Ozone pollution improving in the U.S.

By: Dr. Jeff Masters , 7:03 PM GMT on May 01, 2007

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Air pollution season is here, and the good news is that ozone pollution in 2006 was considerably better than in previous years. Along with pollution due to small particles (particulate matter), ground-level ozone is the most serious pollutant in the U.S. Ozone levels in 2006 showed improvement in 23 out of 35 of the major cities in the U.S. (Figure 1) compared to 2005, and was at or below the 10-year average in all but five cities. Atlanta, Georgia, showed the greatest jump in the number of unhealthy days, from 17 in 2005 to 30 days in 2006; however, this number was still below the 10-year average. Many western cities reached levels at or above the 10-year average, including San Diego, Sacramento, Denver, and Las Vegas. This was in part due to much above average summertime temperatures in the western U.S. (Figure 2). Los Angeles had the worst ozone pollution in the U.S., with 46 unhealthy days. Los Angeles also was the most polluted city overall in 2006, according to the American Lung Association. However, Los Angeles' bad ozone days declined by 16% in 2006 compared to 2005.


Figure 1. The number of days in May through September of 2005 and 2006 in which ground-level ozone reached Unhealthy for Sensitive Groups--an Air Quality Index (AQI) above 100. Corresponding 10-year averages are also shown. Image credit: EPA.

Ozone pollution has improved
Is the improvement seen in ozone levels in 2006 merely due to a lack of meteorological conditions that favor air pollution? To check, I've plotted the difference in surface temperature (degrees C) from May-September 2006, compared to the 10-year average from 1995-2005 (Figure 2). The chemical reactions that form ozone are most efficient at high temperatures, so if the summer of 2006 was cooler than usual, we'd expect a drop in ozone levels. However, the summer of 2006 was the second warmest in U.S. history--but ozone levels still dropped. All of the cities where ozone increased significantly in 2006 over 2005 levels were areas where temperatures were above average. Los Angeles had summer temperatures more than 1 degree C above normal, yet still recorded a drop in ozone, suggesting that strategies to control ozone pollution there are paying dividends. In fact, new rules to limit nitrogen oxide emissions from power plants have been enacted nation-wide in the past few years, and the ozone pollution statistics from 2006 are evidence that these emissions rules are working. Ozone pollution since 1980 has dropped 21% (Figure 3), despite the fact that the average summer temperatures have generally been increasing.


Figure 2. The difference in surface temperature (degrees C) from May-September 2006, compared to the 10-year average from 1995-2005. Temperatures were above the 10-year average across most of the country, except for New Mexico, and portions of the Ohio Valley surrounding Kentucky. Image credit: NCAR/NCEP.


Figure 3. Trends in ozone air pollution in the U.S. (white line) and uncertainty (blue areas, marking the standard deviation). The federal standard of 0.08 ppm is indicated by the dashed line. Since 1980, maximum ozone levels have declined 21%. Since 1990, the decline has been 9%. Note that the lowest ozone levels were recorded in 2004, which was an exceptionally cool summer across most of the U.S. Image credit: U.S. EPA.

Next blog (Thursday): Pollution costs and deaths exceed the impact of a new Hurricane Katrina hitting the U.S. each year.

Jeff Masters

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538. Bamatracker
3:40 AM GMT on May 03, 2007
so what would you call someone who predicts major big storms that never hit land while using only nhc info as the bases of their prediction?
Member Since: May 17, 2006 Posts: 6 Comments: 1367
537. hornfan
3:42 AM GMT on May 03, 2007
i wasn't here for Katrina but I guarantee you it was "wishcaster this" "wishcaster that" 24/7 during that time

Everything makes sense now.
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536. hornfan
3:41 AM GMT on May 03, 2007
nope, because once you do one of the listed above you are then labeled in one of the categories, no such thing as forecasters


Hmm - does that mean that everyone on the blog is listed in the three categories or only the ones which actually attempt to forecast?
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535. StoryOfTheCane
3:41 AM GMT on May 03, 2007
if its like a storm in 75 degree water, 60 knots of shear and high SAL and you are "wishcasting" you are then put into a 4th category, "crazycaster"
534. StoryOfTheCane
3:38 AM GMT on May 03, 2007
so anyone who tries to take an early approach at predicting a storm's formation before the NHC does is automatically considered a "wishcaster", we're just going to have to deal with it
533. Levi32
7:38 PM AKDT on May 02, 2007
Lol....interesting.
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532. StoryOfTheCane
3:37 AM GMT on May 03, 2007
if you dont do any of the above you are just here for the beer (lurker)
531. StoryOfTheCane
3:36 AM GMT on May 03, 2007
lol actually the forecaster would have to only be the NHC, which is the same as the "noncaster" because they simply relay the NHC's information
530. Levi32
7:35 PM AKDT on May 02, 2007
LOL, sounds like there's no room for the right stuff. What if someone doesn't do anything listed above? I mean cmon lol.
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529. StoryOfTheCane
3:35 AM GMT on May 03, 2007
i wasn't here for Katrina but I guarantee you it was "wishcaster this" "wishcaster that" 24/7 during that time
528. StoryOfTheCane
3:34 AM GMT on May 03, 2007
lol but those wishing for the best (hatecasters) are usually the ones getting outraged at the wishcasters
527. StoryOfTheCane
3:33 AM GMT on May 03, 2007
lol nope I moved out of Florida in March.
526. StoryOfTheCane
3:32 AM GMT on May 03, 2007
nope, because once you do one of the listed above you are then labeled in one of the categories, no such thing as forecasters
525. Inyo
3:30 AM GMT on May 03, 2007
Posted By: StoryOfTheCane at 3:18 AM GMT on May 03, 2007.
hey as long as I got food in my stomach and a roof over my head i could care less about polar ice caps, no sense in dwelling over something we can do absolutely nothing about. Only way to stop it is by eliminating half the world's population, until then I bid you all ado


Don't you live in Florida? If the ice caps melted, the OCEAN would be over your head, to say nothing of the roof.
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524. hornfan
3:31 AM GMT on May 03, 2007
Hatecasters - Those that don't think any storm will ever form or hit land, ever.

Well - I am not sure that you would call them hatecasters - just wishing for the best. lol
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523. Levi32
7:31 PM AKDT on May 02, 2007
You forgot one type of people SOTC lol. Forecasters. There are some of us who actually try to do the job right.
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521. StoryOfTheCane
3:30 AM GMT on May 03, 2007
yeah moonlight just came up with that one, not real sure what he means by it but i guess we'll have to wait and see
520. StoryOfTheCane
3:29 AM GMT on May 03, 2007
just so you all know Ive come to the conclusion that there are 3 types of people on this blog:

Wishcasters - Those that want to see large storms.

Noncasters - Those that base all of their decisions from the NHC and don't make predictions. (Playing it safe)

Hatecasters - Those that don't think any storm will ever form or hit land, ever.
519. hornfan
3:26 AM GMT on May 03, 2007
I have never hear the "smelling" issue - but I hear alot of "I am feeling something in the air." lol
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518. StoryOfTheCane
3:24 AM GMT on May 03, 2007
im smelling 19 storms, 13 hurricanes, 7 majors and 7 landfalls this year, hows everybody else's sensory insticts holding up?
517. StoryOfTheCane
3:17 AM GMT on May 03, 2007
hey as long as I got food in my stomach and a roof over my head i could care less about polar ice caps, no sense in dwelling over something we can do absolutely nothing about. Only way to stop it is by eliminating half the world's population, until then I bid you all ado
516. StoryOfTheCane
3:13 AM GMT on May 03, 2007
gonna leave me wondering are we? well I wont do you the pleasure, i no longer wonder
515. franck
3:09 AM GMT on May 03, 2007
Yep..at the present pyramidal rate of corporate expansion coupled with the demand created by exploding populations elsewhere on the planet, all north polar ice should be gone within ten years, and half or so in the south.
Member Since: August 30, 2005 Posts: 0 Comments: 1150
514. moonlightcowboy
3:11 AM GMT on May 03, 2007
...love the Freebird crew...but, I'm outta here tonight...keep the fire burning......this season will have much more into it thankfully....more participants...new tech..and all that....it'll be interesting.

Later on. Nite all.
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513. StoryOfTheCane
3:12 AM GMT on May 03, 2007
you cant say something that random and then not explain where it came from, whatd you mean? good to see you too.
512. StoryOfTheCane
3:11 AM GMT on May 03, 2007
ewww that smell, cant ya smell that smell
511. moonlightcowboy
3:09 AM GMT on May 03, 2007
....no biggie Story. Good to see you on.

As far as MHO can tell, this one will be different from 06...some more serious.
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510. StoryOfTheCane
3:07 AM GMT on May 03, 2007
the smell? we listening to Lynyrd Skynyrd? what do you mean by "the smell"?
509. lilmax
2:59 AM GMT on May 03, 2007
We need to start building an ark.
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508. moonlightcowboy
3:05 AM GMT on May 03, 2007
...yo, STORY!!! Any thoughts on the "smell?" lol
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507. KEEPEROFTHEGATE (Mod)
2:55 AM GMT on May 03, 2007
as for the melting ice american reseachers have confirmed that artic ice is melting three times faster then previously predicted
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506. pottery
11:03 PM AST on May 02, 2007
I'm out too. Got to get some sleep before that Wave gets here. heheheh
Member Since: October 24, 2005 Posts: 0 Comments: 23080
505. StoryOfTheCane
3:04 AM GMT on May 03, 2007
lol thats cute
504. moonlightcowboy
2:57 AM GMT on May 03, 2007
SJ...you are one of the best on here as far as knowledge! I respect that! Sure would like to know your thoughts!
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503. moonlightcowboy
2:56 AM GMT on May 03, 2007
...later kman...Good night, we'll catch up soon!
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502. StoryOfTheCane
2:57 AM GMT on May 03, 2007
the dry air is definitely dissipating all over the Atlantic
501. StoryOfTheCane
2:56 AM GMT on May 03, 2007
500. StormJunkie
2:54 AM GMT on May 03, 2007
After the '05 and '06 season I refuse to answer that moonlight ☺

Basically I am clueless

Night y'all
Member Since: August 17, 2005 Posts: 26 Comments: 15472
499. lilmax
1:57 AM GMT on May 03, 2007
I know that everyone is all excited about this wave. Doesn't anyone else see that there's a slightly deeper low behind this wave???
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498. pottery
10:54 PM AST on May 02, 2007
Later, Kman.
Member Since: October 24, 2005 Posts: 0 Comments: 23080
497. pottery
10:52 PM AST on May 02, 2007
....and the wind has picked up over the last 2 weeks too. The fire dont stop till it reaches the coast !
Member Since: October 24, 2005 Posts: 0 Comments: 23080
496. kmanislander
2:52 AM GMT on May 03, 2007
anyway I am out of here for tonight
great seeing you all
catch you tomorrow
Member Since: August 19, 2006 Posts: 0 Comments: 15671
495. Tazmanian
7:49 PM PDT on May 02, 2007
talking about the N pole the icy there could be gone by the year 2020
Member Since: May 21, 2006 Posts: 5089 Comments: 114060
494. kmanislander
2:48 AM GMT on May 03, 2007
Now that you say that I remember all the cane fires that people set. This is not the time of year to be lighting fires !

I doubt we have had even an inch of rain since last Dec
Member Since: August 19, 2006 Posts: 0 Comments: 15671
493. moonlightcowboy
2:50 AM GMT on May 03, 2007
Hey, SJ! What's going to happen this season?
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491. pottery
10:43 PM AST on May 02, 2007
Kman, the fires are wild allright, but they are set by people. " Its jus' bush, maaaan." All over the dam place. Mostly set by guys clearing land to plant in June !
Member Since: October 24, 2005 Posts: 0 Comments: 23080
490. kmanislander
2:42 AM GMT on May 03, 2007
good night SJ
Member Since: August 19, 2006 Posts: 0 Comments: 15671
489. StormJunkie
2:39 AM GMT on May 03, 2007
CB, your tunnels are going to heat the poles...And go easy with that talk..lol ☺

Good to see you kman and pottery.

See y'all later
Member Since: August 17, 2005 Posts: 26 Comments: 15472
488. kmanislander
2:37 AM GMT on May 03, 2007


Here is one of those planes that crash landed some time ago
Member Since: August 19, 2006 Posts: 0 Comments: 15671

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About JeffMasters

Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.