Asia’s air pollution may be keeping tropical storm activity down

Aerosol_optical_depth

Above, May 2013 Aerosol Optical Depth. Uou can see the United States and Europe is relatively clear, while Asia has high amounts of aerosols. Image: NASA Earth Observatory

From the Law of Unintended Consequences and The Clean Air Act, comes this bit of news. Since the 1970’s The Clean Air Act has benefited breathing in many American cities with tangible results (just look at Los Angeles), but it may have had a role in increasing tropical storm activity.

This new paper suggests that due to the reduction of aerosols and particulates in the atmosphere might have been the main cause of a recent increase in tropical storm frequency in the North Atlantic.

Aerosol levels have increased since the start of industrial revolution, but as we know there have been periods when aerosol emissions declined; the Great Depression, World War II and after clean air legislation was enacted in Europe and the United States in the 1970s and 1980s.

The paper suggests that these periods of reduced emissions eventually increased tropical storm frequency.

Anthropogenic aerosol forcing of Atlantic tropical storms

N. J. Dunstone, et al. Nature Geoscience (2013) doi:10.1038/ngeo1854

Received 04 December 2012 Accepted 15 May 2013 Published online 23 June 2013

The frequency of tropical storms in the North Atlantic region varies markedly on decadal timescales1, 2, 3, 4, with profound socio-economic impacts5, 6. Climate models largely reproduce the observed variability when forced by observed sea surface temperatures1, 8, 10. However, the relative importance of natural variability and external influences such as greenhouse gases, dust, sulphate and volcanic aerosols on sea surface temperatures, and hence tropical storms, is highly uncertain11, 12, 13, 14, 15, 16. Here, we assess the effect of individual climate drivers on the frequency of North Atlantic tropical storms between 1860 and 2050, using simulations from a collection of climate models17. We show that anthropogenic aerosols lowered the frequency of tropical storms over the twentieth century. However, sharp declines in anthropogenic aerosol levels over the North Atlantic at the end of the twentieth century allowed the frequency of tropical storms to increase. In simulations with a model that comprehensively incorporates aerosol effects (HadGEM2-ES; ref. 18), decadal variability in tropical storm frequency is well reproduced through aerosol-induced north–south shifts in the Hadley circulation. However, this mechanism changes in future projections. Our results raise the possibility that external factors, particularly anthropogenic aerosols, could be the dominant cause of historical tropical storm variability, and highlight the potential importance of future changes in aerosol emissions.

h/t to Marc Hendrickx

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34 Responses to Asia’s air pollution may be keeping tropical storm activity down

  1. Latitude says:

    ….use more hairspray

  2. OldWeirdHarold says:

    Emissions declined during WWII? Where does that come from?

  3. arthur4563 says:

    I suggest that , at least in terms of automotive emissions, the reduction was in large measure the result of the advent of electronic fuel injection, fostered by the advent of cheap microprocessors,
    which would have been introduced because of their inherent superiority, with or without any clean air act. Cars have become so clean that sniffers often do not even register certain pollutants.

  4. Robuk says:

    Using simulations from a collection of climate models.

    Say no more.

  5. Ric Werme says:

    Has anyone asked Bill Gray what he thinks of this idea?

    Did the authors consider the role of the AMO? Perhaps that is some of their “natural variability” that no one seems to analyze.

  6. The large red spot west of Africa is mainly salt spray in one of the main birdplaces of tropical storms, by far exceeding the human aerosols there.
    East of Saoudi Arabia it is mostly sand dust.
    Even above China, natural aerosols (SOA – secondary oxidised aerosols – mostly from terpenes) in the free troposphere exceed human induced SO2 some 7-fold and more…

    Thus if aerosols reduce tropical storm occurence, we only need to spray more salt water somewhere high in the atmosphere?

  7. Gerald Kelleher says:

    I am listening to the most powerful politician on the planet and his indoctrination into the wonderful world of mathematical modeling where science goes from interpretation to speculation/prediction. It is no longer a dysfunctional society but something much worse – a dystopian society.

    The aggressive push of empirical modelers has no known counterbalance as the opponents operate off the same script and that,and that alone is the problem.

  8. kwinterkorn says:

    What is it with modern “scientists”?

    “We show that anthropogenic aerosols lowered…….” No you didn’t. At most you showed a correlation in a set of events with innumerable confounding variables, all outside of your control. Yet you assert causation. Maybe changing aerosols caused something, and maybe not. You do not know.

    If modern scientists talk (or write) like this, I can only assume that they think like this. No wonder they can foolishly mistake outputs of computer models for real world data. No wonder after 15+ years of no warming, they can jump from one ad hoc rationalization for the failure of CAGW as a theory to another. No wonder they can think that declining ice in the arctic proves CAGW, but rising ice in the Antarctic means nothing important. Oyyy!

  9. kramer says:

    I don’t believe Asia has the power to lower tropical storm activity.

  10. Anthony writes nice things about EPA regulation and climate models, the fanbase becomes restless.

    REPLY: hey, I call ‘em as I see ‘em – Anthony

  11. crosspatch says:

    Not buying it. Air pollution was much worse in the 1960’s and 1970’s and we had more tropical storms.

  12. Gerald Kelleher says:

    It is so tempting to get done and dirty with people who have no conscience whatsoever by virtue that what they see themselves toiling away at is natural and an extension of their education/indoctrination.In simple terms they have no alternative research approach against which to gauge themselves or their conclusions and likewise their opponents,they may disagree with the conclusion but retain modeling warfare.If things were normal, ‘global warming’ would be seen as only one battle within a modeling war.

    Only very few people since the time of Galileo have recognized the type of personality that now dominates terrestrial sciences but here are a few .Should anyone wish to appreciate how ‘global warming’ morphed into ‘climate change’ they need look no further than Von Humboldt.

    ” I know; such men do not deduce their conclusion from its premises or establish it by reason, but they accommodate (I should have said discommode and distort) the premises and reasons to a conclusion which for them is already established and nailed down. No good can come of
    dealing with such people, especially to the extent that their company may be not only unpleasant but dangerous.” Galileo

    “This empiricism, the melancholy heritage transmitted to us from former times, invariably contends for the truth of its axioms with the arrogance of a narrowminded spirit.Physical philosophy, on the other hand, when based upon science, doubts because it seeks to investigate,distinguishes between that which is certain and that which is merely probable, and strives incessantly to perfect theory by extending the circle of observation.”This assemblage of imperfect dogmas bequeathed by one age to another— this physical philosophy,which is composed of popular prejudices,—is not only injurious becauseit perpetuates error with the obstinacy engendered by the evidence of ill observed facts, but also because it hinders the mind from attaining to higher views of nature. Instead of seeking to discover the mean or medium point, around which oscillate,in apparent
    independence of forces, all the phenomena of the external world, this system delights in multiplying exceptions to the law, and seeks, amid phenomena and in organic forms, for something beyond the marvel of a regular succession, and an internal and progressive development. Ever
    inclined to believe that the order of nature is disturbed, it refuses to recognise in the present any analogy with the past, and guided by its own varying hypotheses, seeks at hazard, either in the interior of the globe or in the regions of space, for the cause of these pretended perturbations. It is the special object of the present work to combat those errors which derive their source from a vicious empiricism andfrom imperfect inductions.”
    Homboldt ,Cosmos

  13. Bob Tisdale says:

    Another model study–yawn.

  14. charles nelson says:

    When they burned the oilfields in Kuwait that sent a fair old squirt of aerosols into the atmosphere…if that didn’t show up on one of their metrics then I suspect that they maybe, kinda guessing?

  15. Warrick says:

    crosspatch says:
    June 25, 2013 at 12:13 pm
    I read it as agreeing with your observation.

    Interesting image – is the grey scatter over SE Asia the smoke from fires clearing forest for oil palm plantations? Singapore government has been complaining about the appalling pollution over them from these fires for some months. Strange this extremely visible pollution does not affect optical depth for the satellite.
    For example http://www.reuters.com/article/2013/06/25/us-southeastasia-haze-idUSBRE95I0WW20130625

  16. Snowlover123 says:

    At least they’re finally admitting that Hurricane Activity is not “worse than we thought” anymore.

  17. Jim Strom says:

    I’m confused. I could swear I’ve been reading about the recent dearth of tropical storms.

  18. It’s been known for some time (>40 years) that anthropogenic aerosols depress hurricane activity. There have even been experiments to try and suppress and/or steer hurricanes. The effect is large when hurricanes approach urban areas, reducing hurricane intensity by a large amount.

    Aerosols influencing the Hadley Cells is new, to my knowledge.

    Of course, that reduced anthropogenic aerosols is increasing hurricane frequency and intensity is an absolutely taboo subject for the media. Instead we get the ‘global warming is the cause’ mantra.

  19. The WRF/SBM was used to investigate the potential impact
    of aerosols ingested into Katrina’s circulation during its passage through the Gulf of Mexico on Katrina’s
    structure and intensity. It is shown that continental aerosols invigorated convection largely at TC periphery, which led to its weakening prior to landfall. Maximum weakening took place ;24 h before landfall, just after its intensity had reached its maximum. The minimum pressure increased by ;15 hPa, and the maximum wind velocity decreased up to 15 m s.

    http://journals.ametsoc.org/doi/pdf/10.1175/2009JAS3210.1

  20. Crispin in Waterloo says:

    @Philip B

    Well spotted.

    RE the East Asian aerosols: are they referring to condensed particles or all particulate matter or…? An ‘aerosol’ is not only a human-origin thing and it also includes black carbon and silica dust – as long as it is suspended. Do they have some definition whereby natural aerosols are subtracted?

    A great deal of the aerosols in the East of China blow off the Gobi desert floor. The yellow sky over Korea is from the Gobi. Even if Beijing brought its emissions to zero it would still have thick haze now and then.

    Re West Africa, when was the image created? The Harmattan Wind which blows south from the Sahel into the tropical rainforest turns everything into a cough-worthy haze from Ivory Coast to Cameroon.

    From Wikipedia:
    Effects:
    In some countries in West Africa, the heavy amount of dust in the air can severely limit visibility and block the sun for several days,[3] comparable to a heavy fog. It can even break the trunk of the pine trees, growing in that region, through their dryness. The effect caused by the dust and sand stirred by these winds is known as the Harmattan haze, which costs airlines millions of dollars in cancelled and diverted flights each year,[4][5] and risks public health by increasing meningitis cases.[5] The interaction of the Harmattan with monsoon winds can cause tornadoes.[1] Humidity drops to as low as 15 percent and can result in spontaneous nosebleeds for some. The wind can cause severe crop damage.[6]”

    As my signature sometimes shows, I am in Mongolia from time to time. In the ghastly pollution of Ulaanbaatar the ‘fugitive dust’ from the Gobi can make up 50% of the total aerosol load. How do we know? Nuclear analysis of filters.

    I want to know how (and if) these guys determined which emissions are anthropogenic.

  21. Louis Hooffstetter says:

    “We show that anthropogenic aerosols lowered the frequency of tropical storms over the twentieth century. However, sharp declines in anthropogenic aerosol levels over the North Atlantic at the end of the twentieth century allowed the frequency of tropical storms to increase.”

    Their conclusion seems counter-intuitive. Experiments carried out by CERN confirm Henrik Svensmark’s hypothesis that cosmic rays produce aerosols, which in turn seed clouds. Anthropogenic aerosols are no different; they seed clouds as well.

    We know that more clouds lower temperatures, resulting in a higher temperature gradient between the equator and the poles. More clouds = more moisture in the atmosphere and a higher temperature gradient between the equator and the poles. Under these conditions, tropical storms are more frequent, not less. More aerosols should = more storms, less aerosols should = fewer storms.

    Correct me if I’m wrong, (and I may be) but I believe they got it “bass ackwards”.

  22. u.k.(us) says:

    David vun Kannon says:

    June 25, 2013 at 12:12 pm

    Anthony writes nice things about EPA regulation and climate models, the fanbase becomes restless.
    ================
    I know there must be a point in your comment, it said something about fanbases and restlessness, is this some kind of play to show the collapse of a consensus ?
    That is how science is decided now, correct ?
    Sorry if I’m being restless, fanbases tend toward obstinacy.

  23. More aerosols should = more storms, less aerosols should = fewer storms.

    It’s more complicated than that. I recently posted a study from Israel that showed urban aerosols depressed rainfall by about 20% near cities, but increased rainfall away from urban areas. I recall a study from China where a new city increased rainfall downwind by 200%.

    The overall effect of anthropogenic aerosols is to form smaller cloud droplets which impedes rainfall near the source. However, there is great deal we don’t know. This is a badly under-funded area of climate science*, especially with the hurricane aerosol interaction.

    * I would argue the underfunding is deliberate, because aerosol cloud interactions explain a lot of the late 20th century warming and more data would deal a fatal blow to the CO2 AGW case.

  24. Crispin, a regular topic of mine is the Weekend Effect, because it has to be anthropogenic in origin.

    There is evidence of a weekly cycle in Atlantic Hurricanes.

    http://www.readcube.com/articles/10.1038/29043?locale=en

    Unfortunately mostly behind a paywall.

    There are also indications urban aerosols actually steer hurricanes away from cities. You’d think this would be newsworthy.

  25. I am a bit confused as to how aerosols were lowered during WW2, given that industrial production in the United States increased by 2 or 3 times; not to mention huge artillery battles and city-wide bombing missions.

    The USAF napalmed one or two hundred Japanese cities in 1945. Surely that would have introduced more aerosols into the atmosphere.

  26. Gail Combs says:

    David vun Kannon says:
    June 25, 2013 at 12:12 pm

    Anthony writes nice things about EPA regulation and climate models, the fanbase becomes restless.

    REPLY: hey, I call ‘em as I see ‘em – Anthony
    >>>>>>>>>>>>>>>>>>>>>>>>>
    Anthony lives in CA and is old enough to remember the smog. I lived in Rochester New York and am old enough to remember when the Genesee River ran in multicolored ribbons of bright colors, stank to high heaven and nothing grew on the banks of the river.

    We in the USA needed to clean up our act. However the EPA as is true of most bureaucracies is interested in preserving its turf, reason for existence and also in expanding. The more people under you the higher the pay grade.

  27. Ulric Lyons says:

    The biggest aerosol impact on the Atlantic should be Saharan dust storms:

    http://www.noaanews.noaa.gov/stories2006/s2719.htm

    NASA was looking at sea surface temperatures:

    http://www.nasa.gov/topics/earth/features/cooling_dust.html

    but recently seems to be focussed on cloud formation:

    http://www.nasa.gov/mission_pages/hurricanes/missions/hs3/news/saharan-dust.html

  28. beng says:

    And modelers think aerosols have decreased globally since the 70s? They have in Europe & NA, but increased everywhere else. Aerosols are higher now, globally, than ever. Stuff that into your “models”.

    And where are all the current Indonesian aerosols on that map? Guess it just started in June…

  29. daddyjames says:

    As this study indicates, the inclusion of pollution (aerosols) data into the climate model better predicted historical hurricane activity in the Atlantic, more so than using natural climatic events.
    Increased level of aerosols were consistent with decreased levels of hurricane activity,more so than was found from natural cycles. So, increased levels of aerosols influenced the climatic conditions that determine whether or not tropical storms develop and intensify into hurricanes.

    Then, explain to me why changes in the amount of CO2 in the atmosphere would not have an effect on climate and weather patterns over a period of time? Why would it not be prudent to adopt measures to mitigate the impact that human activity has on increasing levels of CO2 ?

  30. Ulric Lyons says:

    daddyjames says:
    “Increased level of aerosols were consistent with decreased levels of hurricane activity,more so than was found from natural cycles.”

    It hard to imagine pollution competing with Saharan dust plumes through the Summer months:

    http://earthobservatory.nasa.gov/GlobalMaps/view.php?d1=MODAL2_M_AER_OD

    Theoretically, colder winters result would in more dust storms, reducing tropical cyclone numbers, and very active seasons would follow very mild winters.

  31. daddyjames says:

    @Ulric Lyons
    All I can encourage you to do is read the study and see what natural sources were taken into account.

  32. JPeden says:

    daddyjames says:
    June 26, 2013 at 11:49 am

    “So, increased levels of aerosols influenced the climatic conditions that determine whether or not tropical storms develop and intensify into hurricanes.Then, explain to me why changes in the amount of CO2 in the atmosphere would not have an effect on climate and weather patterns over a period of time? Why would it not be prudent to adopt measures to mitigate the impact that human activity has on increasing levels of CO2 ?”

    1] Because CO2 is not considered to be an “aerosol” by Climate Science. It’s not even a real pollutant…and,

    2] “Mainstream” Climate Science’s CO2 as “driver” of climate hypotheses have a 100% prediction failure rate. That means their idea is falsified. No detectable forcing effect of CO2 has been found in the empirical data of the real world. Moreover, there is nothing new going on in the current, post 1950 allegedly CO2-forced climate, as compared to the pre-CO2-forced climate.

  33. Gail Combs says:

    I will add
    #3. The catastrophic effect of CO2 was based on a model where water vapor is a feedback of CO2 and as CO2 increase so does water vapor. This is how the climate sensitivity of CO2 was multiplied by a factor of 3X. This key feedback also fail to respond as predicted.
    Graph: Global Relativity Humidity

    Graph: NOAA Specific Humidity 37 month running average

  34. Ulric Lyons says:

    daddyjames says:
    “@Ulric Lyons
    All I can encourage you to do is read the study and see what natural sources were taken into account.”

    I’m put off reading any further as they present an aerosol map for May, before the hurricane season, while in the following months, there are large Saharan dust plumes across the Atlantic:

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