years. Meanwhile Dr Shindell's position at NASA's Goddard Institute in New York must now be a potentially stressful one. His boss, Dr James Hansen, is more or less the father of the carbon-driven global warming menace. He won't be pleased at the suggestion that carbon emissions may not be such an overriding concern after all. Dr Hansen has even gone so far as to travel to the UK (http://news.bbc.co.uk/1/hi/england/ kent/7597424.stm), to add his weight to protests against the Kingsnorth coal plant. There are of course many arguments against a deliberate policy of sulphate emissions. They cause acid rain, for one thing: the original anti-sulphur regs weren't introduced just for fun. But the appearance of aerosols at the front of the climate-science stage does indicate that the issue isn't simple, and that environmental policies can have unforeseen and unexpected effects. The goal of simply cutting CO2 emissions by any means possible might have to be reconsidered somewhat: Shindell's research, backed by other recent studies (http://www.theregister.co.uk/2008/03/25/ soot_solution/), suggests that it might be a lot more cost-effective to tackle emissions of black-carbon aerosols. Filtering soot from exhausts would be hugely easier than capturing and sequestering CO2, building a fully wind/electric Blighty or other ambitious eco-schemes. "There's still a lot more that we need to sort out," says Shindell, in understated style. There's more for laymen from NASA here (http://www.nasa.gov/topics/ earth/features/warming_aerosols.html), or subscribers to Nature Geoscience can read the relevant journal article here (http:// www.nature.com/ngeo/journal/v2/n4/full/ngeo473.html), and expert commentary here (http://www.nature.com/ngeo/journal/v2/n4/full/ ngeo486.html). ® On Apr 11, 6:54 pm, Dan Whaley <[email protected]> wrote: > Web address:http://www.sciencedaily.com/releases/2009/04/090408164413.htm > Aerosols May Drive A Significant Portion Of Arctic Warming > > Aerosols can influence climate directly by either reflecting or > absorbing the sun's radiation as it moves through the atmosphere. The > tiny airborne particles enter the atmosphere from sources such as > industrial pollution, volcanoes and residential cooking stoves. > (Credit: NASA Goddard's Scientific Visualization Studio) > > ScienceDaily (Apr. 9, 2009) — Though greenhouse gases are invariably > at the center of discussions about global climate change, new NASA > research suggests that much of the atmospheric warming observed in the > Arctic since 1976 may be due to changes in tiny airborne particles > called aerosols. > > Emitted by natural and human sources, aerosols can directly influence > climate by reflecting or absorbing the sun's radiation. The small > particles also affect climate indirectly by seeding clouds and > changing cloud properties, such as reflectivity. > > A new study, led by climate scientist Drew Shindell of the NASA > Goddard Institute for Space Studies, New York, used a coupled ocean- > atmosphere model to investigate how sensitive different regional > climates are to changes in levels of carbon dioxide, ozone, and > aerosols. > > The researchers found that the mid and high latitudes are especially > responsive to changes in the level of aerosols. Indeed, the model > suggests aerosols likely account for 45 percent or more of the warming > that has occurred in the Arctic during the last three decades. The > results were published in the April issue of Nature Geoscience. > > Though there are several varieties of aerosols, previous research has > shown that two types -- sulfates and black carbon -- play an > especially critical role in regulating climate change. Both are > products of human activity. > > Sulfates, which come primarily from the burning of coal and oil, > scatter incoming solar radiation and have a net cooling effect on > climate. Over the past three decades, the United States and European > countries have passed a series of laws that have reduced sulfate > emissions by 50 percent. While improving air quality and aiding public > health, the result has been less atmospheric cooling from sulfates. > > At the same time, black carbon emissions have steadily risen, largely > because of increasing emissions from Asia. Black carbon -- small, soot- > like particles produced by industrial processes and the combustion of > diesel and biofuels -- absorb incoming solar radiation and have a > strong warming influence on the atmosphere. > > In the modeling experiment, Shindell and colleagues compiled detailed, > quantitative information about the relative roles of various > components of the climate system, such as solar variations, volcanic > events, and changes in greenhouse gas levels. They then ran through > various scenarios of how temperatures would change as the levels of > ozone and aerosols -- including sulfates and black carbon -- varied in > different regions of the world. Finally, they teased out the amount of > warming that could be attributed to different climate variables. > Aerosols loomed large. > > The regions of Earth that showed the strongest responses to aerosols > in the model are the same regions that have witnessed the greatest > real-world temperature increases since 1976. The Arctic region has > seen its surface air temperatures increase by 1.5 C (2.7 F) since the > mid-1970s. In the Antarctic, where aerosols play less of a role, the > surface air temperature has increased about 0.35 C (0.6 F). > > That makes sense, Shindell explained, because of the Arctic's > proximity to North America and Europe. The two highly industrialized > regions have produced most of the world's aerosol emissions over the > last century, and some of those aerosols drift northward and collect > in the Arctic. Precipitation, which normally flushes aerosols out of > the atmosphere, is minimal there, so the particles remain in the air > longer and have a stronger impact than in other parts of the world. > > Since decreasing amounts of sulfates and increasing amounts of black > carbon both encourage warming, temperature increases can be especially > rapid. The build-up of aerosols also triggers positive feedback cycles > that further accelerate warming as snow and ice cover retreat. > > In the Antarctic, in contrast, the impact of sulfates and black carbon > is minimized because of the continent's isolation from major > population centers and the emissions they produce. > > "There's a tendency to think of aerosols as small players, but they're > not," said Shindell. "Right now, in the mid-latitudes of the Northern > Hemisphere and in the Arctic, the impact of aerosols is just as strong > as that of the greenhouse gases." > > The growing recognition that aerosols may play a larger climate role > can have implications for policymakers. > > "We will have very little leverage over climate in the next couple of > decades if we're just looking at carbon dioxide," Shindell said. "If > we want to try to stop the Arctic summer sea ice from melting > completely over the next few decades, we're much better off looking at > aerosols and ozone." > > Aerosols tend to be quite-short lived, residing in the atmosphere for > just a few days or weeks. Greenhouses gases, by contrast, can persist > for hundreds of years. Atmospheric chemists theorize that the climate > system may be more responsive to changes in aerosol levels over the > next few decades than to changes in greenhouse gas levels, which will > have the more powerful effect in coming centuries. > > "This is an important model study, raising lots of great questions > that will need to be investigated with field research," said Loretta > Mickley, an atmospheric chemist from Harvard University, Cambridge, > Mass. who was not directly involved in the research. Understanding how > aerosols behave in the atmosphere is still very much a work-in- > progress, she noted, and every model needs to be compared rigorously > to real life observations. But the science behind Shindell's results > should be taken seriously. > > "It appears that aerosols have quite a powerful effect on climate, but > there's still a lot more that we need to sort out," said Shindell. > > NASA's upcoming Glory satellite is designed to enhance our current > aerosol measurement capabilities to help scientists reduce > uncertainties about aerosols by measuring the distribution and > microphysical properties of the particles. > > Journal reference: > > 1. Drew Shindell, Greg Faluvegi. Climate response to regional > radiative forcing during the twentieth century. Nature Geoscience, > 2009; 2 (4): 294 DOI: 10.1038/ngeo473 > > Adapted from materials provided by NASA/Goddard Space Flight Center. > Email or share this story: > NASA/Goddard Space Flight Center (2009, April 9). Aerosols May Drive A > Significant Portion Of Arctic Warming. ScienceDaily. Retrieved April > 11, 2009, fromhttp://www.sciencedaily.com/releases/ > 2009/04/090408164413.htm MLA > APA --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "geoengineering" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/geoengineering?hl=en -~----------~----~----~----~------~----~------~--~---
