Forecasting Controversy Swirling Around Computer Models and Forecasts

I am intrigued by Fabius Maximus’ We must rely on forecasts by computer models. Are they reliable?

This is a broad, but deeply relevant, question.

With the increasing prominence of science in public policy debates, the public’s beliefs about theories also have effects. Playing to this larger audience, scientists have developed an effective tool: computer models making bold forecasts about the distant future. Many fields have been affected, such as health care, ecology, astronomy, and climate science. With their conclusions amplified by activists, long-term forecasts have become a powerful lever to change pubic opinion.

It’s true. Large scale computer models are vulnerable to confirmation bias in their construction and selection – example being the testing of drugs. There are issues of measuring their reliability and — more fundamentally — validation (e.g., falsification).

Peer-review has proven quite inadequate to cope with these issues (which lie beyond the concerns about peer-review’s ability to cope with even standard research). A review or audit of a large model often requires over a man-years or more of work by a multidisciplinary team of experts, the kind of audit seldom done even on projects of great public concern.

Of course, FM is sort of famous, in my mind, for their critical attitude toward global warming and climate change.

And they don’t lose an opportunity to score points about climate science, citing the Georgia Institute of Technology scientist Judith Curry.

Dr. Curry is author of a recent WSJ piece The Global Warming Statistical Meltdown

At the recent United Nations Climate Summit, Secretary-General Ban Ki-moon warned that “Without significant cuts in emissions by all countries, and in key sectors, the window of opportunity to stay within less than 2 degrees [of warming] will soon close forever.” Actually, this window of opportunity may remain open for quite some time. A growing body of evidence suggests that the climate is less sensitive to increases in carbon-dioxide emissions than policy makers generally assume—and that the need for reductions in such emissions is less urgent.

A key issue in this furious and emotionally-charged debate is discussed in my September blogpost CO2 Concentrations Spiral Up, Global Temperature Stabilizes – Was Gibst?

..carbon dioxide (CO2) concentrations continue to skyrocket, while global temperature has stabilized since around 2000.

The scientific consensus (excluding Professor Curry and the climate change denial community) is that the oceans currently are absorbing the excess heat, but this cannot continue forever.

If my memory serves me (and I don’t have time this morning to run down the link), backtesting the Global Climate Models (GCM) in a recent IPCC methodology publication basically crashed and burned – but the authors blithely moved on to re-iterate the “consensus.”

At the same time, the real science behind climate change – the ice cores for example retrieved from glacial and snow and ice deposits of long tenure – do show abrupt change may be possible. Within a decade or two, for example, there might be regime shifts in global climate.

I am not going to draw conclusions at this point, wishing to carry on this thread with some discussion of macroeconomic models and forecasting.

But I leave you today with my favorite viewing of Blalog’s “Chasing Ice.”

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