HR: 10:45h
AN: A52B-02 INVITED     [Abstracts]
TI: Design of Metrics for Inclusion of NOx in Global Climate Agreements: Scientific Issues
AU: * Berntsen, T
EM: t.k.berntsen@cicero.uio.no
AF: CICERO Center for International Climate and Environmental Research Oslo, P.O. Box 1129, Blindern, Oslo, 0317 Norway
AU: Fuglestvedt, J S
EM: j.s.fuglestvedt@cicero.uio.no
AF: CICERO Center for International Climate and Environmental Research Oslo, P.O. Box 1129, Blindern, Oslo, 0317 Norway
AU: Shine, K P
EM: k.p.shine@reading.ac.uk
AF: Department of Meterorology, The University of Reading, Early Gate, Reading, RG6 6BB United Kingdom
AB: The Kyoto Protocol seeks to limit the emissions of several greenhouse gases, but excludes emissions of short-lived species and their pre-cursors even though these may also have a significant climate impact. We explore the difficulties that are faced when designing a metric to compare the climate impact of NOx emissions with other emissions. There are two dimensions to this difficulty. The first concerns the definition of a metric that satisfactorily accounts for its climate impact. NOx emissions increase tropospheric ozone, but this increase, and its climate impact, depend strongly on the location of the emissions; low latitude emissions have a larger impact. NOx emissions also decrease methane concentrations causing a climate impact that is, to first-order, equal in size but opposite in sign to the ozone impact, at least for the global mean. We use model simulations which examined the impact of regionally constrained emissions of NOx on concentrations of tropospheric ozone and methane, the resulting radiative forcing, surface temperature response and GWPs. Because of the difficulties in modeling these processes, results from 2 chemical transport models (CTMs), 3 radiative forcing codes and 2 general-circulation models (GCMs) are used in order to provide some indication of uncertainties. We explore the use of indicators that could lead to metrics that, instead of using global-mean inputs, are computed locally and then averaged to the global level. The second dimension concerns the inter-model differences in the values of computed metrics. The local metrics may be less dependent on cancellation in the global mean; the possibilities presented here appear more robust to model uncertainty, although their applicability depends on the poorly-known relationship between local climate change and its impact. We conclude that if it becomes a political imperative to include NOx emissions in future climate agreements, policymakers will be faced with a number of difficult choices in selecting an appropriate metric.
DE: 0365 Troposphere--composition and chemistry
DE: 1600 GLOBAL CHANGE (New category)
SC: Atmospheric Sciences [A]
MN: 2005 Joint Assembly