Time-scale and state dependence of the carbon-cycle feedback to climate

Abstract

Climate and atmospheric CO2 concentration are intimately coupled in the Earth system: CO2 influences climate through the greenhouse effect, but climate also affects CO2 through its impact on the amount of carbon stored on land and in the ocean. The change in atmospheric CO2 as a response to a change in temperature (DCO2=DT) is a useful measure to quantify the feedback between the carbon cycle and climate. Using an ensemble of experiments with an Earth system model of intermediate complexity we show a pronounced time-scale dependence of DCO2=DT. A maximum is found on centennial scales with DCO2=DT values for the model ensemble in the range 5–12 ppm C-1, while lower values are found on shorter and longer time scales. These results are consistent with estimates derived from past observations. Up to centennial scales, the land carbon response to climate dominates the CO2 signal in the atmosphere, while on longer time scales the ocean becomes important and eventually dominates on multi-millennial scales. In addition to the time-scale dependence, modeled DCO2=DT show a distinct dependence on the initial state of the system. In particular, on centennial time-scales, high DCO2=DT values are correlated with high initial land carbon content. A similar relation holds also for the CMIP5 models, although for DCO2=DT computed from a very different experimental setup. The emergence of common patterns like this could prove to usefully constrain the climate–carbon cycle feedback

Climate model emulation in an integrated assessment framework: a case study for mitigation policies in the electricity sector

“…that states exhibiting the greatest CO 2 concentration in GENIEem correspond to states exhibiting greatest warming in PLASIM-ENTSem. Many carbon cycle processes are affected directly by changes in temperature, or by variables which covary with temperature (Willeit et al, 2014), so while such a correlation is not absolute, there is a motivation for this approach.…”

Challenges and opportunities to reduce uncertainty in projections of future atmospheric CO<sub>2</sub>: a combined marine and terrestrial biosphere perspective

“…(Frank et al, 2010) instead used the values as representative of the 20th century climate perturbation (the historical 0.7 • C increase of temperature). However, these sensitivities could show a time scale-dependency (Friedlingstein and Prentice, 2010;Woodwell et al, 1998;Willeit et al, 2014). In other words, the response to external drivers has its own temporal scale, which is the result of aggregated subcomponent responses of the ecosystems that act differently with different time response.…”

Intrinsic Environmental Vulnerability as Shallow Landslide Susceptibility in Environmental Impact Assessment

“…Using an ensemble of experiments with an Earth system model of intermediate complexity, a pronounced timescale dependence between CO 2 and temperature variations was found, with a maximum on centennial scales. Furthermore, up to centennial scales, the land carbon response to climate dominates the CO 2 signal in the atmosphere, while on longer timescales the ocean becomes important and eventually dominates on multi-millennial scales [13].…”