CLIMATE CHANGE AND CARBON DIOXIDE: GEOLOGICAL PERSPECTIVE

The climate history of the Earth is a history of continuous change. Through geological time the average global temperature remained always within the constraints set by the presence of abundant liquid water, while the atmospheric CO₂ concentration varied strongly. Its 30% rise since the beginning of the 20th century can, at least partly, be attributed to human activities. According to the 'general circulation models' (GCMs) used by the IPCC the ongoing rise in atmospheric CO₂ concentration will lead to significant global warming. However, in these GCMs the (small) net CO₂ forcing is amplified by strong positive feedbacks, particularly from water vapour and clouds. Real world observations and data of the geologic past do not support the role of CO₂ as the principal climate regulator.