Global and regional temperature-change potentials for near-term climate forcers

cess Atmospheric Chemistry and Physics Open Access Atmospheric Measurement Techniques Open Access Atmos. Chem. Phys., 13, 2471–2485, 2013 www.atmos-chem-phys.net/13/2471/2013/ doi:10.5194/acp-13-2471-2013 © Author(s) 2013. CC Attribution 3.0 License. Sciences Biogeosciences W. J. Collins1,* , M. M. Fry2 , H. Yu3,4 , J. S. Fuglestvedt5 , D. T. Shindell6 , and J. J. West2 Open Access Global and regional temperature-change potentials for near-term climate forcers 1 Met Office Hadley Centre, FitzRoy Road, Exeter, Devon, EX1 3PB, UK Dynamics Correspondence to: W. J. Collins () Received: 30 July 2012 – Published in Atmos. Chem. Phys. Discuss.: 7 September 2012 Revised: 26 January 2013 – Accepted: 20 February 2013 – Published: 5 March 2013 Geoscientific Instrumentation does not directly follow theMethods pattern of the diagnosed radiaand tive forcing. We find that temperatures in the Arctic latitudes Data Systems Open Access appear to be particularly sensitive to BC emissions from South Asia. The northern mid-latitude temperature response to northern mid-latitude emissions is approximately twice as large as the global average Geoscientific response for aerosol emission, and about 20–30 %Model larger than the global average for methane, Development VOC and CO emissions. Open Access Hydrology and Earth System The emissions of reactive gasesSciences and aerosols can influence 1 Open Access Introduction human and ecosystem health by affecting ozone and particulate matter concentrations (HTAP, 2010). They can also affect climate through the burdens of ozone, methane and aerosols, having both cooling and warming effects. Because Ocean Science of the short lifetimes of aerosols (days), ozone (weeks), methane (a decade), and their precursors, their climate effects are predominantly in the near term (less than 30 yr) so we refer to these species as “near-term climate forcers (NTCFs)”. They are also often called short-lived climate pollutants (SLCPs). Solid Earth UNEP and WMO (2011) and Shindell et al. (2012) have suggested that the mitigation of ozone precursors and black Open Access Open Access Abstract. We examine the climate effects of the emissions of near-term climate forcers (NTCFs) from 4 continental regions (East Asia, Europe, North America and South Asia) using results from the Task Force on Hemispheric Transport of Air Pollution Source-Receptor global chemical transport model simulations. We address 3 aerosol species (sulphate, particulate organic matter and black carbon) and 4 ozone precursors (methane, reactive nitrogen oxides (NOx ), volatile organic compounds and carbon monoxide). We calculate the global climate metrics: global warming potentials (GWPs) and global temperature change potentials (GTPs). For the aerosols these metrics are simply time-dependent scalings of the equilibrium radiative forcings. The GTPs decrease more rapidly with time than the GWPs. The aerosol forcings and hence climate metrics have only a modest dependence on emission region. The metrics for ozone precursors include the effects on the methane lifetime. The impacts via methane are particularly important for the 20 yr GTPs. Emissions of NOx and VOCs from South Asia have GWPs and GTPs of higher magnitude than from the other Northern Hemisphere regions. The analysis is further extended by examining the temperature-change impacts in 4 latitude bands, and calculating absolute regional temperature-change potentials (ARTPs). The latitudinal pattern of the temperature response Open Access Hall, CB #7431, Chapel Hill, North Carolina 27599, USA Climate 3 Earth System Science Interdisciplinary Center, University of Maryland, College Park, Maryland, 20740, USA 4 Earth Science Directorate, NASA Goddard Space Flight Center, Greenbelt, Maryland, 20771, of the Past USA 5 Center for International Climate and Environmental Research – Oslo (CICERO), P.O. Box 1129 Blindern, 0318 Oslo, Norway 6 NASA Goddard Institute for Space Studies, 2880 Broadway, New York, New York, 10025 USA * now at: Department of Meteorology, University of Reading, P.O. Box 243, Reading, RG6 6BB, UK Earth System Open Access 2 Department of Environmental Sciences and Engineering, The University of North Carolina at Chapel Hill, 146B Rosenau The Cryosphere Open Access Published by Copernicus Publications on behalf of the European Geosciences Union. M 2472 W. J. Collins et al.: Temperature-change potentials for near-term climate forcers carbon (BC) would be attractive for both air quality and climate on a 30-yr timescale, provided it is not at the expense of CO2 mitigation. Typical air quality policies target both warming and cooling species and tend to have an overall detrimental effect on climate (in terms of surface temperatures). Therefore, it is important to understand how the effects of NTCFs vary by location of emissions, when air quality policies are considered. This can also be important for climate policies that affect both short and long-lived species (Berntsen et al., 2006). Many metrics have been proposed to compare these effects on climate, but here we consider the integrated radiative forcing (RF) using the global warming potential metric (GWP) (IPCC, 1990) and the surface temperature change using the global and regional temperaturechange metrics (GTP and RTP) (Shine et al., 2005; Shindell and Faluvegi, 2010). The NTCFs we consider in this paper are sulphate, particulate organic matter (POM), black carbon (BC), methane and ozone precursors. Some halogenated species have short lifetimes and are therefore NTCFs, but we do not consider those here. NTCFs with lifetimes longer than the interhemispheric mixing time (such as methane) are considered reasonably well mixed, with the concentrations and RF patterns independent of the emission location. Species with shorter lifetimes such as ozone and aerosols have heterogeneous distributions and RF patterns that are dependent on the emission location (Fuglestvedt et al., 1999; Berntsen et al., 2005; Naik et al., 2005; Fry et al., 2012; Yu et al., 2013). The surface temperature response does not directly follow the spatial details of the RF pattern, rather it smoothes out the pattern over scales of ˜3500 km in the meridional direction and over 12000 km in the zonal direction (Shindell et al., 2010). The RFs and GWPs for the Task Force on Hemispheric Transport of Air Pollution (HTAP) Source-Receptor global chemical transport model (CTM) simulations (HTAP, 2010) were previously documented by Fry et al. (2012) for reactive gases, and by Yu et al. (2013) for aerosols. In this study we have moved further down the chain of climate impacts, showing how analytical formulae can be used to relate equilibrium RF values to the evolution of global and latitudinal temperature changes. We use the HTAP RF estimates to calculate GWPs in Sect. 3.1. From these, we derive the global mean surface temperature responses as functions of time for emissions of different components in d (...truncated)