How vegetation impacts affect climate metrics for ozone precursors

Abstract

[1] We examine the effect of ozone damage to vegetation as caused by anthropogenic emissions of ozone precursor species and quantify it in terms of its impact on terrestrial carbon stores. A simple climate model is then used to assess the expected changes in global surface temperature from the resulting perturbations to atmospheric concentrations of carbon dioxide, methane, and ozone. The concept of global temperature change potential (GTP) metric, which relates the global average surface temperature change induced by the pulse emission of a species to that induced by a unit mass of carbon dioxide, is used to characterize the impact of changes in emissions of ozone precursors on surface temperature as a function of time. For NO x emissions, the longer-timescale methane perturbation is of the opposite sign to the perturbations in ozone and carbon dioxide, so NO x emissions are warming in the short term, but cooling in the long term. For volatile organic compound (VOC), CO, and methane emissions, all the terms are warming for an increase in emissions. The GTPs for the 20 year time horizon are strong functions of emission location, with a large component of the variability owing to the different vegetation responses on different continents. At this time horizon, the induced change in the carbon cycle is the largest single contributor to the GTP metric for NO x and VOC emissions. For NO x emissions, we estimate a GTP 20 of −9 (cooling) to +24 (warming) depending on assumptions of the sensitivity of vegetation types to ozone damage.

Comparison of physically- and economically-based CO<sub>2</sub>-equivalences for methane

“…Moreover, there is an increasing recognition that different species have different impacts on the Earth system. For instance, CO 2 has a radiative effect, a fertilisation effect on plants and an acidification effect on the ocean, while CH 4 has an indirect effect on ozone, which may further affect the carbon cycle (Collins et al, 2010). These different effects may result in different impacts on ecosystem services, and this needs to be factored in climate metrics (Huntingford et al, 2011).…”

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

“…Sitch et al, 2007). Collins et al (2010) showed that adding in the effects of surface ozone on vegetation damage and reduced uptake of CO 2 added about 10 % to the methane GTP(20) and could change the sign of the NO x GTPs. Hence the sign of the net impact of NO x emissions is still uncertain.…”

General overview: European Integrated project on Aerosol Cloud Climate and Air Quality interactions (EUCAARI) – integrating aerosol research from nano to global scales

“…Feed-back processes in the interaction between the atmosphere and the natural ecosystem and/or the natural oceans in a changing climate have been investigated using models updated with new parametrizations developed in EUCAARI (e.g. Collins et al, 2010). …”