Abstract

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 does not directly follow the pattern of the diagnosed radiative forcing. We find that temperatures in the Arctic latitudes 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 response for aerosol emission, and about 20–30% larger than the global average for methane, VOC and CO emissions.

Highlights

  • Hydrology and Earth SystemThe emissions of reactive gasesSacndieanercoseosls can influence human and ecosystem health by affecting ozone and particulate matter concentrations (HTAP, 2010)

  • They can affect climate through the burdens of ozone, methane and aoefrothseolss,hhoarvt inligfebtiomthescOooofclienaegaroannsodlSswca(drimeayinns)gc, eeofzfeocntes. Because, methane, and their precursors, their climate effects are predominantly in the near term so we refer to these species as “near-term climate forcers

  • 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)

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Summary

Introduction

The emissions of reactive gasesSacndieanercoseosls can influence human and ecosystem health by affecting ozone and particulate matter concentrations (HTAP, 2010). Because (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 often called short-lived climate pollutants (SLCPs). It is important to understand how the effects of NTCFs vary by location of emissions, when air quality policies are considered This can 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).

Methodology
Global warming potentials
Aerosols
Methane
Ozone precursors
Global temperature-change potentials
Regional climate change
Changes in stratospheric ozone
Aerosol interactions with clouds and snow albedo
Nitrate aerosols
CO2 from methane oxidation
Carbon cycle effects
Temperature response
Findings
Conclusions
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