Transcript PM 2.5 and O 3 concentration changes in 2100

Effect of changes in emissions and climate change on global air quality:
A study of the air quality co-benefits of GHGs mitigation
Yuqiang Zhang1, J. Jason West1, Meridith M. Fry1, Raquel A. Silva1, Steven J. Smith2, Vaishali Naik4,
1
3
4
5
5
Zachariah Adelman , Susan C. Anenberg , Larry W. Horowitz , Jean-Francois Lamarque , Louisa Emmons
1
834285
Environmental Sciences and Engineering, Univ. of North Carolina, Chapel Hill. 2 Joint Global Change Research Institute. 3 US Environmental Protection Agency.
4 NOAA Geophysical Fluid Dynamics Laboratory. 5 National Center for Atmospheric Research.
1. Introduction
4. Analysis
3. Preliminary Results
Actions to reduce emissions of greenhouse gases (GHGs) will benefit global
and regional air quality through two mechanisms in the future: 1) directly
through reductions in emissions of co-emitted air pollutants (short-term and
local), and 2) indirectly by slowing the influence of climate change on air
pollution (long-term and global). While a large literature discusses the
impacts of climate change on air quality, through meteorological changes,
biogenic emissions, and other factors, we focus on the co-benefits of GHG
mitigation on air quality.
Here we aim to quantify the global air quality benefits of GHG mitigation
through these two mechanisms, in realistic future scenarios to 2100. We use
the global chemical transport model MOZART-4 to simulate changes in
ozone and fine particular matter (PM2.5) due to changes in co-emitted air
pollutants and climate due to the GHG mitigation. We present results for the
changes in global air quality due to GHG mitigation in 2030, 2050, and
2100.
Emissions
Problems
Global and regional Air Quality
OC (Tg C/yr)
PM2.5 concentration (population-weighted annual average)
Global
East Asia
India
North America
Global
Global and regional anthropogenic emissions
North America
India
East Asia
North America
India
East Asia
India
East Asia
SO2 (Tg SO2/yr)
O3 concentration (population-weighted 6-month of average of 1-hr daily maximum)
Global
East Asia
India
North America
Global
a
b
c
Air
pollutants
1
Air
pollution
NO (Tg NO/yr)
Sources &
Policies
a: Total co-benefit; b: Emission co-benefit; c: Meteorology co-benefit
GHGs
2
Climate
Change
Connections between air quality and climate change,
showing two mechanisms of co-benefits of GHG mitigation
on air quality: #1 is immediate and local, #2 is long-term
and global.
 Over the long term, the global PM2.5 and O3 both decrease for all scenarios, reflecting the assumptions in the RCPs of a
cleaner world as economic well-being increases.
 The air quality co-benefits of GHG mitigation are large—2.37 ug/m3 for PM2.5 and 8.11 ppb for O3, for the global
population-weighted concentrations in 2100.
Total Co-benefit
North America
.
PM2.5 and O3 concentration changes in 2100
#2 Meteorology Co-benefit
#1 Emissions Co-benefit
s
2. Methodology
•
We use scenarios from the GCAM global energy economics model,
developed as Representative Concentration Pathway Scenarios (RCPs) for the
IPCC 5th Assessment report– a Reference Case and RCP4.5.
• In GCAM, RCP4.5 differs from the Reference Case only in the application
of a climate policy. Therefore, we simulate directly the effects of global GHG
mitigation on co-emitted air pollutants.
Global
 Anthropogenic changes of organic carbon and sulfur dioxide, due to GHGs mitigation, among different scenarios contribute
to the global and regional PM2.5 benefit.
 Organic carbon and sulfur dioxide play different roles in different regions.
Methane and isoprene emission change on Tropospheric O3 burden
Methane concentration (ppb)
ISOP emission (Tg C/a-1)
∆O3 burden (Tg /a-1)
PM2.5
• Global meteorology for these future scenarios is from the GFDL general
circulation model (AM3) simulations of RCP8.5 (with similar forcing as the
Reference Case) and RCP4.5.
Simulations Modeled in the study
Years
Emissions
Meteorology
Name
2000
Historical
Historical
2000
GCAM
Reference
RCP8.5
erefm85
2030,
2050,
2100
RCP4.5
GCAM
Reference
RCP4.5
RCP4.5
 Methane emissions changes likely contribute substantially effect the tropospheric ozone burden
 Changes in isoprene emissions, due to meteorological changes, have a smaller influence on tropospheric ozone burden
5. Conclusions
• The air quality co-benefits of global GHG mitigation are substantial.
rcp45
erefm45
O3
• The direct co-benefits via changes in co-emitted air pollutants (mechanism #1) appear much more important than the longterm influence via climate change (#2), even in 2100.
• Co-benefits would likely be larger if the Reference Case scenario had not assumed decreased air pollution in the future.
• Methane changes in these emissions scenarios are likely important in contributing to the tropospheric O3 burden change.
•
We will present the total co-benefits and those resulting from the two
mechanisms as:
Total co-benefit: rcp45−erefm85
Emission co-benefit: rcp45−erefm45
Meteorology co-benefit: erefm45−erefm85
 The emission reductions due to the GHG mitigation have a large positive effect on both PM2.5 and O3, while the changing
meteorology has less influence.
 Slowing future climate change increases O3 in remote areas, as increasing water vapor decreases the ozone lifetime. In
polluted regions, slowing climate change causes O3 to decrease due to decreasing temperature and biogenic emissions, and
other meteorological factors.
• Future work will include assessing the global health impacts of these air quality changes, and meteorological and chemical
downscaling of these results to the US using the WRF and CMAQ models.
Acknowledgements: This work was funded by an EPA STAR grant #834285, an EPA STAR Graduate Fellowship (MMF),
the EPA Office of Air Quality Planning and Standards, and the Department of Energy Office of Science.
Contact: [email protected], www.unc.edu/~jjwest