A benefit of 'climate change' – reduced ozone pollutants in coastal cities

University of Houston researchers: Climate change helped to reduce ozone levels –

Houston findings should hold for coastal regions around the world

This graph shows days in which ozone levels in Aldine exceeded EPA standards during a one-hour period over the past 23 years (blue line), contrasted with number of hours of southerly wind flow (red). Credit: University of Houston

This graph shows days in which ozone levels in Aldine exceeded EPA standards during a one-hour period over the past 23 years (blue line), contrasted with number of hours of southerly wind flow (red). Credit: University of Houston

Researchers at the University of Houston have determined that climate change – in the form of a stronger sea breeze, the result of warmer soil temperatures – contributed to the drop in high-ozone days in the Houston area.

Robert Talbot, professor of atmospheric chemistry, said that also should be true for coastal regions globally.

The researchers describe their findings in a paper published this week in the journal Atmosphere. In addition to Talbot, they include first author Lei Liu, a doctoral student, and post-doctoral fellow Xin Lan.

The study relied upon ground-level ozone data collected over the past 23 years by the Texas Commission on Environmental Quality. The meteorological data was collected by the National Oceanic and Atmospheric Administration.

The researchers said they did not set out to find a connection between climate change and lower ozone levels – the number of days in which ozone levels exceeded federal standards varied from year to year but overall, dropped dramatically between 1990 and 2013. For example, in Aldine, one of four sites studied, the number of days during which ozone levels exceeded federal standards over an eight-hour period dropped to an average of 11 days per year during 2001-2013, down from 35 days per year during 1990-2000.

Talbot said the steep decline made him suspect something was happening beyond a city-led effort to reduce nitrogen oxide emissions, one of the components of ozone.

Liu said they first ruled out other meteorological factors, including temperature, humidity and solar radiation. After they discovered the lower ozone readings coincided with days the southerly flow was strongest, they realized that climate change – in the form of warmer soil temperatures – had increased the southerly flow, she said.

“The frequency of southerly (air) flow has increased by a factor of ~2.5 over the period 1990-2013, likely suppressing O3 (ozone) photochemistry and leading to a ‘cleaner’ Houston environment,” they wrote. “The sea breeze was enhanced greatly from 1990 to 2013 due to increasing land surface temperatures, increased pressure gradients, and slightly stronger on-shore winds. These patterns driven by climate change produce a strengthening of the sea breeze, which should be a general result at locations worldwide.”

Industrial plants and vehicle exhaust mix with heat and sunlight to produce ground-level ozone, which can worsen asthma and other conditions. The city’s rapid population growth – more people means more cars – and the refineries and petrochemical plants along the Houston Ship Channel are key factors in Houston’s ground-level ozone.

The U.S. Environmental Protection Agency in 1997 classified Houston as a “severe” nonattainment area due to ozone levels measured over an eight-hour period. By 2008, the city was classified as a “moderate” nonattainment area.

For the study, researchers focused on data from four locations: Galveston, Clinton Drive near the Houston Ship Channel, Aldine and a site in Northwest Harris County. They also used data on background ozone levels collected from the roof of Moody Tower, a high-rise residence hall on the UH campus.

Background ozone levels have remained constant over the past seven years, they report, dropping just one part per billion. The average background level over that period was 30 parts per billion.

But the number of days in which ground-level ozone exceeded federal standards in one-hour and eight-hour measures dropped sharply at all four sites between 1990 and 2013. (Data for the Galveston site is available only back to 1997.)

In contrast, “the length of time per year Houston is under the influence of southerly flow has more than doubled from 1990 to 2013,” the researchers wrote. ” … We propose that the increased flow of ‘cleaner’ air is diluting the dirty Houston air, lowering the mixing ratios of NOX, O3 and precursor hydrocarbons. It also would advect the polluted air away from Houston,” leading to lower potential to produce ozone.

They compared land and sea temperatures over the 23-year period to determine how temperature differences impact southerly flow. Land temperatures increase faster than water temperatures on a daily time scale, Liu said. As the heated air over land rises, cooler air from the sea rushes in, dispersing both ozone and the chemical elements that contribute to ozone.

“We weren’t looking at it from a climate change perspective at first,” Talbot said. “Then once we saw it was the sea breeze, we knew it had to be climate.”

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41 thoughts on “A benefit of 'climate change' – reduced ozone pollutants in coastal cities

    • Its called ‘feedback’.
      The thing that makes AGW scary, and keeps the climate stable,but chaotic in the real world.

    • I wondered about the accuracy of this once I read
      “city-led effort to reduce nitrogen oxide emissions, one of the components of ozone.”
      No, sorry O3 has no nitrogen in the molecule at all. Nitrogen Oxide might be one of the components in the reaction that produces ozone, that is true, but a very different thing.
      The above inexcusable scientific illiteracy, akin to mixing up carbon ( an element) with carbon Dioxide ( a compound ) just irritates the heck out of me.

  1. Did they find a ‘connection’ as they claim or simply a correlation? What’s the r^2 value?

  2. Wouldn’t the enhanced seabreeze also contribute to an increased feed to any new or existing wind turbines, thereby lessening our dependence on fossil fuels? In other words, global warming would be contributing to global cooling.

  3. First they “ruled out [..] temperature” then they found that because of climate change “The sea breeze was enhanced greatly from 1990 to 2013 due to increasing land surface temperatures“.
    Did they check that the increased winds were caused by increased land surface temperature, and did they check whether global warming (“climate change”) had actually been operating during that period, or was there simply a latitudinal shift of weather patterns? By that I mean the highs and lows coming through at a different latitude, something which happens in my neck of the woods and brings soetimes drought, sometimes rain.
    (They do talk about how high land temperatures bring sea breezes, but they didn’t say the land temperatures had been increasing. Given that they ruled out temperature, it seems unlikely.)

  4. Color me skeptical of these findings. It seems “climate change” was latched onto as a convenient cause.

  5. Looks to me like the 1-hour Exceedance Days has gone into a “pause” since 2004, while the Southerly Flow Hours has continued to climb. I’m pretty sure that means to some folks this is proof of no correlation – and therefore that means this is not a benefit of climate change…

  6. No word about the rains falling in Los Angeles, they add another variable when trying to handicap a horse race.
    Might as well just throw a dart now.
    Luv the challenge tho.

  7. This is just a thought, but is the 23-year temperature increase they are talking about due to climate change/global warming, or is it due to the Urban Heat Island Effect?
    http://en.wikipedia.org/wiki/Houston
    Houston metro population increase by decade:
    1960 938,219 57.4%
    1970 1,232,802 31.4%
    1980 1,595,138 29.4%
    1990 1,630,553 2.2%
    2000 1,953,631 19.8%
    2010 2,100,263 7.5%
    Est. 2013[80] 2,195,914 4.6%
    If my math is right, the metro area of Houston saw a population increase of nearly 35% from 1990 to 2013.

  8. “Liu said they first ruled out other meteorological factors, including temperature, humidity and solar radiation. After they discovered the lower ozone readings coincided with days the southerly flow was strongest, they realized that climate change – in the form of warmer soil temperatures – had increased the southerly flow, she said.”
    I suppose Liu means that he ruled out air temperatures and found that soil temperatures were to blame for the increased sea breezes.
    How can warm soil cause convection to cause stronger sea breezes without first causing an air temperature increase?
    Anyway, every coastal sailor knows that warm land near the shore will bring in more sea breezes by the end of a sunny day.

  9. I love this stuff! I’m thinking hard on an angle to get in on the stash. Something that hasn’t occurred to anyone yet, has got to be caused by global warming. I just got to find it first. Yea baby!

  10. In Western Australia strong sea breeze cycles are usually associated with high ozone days in summer, so I am not sure why these researchers have come to this conclusion- maybe they should model it :-/

  11. Liu said they first ruled out other meteorological factors, including temperature, humidity and solar radiation. After they discovered the lower ozone readings coincided with days the southerly flow was strongest, they realized that climate change – in the form of warmer soil temperatures – had increased the southerly flow, she said.

    It seems climate change is making Texan marijuana more potent.

  12. “nitrogen oxide emissions- one of the components of ozone” This, in a supposed scientific presentation? Somebody please tell them that ozone is O3! Under some circumstances, nitrogen oxide emissions are precursors to O3. Ozone is easy to detect and is often used as a proxy for harmful NOX.

  13. In a story about the reduction in ground level ozone, it seems to me that there should be a discussion about federally mandated pollution controls that have been implemented to control ground level ozone. Certainly it effects the data and should have been included in the analysis.

    • I think that Tom’s point is important. There have been pollution control programs in play since the start of their analysis that were implemented to reduce ozone. I would like to see a plot of ozone concentration during southerly flow hours over time. If that was trending down then you would have to say that the pollution control programs were the driver for the decease.

  14. Firstly, the authors should have used urban-heat-island instead of climate change. Urban-heat-island creates more temperature gradient — land to sea. However, sea-breeze relates to several factors. For example, in India along the west coast sea-breeze moves from sea to land but on the east coast it is reverse — land to sea [land-breeze]. Also, hills along the coast change the sea and land breeze patterns.
    Dr. S. Jeevananda Reddy

  15. I thought the EPA said that CO2 emitting power plants caused ozone to go up. Gee, I haz confuse.

  16. Does this mean the pause is an imposter? How can the ozone variation be tied to climate change if the climate hasn’t changed in a generation? Is something we’re sure of wrong, again?

  17. Researcher; Look at these ozone readings. I bet you its caused by climate change. Try and correlate these with temperature.
    Assistant; nope not temeperature.
    Researcher; Still go to be climate change, what about correlation with humiditiy>
    Ass; nope nothing there either.
    Res: Still got to be climate change, check solar variation.
    Ass; Not, nothing there either.
    Res: OK, what about temperature wind direction>
    Ass; OF found something. That has a correlation.
    Res; See, I KNEW s was climate change. Even though temperature, humidity and solar have a been unchained, and so it is the new metric for climate change. I KNEW it was climate change, I just knew it.

  18. Friends
    The report says

    Liu said they first ruled out other meteorological factors, including temperature, humidity and solar radiation. After they discovered the lower ozone readings coincided with days the southerly flow was strongest, they realized that climate change – in the form of warmer soil temperatures – had increased the southerly flow, she said.

    Climate change or weather?
    It was not temperature, not humidity, not solar radiation, and not some not stated “other meteorological factors”. But Liu says it was “climate change – in the form of warmer soil temperatures”.
    The Texas Sharpshooter paints another target on his barn door after seeing which ‘shots’ hit where.
    The above claim that ‘it was climate change that dunnit’ is very similar to the first Example cited in the wicki explanation of the Texas Sharpshooter Fallacy which I have linked.
    Richard

  19. Ozone has a very distinct smell even at low concentrations. Based on my experience the smell is the strongest in nature right after thunder storms, which in turn tend to follow warm spells. Now I’m wondering why is there less ozone in the sea breeze? Would it be because the heat is hiding in the bottom of the oceans, beyond the reach of thunder storms?

      • Jaakko Kateenkorva
        As in most contentious climate issues, there is an unresolved cause&effect issue.
        You say

        Based on my experience the smell (of ozone) is the strongest in nature right after thunder storms, which in turn tend to follow warm spells.

        That may be true in Texas, I don’t know. But let us take that as being an empirical observation.
        Then
        are the electrical storms caused by the ionisation which creates the ozone
        or
        is the ozone caused by the lightening of the electrical storms?
        It cannot be known if there would be “Less storms then” until that issue is resolved.
        As to your original point that I answered n egatively; viz

        Now I’m wondering why is there less ozone in the sea breeze? Would it be because the heat is hiding in the bottom of the oceans, beyond the reach of thunder storms?

        Any heat “hiding in the bottom of the oceans” is not relevant to thunder storms. The atmosphere interacts with the ocean surface layer and not the ocean deeps.
        I apologise if my monosyllabic answer was inadequate, and I hope this explanatory answer is sufficient.
        Richard

      • are the electrical storms caused by the ionisation which creates the ozone
        or
        is the ozone caused by the lightening of the electrical storms?

        Perhaps they aren’t mutually exclusive. Doesn’t matter really, evidence is needed to demonstrate tropospheric ozone 1) anthropogenic and 2) persist in harmful concentrations.

  20. “The incident solar radiation at the top of the atmosphere
    varies on different time scales. Variations in the total solar
    irradiance (TSI), i.e. the spectrally integrated solar irradiance,
    over the 11-yr solar cycle are very small (with an amplitude
    of approximately 0.1 %). However, as noted above,
    variations in solar irradiance are spectrally dependent and increase
    considerably with decreasing wavelength in the ultraviolet
    (UV) part of the spectrum, reaching several percent
    lar heating associated with changes in TSI (blue) and in SSI
    (green) are shown. As seen from Fig. 1, taking into account
    variability in TSI only provides a reasonable solar heating
    signal in the troposphere, where absorption in visible and
    near-infrared regions dominates the heating rates, but significantly
    underestimates it in the middle atmosphere. In
    this case the signal is very small (less than 0.0012 K day−1
    from solar minimum to maximum at 8 km) and has a relatively
    weak variation with height. With variability in SSI included,
    the solar signal considerably increases with height as
    absorption at shorter wavelengths becomes more important.
    In this case, the shortwave heating rates between solar minimum
    and maximum vary by about 0.03, 0.3 and 1 K day−1
    at 32, 48 and 80 km levels, respectively.
    To calculate photolysis rates the CMAM chemistry
    scheme uses a look-up table, which uses solar zenith angle,
    partial ozone column and geometric height as parameters.
    Photo-dissociation rates are provided for 165 spectral
    intervals with a width ranging from 1 to 10 nm between 121
    and 852.5 nm. These spectral ranges and spectral resolution
    are quite sufficient for the purpose of solar variability studies.”
    http://www.atmos-chem-phys.net/11/5045/2011/acp-11-5045-2011.pdf

  21. The primary results of this study are as follows:
    The ion temperature in the upper atmosphere during the winter season of 2007–2009 is significantly lower than during earlier periods of low solar activity. This is consistent with multiple reports of a colder thermosphere during the recent solar minimum. The largest differences are observed during the daytime and reach ~100 K.
    A strong temperature variation with ~10–13 h period and ~50–90 K amplitude is found in the altitude range of 200–250 km and interpreted as an evidence of an enhanced semidiurnal tide that propagated to the upper thermosphere. This enhancement is observed during the first part of the campaign (18–24 January) and is likely to be associated with the sudden stratospheric warming.
    A weaker 20–50 K variation with a period of ~6.5–8 h is retrieved from the data below ~250 km altitude. This variation could result from the enhancement of the terdiurnal tide during sudden stratospheric warming.
    Ion temperature variations of different strength are found at multiple nontidal periods, with the largest variations reported for periods of 16–17 h, 30–40 h, 10–13 d, and 3–4 d. This variability appears to be driven by planetary waves with periods of 4 d, 5 d, and 10–13 d.
    The oscillations with a 3–4 d period and a 10–13 d period can result from upward propagation of planetary waves with these periods. The oscillation with 16–17 h period could result from the nonlinear interaction of the quasi 2 d wave with a semidiurnal tide.
    Analysis of data for one experimental campaign limits our ability to distinguish whether temperature oscillations with nontidal periods (16 h, 30–40 h, 3–4 d, and 10–13 d) are solely associated with sudden stratospheric warming or are part of the regular ionospheric variability.
    Multiple studies of ionospheric disturbances with planetary wave periods are focused on variations in electron density and interpret their findings using the E region dynamo mechanism, as planetary waves are not expected to propagate to F region altitudes. However, our observations of ion temperature variations with planetary wave periods (and periods resulting from interaction of planetary waves with tides) do not necessarily require a distinct E region dynamo driver. These results indicate that such waves can propagate up to ~250 km, at least in the case of deep solar minimum, and dissipate at altitudes above ~250 km. To the best of our knowledge, this is the first experimental evidence of direct (or indirect) propagation of planetary waves to the upper thermosphere.
    http://onlinelibrary.wiley.com/doi/10.1029/2012JA018251/full

  22. At first blush, this looks more like an Urban Heat Island effect than global climate change.

  23. “Atmospheric chemists have already studied the effects of cosmic ray ionization on CFCs, according to Sanche, but no one has looked at the effects of cosmic rays inside polar clouds. To simulate a dense, antarctic cloud, Sanche and Lu cooled a metal rod down to temperatures between 20 and 100 K and condensed water vapor and CFCs onto its surface. They then bombarded the condensate with low-energy electrons like those created by cosmic rays ionizing atoms in the atmosphere. The electrons reacted with the CFCs and made active chlorine, and the team determined the likelihood of this reaction by measuring the charge buildup on the end of the rod.
    The results suggest that electrons from cosmic rays are about a million times more likely to interact with CFCs inside polar clouds than anyone previously believed, says Sanche. Robert Compton of the University of Tennessee says that Sanche and Lu’s revised estimations could help atmospheric scientists and meteorologists to improve their models of ozone loss. Sanche says these observations may also change the way we understand the ozone hole. A rise in global temperatures could cause an increase in polar cloud cover that would lead to more cosmic-ray-induced CFC reactions, he says. “So here you would predict some link between global warming and [the ozone hole].”
    http://physics.aps.org/story/v8/st8

  24. “There are two ways in which the charged secondary particles are produced by cosmic rays. High-energy gamma rays can decay into pairs of electrons and positrons (anti-electrons); and cosmic rays can collide with atmospheric atoms and kick out electrons. Each of these charged products will create a radio-frequency pulse as it moves in the geomagnetic field. In general, the radio waves are polarized in a direction that depends on the relative orientation of the particles’ motion and the magnetic field.”
    http://physics.aps.org/articles/v8/37

  25. If all the ozone in this column were to be compressed to standard temperature and pressure (STP) (0 deg C and 1 atmosphere pressure) and spread out evenly over the area, it would form a slab approximately 3mm thick.
    1 Dobson Unit (DU) is defined to be 0.01 mm thickness at STP.
    The total ozone maps for the northern hemisphere are based on near-real time NASA Earth Probe Total Ozone Mapping Spectrometer (TOMS) gridded satellite data available from the NASA TOMS home page, NOAA SMOBA (Stratosphere Monitoring Ozone Blended Analysis) data (if TOMS data are not available) and on ground-based measurements. Ground-based data are provided by Environment Canada, by the Russian Central Aerological Observatory, and by other agencies. Over the polar night area Dobson and Brewer moon observations and/or NOAA’s TIROS Operational Vertical Sounder (TOVS) satellite data are used. TOVS data are also used when the more reliable TOMS data are not available. To see ozone maps from the individual data sources (TOMS, SMOBA, TOVS and ground-based) click here. The mapping algorithm is similar to those used by the WMO Ozone Mapping Centre . Total ozone values are given in Dobson Units.
    http://exp-studies.tor.ec.gc.ca/ozone/images/graphs/gl/current.gif
    http://exp-studies.tor.ec.gc.ca/e/ozone/Curr_allmap_g.htm

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