For twenty years and more, sceptical or dissident accounts of global warming, and more recently of ‘climate change’, have been ignored by the orthodoxy. Because governments had accepted the orthodoxy, at least in public, there was no need for debate about the science. That was settled. Now for the really important and exciting action: carbon taxes, subsidies for alternative energy, and the rest! The highpoint was probably 2009, just before the Copenhagen climate summit.
But things have changed more than a little. The lack of significant warming for a decade and more while greenhouse gas emissions have risen steadily, the real cost of the orthodoxy in practice when governments are short of money, the rise of international troubles that have nothing to do with ‘climate change’ — these factors have greatly reduced the confidence of the orthodox that they are are the Truth, and that they will prevail. The Abbott Government’s ending of the Australian carbon tax has been widely noted overseas, and heads of state of Germany, India and China are not going to the next climate summit on 23 September.
One consequence has been the generation of even shriller accounts of the doom that awaits us, as I pointed out in my last post. As interest in the whole issue wanes the orthodox feel the need to scream even more loudly, which may put even more people off. In economics this is known as a backward-sloping supply function, and you can see it today in our mineral exports: as iron ore prices decline our big miners are shipping even more of it abroad, which will further reduce the price.
Another consequence, to which I first referred a couple of posts ago, is that for the first time there exists a real debate about one quite important issue — the extent to which human activity has been responsible for any of the warming over the last century. The debate has taken place on two websites, Climate etc., whose hostess is Professor Judith Curry of Georgia Tech, and RealClimate, whose presiding genius is Gavin Schmidt, the new head of the Goddard Institute of Space Studies, which produces one of the important historical temperature datasets, GISTEMP. The two important links are here and here, but each has lots of comments and many references elsewhere.
Professor Curry has from the beginning of her website, four years ago, maintained that the level of real uncertainty in the whole global warming debate is much greater than the IPCC and the orthodox accept, and believes that the most recent IPCC Assessment Report, AR5, is disingenuous in both recognising (in the most oblique way) that there has been a long ‘hiatus’ in the warming and being even more confident that the orthodoxy is right. She highlights this little assertion on the question of attribution:
The AR5 provides an answer:
‘The best estimate of the human induced contribution to warming is similar to the observed warming over this period.’
She interprets it to imply that the IPCC’s best estimate is that 100% of the warming since 1950 is attributable to humans, and they then down weight this to ‘more than half’ to account for various uncertainties. And then assign an ‘extremely likely’ confidence level to all this.
She then wonders whether this is equivalent to ‘making things up’. The essay has drawn so far more than 800 comments, several of them from supporters of the orthodoxy, though not from Gavin Schmidt, who writes at RealClimate. He has taken Professor Curry to task in 2012 and 2013, essentially on the same issue: how much warming can be attributed to human activity? He supports the IPCC reports, and works hard, and ingeniously, to show that they must be right, and Professor Curry simply wrong: The bottom line is that multiple studies indicate with very strong confidence that human activity is the dominant component in the warming of the last 50 to 60 years, and that our best estimates are that pretty much all of the rise is anthropogenic.
Though I admire the way he argues, I don’t think he has won. He is committed to the AR5 statement that the world has warmed by so much since 1950, which (at least in my view) was the way in which the IPCC set to one side the real problem of the ‘hiatus’. And Dr Schmidt then ignores the other observational finding, that this warming didn’t really begin until 1975 — the earlier period, 1950 to 1975 — was one of a very small cooling. He states that the even earlier warming period, in the first half of the 20th century, was not caused by human activity (the models tell him so), but then dismisses the implication: that if the planet could warm without human activity, why could not the recent period of warming have been caused by whatever caused the earlier? Or was it a mixture of natural and human causes, and if so, by how much of each?
It is the impossibility of finding observational answers to these questions that caused Professor Curry to shake her head and state that the IPCC was simply over-confident in its statements about attribution.
I’ve done my best to summarise, but the exchange is really worth reading and reflecting on. Read Curry first, is my suggestion, then Schmidt.