Aerosols Could Be Responsible For Arctic Warming
Written by Nancy Atkinson
Since the 1890s, surface temperatures on Earth have risen faster in the Arctic than in other regions of the world. Usually, discussions on global warming tend to focus on greenhouse gases as the culprit for the trend. But new NASA research suggests about half the atmospheric warming measured in the Arctic is due to airborne particles called aerosols.
Aerosols are emitted by both natural and human sources. They can influence climate by reflecting or absorbing sunlight. The particles also affect climate by changing cloud properties, such as reflectivity. There is one type of aerosol that, according to the study, reductions rather than increases in its emissions seem to have promoted warming.
The research team, led by climate scientist Drew Shindell of the NASA Goddard Institute for Space Studies used a computer model to investigate how sensitive different regional climates are to changes in levels of carbon dioxide, ozone, and aerosols.
They found that Earth’s middle and high latitudes are particularly responsive to changes in aerosol levels. The model suggests aerosols likely account for 45 % or more of the warming measured in the Arctic since 1976.
Though there are several types of aerosols, previous research indicates two in particular, sulfates and black carbon, play leading roles in climate. Both are products of human activity. Sulfates, which come mainly from the burning of coal and oil, scatter sunlight and cool the air. Over the past three decades, the United States and European countries have passed clean-air laws that have halved sulfate emissions.
Since the 1890s, surface temperatures have risen faster in the Arctic than in other regions of the world. In part, these rapid changes could be due to changes in aerosol levels. Clean air regulations passed in the 1970s, for example, have likely accelerated warming by diminishing the cooling effect of sulfates. Credit: Drew Shindell, Goddard Institute for Space Studies
The models showed that regions of Earth that showed the strongest responses to aerosols in the model are the same regions that have witnessed the greatest actual temperature increases since 1976, specifically the Arctic. However in the Antarctic, aerosols play less of a role.
Researchers with the NOAA, the National Oceanic and Atmospheric Administration reported in the April 3 issue of the journal Geophysical Research Letters that Arctic summers may be ice-free in as few as 30 years.
The Arctic region has seen its surface air temperatures rise by 1.5 C (2.7 F) since the mid-1970s. In the Antarctic, surface air temperature has increased about 0.35 C (0.6 F). That makes sense, Shindell said, because the Arctic is near North America and Europe, highly industrialized regions that produce most of the world’s aerosols.
“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,” said Shindell. "We will have very little leverage over climate in the next couple of decades if we're just looking at carbon dioxide. 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 short lived, staying in the atmosphere for just days or weeks, whereas greenhouses gases can persist for centuries. Atmospheric chemists thus think the climate may respond most quickly to changes in aerosol levels.
NASA’s upcoming Glory satellite is designed to enhance current aerosol measurement capabilities to help scientists reduce uncertainties about aerosols by measuring the distribution and properties of the particles.
Source: NASA
Filed under: Earth Observation, Environment
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April 9th, 2009 at 4:12 pm
Don't let this get in the hands of coal and oil nuts…they will want to take us back to the 60's and 70's
April 9th, 2009 at 6:13 pm
I think the world community wants to take active steps in its own defense. We want to be told the causes of our problems in such a way that we can ram solutions into place.
The recent example of dealing with CFC's and ozone holes shows that change is not an impossible goal.
If you can name what specific things are responsible for short term global warming then we can get the pitchforks and torches ready to attack it.
With that victory under your belt, dealing with longer term problems isn't so complicated.
April 9th, 2009 at 6:29 pm
That graph appears to me to show no such thing as the article claims… pre '39 was climbing at the same apparent rate…
What is intriguing is the drop in temps between '39 and '69 !
April 9th, 2009 at 7:38 pm
When are we changing the blog name to Global Warming Today according to Nancy so I can unsubscribe?
April 9th, 2009 at 9:52 pm
Arctic has two cs in it.
In the title.
April 10th, 2009 at 12:11 am
Haven't we been in "global warming" since the end of the last ice age, when the glaciers started to melt?
I look forward to palm trees in Ontario.
Give me a break on this topic – why doesn't every "researcher" shut up, until they know for sure?!
They feed off this hysterical new religion.
April 10th, 2009 at 1:32 am
The botanists put the blame on VOCs volatile organic compounds acting as aerosols. Solar System astronomer should consider the role of micrometeorites.
The role of micron and submicron sized particles in the atmosphere does need further exploration.
April 10th, 2009 at 1:57 am
omnivorr has a very good point-I"ve checked
through climatology records for regional areas as one of my Earth science interests.
The temperature drop omnivorr pointed out is interesting as the drop in temperatures was going on druing WW2 then the booming post war years. This is very odd, did the global warming advocates mentioned this? No doubt the Arctic is losing its ice cover, but has been doing since the end of the last ice age, except for the Maunder Minimum and super large VEI 7 eruption of Mt Tambora 1815 and the smaller Krakatoa eruption in 1883. One thing I studied over the years is when weather instuments are moved from site to site in a metro area and the method of weather recordings.The height above the ground for the weather instruments is very important, so is the environment they are in.
One interesting case of error recording for precipitation is Downtown San Francisco,
the instruments were remotely giving rainfall data for 25 years that was 20-25% lower than true readings because the instuments were sited in an area where hi-rise buildings were built surrounded the buildings, most important, it was difficult for the climatologist to spot check the instuments themselves, and it was found the housing for the instuments had many years of pidgeon droppings on the housing and the precipitation auto-bucket!!!
The readings for the precipation was revised from a TV staion about 8 blocks away that had none of the problems I noted and the TV station did follow NOAA guidelines. Another interesting result was the max-min of the day reflected the true readings for that part of San Francisco, the old site showed higher minimums than what was really true due to 'heat island' causes. I can't believe they did the exact temperature recording guidelines and instument settings 130 years ago as what is standard guidelines for today. Digital recordings have only been around for just a few decades.
April 10th, 2009 at 2:10 am
I've been looking at this article, and it makes good sense to me. I'm quite active in discussion forums as a defender of conventional science on climate.
I don't think there's any conflict. I'd love to hear Dr Shindell address this more directly himself. You folks are in the space science loop, he's at NASA. Would you consider inviting him to comment himself? I would really love to hear his reaction to my own feelings, and whether I've understood correctly.
His paper is, of course, focused on Arctic warming; not global warming. Arctic trends are quite different from global trends, and that is what his paper is addressing. It involves looking at the differences in forcings and responses at different latitude bands.
As far as greenhouse effects go: here's some back of the envelope numbers for the CO2 contribution. CO2 has increased over the last century from 280 to 385 ppm, about. Log2(385/280) = 0.46. Expected climate sensitivity is about 3C per doubling. So that's about 1.4 degrees per century, or 0.14/decade, expected from the CO2 rise. Or, focusing on the immediate present, we are getting about an extra 2ppm/year. Log2(387/385) = 0.0075 doublings, which should be about 0.022 degrees/year; 0.22 C/decade from present CO2 rises. So, ball park, CO2 alone should be expected to have roughly 0.2C/decade warming.
Given that there's presently excess heat going into increasing ocean temperatures (recently published work based on satellite data), some of the warming effect won't yet be realized, so CO2 can really only hope to account for something rather less than the above. Total greenhouse effects are more than CO2 alone, but they can't be a lot more, as CO2 is the largest contributor for WMGHGs.
Measured global temperature trends are currently about 0.17 C/decade, more or less. That's a reasonable fit with greenhouse effects being a major cause. Other factors will contribute, of course, but the magnitude of the greenhouse contribution is broadly similar to the magnitude of the total effect. Ergo: greenhouse changes are most likely a major player for global trends. There will be others, but greenhouse should be a big one. Climate models (like those used by Dr Shindell) test out this idea more thoroughly.
Shindell and Faluvegi focus on DIFFERENCES between the Arctic and other latitudes, and so they are looking for effects which impact the Arctic more than other regions. The Arctic is some 7% of the globe (that's the number used in the paper). And temperature trends in the Arctic are way WAY up around 1.5 C/decade. There's something different about the Arctic in comparison with the rest of the globe. (Just look at a temperature graph, this sticks out a mile.)
Ergo: CO2 cannot account directly for the Arctic temperature rises. Other GHGs that distribute differently may be a factor, but there's a huge difference between 0.2 C/decade and 1.5C/decade. Hence it is no surprise to me at all that something other than greenhouse should be the major cause of warming IN THE ARCTIC. And that is a really really useful caution for those of us who may be inclined to point to the Arctic as a sign of global warming.
What we have up there is Arctic warming. It's in part due to greenhouse effects, but mostly due to other factors. I'm convinced on that point by the paper.
And I'll eat my hat if Dr Shindell thinks his work is a refutation of the major significance for greenhouse gases in the global trend.
April 10th, 2009 at 3:51 am
Alot of things happened in the WWII years.
We ramped up our industry to full capacity and generated a crapload of dust. Not only from manufacturing but also from the acts of war (bombs, burning cities, trucks moving, farming activities, ore mining).
Fishing in the north Atlantic practically came to a halt because of U-Boat attacks, we started using more electricity and rationed supplies back at home (which probably cut down on certain kinds of waste… think eating a pig down to the bone marrow instead of leaving half of it to rot in a landfill).
Then there were the first nuke tests and the ones following.
Lots of things happened in WW2 and the post war that could have affected the global climate… and now that I'm looking at the graph, something happened between 1910 and '20 that also had an effect.
Could just be a damned interesting coincidence…
I think unhitching Al Gores "its all about the carbon" global warming bandwagon from climate change in general could be a very productive move.
We need to get politics out of our science.
April 10th, 2009 at 4:39 am
What about all the natural methane deposits on the Ocean floor? What happened to all the science around those expelling at dangerous rates..where ..why at the Top and Middle of the planet. I guess that would be important if I had "scientist" in my title.
We were going to have a Ice Age when I was young, no we are going to have global warming. I think it's all just a scam for governments to control us.
One Single Super Volcano and all this debate is MUTE.
Why is that all the space launches have no effect on the atmosphere? What's all the junk Floating around up there helping?
April 10th, 2009 at 5:02 am
>Aerosols Could Be Responsible For Artic Warming
Didn't we know all about this 25 years ago? So how come it makes headline news now??
April 10th, 2009 at 5:08 am
What we have here is a failure to communicate.
April 10th, 2009 at 5:14 am
If Global warming continues it won't take a heroic explorer to reach the North Pole.
It'll be warm enough for anyone with a beach towel and a pair of skimmys to make it. (as long as they bring some factor 4,000 to protect themselves from intense Solar radiation)
April 10th, 2009 at 5:36 am
i love how they always use words like "could" or "maybe" or "presumed to be". Why don't the scientists actually figure it out before releasing data. All it does is stir up the media into a global catastrophe mentality and fir up the moon bats…. let it rest! i personally would prefer a warmer climate. who is to say what the "normal" is for our climate? It is always changing wither we are polluting or not.
April 10th, 2009 at 7:00 am
What I noticed in the graph in the article is that surface air temps started to decline shortly after WW II and did not rebound until around 1964. It is in this time period that numerous nuclear weapons were being tested above ground and exoatmospherically (and mainly in the Northern Hemisphere). Just think of the amount of aerosols, dust and other particulates that were created and then lofted over 60,00ft into the stratosphere where they remained for some time. I do not mean to imply that this was the sole cause of the surface temperature drop, but along with other factors (several major volcanoes had strong eruptions during those years and human activity (besides testing H-bombs) surely had some part to play. But the question remains, what were the actual effects of numerous above-ground Hydrogen Bomb tests made during this period?
April 10th, 2009 at 7:47 am
I’m having problems again with reading previous comments. I’m using Firefox 3.0.8, so what's the problem?
April 10th, 2009 at 8:46 am
We should lift the clean air ban so the air temps will go back down.
We should maybe even think about pumping some of the "good" aerosols back into the air so the air temps go back down.
April 10th, 2009 at 8:49 am
Aerosols might be responsible for global warming, of course.
But there have been other studies about the influence of volcanic activity.
See for instance: http://www.canada.com/topics/news/story.html?id=81bb2fd3-63f1-476f-b0be-f48c0dc90304
We are living at an extreme thin crust and below us there is an unseen realm of incredible energy and power.
We don´t know anything about it.
Still we claim again and again to know the `truth` about global warming.
April 10th, 2009 at 9:10 am
Bob Says:
Give me a break on this topic – why doesn’t every “researcher” shut up, until they know for sure?!
Well said Bob. I completely agree.
Now is there anyone up for a witch hunt ……
April 10th, 2009 at 10:36 am
@omnivorr
Nova on PBS had a documentary a couple years back about Global Dimming, or less radiation reaching lower levels in the atmosphere, from aerosols and soot that block the sun. That would explain the drop in temps between '39 and '69 after the Clean Air Act which the show alluded to. Without the aerosols and soot we have now, we'd have appreciably higher temps from CO2.
@Duae Quartunciae
Were at closer to 388 ppm C02 right now, from recent readings (can't find citation).
Also, CO2 is rising close to 3 ppm per year recently.
There was also recent research about super fine pollution particles all over the Arctic
snow and ice, which could explain away two effects: increased melting from higher radiation absorption and a drop in albedo.
Hey, and I am all for the Precautionary Principle when it comes to Global Warming/Climate Change. Its also a good excuse to develop new tech, cutting down on fossil fuels, and leaving a little goop for the next couple generations. The Earth can handle the yearly 6-7 Billion tons of CO2 et al, but only after a couple millenia.
April 10th, 2009 at 1:11 pm
Very interesting posts. I do have to agree with this part of @Duae Quartunciae 'a good excuse to develop new tech, cutting down on fossil fuels'. For the US, this must be done in slow stages without drastically affecting other areas of the economy- the US car makers, there are many other industries dependent on the car makers, fuel economy must get better and there is much improvements that can be made with new tech-my country imports nearly 70% of petroleum, this is ruining the US economy and this figure must be dropped. very much, and this major drop can be done with new tech for autos. Autos in the US accounts for over 90% of our imported petroleum!!! Again, this must be done in stages without drastically affecting the welfare of other industries dependent on the automobile.
The US power grid to develop electricity for consumers can be improved greatly by better technology and importantly, more intelligent use of outdoor lighting to cut down on light pollution
which causes over 2/3 or the population to not know what the night sky really looks like.
I get too many conflicting reports about CO2 ,
so I have no say about that . I do have to thank the posters, so far, no one has gone crazy pro or con
about C02
April 10th, 2009 at 1:23 pm
Jon Hanford Says:
I believe the host server, or the server for this site
is overwhelmed by much traffic during certain times because I switch between IE8 and Firefox and I also have this problem so I just wait awhile then get back into this site.
April 10th, 2009 at 2:51 pm
@ Archon
you miss my point.
so-called aerosols ( largely micro particulate matter) has been poring into the atmosphere from the beginning of the Industrial Revolution. The graph clearly shows rising temps that, with the '39-'69 period removed from the graph, is almost a linear rate of change. Between '39 and '69 went against the trend. Post '70 merely resumes the trend.
My observation pushes no barrow, I only ask 'What happened during those years to buck the trend?" Are you suggesting that those years were abnormally high in producing 'aerosols', and that 'clean air acts' had an instantaneous impact on setting temp rises back to the trend ?
April 10th, 2009 at 4:45 pm
Omnivorr, your questions are addressed directly in the paper being discussed. See page 297, the section "Comparison with historical emissions".
The answers are not definitive, as the historical emissions data is uncertain. But from 1931 to the present, Shindell and Faluvegi consider that their inferred forcings are broadly consistent with historical emissions.
1931-1975 is listed in the paper as a band of negative forcings in the north. This is a time of large sulphate increases (cooling effect increasing) and constant black carbon (warming effect constant). After 1975, this reverses. You have decreasing sulphates (clean air act) and increasing black carbon (largely from Asia).
Prior to 1930 you have the increasing trend, but here the emissions data is less clear. Shindell and Faluvegi speculate about a strong black carbon emission from biomass burning.
The clean air act probably did have an instantaneous effect on trends, which is what we are measuring. An increasing trend in sulphates suddenly becomes a negative trend in sulphates.
April 10th, 2009 at 11:19 pm
Thanks Duae Q , for some reason I cannot acces the first page of replies so may have missed something, and not being in the US don't see PBS. Neither would I know where to find the paper in question.
Based only on the article and the graph therein I sought clarifaction.
In short then, we could grossly simplify the larger trend as "dirty coal" (or wood-burning, etc) the intervening cooling period as "dirty oil", and post '70 as "clean oil", sofar as "aerosols" are concerned…. ?
April 11th, 2009 at 12:46 am
I guess so. Maybe. I'm just reading the paper; I have no other qualification to give suggestions on my own behalf!
I didn't realize the paper was not fully referenced here, and on checking I see that even the NASA press release only names the journal. But try this:
Shindell, Drew, and Faluvegi, Greg. Climate response to regional radiative forcing during the twentieth century, in Nature Geoscience 2, 294 – 300 (2009). Published online: 22 March 2009 | doi:10.1038/ngeo473.
Link: http://www.nature.com/ngeo/journal/v2/n4/full/ngeo473.html
There's also a commentary article by Noel Keenlyside in the same issue.
April 11th, 2009 at 3:51 am
John Hanford,
I don't believe the server problem has anything to do with the traffic. It's _one_ feature of the site, it suddenly broke, and it remains broken.
It happened before, and somebody fixed it in two stages: first, all responses became accessible in a single page – next, it all went back to "normal".
"Murphy's Law" dictated that this current error happened just before the extra long weekend, resulting in a Big Bummer With Extra Impact (TM)
April 11th, 2009 at 8:07 am
Feenixx, I think you got it right. I had identical problems (and experiences, like the single page responses that were there a few days then vanished) and numerous work-no work sessions at this site. I'm with you here – a Big Bummer With Extra Impact.
April 11th, 2009 at 11:28 am
Feenixx Says
Yes, you're right-this site is unstable. There are times I can't even access the site and it does go into a single page numberous responses . I hope the site administrator can fix this site.