Limited mitigation potential of forestation under a high emissions
scenario: results from multi-model and single model ensembles
Abstract
Forestation is a major component of future long-term emissions reduction
and CO$_2$ removal strategies, but the viability of carbon stored in
vegetation under future climates is highly uncertain. We analyze the
results from seven CMIP6 models for a combined scenario with high fossil
fuel emissions (from SSP5-8.5) and moderate forest expansion (from
SSP1-2.6). This scenario aims to demonstrate the ability of forestation
strategies to mitigate climate change under continued increasing
CO$_2$ emissions and includes the potential impacts of increased
CO$_2$ concentration and a warming climate on vegetation growth. The
model intercomparison shows that moderate forestation as a CO$_2$
removal strategy has limited impact on global climate under a high
global warming scenario, despite generating a substantial cumulative
carbon sink of 10–60 Pg C over the period 2015–2100. Using a single
model ensemble, we show that there are local increases in warm extremes
in response to forestation associated with decreases in the number of
cool days. Furthermore, we find evidence of a shift in the global carbon
balance, whereby increased carbon storage on land of
$\sim$25 Pg C by 2100 associated with forestation has a
concomitant decrease in the carbon uptake by the ocean due to reduced
atmospheric CO$_2$ concentrations.