Different variants of global climate change predictions can be made by means of combining a limited number of climatic and biospheric mechanisms. The worst cases are of main interest. Russian scientists look for such cases within the RAS General Committee “Biosphere Origin and Evolution” Program.

Experts from RAS SB Biophysics Institute have suggested mathematical model of long-term carbon atmosphere dynamics, which supposed the possibility of irreversible climate changes and biosphere collapse. Biosphere will stop growing under conditions of strong carbon dioxide contamination of atmosphere.

Today there is no shortage in mathematical models of climate. Most models suggest steady and gradual changes in CO2 atmospheric concentration and near-surface temperature due to fossil fuel burning. But among numerous future possibilities steady global change is the most optimistic one. Steadiness means a chance to retard negative changes by reducing anthropogenic influence. But we should not forget about catastrophic variant, when change intensity exceeds stability threshold of climate-biosphere system. In this case global change becomes irreversible and demonstrates the avalanche effect. We should be alarmed because temperature and CO2 atmospheric concentration grow very fast these days. Earth’s surface temperature has shown a growth for half a degree since 1860, while for 10 000 years since last glacial period it has gained only 5 degrees, which means that temperature growth rate is now a sequence higher. And carbon dioxide concentration today is the highest for last 420 thousand years or even for the last 20 million years.

Biophysicists from Krasnoyarsk have developed a model describing dynamics of three carbon pools: atmosphere, living plants and organic debris. The model covers only ground surface processes, which allows ignoring ocean’s thermal inertia.

Computational experiments for future carbon pool dynamics modeling showed that catastrophic processes would appear in the biosphere even under moderate fossil fuel burning. They have predicted the “date of irreversibility”, which is followed by system irreversible changes. The more powerful the “greenhouse effect” is, the closer is this date. The danger hides in stability of climate and biosphere parameters before and shortly after this date. On the other hand, if greenhouse effect weakens, the “date of irreversibility” moves further to the future. Thus, the model says that zero anthropogenic carbon dioxide emission in 2059 saves the biosphere. If it stops five years later, in 2064, irreversible changes start in the middle of XXIV century and end in the beginning of XXV century. And if the mankind burns fossil fuel till 2090, it won’t last till 2200. This is what the model predicts.

Model authors are aware that it is vulnerable for criticizing. But it is absolutely impossible to make correct predictions for climate global change, because of global parameter estimation and economic prediction uncertainties. It is more real to develop several forecasts with various encouraging patterns. The most pessimistic ones should be tested first.