Sunday, November 18, 2007
Their estimate of man-made contribution to global temperature rise is expressed as somewhere between 0.6 watts/m² and 2.4 watts/m². That is a variance of a factor of four. It could be a little, it could be four times that amount!
Also, note that the level of scientific understanding of many important factors influencing global temperature is still admittedly low. On the column farthest to the right, the "LOSU" (level of scientific understanding) of aerosols, surface albedo (reflectivity), contrails, ozone, is all medium to low.
The IPCC claims to be 90% sure. Are they 90% sure that their understanding of these important factors is low? It would appear so. Here it is, in black and white (and red and blue) in the graph published in their report.
The BBC has been bearing down hard on the global warming alarmism for several years. Never was heard a skeptical word. Now, their tone seems to be softening somewhat. At least they are letting other voices be heard, voices of those who doubt the central thesis and wisdom of dire predications about climate. This article discusses the intertwining of political and scientific interests in the publication of the IPCC reports.
At an IPCC Lead Authors' meeting in New Zealand, I well remember a conversation over lunch with three Europeans, unknown to me but who served as authors on other chapters. I sat at their table because it was convenient. After introducing myself, I sat in silence as their discussion continued, which boiled down to this: "We must write this report so strongly that it will convince the US to sign the Kyoto Protocol." Politics, at least for a few of the Lead Authors, was very much part and parcel of the process. And, while the 2001 report was being written, Dr
Robert Watson, IPCC Chair at the time, testified to the US Senate in 2000 adamantly advocating on behalf of the Kyoto Protocol, which even the journal Nature now reports is a failure.
The author is a scientist who builds computer climate models -- of the type upon which the IPCC report's predictions depend so heavily. Models are designed to conform to past climate records. What we don't know is whether these models will perform well in the future. That will be the true scientific test.
Mother Nature is incredibly complex, and to think we mortals are so clever and so perceptive that we can create computer code that accurately reproduces the millions of processes that determine climate is hubris (think of predicting the complexities of clouds).
Of all scientists, climate scientists should be the most humble. Our cousins in the one-to-five-day weather prediction business learned this long ago, partly because they were held accountable for their predictions every day.
Answering the question about how much warming has occurred because of increases in greenhouse gases and what we may expect in the future still holds enormous uncertainty, in my view.
To counter overconfidence in computer modelling, the author offers an anecdote from his formative ears:
The best advice regarding scientific knowledge, which certainly applies to climate, came to me from Mr Mallory, my high school physics teacher.
He proposed that we should always begin our scientific pronouncements with this statement: "At our present level of ignorance, we think we know..."