At the time this study was carried out, land use change (LUC) resulting from deforestation and other smaller sources contributed ~17% of global anthropogenic greenhouse gas emissions, whilst more recently (29) the deforestation component alone has been estimated to contribution 11% of the global total.. SRES baselines assume LUC emission decrease and reverse, whereas deforestation is continuing unabated. Hence the AVOID project analyses, being based on SRES baselines, likely under-estimate future emissions from deforestation.
This study focuses on tropical deforestation, assuming that action is taken to reduce emissions from other land use change. We find that in the absence of tropical deforestation, rapid emissions reductions of 80% between 2000 and 2050 in fossil fuel and other sectors would deliver a 65% chance of staying below the 2°C threshold. If tropical deforestation instead continues at current rates, the chance falls to 34%. To compensate for the additional climate change caused by continued current rates of tropical deforestation, a doubling of global mitigation efforts (from 3% to 6% per year) would be required to maintain the same 65% chance to avoid temperature rise in excess of 2°C above pre-industrial levels. Only deforestation rates between 0 and 0.8GtC/yr have a greater than evens chance of constraining temperature change to 2°C. Failing to reduce deforestation also increases the difficulty of avoiding a 3°C increase in global temperature. Tackling deforestation could avoid an increase in CO2e concentrations of up to 100 ppm and concomitant temperature rise of 0.6°C.