Changes in the Response of the Northern Hemisphere Carbon Uptake to Temperature Over the Last Three Decades

Abstract

The CO2 seasonal cycle amplitude (SCA) in the Northern Hemisphere has increased since the 1960s—a feature attributed mainly to enhanced vegetation activity along climate warming and CO2 increase. We identified a temporal change in the sign of the correlation between SCA and air temperature (T) from positive to negative around the year 2000 at most Northern Hemisphere ground stations, consistent with signals from satellite column CO2 measurements since the mid‐2000s. Further, we explored potential causes of this change using net biome productivity estimates from three atmospheric inversions for the period 1980–2015. The change in the SCA‐T relationship is primarily attributable to changes in the net biome productivity‐T relationship: positive correlations weakened in the spring in the high latitudes, confirming a limit to the “warmer spring‐bigger carbon sink” mechanism; negative correlations diminished in the autumn/winter in the mid‐to‐high latitudes, challenging the “warmer winter‐larger carbon release” assumption and highlighting the complexity of carbon processes outside the peak growing season.

Contrasting effects of CO<sub>2</sub> fertilisation, land-use change and warming on seasonal amplitude of northern hemisphere CO<sub>2</sub> exchange

“…Such a negative relationship, however, has also been reported by (Schneising et al, 2014) for interannual changes in the SCA N BP of total column CO 2 for 2004-2010. Yin et al (2018) have further shown that, at latitudes between 60°N and 80°N, the relationship between SCA NBP and T has transitioned from positive in the early 1980s, to negative in recent decades, reconciling the results by Keeling et al (1996) and Schneising et al (2014).…”

Satellite and In Situ Observations for Advancing Global Earth Surface Modelling: A Review

“…For methane, it could allow wetland models to better represent the response to extreme events [317]. For carbon dioxide, it could facilitate the sophistication of carbon processes representation outside the peak growing season, such as leaf flushing [318]. For aerosols, it could improve binding energy or other parameters in mineral dust emission models [319].…”

Interannual variation of terrestrial carbon cycle: Issues and perspectives

“…Changing γ IAV can result either from geographical reasons, as temperature anomalies of the tropical region became more coherent over time (Yang et al, ), leading to expansion of the geographical area that have synchronous temperature‐driven variations of net ecosystem carbon flux (Jung et al, ), or from a physiological response of tropical ecosystems becoming more sensitive to temperature variations under drier conditions (Luo & Keenan, under review; Wang, Piao, et al, ), leading to increasing variability of CO 2 growth rate (Anderegg et al, ) under similar magnitude of temperature variability. The changing sensitivity of net land carbon flux to interannual temperature variations not only took place in the tropics, but also in the northern hemisphere, where positive temperature effects over IAV of net land carbon flux have been weakening over the past three decades (Piao et al, ; Wang, Liu, et al, ; Yin et al, ). There is growing concern that these findings are early warning signals of driver shift or even abrupt status shift of the terrestrial ecosystem dynamics (Lewis et al, ; Liptak, Keppel‐Aleks, & Lindsay, ; Peñuelas et al, ).…”