Abstract
Abstract. Reducing greenhouse gas emissions to limit damage to the global economy climate-change-induced and secure the livelihoods of future generations requires ambitious mitigation strategies. The introduction of a global carbon tax on fossil fuels is tested here as a mitigation strategy to reduce atmospheric CO2 concentrations and radiative forcing. Taxation of fossil fuels potentially leads to changed composition of energy sources, including a larger relative contribution from bioenergy. Further, the introduction of a mitigation strategy reduces climate-change-induced damage to the global economy, and thus can indirectly affect consumption patterns and investments in agricultural technologies and yield enhancement. Here we assess the implications of changes in bioenergy demand as well as the indirectly caused changes in consumption and crop yields for global and national cropland area and terrestrial biosphere carbon balance. We apply a novel integrated assessment modelling framework, combining three previously published models (a climate–economy model, a socio-economic land use model and an ecosystem model). We develop reference and mitigation scenarios based on the narratives and key elements of the shared socio-economic pathways (SSPs). Taking emissions from the land use sector into account, we find that the introduction of a global carbon tax on the fossil fuel sector is an effective mitigation strategy only for scenarios with low population development and strong sustainability criteria (SSP1 Taking the green road). For scenarios with high population growth, low technological development and bioenergy production the high demand for cropland causes the terrestrial biosphere to switch from being a carbon sink to a source by the end of the 21st century.
Highlights
Combating climate change is one of the greatest challenges of the 21st century
While in SSP5 “Taking the highway”, fossil fuel dominates, in all other reference scenarios, renewable energies and bioenergy contribute to the rising energy demand, especially for the sustainability-oriented SSP1 “Taking the green road”
Globally collaborating institutions and environmental awareness contribute to low challenges for mitigation in SPP1 “Taking the green road” and result in high carbon taxes (USD 115 per tonne of carbon at 2010 GWP), decreasing the contribution of fossil fuel to total energy use to around 10% in 2100
Summary
Combating climate change is one of the greatest challenges of the 21st century. Currently the world is on an emission pathway that approaches the highest of the four representative concentration pathways (RCPs; Fuss et al, 2014; Peters et al, 2012). If emissions are not drastically curbed within the few decades a global average surface warming of 3.7 to 4.8 ◦C compared to pre-industrial levels and more frequent extreme weather events will be the likely consequence (IPCC, 2014a). Such profound changes in the climate system are strongly linked with changes in the terrestrial biosphere. During the last 250 years a share of carbon dioxide (CO2) emissions has been taken up by the terrestrial biosphere, referred to as a carbon sink (Canadell and Schulze, 2014).
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