Net greenhouse gas emission pathway for Finland based on fair share of allowed warming

Abstract

Finland has set a legally binding goal of achieving “carbon neutrality” by 2035 and net-negative greenhouse gas emissions thereafter. The scientific background for this goal is based on an interpretation of what a nationally fair share of global carbon budget compatible with 1.5 °C warming is. This national carbon budget includes also non-CO2 greenhouse gas (GHG) emissions and is thus stricter than the original, global CO2-only carbon budget. Finland’s pathway to carbon neutrality relies not only on emission reductions but also on carbon sinks in the land use, land-use change and forestry (LULUCF) sector. The net sink in the LULUCF sector, as estimated in the national greenhouse gas inventory, is interpreted as negative emissions. This assumption is problematic, as part of the LULUCF sink is considered natural sink in the conceptual framework behind the global carbon budget estimates and assuming it entirely anthropogenic leads to underestimation of the net CO2 emissions.   Here we present an analysis and revision of the Finnish net greenhouse gas emission pathway with two major improvements. First, we extend the carbon budget framework to nationally allowed warming to be able to account explicitly also for national non-CO2 GHG emissions. The global allowed warming until 2050 from future GHG emissions is calculated as the sum of the remaining warming to 1.5 °C, the global decreasing warming impact of past non-CO2 GHG emissions by 2050, and future warming due to reduced aerosols by 2050. We use the fair share used previously for allocating national carbon budget to calculate national allowed warming contribution until 2050 and subtract non-CO2 GHG contribution based on a Finnish carbon neutrality scenario and simulations with a simple climate model FaIR 2.1. The remaining allowed warming is then used to calculate the national CO2-only carbon budget.   The second improvement is to consider the recent advancements in disentangling natural and anthropogenic carbon fluxes in the LULUCF sector. National results from a recent global study indicate that the Finnish LULUCF sector has been a carbon sink due to the natural sink induced by CO2 fertilization and climate change. The large natural sink is expected to decrease especially in the most stringent global emission reduction scenarios.    The preliminary results indicate that Finland’s currently planned pathway is not compatible with its national fair share of allowed warming compatible with the 1.5-degree target, and more stringent emission reductions coupled with strengthening of the land sink and other forms of negative emissions are very likely needed.