The substitution of high-resolution terrestrial biosphere models and carbon sequestration in response to changing CO2 and climate

Strategies are developed to analyze and represent spatially resolved biosph ere models for carbon sequestration in response to changes in atmospheric C O2 and climate by reduced-form, substitute models. We explore the High-Reso lution Terrestrial Biosphere Model as implemented in the Community Terrestr ial Biosphere Model (HRBM/CTBM), the Frankfurt Biosphere Model (FBM), and t he box-type biosphere of the Bern model. Storage by CO2 fertilization is de scribed by combining analytical representations of (1) net primary producti vity (NPP) as a function of atmospheric CO2 and (2) a decay impulse respons e function to characterize the timescales of biospheric carbon turnover. St orage in response to global warming is investigated for the HRBM/CTBM. The relation between the evolution of radiative forcing and climate change is e xpressed by a combination of impulse response functions and empirical ortho gonal functions extracted from results of the European Center/Hamburg (ECHA M3) coupled atmosphere-ocean general circulation model. A box-type, differe ntial-analogue substitute model is developed to represent global carbon sto rage of the HRBM/CTBM in response to regional changes in Temperature, Preci pitation and cloud cover. The substitute models represent the spatially res olved models accurately and cost-efficiently for carbon sequestration in re sponse to changes in CO2 or in CO2 and climate and for simulations of the g lobal isotopic signals. Deviations in carbon uptake simulated by the spatia lly resolved models and their substitutes are less than a few percent.