Whoops! An inconvenient truth for ‘global warming makes more rain’ advocates: reduced pollution increases rainfall

Rainfall Raindrops

Rainfall Raindrops (Photo credit: Rubber Dragon)

From the “Department of Unintended Consequences” and Georgia State University  comes this oops moment in science. And all that time we are being told by people like Peter Stott that it was the increase in “global warming” that has increased rainfall.

Georgia State University research finds Clean Air Act increased Atlanta rainfall

A Georgia State University researcher is the first to show that the Clean Air Act of 1970 caused a rebound in rainfall for a U.S. city.

Jeremy Diem, an associate professor in the Department of Geosciences, analyzed summer rainfall data from nine weather stations in the Atlanta metropolitan area from 1948 to 2009. He discovered that precipitation increased markedly in the late 1970s as pollution decreased following passage of the Clean Air Act of 1970.

Diem also noted that pollution in the 1950s and 1960s caused rainfall to drop in the Atlanta area.

Previous studies have found a general link between air pollution and rainfall, with higher concentrations of particulates in the air suppressing rainfall. 

Diem’s research shows, for the first time, that a substantial decrease in pollution in a specific metropolitan area caused an increase in rainfall, Diem said, noting the findings are likely to apply to other urban areas across the United States that saw similar pollution decreases.

“Really, the only plausible reason for this increased rainfall is the reduced pollution due to the passage of the Clean Air Act,” Diem said. “This probably happened in many cities other than Atlanta.”

The study may also have implications for other urban areas around the world that may be experiencing drop-offs in rainfall due to pollution, Diem said.

###

To view Diem’s study, published in the journal Atmospheric Environment, visit: http://www.sciencedirect.com/science/article/pii/S1352231013002951.

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48 thoughts on “Whoops! An inconvenient truth for ‘global warming makes more rain’ advocates: reduced pollution increases rainfall

  1. Why do I have to disable javascript, to be able to reply?

    Isn’t this less pollution = more rainfall just post hoc ergo propter hoc?

  2. While holidaying in north east China recently we told that the area had been in almost drought conditions for 18 years. Smog has of course been an increasing problem there over the same period. Coincidence or causation?

  3. “Really, the only plausible reason for this increased rainfall is the reduced pollution due to the passage of the Clean Air Act,” Diem said.

    —–

    Not “cleaner air” but “the Clean Air Act.” Talk about pushing an agenda.

  4. How do they establish specifically that it was a reduction in air pollution that caused the change?

    There was a similar change in rainfall precipitation in Iowa in approximately 1970. I doubt that the effect of pollution on rural areas like Iowa would have been as severe as in Atlanta, but there is a shift. Depending on the station the shift was as early as 1960 and as late as 1980. The shift in the statewide average happens to be approximately 1970.

  5. This has been obvious from multiple lines of evidence; the Weekend Effect, increased SSTs downwind of the US east coast cities, etc.

    I wonder how long it will take them to get to the more important realization. The reason aerosols decrease precipitation is they cause more persistent clouds (smaller droplets), decreasing solar insolation at the surface. Reduce aerosols and solar insolation increases, causing increasing temperatures. And incidentally contributing to UHI.

    And there is the fact aerosol seeded clouds are low level and block early morning sunshine reaching the surface, delaying and decreasing minimum temperatures. When those clouds decrease, minimum temperatures increase.

    BTW, the late 20th century warming began in 1976, the same year vehicle catalytic converters were mandated in N America.

  6. I was given the impression that pollution would provide more sites for water to start condensing and thus caus *more* rain rather than less but maybe too high a concentration makes too many drops so they don’t get large enough to fall. If this is the case, shouldn’t the line graphing rainfall against pollution concentration rise to an ideal concentration then fall back as it is exceeded? But then different pollutants would have different maximum precipitation concentration so it might be hard to see the curve in real world data, right?

  7. Dear Sleep a Lot,

    “Post hoc ergo propter hoc” means: after, therefore because of.

    Thoughts:

    1) WUWT posters above who assert that there is a strong correlation between air quality and rainfall are not asserting that they know absolutely that rainfall increased because of the cleaner air that preceded it. They are simply declaring a highly plausible conclusion.

    Further, while

    2) Mr. Diem’s asserting with high confidence: “Really, the only plausible reason for this increased rainfall is the reduced pollution due to the passage of the Clean Air Act,” [emphasis mine] appears overly certain, that does not make it necessarily a logical fallacy (i.e., post hoc ergo propter hoc).

    And

    3) Given Mr. Diem’s high level of knowledge of this subject matter, while his assertion may be disprovable, it is not per se mere reckless talk, based solely on sloppy thinking supported only by post hoc ergo propter hoc simplemindedness.

    Finally,

    4) Using “after, therefore because of” reasoning is what rational minds do all the time.

    “For a change, I smiled and was polite at the store today. I got better service than I usually do. It was because clerks treat people well who treat them well that I got better service. I’m going to smile and be polite so that I get better service next time, too,” we might think. Now, we may be correct, and there is a high likelihood that we are, given human nature, but, we may be wrong…. . Perhaps, when I smile and am polite I appear to be insane and the clerk was only humoring me and I will never be allowed inside that store again. More data may prove that our reasonable guess was incorrect, but that doesn’t make our guess, at the time we made it, any less reasonable.

    It is our asserted confidence level, given our actual knowledge, that makes our guess reasonable or not.

    Perhaps, this common sense response only told you what you already knew very well. It appeared highly plausible to me, however, from your post at 10:41AM, that you (and another poster or two, perhaps may benefit) needed to hear it.

    Glad you were able to stay awake long enough to post above! Hope you are well. Take care.

    Sincerely,

    Janice

  8. “Really, the only plausible reason for this increased rainfall is the reduced pollution due to the passage of the Clean Air Act,” Diem said. “This probably happened in many cities other than Atlanta.”
    =============
    I’ll let the much more learned posters destroy this assertion, cus they probably have the data needed.
    Not that they would waste their time.

  9. I was surprised that it wasn’t published in The Onion. Post hoc, correlation = causation and ergo his logic is unassailable.

  10. How does he account for the increased moisture content in the atmosphere created by and from the industrial coolers installed in Atlanta? Their numbers have also increased each and every year from the early 1970′s. Pictures are often posted on the internet of clouds caused by power plant cooling towers, and the industrial coolers are known for causing heavy fog conditions (on occasion) in Texas.

  11. “Diem’s research shows, for the first time, that a substantial decrease in pollution in a specific metropolitan area caused an increase in rainfall, Diem said, noting the findings are likely to apply to other urban areas across the United States that saw similar pollution decreases.”

    Great! So if I get flooded out, now I can sue the EPA!

    So who funded this study? The American Bar Association? :-)

  12. PM10 (particles larger than 10 microns) are pretty big, compared to most particles humans put in the air today. After passage of the Clean Air Act in 1970, the first types of particles to be controlled were the largest, the ones that most obviously turn the air dusty and/or black. These were referred to as Total Suspended Particulates (TSP). You can see from Fig. 1, in the link to the article, that national PM10 emissions fell as national Total Suspended Particulate (TSP) emissions fell. This makes sense for two reasons. First, TSP is mostly PM10, and secondly, in 1974/5, the first oil embargo, the US lost much of its oldest, dirtiest steel and other industry, because these plants were the least efficient, and the economy was in severe recession. Those that didn’t close, had to reduce TSP. Perhaps some that closed did so because they couldn’t afford to meet the new regulations as well.

    You will notice that Fig. 1 is for national data, not for Atlanta. None of the figures show reduction of PM10 in Atlanta specifically. That is a pretty big weakness, if much of the reduction of PM10 nationwide occurred by closure or cleanup of heavy industry., and Atlanta had little of such industry. You will see that the biggest drop, nationwide, occurred between 1970 and 1975. So to what extent was there much of a drop in PM10 in Atlanta in these years?

    Also, EPA didn’t actually issue any regulations for PM10 until 1987. Therefore reductions in PM10 before then were caused either by loss of major polluters in economic downturns, or because of TSP regulations, not PM10 regulations.

    It seems wrong to conclude from this correlation that reduction of PM10 is what necessarily caused the increase in rainfall — even if your Figures showed reductions in PM10 in Atlanta, not nationwide. While correlation could mean causation, we all know that this isn’t necessarily true, in particular where there are other competing theories.

    One of the competing theories might also be due to the Clean Air Act — that is the steady reduction of sulfur dioxide (SO2), which becomes sulfate. Sulfate is much smaller than PM10, it is controlled today by EPA’s regulations of PM2.5 (particles 2.5 microns or smaller). SO2 emissions also decreased with the closure of older factories post 1974/75. Laws requiring scrubbers on new coal fired power plants, and requiring reductions in SO2 from some existing ones, also caused reductions in prior to 1990. But the largest reductions in sulfate occurred after the 1990 amendments to the Clean Air Act (the Acid Rain legislation).

    If the increase in rainfall is related to reduction in pollution (I can’t judge whether that is true or not), it seems to me that the continual increase in observed vs. predicted rainfall, in Fig. 3 (1948-2008) could just as easily be correlated to reduction of PM2.5 (which includes other pollutants, such as black carbon and nitrates), as to reduction of PM10. The reduction didn’t stop in 1975.

    My verdict: an interesting hypothesis, with some glaring weaknesses:

    1. What are the timings of declines in PM10 and PM2.5 in Atlanta (not nationwide), and how do these correlate with rainfall?

    2. What are the mechanistic theories for why particles of different sizes would cause rainfall to increase when the amounts of such particles in the air are reduced? Do the theories differ for particle size and composition?

    Despite these weaknesses, the paper is very strong in its conclusions (see highlights):

    ” • There was a major decrease in particulate emissions after the passage of the Clean Air Act of 1970.
    • The reduction in emissions caused a rapid rebound in summer rainfall in the Atlanta region in the late 1970s.”

    Even if you had pollution data for Atlanta, how could you come to such a strong conclusion, when the study is essentially a study of correlations? And the authors do not have Atlanta specific PM10 or TSP data.

  13. “I was surprised that it wasn’t published in The Onion. … .” [Bob]

    It appears to be a “house divided” issue (hopefully, the Environ-z-ee house will fall!):

    Soft Greens (humans’ (whom our high priests loathe) CO2 emissions cause global warming which causes more rain) v.

    Hard Greens (air pollution is bad for humans whom we care about and clean air, NOT human CO2-warming, causes more rainfall (IF Diem above is correct which John’s post (above) makes seem unlikely).

    Result: Crisis for AGW Camp! Clean air (one of the pillars of the Cult of Climatology’s U.S. archdiocese, the EPA) as a cause of rain diminishes the power of the magical gas, human-sourced CO2.

    So, over at the Onion… “What to do? What to do?”

    The pro-AGW crowd will no doubt end up resolving their internal conflict* by claiming: “Hey, what do you know? Human-sourced CO2 doesn’t cause increased rain. Shrug. Oh, well, IT STILL DOES A WHOLE LOT OF OTHER REALLY BAD STUFF. Act now.

    *Persuasion being the key ["... the agenda of the ‘climatologists’ is not proof of the science but persuasion of the audience. ... ." tadchem, 6/5/13, 6:23 AM on "Quote of the Week... 97%" thread], “The Onion,” et. al. will just ignore the facts, such as those in John’s excellent post above, and not even try to determine the most scientifically accurate answer.

  14. Or maybe……….., this is another cardboard brick in their remodeling of their flimsy pseudo-science wall (but, what is obviously fake onstage under bright lights, with dim lighting looks real to the audience) in their latest attempt to control the human race by CO2 scare tactics. That is, they’re positioning themselves, perhaps, to argue that aerosols (from human industry, of course) and other stuff combine with human-sourced CO2 to cause CATASTROPHIC COOLING (under certain inevitable conditions) UNLESS… we…….. Act Now.

    Truth will win.

    As others have pointed out many times on WUWT, tragically, truth and freedom often win at a very high cost to the warriors and only after terrible damage has been done by the forces of deception.

    In the end, nevertheless, truth wins.

    All you wonderful soldiers in the perennial War for Truth have WON the AGW Battle (mopping up, now). You smashed down the fantasy science wall of AGW! That’s why the Control the Planet climatologists are having to regroup!

    Yes, the war goes on. It will be fought, on many fronts, until the end of time. Each battle won, however, is worth the fight.

    Have you ever read Dava Sobel’s fine book: Longitude? Thousands of sailors’ and passengers’ lives were lost, largely due to Neville Maskelyne’s pride and obstruction for years of the heroically determined inventor (John Harrison) of the timepiece that solved the longitude problem. Evil had its day but, truth won.

    HANG IN THERE! You are on the winning side.

    “The wicked plot … and gnash their teeth … ; but the Lord laughs at the wicked, for he knows their day is coming.” Psalm 37:12, 13.

    It is just a matter of time.

  15. Thats interesting since the actual data seems to imply the opposite, While the flip to a warm PDO in 1978 made the nation as a whole wet,the atlanta area was drier http://1.usa.gov/1844EUg
    than the previous years with a cold pdo http://1.usa.gov/11iw7bs the nation was drier, but N Georgia wetter. Very interesting how this contradicts that, though I suppose it may be that the Atlanta metro area has exclusive rights to the affects of all the clean air around

    Always man, never nature. seems the motto of alot of studies even if one goes to example after example of natural drivers and then the results

  16. Here is a 2004 paper from Israel that does a rather better job of documenting the effect.

    Enhancement of precipitation by cloud-seeding operations has been reported in many studies around the
    world in the last several decades. On the other hand, suppression of rain and snow by urban and industrial
    air pollution recently has been documented and quantified. Here it is shown that the two effects are the
    opposite sides of the same coin, demonstrating the sensitivity of clouds to anthropogenic aerosols of
    different kinds. This is done by analyzing the rainfall amounts in northern Israel during the last 53 years and
    explaining the changes there as the combined opposite effects of precipitation suppression by air pollution
    and enhancement by glaciogenic cloud seeding.

    http://earth.huji.ac.il/data/pics/Givati_Seperation_JAM05.pdf

    And a pet issue of mine is that this effect and the associated effect on surface temperatures can be studied in any city in the developed world over the weekly aerosol cycle (the Weekend Effect). It is scandalous that with the billions spent on climate science, no one has ever published a study relating weekly changes in aerosol levels, with minimum, maximum or average temperatures.

  17. “Really, the only plausible reason for this increased rainfall is the reduced pollution due to the passage of the Clean Air Act,” Diem said.

    For some reason I’m reminded of CAGW supporters claiming that the only plausible reason for the increase in warming is the increase in CO2.

  18. Joseph, It’s well documented that urban aerosol suppression of precipitation results in substantial increases in downwind precipitation. Sometimes downwind rainfall is double that of upwind rainfall.

    This study compares upwind (of an urban area) with downwind precipitation.

    http://journals.ametsoc.org/doi/abs/10.1175/1520-0450(2002)041%3C0689%3ARMBMUA%3E2.0.CO%3B2

    On a related note, I commonly observe on the rainfall radar here in Perth a ‘hole’ in the rainfall centered exactly on the Perth CBD and usually extending 5 to 10 kms.

    Rainfall in Perth occurs from air that has come across many thousands of kms ocean and will have very low levels of aerosols. But my observation suggests that urban aerosols suppress rainfall directly, rather than (or as well as) by seeding droplets too small to precipitate out.

  19. I am going to throw what little weight I have to those who argue that correlation is not causation.

    My own take on pollution dates to my time in the eastern Cleveland suburbs in 1969-1974, right in the heart of the pollution just around the time of the Clean Air Act, but before the effects could really take effect. In fact, I started my working career in engineering on air pollution control equipment, all of which was contracted for because of the dictates of the Clean Air Act.

    The eastern suburbs of Cleveland have another name: The Snow Belt. But it wasn’t just snow. It was also rain. It was the rainiest place I’ve been in. I recall several times on my Army missile base in 1969-1970 such sustained rains that we referred to them as monsoons – conditions rare in the U.S. Midwest. It also happened to be directly downwind of the steel mills and a lot of other heavy industry in the Flats of the Cuyahoga River (yes, the one that “caught on fire”) and all over the city.

    The prevailing westerly winds came across Lake Erie before passing over Cleveland. The shore runs very much SW to NE. As I had it explained to me back then – and it made a lot of sense – the air picked up moisture over the lake and then the pollution gave the water vapor particles to condense upon, at which time it was very likely to fall as precipitation, winter or summer.

    The reason this made and continues to make sense so much is that the Snow Belt was only east of Cleveland, not east of other areas along the Lake Erie shore. (I also experienced several snowfalls beyond anything I’ve gone through elsewhere in the Midwest. In one 12″ of snow fell in slightly less than an hour.) It also makes sense in the light of recent articles about (as I recall off the top of my head) nucleation and particles contributing to water vapor condensation.

    This paper seems to fly in the face of all of this. It appears to me to be exactly 180° wrong.

    Steve Garcia

  20. Philip: Are you sure that the lack of rain in your studies, around urban areas is not as a result of the UHI? That is, warmer air rises and raises the dewpoint, thereby preventing precipitation that cooler air would otherwise allow?

  21. Maybe someone from Oz BOM could comment on Sydney. Newcastle & Wollongong historical rainfall? A generally high summer rainfall, prevailing moisture laden – from the Pacific – N.E. winds, reduced air pollution and steel making industries shut down. Anyone with BOM contacts? Cheers from cool Sydney.

  22. Mario, UHI is substantially a reduced evapotranspiration effect. Urban air is warmer because it is less humid. Humid air is less dense than lower humidity air and thus rises, causing convection. Therefore it’s not clear there is enhanced convection over urban areas. No studies finding this came up in a quick search.

    And how to explain the increased the increased precipitation downwind?

  23. Urban air is warmer because of heat released from surfaces that warm during the day and from energy use in concentrated areas. Warmer air can hold more water, and therefore reduce humidity. Warmer air rises too. All of these effects can cause circulation patters and of course affect rain amounts around urban areas. I’m just pointing out that these statements are true and separation of these truths is difficult. That is all.

  24. The magical thinking in this study is apparent: “Look – passing legislation changes the climate!” and makes me doubt it much more than if the author had simply provided data on particulate levels and rainfall. As someone above noted, even if particulates have a strong effect, it may be that the closure of old industrial plants, changes in land use and a host of other factors need to be taken into account.

    I am surprised that he didn’t use the LA basin as the poster child for this study. There must be plenty of data out there about particulates and rainfall, and there have been dramatic changes in the former in the last 40 years or so.

  25. Philip Bradley says:
    June 5, 2013 at 12:15 pm

    This has been obvious from multiple lines of evidence; the Weekend Effect, increased SSTs downwind of the US east coast cities, etc.

    ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,

    BTW, the late 20th century warming began in 1976, the same year vehicle catalytic converters were mandated in N America.

    Philip, perhaps the other studies have more useful data than this one does? This study proves nothing at all which I will explain. Catalytic converters are probably not the cause of the warming either. Warming started prior to that, and even than people probably did not switch over because at first those regulations only cover newer vehicles. This is not to say that this theory is not true, but this study certainly does not prove a darn thing in general in this department. Personally, I would just sit, measure and wait 30 more years to see if the weather patterns change because I am willing to bet that most of the change was probably natural.


    “Really, the only plausible reason for this increased rainfall is the reduced pollution due to the passage of the Clean Air Act,” Diem said. “This probably happened in many cities other than Atlanta.”

    WOW….the scientific method tells us that the null hypothesis is that all changes in precipitation are due to natural causes. And you did not find that plausible? You did a statistical test and think a statistical test DISPROVES anything? Wow again!

    Basically, their argument boils down to the fact that rainfall is not supposed to ever change more than it has in the 30 years of their test sample. (approx from 1945-1975) Their “base-line” which is weak as heck is a 30 year time period and they claim that the climate of any area is never going to change more than it does in 30 years. Quite a preposterous claim logically.

    Especially since they have no control in their study like “other cities” which shows similar levels of change. And to top this off, their data for pollution levels is NOT EVEN in Atlanta. This is similar to a study I saw about fish in California going extinct about a week ago. They came to conclusions without even checking California river temperatures and instead used a study that covered the entire US. How do you know pollution levels decreased in Atlanta at the same rate as the rest of the US? What if the pollution in Atlanta actually went up and your conclusions are directly opposite of reality? How do you know that California rivers did not actually cool and will continue to cool?

    If you do not even know the answer to those key questions, you can stop, and hang your head in shame over releasing your name on this study combined with a very pointed conclusion.

    They do not control other variables at all (as this is impossible with such little data). They can not rule out other causes (including natural causes.) and to top all of that off, they find it implausible that anything ELSE could have caused this? What if CO2 rise by itself is causing this with increased warmth? Is that not plausible with “97% of scientists” agreeing that global warming is happening and that “Warmer air holds more moisture”. Perhaps prior to the 1980′s CO2 was not high enough and we were too cold for the rainfall to increase.

    I bet there are about 40 other things I could “find just as possible” as pollution as the cause of change if I used just US data. Does not mean that any of those things is anymore likely though.
    And that is the entire point, There are tons of other explanations including the null hypothesis and these “scientists” claim that there is nothing more plausible than their own pet theory. Rubbish as usual.

  26. Urban air is warmer because of heat released from surfaces that warm during the day

    I know a lot of people believe this, but for it to be true, urban albedos must be lower than the albedo of surrounding rural areas and this is not the case for most cities. The exceptions are older cities, Munich and Tokyo in the paper below. The reason is modern cities use more high albedo materials, particularly concrete. The albedo of concrete ranges from 0.3 to over 0.5. Whereas, the albedo of a forest is about 0.1.

    The main source of additional heat (as opposed to increased temperatures) is the Urban Canyon Effect. But this is complicated by additional boundary layer mixing from taller buildings.

    The paper says that while waste heat can heat urban centers by as much as 3C, the effect is negligible in suburban areas.

    http://www.javeriana.edu.co/arquidis/educacion_continua/documents/Urbanclimates.pdf

  27. Philip you wrote: The paper says that while waste heat can heat urban centers by as much as 3C, the effect is negligible in suburban areas.
    +++++
    I believe I said this as one of the reasons urban areas are warmer. I’m not sure what you are arguing about. Forests might have a lower albedo, but they also use energy in growth, and they sweat water, which cools them. You are trying to oversimplify subjects with single parameter arguments.

  28. “I’m not sure what you are arguing about.” [Mario Lento to P. Bradley]

    So, PB is at it again over HERE (just ran into his inanity on the latest Bob Tisdale thread — head shake). He obviously just argues for the sake of it. Only a warped mind engages in perversity for perversity’s sake.

    Whatever Mario says either: 1) say the opposite; or 2) mischaracterize what he said and argue against that. It is, apparently, called “The PB Principle.”

    Yeah, PB, this is an ad hominem post because YOU are the problem.

  29. Yes Janice… It’s not possible to have a cogent exchange with some people…

    Philip, do you believe in CAGW? This is a yes or no question. But feel free to elaborate.

  30. So, PB is at it again over HERE (just ran into his inanity on the latest Bob Tisdale thread — head shake). He obviously just argues for the sake of it. Only a warped mind engages in perversity for perversity’s sake.

    It’s the scientific method.

    Philip, do you believe in CAGW? This is a yes or no question. But feel free to elaborate.

    No. I think AGWism is mostly misinterpretation of a limited dataset, combined with the selling of climate models as scientific predictions, which they aren’t. And sold to a scientifically naive audience.

    If you read WUWT on a regular basis, you will see that the motivation of many posters here is drag climate science back towards science.

  31. Reduced pollution may have caused both the rain and the warming. After all, CO2 can’t “match” the mid-century cooling or the rapid increase in temperature of the 80s or 90s without anthropogenic aerosol forcing as well. However the increase in precipitation associated with the warming is not just urban but global (per Wentz 2007) and both the increase and the failure of the models to represent even half of this negative feedback from acceleration of the hydrological cycle were more recently confirmed by a salinity/freshening study.

    http://www.sciencemag.org/content/336/6080/455.abstract

  32. To Philip Bradley and others:

    My comment at 1:27 PM yesterday was agnostic about whether and how urban pollution may increase or decrease rain downwind of a city. The article says that decreasing pollution increased rain downwind.

    My point was that the study did not actually do what the conclusions said it did. The conclusions said that reduction of PM10 in Atlanta, caused by the Clean Air Act, was correlated with increase in rainfall downwind.

    But the PM10 data was national, not local. Strike one.

    The reasons for reduction in PM10, nationally, in the 1970s included major issues that had little to do with the Clean Air Act — mainly the closure of so much of our older factories during the severe recession of 1974/5, caused by the first oil embargo. Atlanta didn’t have any of these massive old, highly polluting factories. So I would have expected that pollution reduction in Atlanta would have taken a substantially different pattern than the national data. Strike two.

    The author attributes the increase in rainfall to reduction in PM10 (which wasn’t regulated per se by the EPA until 1987). But EPA also regulates, now, a smaller type of particle, PM2.5. The data appear to me to fit the PM2.5 regulatory time line as well as PM10 (which consists of larger PM, of a different chemical makeup. PM2.5 has a major regional component, PM10 less so. Strike three.

    Whatever the effect of urban pollution on rainfall, this study shows nothing of the kind, because it CANNOT show anything of the kind, using national data for local effects. That was my point.

  33. Thanks, John. My post was along similar lines, although not as admirably specific as yours.

    Has anyone done the numbers for LA?

  34. Hmmmn.

    I am not at all surprised that any university generic meteorological “scientist” could be wrong given their belief system in their precious CAGW doctrine, but I am actually surprised that a Georgia State (a local!) meteorologist could be so wrong about local Atlanta-based weather events as simple as Atlanta rainfall!

    At an elevation of between 980 feet and 1300 feet, Atlanta’s (northwest GA in general) rain and weather has one dominant pattern: weather comes from the west as a series of fronts coming through the low hills and pine-forested western Alabama edge of the very southern tip of the Appalachian mountains. (80% of the time. The rest of the time, we are under the west edge of the Bermuda high: very low winds, high pressures, medium cloud cover, no rains of any amount.) At that time, we get very light winds from the east, with scattered puff-balls clouds.) Atlanta’s airport, for example, has its five runways due east-west: they catch the prevailing winds either way.

    NO area near Atlanta produces ANY human pollution – not now, not in the mid-1860′s (except for a few fires as a certain unnamed general fought his way through the rural south), not in the mid-1940′s, not in the mid-70′s, not in the 80′s 90′s, or 2000′s.

    The ONLY “pollution” is the natural ozone from the billions (trillions?) of rapidly-growing and pollinating pine trees: Atlanta’s ozone levels are as high as any in the world due to the pine forests it is built inside of. It’s “atmosphere” is either western Alabama (equally rural) 80% of the time or eastern GA and the clean air from the mid-Atlantic after passing over South Carolina and the east Georgia mountains.

    Others have pointed out the fallacy of the Nixon’s mid-1970′s Clean Act as a national factor, but not an Atlanta factor. But, to claim that west Alabama or south Tennessee is “contaminated” by particulate pollution of ANY (man-made) kind is dead wrong.

  35. RACookPE1978:

    I also tended to notice when living in Atlanta (for one year) that weather patterns would wrap themselves up around the Appalachians and head down-hill towards Atlanta, than they tended to start heading East towards the Carolinas (mostly South).

    It was almost as if sometimes the storms would hug the mountain range (and yes they would be heading over Southern Tennessee and Alabama ) and head south. Yes, the amount of pollution in that area tends to be rather mild as even Chattanooga can not possibly hope to pollute as much as a major city.

    The winter I was there we had 2 snow storms and both were storms caused by that. They would head in from the north and wrap around and start heading to the east after that. I also saw the problems in the study right off the bat because frankly we aren’t talking about a heavily industrialized Eastern city that does tend to get pollution in all areas, Atlanta is a central hub where all the pollution is concentrated in the center. Head away from that central area and the air is clean and crisp. Now Eastern Atlanta (metro area) (that is the area I hated) was smelly and dirty if it was over-cast. (and sometimes when it was not as well….. and you could tell that the air was the result of the city blowing air across this part of Atlanta. We lived in Northern Atlanta, and I know for a fact that most of the time we tended to have rather clean air. The only problem areas were downtown depending on the wind and Eastern Atlanta. I knew people who lived 5 miles from the airport and they too had clean air. You had plenty of noise pollution, but other types of pollution? Doubtful if it made any difference in weather patterns. To get that, you would have to look at Eastern Atlanta exclusively. But that is not from a science perspective, just someone who lived there for a year.

  36. @Philip:

    Mario Wrote:
    Philip, do you believe in CAGW? This is a yes or no question. But feel free to elaborate.

    Philip Wrote:
    No. I think AGWism is mostly misinterpretation of a limited dataset, combined with the selling of climate models as scientific predictions, which they aren’t. And sold to a scientifically naive audience.

    If you read WUWT on a regular basis, you will see that the motivation of many posters here is drag climate science back towards science.
    ++++++++++
    Well that was not expected. Now I’m really confused.
    Cheers and touche’
    Mario

  37. @Joseph Bastardi June 5, 2013 at 4:43 pm:

    Thats interesting since the actual data seems to imply the opposite, While the flip to a warm PDO in 1978 made the nation as a whole wet,the atlanta area was drier http://1.usa.gov/1844EUg
    than the previous years with a cold pdo http://1.usa.gov/11iw7bs the nation was drier, but N Georgia wetter. Very interesting how this contradicts that, though I suppose it may be that the Atlanta metro area has exclusive rights to the affects of all the clean air around

    Joe, you probably know all this, but when I first heard of the PDO over 10 years ago, one of the first things they noted was that a warm PDO was tied in with a cool continental USA – except for the SE. And cool PDO was the opposite. No attempt was made that I remember to explain why the SE would go in-phase with the PDO while the rest of the USA was inversely affected. That was all based on actual real world data. At the time I understood that they were simply trying to note down what evidence they found.

    If I had to speculate, as a place to start looking for mechanisms going on, it would be guessing that the PDO affects the prevailing wind patterns/jet streams, so that the SE either does or doesn’t get prevailing wet and warm winds from the Gulf.

    Always man, never nature. seems the motto of alot of studies even if one goes to example after example of natural drivers and then the results

    In my curiosity a couple of years ago, I read parts of a couple of old science textbooks from the late 1800s. It was very interesting. The authors seemed to apply the prevailing paradigms as explanations for just about everything. (SOME of those paradigms turned out to not be true, and from a 21st century POV, seeing how blithely they applied them was kind of like having a time machine and 20-20 hindsight.) This ubiquitous applying of the current paradigm seems to be still true. I think it might be just a coward’s way of doing science – you can’t get in trouble if you go along with the flow. (I used to think that only applied to bureaucrats!) It’s not just publish or perish, but publish with the right meme. How many papers have I seen that were only tangentially connected with climate, yet near the end I saw a seemingly obligatory connection with global warming.

    I wonder how embarrassed some of them will be in ten or so years, to have those mentions of the by-then disproven paradigm. I can hear the lame excuses already.

    I may be wrong, but that is the way I put this all together in my head.

    Steve Garcia

  38. The entire world was intimidated into claiming they actually believed and believe in this bullsh** and the only people you find around in media, STILL claim they do. It’s been the price of being popular in the eyes of men.

    Those who gave into it are responsible for things such as this:

    Question: you have a warm rock spinning at the bottom of a miles deep, frigid, fluid gas bath. The frigid gas bath is augmented in it’s direct contact cooling through convection and a small percentage additionally of atmospheric-pressure naturally cycling phase change refrigerant which enhances convective processes and removes additional heat.

    The most typical analysis of the miles deep frigid fluid bath are those compatible with analyzing:

    (A)a deep frigid fluid bath augmented with phase change refrigeration driven convectively

    (B)A big, warm, blankie.

    In today’s GHGE believer world, the answer your child will be taught is (B).

    Thank your GHGE believer for that.

    Question 2: You are warming a spinning rock by irradiating it with broad band light.
    The rock has temperature, T.

    You immerse and spin the rock in a fluid, gas, refrigerated bath.

    The temperature of the rock, T,
    will go:

    (A)down

    (B)up

    Thanks to every single human being who endorsed the GHGE “theory” if your child doesn’t answer (B) that test question will be graded as wrong.

  39. Hi,

    I thank all of the people who have left comments for taking the time to read my paper thoroughly. As you know from reading the paper, summer rainfall totals at the nine “urban” stations (Atlanta,
    Ball Ground, Covington, Dallas, Experiment, Gainesville, Newnan, Norcross, and Winder) were predicted for each of the 62 years using weighted totals at the reference stations (Athens, Cedartown,Cleveland, Curryville, Ellijay, Hightower, La Grange, Monticello, and Woodbury). Therefore, an “urban” station had an observed and predicted rainfall value for each year. The prediction procedure described above minimized the impact of interannual variability in synoptic circulation on discontinuities; therefore, the abrupt shift away negative rainfall anomalies (i.e. rainfall suppression) identified in the 1970s reflects mostly changes in the urban boundary layer relative to the rural boundary layer. In other words, PDO, global warming, etc. are certainly not the causes. I found positive rainfall anomalies in the subsequent decades, but they were not statistically significant; overlapping 30-year periods were tested for significant differences between observed and predicted rainfall totals (see Figure 4 in the paper). As I note in the paper, multiple studies have examined the effects of the Atlanta urban area on rainfall and lightning enhancement (Dixon and Mote, 2003; Diem and Mote, 2005; Mote et al., 2007; Diem, 2008; Rose et al., 2008; Shem and Shepherd, 2009; Bentley et al., 2010; Ashley et al., 2012; Bentley et al., 2012; Stallins et al., 2013), but no studies have focused on the potential impacts of changes in particulate concentrations on rainfall.

    JED

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