The Hockey stick graph is featured prominently in most alarmist literature on global warming. It is meant to show that temperature anomalies were nice, small fluctuations throughout the past millenium, and that industrial revolution messed the whole thing up.
The Wegman Report is prepared by independent, respectable statisticians who examine the debate surrounding the graph. The debate was initiated by Steven McIntyre and Ross McKitrick when they did something I have been too lazy to do: They tried to replicate the results obtained by Michael Mann and colleagues.
Contrary to scientific convention, they faced obstacle after obstacle when trying to obtain specifics on methodology and data from Dr. Mann. Eventually, they found that Dr. Mann's incorrect use of well established statistical methods had a tendency to pick hockey stick shapes out of randomly generated data.
The Wegman Report report is a vindication of those of who have been disappointed by the lack of scientific rigor in climate reconstruction and modeling exercises that result in, for example, Time Magazine's Global Warming Bias.
- The global mean surface temperature is always changing. Over the past 60 years, it has both decreased and increased. For the past century, it has probably increased by about 0.6 ±0.15 degrees Centigrade (C). That is to say, we have had some global mean warming.
- CO2 is a greenhouse gas and its increase should contribute to warming. It is, in fact, increasing, and a doubling would increase the greenhouse effect (mainly due to water vapor and clouds) by about 2%.
- There is good evidence that man has been responsible for the recent increase in CO2, though climate itself (as well as other natural phenomena) can also cause changes in CO2.
Taking these points as given, the next question is:
How much world wellbeing are we willing to give up to reduce carbon emissions to the extent advocated by, say, Al Gore?
An indirect answer to that comes from the Copenhagen Consensus which prioritized among many issues that we face today. The ranking takes in to account how much benefit a particular proposal can generate per dollar spent.
Unsurprisingly, simple things that can ensure children can grow up, live healthy lives, and accumulate human capital are ranked highest. It is far easier to mitigate the effects of climate change if people are not uneducated, hungry and poor.
Trade and markets play a huge role in raising the living standards in poor countries. Severely cutting carbon emissions over a very short term would result in reduced incomes in the industrialized nations, and would reduce their imports from poor countries. That would make the poor countries even poorer, and more prone to whatever nature throws their way.
By the way, there will be a hearing in the U.S. house of representatives on the questions surrounding the Hockey Stick on July 19, 2006, at 10 am. Should be interesting.