Abstract
Several studies have shown that the greenhouse gas reduction resulting from the current nationally determined contributions (NDCs) will not be enough to meet the overall targets of the Paris Climate Agreement. It has been suggested that more ambition mitigations of short-lived climate forcer (SLCF) emissions could potentially be a way to reduce the risk of overshooting the 1.5 or 2 °C target in a cost-effective way. In this study, we employ eight state-of-the-art integrated assessment models (IAMs) to examine the global temperature effects of ambitious reductions of methane, black and organic carbon, and hydrofluorocarbon emissions. The SLCFs measures considered are found to add significantly to the effect of the NDCs on short-term global mean temperature (GMT) (in the year 2040: − 0.03 to − 0.15 °C) and on reducing the short-term rate-of-change (by − 2 to 15%), but only a small effect on reducing the maximum temperature change before 2100. This, because later in the century under assumed ambitious climate policy, SLCF mitigation is maximized, either directly or indirectly due to changes in the energy system. All three SLCF groups can contribute to achieving GMT changes.
Highlights
In the 2015 Paris Agreement on Climate Change, parties have agreed to limit the global mean temperature (GMT) rise to well below 2 °C relative to pre-industrial levels and to pursue efforts to further limit this increase to a maximum of 1.5 °C (UNFCCC 2015b).This article is part of a Special Issue reporting results from the "Energy Modeling Forum (EMF)-30 Study on Short-Lived Climate Forcers (SLCF) and Air Quality” edited by John Weyant, Steven J Smith, and Zbigniew Klimont Electronic supplementary material The online version of this article contains supplementary material, which is available to authorized users.Extended author information available on the last page of the articleClimatic Change (2020) 163:1443–1461Countries around the world have currently proposed emission reductions towards this goal, termed nationally determined contributions (NDCs) (UNFCCC 2015a)
Earlier found key limiting factors that played a part in this study are as follows: (1) a more limited mitigation potential, as substantial SLCF reductions are already assumed to occur in the reference case and (2) black carbon (BC) reduction measures lead to a reduction of global cooling aerosols, such as SO2 and OC, which offset the effect of BC mitigation
This study examines the climate impact of intensified SLCF policy, using the existing global climate policy regime, the NDCs, as a starting point
Summary
Studies show that ambitions in the NDCs are too weak to reach greenhouse gas (GHG) reduction levels consistent with a 1.5 or 2 °C target (Den Elzen et al 2016; Fawcett et al 2016; Rogelj et al 2016; UNEP 2016a; Vandyck et al 2016). This means that the ambition of the NDCs needs to be strengthened to reach the goals of the Paris Agreement. One option would be to strengthen non-CO2-related action with respect to short-lived climate forcers (SLCFs), of which the most relevant are methane (CH4), ozone (O3), black carbon (BC), and hydrofluorocarbons (HFCs)
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