“Natural” Climate Solutions Could Speed Up Mitigation, With Risks. Additional Options Are Needed.

Abstract

Mitigation of climate change by intentionally storing carbon in tropical forests, soils, and wetlands and by reducing greenhouse gas fluxes from these settings has been promoted as rapidly deployable and cost-effective. This approach, sometimes referred to as “natural climate solutions,” could keep post-industrialization warming below 1.5 °C, when coupled with reductions in fossil fuel emissions, as confirmed here with a simple numerical model of future emissions. However, such mitigation could cease in response to changes in future climate, land use, or natural resource policies, or there could be CO2 released from reservoirs of stored carbon. Model simulations suggest cumulative emissions could be similar, under scenarios where carbon storage ceases, or stored carbon is released, to emissions expected in the absence of any natural mitigation. If climate change is to be minimized, no-regrets approaches to natural mitigation should be considered (e.g., by reducing deforestation), as emissions targets that could limit warming to 1.5 °C cannot be met without mitigation of this magnitude. However, additional mitigation options should also be evaluated that can reduce CO2 emissions and remove CO2 from the air (and store it permanently).