Principle of the worst scenario in the modelling past and future of biosphere dynamics

The “biosphere–climate” system is subjected to different influences (influx of anthropogenic CO2 and pollutants, deforestation, harmful land management, biological species depopulation, etc.). Therefore, the vital question arises: “Can these influences lead to irreversible negative changes in the climate–biosphere system or a global ecological catastrophe?” The possibility of irreversible changes may be not very high, but one cannot ignore it. So the main aim of our investigation is to evaluate possible consequences of human impact on the biosphere focusing on irreversible changes of it. ional mathematical complicated models describe the biosphere in great detail, but the large number of equations and parameters leads to accumulation of uncertainties in the forecast due to inevitable uncertainties of experimental estimations of model parameters. An approach based on the principle of the worst scenario was proposed. Minimization of mathematical model with respect to this principle is conducted to study limiting (but possible) versions of models in which the contribution of the possible compensatory and smoothing mechanisms is minimal. Namely the most unfavorable scenarios (corresponding to the values of parameters at the boundaries of confidence interval) have to be considered in estimating consequences of anthropogenic impact. the fastest CO2 releasing mechanisms, based on the positive feedback effect, was considered in the context of the worst scenario principle. The family of simple mathematical models was created for biosphere dynamics representation on different timescales. The main result of the investigation consists in confirmation of the possibility of negative and irreversible changes in the “biosphere–climate” system, caused by amplification of the positive feedback: “anthropogenic emission of CO2 – temperature increase – additional CO2 emission due to decomposition of soil organics”. Crucial parameters of models, responsible for avalanche-like biosphere changes, are determined. izability of hypotheses on anthropogenic causes of Little Ice Age was estimated by corresponding minimal model. Model were used to show the feasibility of the mechanism describing the changing of agricultural field species into indigenous forests in Europe during the Plague, which led to CO2 decrease and temperature fall.