by From Nature Communications, June 18 in WUWT

Abstract

Most Earth system models agree that land will continue to store carbon due to the physiological effects of rising CO₂ concentration and climatic changes favoring plant growth in temperature-limited regions. But they largely disagree on the amount of carbon uptake. The historical CO₂ increase has resulted in enhanced photosynthetic carbon fixation (Gross Primary Production, GPP), as can be evidenced from atmospheric CO₂ concentration and satellite leaf area index measurements. Here, we use leaf area sensitivity to ambient CO₂ from the past 36 years of satellite measurements to obtain an Emergent Constraint (EC) estimate of GPP enhancement in the northern high latitudes at two-times the pre-industrial CO₂ concentration (3.4 ± 0.2 Pg C yr⁻¹). We derive three independent comparable estimates from CO₂ measurements and atmospheric inversions. Our EC estimate is 60% larger than the conventionally used multi-model average (44% higher at the global scale). This suggests that most models largely underestimate photosynthetic carbon fixation and therefore likely overestimate future atmospheric CO₂ abundance and ensuing climate change, though not proportionately.