Forecasts all up in the air

KEVIN Trenberth is head of the large US National Centre for Atmospheric Research and one of the advisory high priests of the UN's Intergovernmental Panel on Climate Change (IPCC).
A New Zealander by birth, Trenberth has had a distinguished career as a climate scientist with interests in the use of computer General Circulation Models (GCMs), the basis for most of the public alarm about dangerous global warming.

When such a person gives an opinion about the scientific value of GCMs as predictive tools, it is obviously wise to pay attention.

In a remarkable contribution to Nature magazine's Climate Feedback blog, Trenberth concedes GCMs cannot predict future climate and claims the IPCC is not in the business of climate prediction. This might be news to some people.

Among other things, Trenberth asserts ". . . there are no (climate) predictions by IPCC at all. And there never have been". Instead, there are only "what if" projections of future climate that correspond to certain emissions scenarios.

According to Trenberth, GCMs ". . . do not consider many things like the recovery of the ozone layer, for instance, or observed trends in forcing agents".

This is what I and others have been saying.
There is no way to predict the weather 10-20-50 years from now because there are so many variables that can come into place. We cannot even get computer models to be accurate with weather forecasts for 5 days people really believe a temperature forecast for the next 40 years?

Be real here people!