Residual fossil CO2 emissions in 1.5-2 °C pathways

The Paris Agreement-which is aimed at holding global warming well below 2 degrees C while pursuing efforts to limit it below 1.5 degrees C-has initiated a bottom-up process of iteratively updating nationally determined contributions to reach these longterm goals. Achieving these goals implies a tight limit on cumulative net CO2 emissions, of which residual CO2 emissions from fossil fuels are the greatest impediment. Here, using an ensemble of seven integrated assessment models (IAMs), we explore the determinants of these residual emissions, focusing on sector-level contributions. Even when strengthened pre-2030 mitigation action is combined with very stringent long-term policies, cumulative residual CO2 emissions from fossil fuels remain at 850-1,150 GtCO(2) during 2016-2100, despite carbon prices of US$130-420 per tCO(2) by 2030. Thus, 640-950 GtCO(2) removal is required for a likely chance of limiting end-of-century warming to 1.5 degrees C. In the absence of strengthened pre-2030 pledges, long-term CO2 commitments are increased by 160-330 GtCO(2), further jeopardizing achievement of the 1.5 degrees C goal and increasing dependence on CO2 removal.