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.
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?
Does post hoc ergo propter hoc = BS?
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?
Makes sense. The pollutants adhere to some of the water vapor and move on.
Where’s Svensmark when you need him?
Doesn’t it also correlate well with PDO shift in the last 70s?
Perhaps CERN and Jasper Kirkby’s upcoming paper will speak to this work from GSU.
http://wattsupwiththat.com/2013/05/29/update-on-the-cloud-experiment-at-cern/#more-87267
“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.
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.
So per Diem increases will continue? Great news!
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.
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?
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.
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
“per Diem” [S. Geiger]
LOL.
“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.”
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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.
I was surprised that it wasn’t published in The Onion. Post hoc, correlation = causation and ergo his logic is unassailable.
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.
“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? 🙂
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.
“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.
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.
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
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.
“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.
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.