There has been recent comments regarding the views of Hans Schellnhuber on climate science, who is a major advisor on climate issues with the German government; i.e. see
In 2003, I co-authored a paper with Hans and feel it is useful to post on this paper today, including several extracts from the text that he agreed with. The article is
Pielke, R.A. Sr., H.J. Schellnhuber, and D. Sahagian, 2003: Non-linearities in the Earth system. Global Change Newsletter, No. 55, 11-15.
“On all time scales, the various non-linear interactions are characterised by drivers and responses that are not proportional. Changes in state are often episodic and abrupt, and multiple equilibria commonly exist. One consequence of such a non-linear system is that forecasts based on current modelling tools should be viewed sceptically. For example, since none of the general circulation models (GCMs) used to project climate change over the next hundred years include all of the important forcings and feedbacks, they should be considered as sensitivity studies rather than forecasts . In Earth System science, climate is not the long term average of weather statistics, but involves the non-linear interactions between the atmosphere, oceans, continental ice, and land surface processes, including vegetation, on all time scales.”
“Research to-date has revealed the need to establish the limits to predictability within the Earth System. It has been shown that climate prediction needs to be treated as an initial value problem with chaotic behaviour. This perspective acknowledges that beyond some time period, our ability to provide reliable quantitative and detailed projections of climate must deteriorate to a level that no longer provides useful information to policymakers.”
These views present a much less certain view in the understanding of the climate system, and the ability to skillfully predict climate in the coming decades than has been presented by Hans in his Die Spiegel article.