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Low probability, but high impact scenarios: Introducing the backgrounds of a “Dangerous Climate Change”

The balance of scientific evidence now suggests that anthropogenic greenhouse gas emissions are having a significant effect on the earth’s system and especially on the earth’s climate. Since the 1970s, there has been a significant increase of extreme weather events. Tropical and extra-tropical storm frequency and magnitude have considerably increased and so have the flood risks and heatwave occurrences along with very severe socio-economic and ecological impacts all over the globe. Even though the natural science of extreme weather events has progressed over the last decades, modelling climate scenarios still remains pretty speculative. However, it is now scientific consensus that if we continue to follow our “Business as usual”-path and if the greenhouse gas emissions weren’t cut drastically within the next decades, the impacts of a changing climate will intensify throughout the 21st century, with dangerous high impact scenarios becoming more likely to happen. A “dangerous climate change” with raising temperatures especially above 2°C (above pre-industrial levels) could tip certain ecological thresholds and trigger non-linear processes and feedback loops within the earth’s system, forcing the system rapidly into a totally new equilibrium. Dramatic changes within the carbon cycle, the eco- and hydrosphere and most obviously within the kryosphere would exceed our society’s ability to adapt to these changes. Unmanageable and most likely irreversible consequences could put our mankind on the edge of extinction. (1)