2011 - Cooperative Institute for Research in Environmental Sciences ...

CSD-12EmissionsandAtmosphericComposition
FEDERAL LEAD: SUSAN SOLOMON
CIRES LEAD: CHRISTINE ENNIS
NOAA Goal 2: Climate
Project Goal: Improve understanding of past and projected
future anthropogenic and natural emissions of atmospheric
trace gases that influence climate and climate variability.
Milestone 1. Evaluate anthropogenic and natural surface
emissions of atmospheric chemical compounds during
the past two decades by making detailed comparisons of
available emissions inventories, and evaluate the consistency
between global and regional emissions, and the impact
on the composition of the atmosphere. Impact: This
study will provide information used as inputs in climate
models, focusing on the chemical compounds detected
from space (CO, NO2, ozone) and on hydrocarbons from
natural and anthropogenic origins.
Several different inventories of global and regional
anthropogenic and biomass burning emissions have been
assessed for the 1980-2010 period. The species considered
so far are CO, NOx, SO2 and black carbon. The Atmospheric
Chemistry and Climate Model Intercomparison Project
Figure 1: Comparison of SO2 emissions in China from 1980 to 2010 from
different surface emissions inventories.
Figure 2: European-wide composite of modelled and observed monthly
means of NO2 trend (µg/m 3 ) at the air quality monitoring stations of
background suburban and rural type. The straight line shows the best
linear least square fit for each model results.
110 CIRES Annual Report 2011
(ACCMIP) historical emissions developed in support of the
simulations for the Intergovernmental Panel on Climate
Change Fifth Assessment Report are also considered. Emissions
from the Representative Concentration Pathways
(RCPs) are also included. Large discrepancies between the
global and regional emissions are identified, which shows
that there is still no consensus on the best estimates for
surface emissions. At the global scale, anthropogenic emissions
of CO, NOx and SO2 show the best agreement for
most years, although agreement does not necessarily mean
that uncertainty is low. The agreement is low for BC emissions,
particularly in the period prior to 2000. The best consensus
is for NOx emissions for all periods and all regions,
except for China, where emissions in 1980 and 1990 need
to be better defined. Emissions of CO need better quantification
for all periods. The agreement between the different
SO2 emissions data sets is rather good for the United
States, but better quantification is needed elsewhere. The
comparisons show that the use of RCP 8.5 for the extension
of the ACCMIP inventory beyond 2000 is reasonable,
until more global or regional estimates become available.
Biomass burning inventories agree within 50-80 percent,
depending on the year and season. The large differences
between datasets are due to differences in the estimates of
burned areas from the different available products, as well
as in the amount of biomass burned.
Product: Granier, C, B Bessagnet, T Bond, A D’Angiola,
H Denier van der Gon, G Frost, A Heil, J Kaiser, S Kinne,
Z Klimont, JF Lamarque, C Liousse, T Masui, F Meleux, A
Mieville, T Ohara, K Riahi, M Schultz, S Smith, A Thomson,
J van Aardenne and G van der Werf (2011), Evolution
of anthropogenic and biomass burning emissions at global
and regional scales during the 1980-2010 period,
Clim. Change, accepted for publication.
Milestone 2. Evaluate the evolution of the chemical
composition of the atmosphere during the next two to
three decades, using the different emissions scenarios
developed in support of the Intergovernmental Panel on
Climate Change (IPCC) Fifth Assessment Report (AR5) to
assess different Representative Concentrations Pathways
(RCPs). Impact: This research will support the IPCC AR5
report by determining the effects of different RCPs on the
distribution of chemical species and on their deposition
at the surface, which will enable improved understanding
and modeling of the effect of atmospheric chemical
composition on climate.
The proposed work has started with an evaluation of
the capability of chemistry-transport models to reproduce
past trends in air quality. Documenting these strengths
and weaknesses on the basis of historical simulations is
essential before the models can be used to assess future
air-quality projections. Different regional and global models
have been used to simulate the evolution of air quality
during the 1997-2008 period. The analysis has so far
focused on ozone and nitrogen dioxide, for which surface,
as well as satellite, observations are available. A paper has
been submitted in June 2011, which focuses on the results
obtained for the European region. The analysis of the
model results has shown that the year-to-year interannual
changes in the distributions of the constituents are rather
well reproduced, although capturing the more moderate
trends of chemically produced species such as O3 is more
challenging. The modeled monthly variability is consistent
with the observations but the year-to-year variability is
generally underestimated.