# CA

TF Comments on Ozone NAAQS Revision, and Related International and Climate Matters Corrected Ve rsion September 15, 2010

# Key points

• Ti ght new ozone standards are necessary to protect health and the environment but CA TF recognizes they will provide a significant compliance challenge for the states. • There are multiple levers we can pull to drive ozone down:

– Reducing international ozone precursors will drive down significant anthropogenic (15 ppb) global ozone background.

– Methane reductions in the US and globally can provide a portion of those background reductions. • Reducing ozone and methane will also combat global warming and provide nearterm cooling in at - risk areas like the Arctic. • The US is already making a significant commitment to drive down global methane (hence ozone and global warming) via its Global Methane Initiative and this should be pointed out to stakeholders. • Additional actions CA TF recommends to enhance likelihood of lower cost US compliance:

– Highlight methane ozone impacts and options in the final ozone NAAQS preamble, and in future compliance strategy documents.

– Ta ke up climate co -benefits of ozone and ozone precursor reduction in future ozone NAAQS.

– Support consideration of ozone for inclusion in the LRTA P protocol revision.

– Support of Global Methane Facility to enhance global methane reductions. 2

# Global background ozone is a significant portion of total, and has been increasing Afternoon ozone averages in US quadrants: Sources Long - term trends at remote sites worldwide

Source: Oltmans, 2006 Source: Fiore 2003 (used in 2007 NAAQS Criteria Documents) Mod el , Po li cy Re le vant

B ackgr ound Mod el , nat ur

ale mi ss io ns onl y Mod el , stra tosphe ri c ozon e onl y Ru ral(C AS TNE T)o bservati ons Mo del , al l em ission s, CA ST NET s it es Mo del , al l em ission s, wh ol e quad ra nt 3

## Methane is a significant component of both anthropogenic global background and regional Midwest - Northeast US ozone (as much as 7 ppb)

Difference in Daily Maximum 8-hour Av erage Ozone between base case (1.85 ppm methane) and pre anthropogenic methane (0.70 ppm methane) case for July 13, 2002. 4 

### Above: change in global ozone levels (ppb) from 31% decrease in global anthropogenic CH 4 

### emissions (Fiore, et. al. JGR, 2008)

# The importance of methane - derived background ozone increases as standards tighten

50% 60% 70% 80% 90% 100%Estimated Contribution Oz one from O ther A nthropogenic

Oz one from n on - CH4 Bac kground Oz one From C H4 Oxidation



### Difference between base case (1.85 ppm) and pre anthropogenic (0.70 ppm) case methane for July W126 O3 Concentrations (ppm -hours). Contribution of methane to ozone increased from 4% of the 1 -hour standard to 6% under the 1997 8-hr . standard, and would be 8% under a revised 8-hr . standard. 0% 10% 20% 30% 40%

1 - Hr. Std (125) 8 - Hr. St d (85) 8 - Hr. St d (60) W126 (7) W126 (15)Estimated Contribution

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# Global health benefits of ozone reduction via methane

Annual avoided mortalities in the northern hemisphere due to 20% reduction in methane = 14,100 to 40,100 Sources: West West & Fiore, ES&T

, 2005; Anenberg et al., ES&T

, 2009 6Integrated Radiative Forcing for

year 2000 Global Emissions: 20 - year and 100 - year weighting (gas - phase only)yr time horizon 

## Ozone and methane are significant components of global climate change, and short term Arctic war ming; methane and ozone reductions wi ll cool much faster than CO 2 

## reductions100-yr time horizon20-yr time horizon



### From IPCC 2007 7

# Another w ay to look at it: methane climate forcing from multiple pathw ays

Source: Shindell et al., Science, 2009 8

# In the current NAAQS reconsideration, EP A should:

• Call out methane role more clearly • Include specific methane reduction strategies for states to consider • [In messaging, note Administration work in related international forums (CLRTA P, GMI, GMF) on both ozone and methane to support states.]

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# In future NAAQS revisions:

• EP A should consider ozone climate ef fects in setting standard

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# Opportunities to increase international focus on ozone and methane

• Include ozone in LRTA P Gothenburg Protocol revision (this could enhance international support for Global Methane Initiative) • Global Methane Initiative • Global Methane Fund

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# Additional

material

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# Low er tropospheric ozone = lives saved 

# Methane reductions of 65 Mt/yr beginning in 2010 would prevent 370,000 premature deaths over the next 20 years Chart shows avoided premature mortalities in 2030 by wo rld region and avoided mortalities per million people in 2030, resulting from decreases in surface O3 due to a global CH4 emission 

## reduction of 65 Mt/yr West,et.al, PNAS, 2006 13

# Elevated tropospheric ozone results in crop losses

• Ozone is well documented as the air pollutant most damaging to agricultural crops and other plants. Most crops are grown in summer when ozone concentrations are frequently sufficiently elevated to reduce yields.
• East Asia, a region that produces over

Asia, a region produces 20% of the world’s grain , could see major reductions in agricultural yields due to projected increases in surface ozone concentrations.
• Yi elds could be substantially increased through reduction of surface O 3 concentrations

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# Double dividend of Methane Controls: Decreased greenhouse w arming and improved air quality Methane Ozone To tal W/m2 IIASA - (current legislation) 0.099 0.065 0.164 As methane decreases, ozone and methane Adjusted Radiative Forcing (W/m 2 

### ) in 2030 V

ersus 2005 Due to Changes in T

ropospheric CH4 and O3


## legislation)

- 75 Tg (18% ) 0.033 0.048 0.081

- 125 Tg (29% ) - 0.029 0.032 0.003

- 180 Tg (42% ) - 0.097 0.014 - 0.083
Fiore,et.al, JGR, 2008 

## methane forcing decrease

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