It is hoped that the “Summary for Policymakers” will be an accurate distillation. Hundreds of scientists have been involved in the review process, and it is safe to say that means hundreds of bored scientists, because there is very little in it that is scientifically new. For example, it will report with increasing certitude that humans are responsible for most of the surface warming that began in the mid‐1970s. That’s been pretty obvious for years.
Graphs in today’s summary will show that the rate of global warming has been remarkably constant — about 0.18 degrees Centigrade per decade — since 1975. So, any news report that “U.N. panel says the planet is warming at an increasing rate” (and there will be many) will be dead wrong.
For more than a century, it has been known that increasing the atmospheric concentration of carbon dioxide will eventually lead to a warming of surface temperatures, concentrated more in winter than summer, and more in mid and high‐latitudes over land. That’s exactly what’s been observed for years, as is a global cooling of the stratosphere, another prediction of greenhouse theory.
More interesting, and, again, less newsy, is that the communal behavior of the dozens of computer models for future climate also predicts a constant (rather than an increasing) rate of warming.
That means that unless the collective conclusions of all of the models is wrong, we can confidently estimate a warming of about 1.8 degrees Centigrade from 2000 to 2100. That’s very near the low end of the range of projections released today. The fact that the most logical distillation of observed and predicted warming yields such a modest heating should be reassuring, rather than alarming.
The new estimate for maximum rise in sea level, assuming a middle‐of‐the‐road estimate for carbon dioxide changes, is going to be lower than in previous IPCC reports. The last figure I saw was around 17 inches by 2100, down 40 percent from their previously estimated maximum.
A small, but very vocal, band of extremists have been hawking a doomsday scenario, in which Greenland suddenly melts, raising sea levels 12 feet or more by 2100. While this forecast enjoys no real support in the traditionally refereed scientific literature, it is repeated everywhere, and its supporters are already claiming that the IPCC — the self‐proclaimed “consensus of scientists” — is now wrong because it has toned down its projections of doom and gloom.
But the integrated warming of southern Greenland (the region that sheds ice) was much greater for several decades in the early and mid‐20th century than in the last decade. In fact, with the exception of one year (2003), Greenland’s recent temperatures aren’t particularly unusual, nor is its rate of ice loss.
As measured recently by satellite, and published in Science magazine, Greenland is losing .0004 percent of its ice per year, or 0.4 percent per century. All modern computer models require nearly 1,000 years of carbon concentrations three times what they are today to melt the majority of Greenland’s ice. Does anyone seriously believe we will be a fossil‐fuel powered society in, say, the year 2500?
In summary, what’s not new in today’s IPCC report — that humans are warming the planet — will be treated as big news, while what is new — that sea levels are not likely to rise as much as previously predicted — will be ignored, at least by everyone except the extremist fringe.