There was a global cooling consensus in the 1970s and there is now a global warming consensus. Available data for the last 12,000 years show that the Earth has gone through many of both as parts of continuous cycling.
The current controversy involves charges that the latest warming trend can be traced to our sins -- and that we had better reform. But most of the measurements are taken near cities. These are misleading beacuse cities are "heat islands".
And the heat islands are hottest in their centers and less so in their suburbs. One more reason to be wary of industrial policies that seek to reverse suburbanization and create strong city centers.
"Confessions of an 'Exx-Con'"
By ROBERT L. POLLOCK WSJ, June 17, 2006; Page A10
"Global-warming alarmists take it for granted that they have the 'scientific consensus' on their side. The truth is that their views can be as much an article of faith that avoids or elides basic facts.
"I was reminded of this recently after suggesting on our weekly television show -- The Journal Editorial Report on Fox News Channel -- that 'everyone agrees there has been some warming over the past century, but most of it happened before 1940.'
"'Not true,' declared a subsequent editorial in the New Republic magazine. 'The last three decades have seen the sharpest rise.' TNR suggested I was what they've dubbed an 'Exx-Con' -- that is, a conservative whose views on climate change are so unmoored from reality that they can only be explained by a slavish devotion to Exxon and other big oil firms.
"But it is TNR that's having trouble with the facts here. I'll grant that my off-the-cuff remarks could have been worded a bit more precisely. I probably should have said 'more than half' instead of 'most.' But that doesn't change the fact -- as the NASA charts nearby illustrate -- that the early 20th century saw a rise in global and U.S. temperature, followed by about three decades of declining or stable temperatures that global-warming alarmists have a hard time trying to explain. (Don't let the slope of the chart scare you either; we're looking at small variations here.)
"The relevant part of TNR's May 25 piece seems to be based on an innumerate May 16 attack on me at the far-left Web site Mediamatters.org. Mediamatters said almost identically that 'the last three decades (1976-2005) have seen a sharper rise in global air temperature.' But rather than fess up to its source, TNR responded to my complaint with the pretense of assigning a fact-checker to the case before deciding there would be no correction.
"The Mediamatters attack suggests I'm wrong because the difference between the coldest early-20th-century year and the warmest mid-century year is very slightly smaller that the difference between 1976 and 2005. But if the issue is by what date 'most' of the warming occurred, there are three relevant data points, not four -- the 1970s trough doesn't matter. And the difference between 1907 (the coldest year) and 1944 (the warmest mid-century) is .59 degrees Celsius, while the difference between 1944 and 2005 is .42 degrees. "Most" of the warming that has taken place over the last century had indeed occurred by about 1940.
"One could leave it at that. But I want to avoid the other mistake my critics make, which is thinking that long-term temperature trends should be measured by the difference between single, and possibly anomalous, years. That's why the NASA graphs contain a line representing the five-year rolling average. Looking at things this way still supports my point, admittedly a bit less so.
"In any case, the graph at issue presents a challenge to those who claim that the recent warming trend is primarily caused by carbon dioxide and is not part of a natural rebound from a cool 19th century. The early 20th century saw a rise in temperature rise at least as great. And far, far more CO2 has been pumped into the atmosphere in the years following 1940 than the years before.
"What's more, there's a debate over whether recent global data is biased upward by the fact that many measuring stations are located in or near cities around the world that have grown rapidly over the past half-century. Anyone who's ever crossed the George Washington Bridge can understand the concept of the urban 'heat island' effect.
"In that regard, a recent study of Greenland -- where allegedly melting glaciers are allegedly threatening a catastrophic sea-level rise -- published in Geophysical Research Letters is fascinating. It finds that Greenland is no warmer today than it was in the 1920s, and that 'although there has been a considerable temperature increase during the last decade (1995-2005) a similar increase occurred during the early part of the 20th century (1920-1930) when carbon dioxide or other greenhouse gases could not be a cause.' The U.S. temperature graph shows much the same. The U.S. inarguably produces more reliable data than most other countries, or the sparsely sampled oceans that cover most of the globe, and we've seen very little warming since the 1930s.
"Finally, a word about motive. Why wouldn't I want to be on the safe side and embrace the Kyoto Protocol? Not because of an attachment to oil companies, but because meaningful CO2 cutbacks would entail drastic reductions in energy use by billions of people in places like China and India who are finally getting a chance at a better life. The New Republic doesn't seem to have addressed such consequences in any serious way. Attempting to wave someone out of the argument by calling them an Exx-con is much easier than confronting the difficult facts beneath the global warming debate."