# Presentation: 135720

## Tropospheric ozone response to methane emission controls:

**Tropospheric ozone response to methane emission controls:**
**Implications for climate and global air quality**

- IGERT Joint Program Colloquium, Columbia University
- April 5, 2007

**Arlene M. Fiore**
**(arlene.fiore@noaa.gov)**

**Acknowledgments: **
**Larry Horowitz, Chip Levy (NOAA/GFDL)**
**Jason West, Vaishali Naik (Princeton University)**
**Ellen Baum, Joe Chaisson (Clean Air Task Force)**
**Frank Dentener, Kees Cuvelier (JRC, Italy) **
**The TF HTAP Modeling Team **
**Funding from Luce Foundation via Clean Air Task Force**

## Nonattainment Areas (2001-2003 data)

***U.S. EPA*****, 2006**

**Nonattainment Areas (2001-2003 data)**

**4****th**** highest daily max **
**8-hr mean O****3**** ****>**** 84 ppbv**

**The U.S. ozone smog problem is spatially widespread, ****affecting >100 million people**

## Radiative forcing of climate (1750 to present):Important contributions from methane and ozone

**IPCC,***** 2007***

## O3

**NO****x**
**VOC**

**NO****x**
**VOC**

**CONTINENT 2 **

**OCEAN**

**O****3**

**Boundary layer**
**     ****(0-3 km)**

**Free Troposphere**

**CONTINENT 1 **

**OH**

**HO****2**

**VOC, CH****4****, CO**

**NO**

**NO****2**

**h******

**O****3**

**O****3**

**Hemispheric Pollution**

**Direct Intercontinental Transport**

**air pollution (smog)**

**air pollution (smog)**

**    **

**Stratospheric O****3**

**Stratosphere**

**~12 km**

**Air quality-Climate Linkage:****CH****4****, O****3**** are greenhouse gases****CH****4**** contributes to background O****3**** ****in surface air**

- A.M. Fiore

## IPCC [2001] scenarios project future growth 

**Change in 10-model mean **
**surface O****3**

**Attributed mainly to increases in methane and NO****x**** **
**[*****Prather et al*****., 2003]**

**IPCC [2001] scenarios project future growth**** **

**2100 SRES A2 - 2000**

**Projections of future CH****4**** emissions **
**(Tg CH****4****) to 2100**

## Rising background O3 has implications 

**Rising background O****3**** has implications **
**for attaining air quality standards**

**20**

**40**

**60**

**80**

**100**

**O****3**** (ppbv)**

**U.S. 8-hr **
**average**

**Recent observational analyses suggest that surface O****3**** background is rising**
**[e.g. *****Lin et al*****., 2000; *****Jaffe et al*****., 2003, 2005; **
***Vingarzan*****, 2004; *****EMEP/CCC-Report 1/2005 *****]**

**Europe**
**seasonal**

**WHO/Europe**
**8-hr average**

- A.M. Fiore

##  50% 

**50% **
**anth.**
** ****NO****x**

**2030 **
** ****A1**

** ****50% **
**anth.**
** ****CH****4**

**50% **
**anth.**
**VOC**

**2030 **
** ****B1**

| IPCC scenario | Anthrop. NOx emissions
  (2030 vs. present)
   Global              U.S. |  | Methane emissions
(2030 vs. present) |
| --- | --- | --- | --- |
| A1 | +80% | -20% | +30% |
| B1 | -5% | -50% | +12% |

**Radiative Forcing* (W m****-2****)**

**CH****4**** links air quality **
**& climate via **
**background O****3**

*Fiore et al., GRL, 2002*

**Double dividend of Methane Controls:**
**  ****Decreased greenhouse warming and improved air quality**

**GEOS-Chem Model (4°x5°)**

## Impacts of O3 precursor reductions on 

**Impacts of O****3 ****precursor reductions on **
**U.S. summer afternoon surface O****3**** frequency distributions**

*Fiore et al., 2002; West & Fiore, ES&T, 2005*

**GEOS-Chem Model Simulations (4°x5°)**

**Results add linearly when both methane and NO****x**** are reduced**

**CH****4**** controls**
**affect the entire**
**O****3**** distribution**
**similarly**
**(background)**

**NO****x**** controls**
**strongly decrease**
**the highest O****3**
**(regional pollution**
**episodes)**

## Methane trends and linkages with chemistry, climate, and ozone pollution

**Methane trends and linkages with ****chemistry, climate, and ozone pollution**

**1) Climate and air quality benefits from CH****4**** controls**
** ****Characterize the ozone response to CH****4 ****control**
** ****Incorporate methane controls into a future emission scenario**
**2) Recent methane trends (1990 to 2004)**
** ****Are emission inventories consistent with observed CH****4**** trends?**
** ****Role of changing sources vs. sinks?**

## More than half of global methane emissions 

**More than half of global methane emissions **
**are influenced by human activities**
- ~300 Tg CH4 yr-1 Anthropogenic [EDGAR 3.2 Fast-Track 2000; *Olivier et al*., 2005]
- ~200 Tg CH4 yr-1 Biogenic sources [*Wang et al*., 2004]
- >25% uncertainty in total emissions

**ANIMALS**
**90**

**LANDFILLS +**
**WASTEWATER**
**50**

**GAS + OIL**
**60**

**COAL**
**30**

**RICE 40**

**TERMITES**
**20**

**WETLANDS**
**180**

**BIOMASS BURNING + BIOFUEL    **
**            ****30**

**GLOBAL METHANE**
**SOURCES **
**(Tg CH****4**** yr****-1****) **

- A.M. Fiore

## Characterizing the methane-ozone relationship with idealized model simulations

**Model approaches a new steady-state**** ****after 30 years of simulation**

**Is the O****3**** response sensitive to the location of CH****4**** emission controls?**

**Simulation Year**

**Reduce global anthropogenic CH****4**** emissions by 30%**

- A.M. Fiore

## Change in July surface O3 from 30% decrease in anthropogenic CH4 emissions 

**Globally uniform emission reduction**

**Emission reduction in Asia**

- A.M. Fiore

## Decrease in summertime U.S. surface ozone  from 30% reductions in anthrop. CH4 emissions

**MAXIMUM DIFFERENCE **
**(Composite max daily afternoon mean ozone JJA) **

**NO ASIAN ANTH. CH****4**

****** ****Largest decreases in NO****x****-saturated regions**

- A.M. Fiore

## Tropospheric O3 responds approximately linearly to anthropogenic CH4 emission changes across models

**Tropospheric O****3**** responds approximately linearly to anthropogenic CH****4**** emission changes across models**

**Anthropogenic CH****4**** contributes ~50 Tg (~15%) to tropospheric O****3**** burden**
**	****	****	****            ****~5 ppbv to global surface O****3**

- A.M. Fiore

## Multi-model study shows similar surface ozone decreases over NH continents when global methane is reduced

**Full range of **
**12 individual **
**models**

** ****>1 ppbv O****3**** decrease over all NH receptor regions**
** ****Consistent with prior studies**

**TF HTAP 2007 Interim report draft available at www.htap.org**

**EUROPE**

**N. AMER.**

**S. ASIA**

**E. ASIA**

- A.M. Fiore

## How much methane can be reduced?

**How much methane can be reduced?**

- Comparison: Clean Air Interstate Rule (proposed NOx control) reduces 0.86 ppb over the eastern US, at $0.88 billion yr-1

*West & Fiore, ES&T, 2005*

** ****IEA [2003] for 5 industrial sectors**

**10% of anth. **
**emissions**

**20% of anth. **
**emissions**

**0****	****20****	****40****	****60****	****80****	****100****	****120**
** ****Methane reduction potential (Mton CH****4**** yr****-1****)**

**(industrialized nations)**

## Will methane emissions increase in the future? 

**Will methane emissions increase in the future? **

- PHOTOCOMP for IPCC AR-4  used CLE, MFR, A2 scenarios for all O3 precursors
**[Dentener et al., 2006ab; Stevenson et al., 2006; van Noije et al., 2006; Shindell et al., 2006] **

**Anthropogenic CH****4**** emissions (Tg yr****-1****)**

**Current**
**Legislation**
**(CLE)**
**Scenario**

**Our approach: use CLE as a baseline scenario & apply methane controls**

*Dentener et al., ACP, 2005*

**A2**

**B2**

**MFR**

## Emission Trajectories in Future Scenarios  (2005 to 2030)

**Anthropogenic CH****4**** **
**Emissions (Tg yr****-1****)**

**Control scenarios reduce 2030 CH****4**** emissions relative to CLE by:**
**A)****  ****-75 Tg   (18%) – cost-effective now**
** ****-125 Tg (29%) – possible with current technologies**
** ****-180 Tg (42%) – requires new technologies**
**Additional 2030 simulation where CH****4**** = 700 ppbv (“zero-out anthrop. CH****4****”)**

**A**

**B**

**C**

**CLE Baseline**

- A.M. Fiore

## OZONE

**OZONE**
**METHANE**

- +0.16 Net Forcing

- +0.08

- 0.00

- -0.08

**Reducing tropospheric ozone via methane controls decreases ****radiative forcing  (2030-2005)**

- -0.58

**CH****4****=700 ppb**

- (W m-2)

- Methane Control Scenario

****** ****More aggressive CH****4 ****control scenarios offset baseline CLE forcing**

- A.M. Fiore

## Future air quality improvements from CH4 emission controls

**Percentage of model grid-cell days where surface ozone > 70 ppbv**

**Europe**

**2030 European high-O****3**** events under CLE emissions scenario**
**show stronger sensitivity to CH****4 ****than in USA**

- A.M. Fiore

## Summary: Connecting climate and air quality via O3 & CH4

**CLIMATE AND AIR QUALITY BENEFITS FROM CH****4 ****CONTROL**
** ****Independent of reduction location (but depends on NO****x****)**
**Target cheapest controls worldwide**
** ****Robust response over NH continents across models**
**~1 ppbv surface O****3**** for a 20% decrease in anthrop. CH****4**
** ****Complementary to NO****x****, NMVOC controls**
** ****Decreases hemispheric background O****3**** **
****** ****Opportunity for international air quality management**** **

**How well do we understand recent trends in atmospheric methane?**
**How will future changes in emissions interact with a changing climate?**

- A.M. Fiore

## Observed trend in surface CH4 (ppb) 1990-2004

- Data from 42 GMD stations with 8-yr minimum record is area-weighted, after averaging in bands
- 60-90N, 30-60N, 0-30N, 0-30S, 30-90S

**NOAA GMD Network**

**Global Mean CH****4**** (ppb)**

**Hypotheses for leveling off**
**discussed in the literature:**
**1. Approach to steady-state**
** **
**2. Source Changes   **
**       ****Anthropogenic**
**Wetlands/plants**
**(Biomass burning)**
**3. (Transport)**
**4. Sink (CH****4****+OH)**
**         ****Humidity**
**         ****Temperature**
**         ****OH precursor emissions**
**         ****overhead O****3**** columns**

**Can the model capture the observed trend (and be used for attribution)?**

- A.M. Fiore

## Bias and correlation vs. observed surface CH4: 1990-2004

**Bias and correlation vs. observed surface CH****4****: 1990-2004**

**Global Mean Surface Methane (ppb)**

**OBSERVED**
**MOZART-2**

**Captures flattening post-**
**1998 but underestimates **
**abundance**

**Overestimates 1990-1997 **
**but matches trend**

**BASE ****simulation **
**EDGAR 2.0 emissions held constant**

- A.M. Fiore

## Estimates for changing methane sources in the 1990s

**547**

**Tg CH****4**** yr****-1**

**EDGAR anthropogenic inventory**

- Biogenic adjusted to maintain
- constant total source

**BASE**

- A.M. Fiore

## Bias & Correlation vs. GMD CH4 observations: 1990-2004

**Mean Bias (ppb)**

**ANTH+BIO**** ****simulation with**** time-varying EDGAR 3.2 ****+ wetland emissions ****improves:**
****** ****Global mean surface conc.**
****** ****Interhemispheric gradient **
** ****Correlation at high N latitudes**

**OBS**
**BASE**
**ANTH**
**ANTH+BIO**

**r****2**

*Fiore et al., GRL, 2006*

**S ****	****Latitude****	**** ****	****N**

**Bias & Correlation vs. GMD CH4 observations: 1990-2004**

**Global Mean Surface Methane (ppb)**

## How does meteorology influence methane abundances? 

**Why does ****BASE ****run with constant emissions level off post-1998?**
****** ****Examine sink**

- A.M. Fiore

## Small increases in temperature and OH  shorten the methane lifetime against tropospheric OH 

**Deconstruct ********(-0.17 years) from 1991-1995 to 2000-2004 into individual contributions by varying OH and temperature separately**

******OH**

- A.M. Fiore

## Additional evidence for a global lightning NOx increase?

**  ****NCEP(nudged)**

**Lightning NO****x**** % change (91-95 to 00-04)**

**Estimate lightning NO****x**** changes using options available in the GFDL Atmospheric General Circulation Model:**
** ****Convection schemes (RAS vs. Donner-deep)  **
** ****Meteorology (free-running vs. nudged to NCEP reanalysis)**

***c/o L.W. Horowitz***

**More physically-based lightning **
**   ****NO****x**** scheme **[Petersen et al., 2005]
**Evidence from observations?**

- A.M. Fiore

## Summary: Connecting climate and air quality via O3 & CH4

**CLIMATE AND AIR QUALITY BENEFITS FROM CH****4 ****CONTROL**
** ****Independent of reduction location (but depends on NO****x****)**
**Target cheapest controls worldwide**
** ****Robust response over NH continents across models**
**~1 ppbv surface O****3**** for a 20% decrease in anthrop. CH****4**
** ****Complementary to NO****x****, NMVOC controls**
** ****Decreases hemispheric background O****3**** **
****** ****Opportunity for international air quality management**** **

- A.M. Fiore