David Evans, greenhouse sceptic debates his views on Troppo

But the opposite occurred. By 2003 it had been established to everyone’s satisfaction that temperature changes preceded corresponding carbon changes by an average of 800 years: so temperature changes caused carbon changes - a warmer ocean supports more carbon in the atmosphere, after delays due to mixing. [4] So the ice core data no longer supported AGW. The alarmists failed to effectively notify the public.

After several prominent public claims by sceptics in 2008 that there is no evidence left for AGW, alarmist scientists offered only two points.

First, laboratory tests prove that carbon dioxide is a greenhouse gas. But that observation tells us nothing about how much the global temperature changes if extra carbon enters the real, complicated atmosphere. Every emitted carbon atom raises the global temperature, but the missing hotspot shows that the effect is negligible.

Second, computer models. Computer models are just huge concatenations of calculations that, individually, could have been performed on a handheld calculator. They are theory, not evidence.

Governments have spent over $50 billion on climate research since 1990, and we have not found any actual evidence for AGW. [5]

So if there is no evidence to support AGW, and the missing hotspot shows that AGW is wrong, why does most of the world still believe in AGW?

Part of the answer is that science changed direction after a large constituency of vested interests had invested in AGW. The old ice core data provided support from 1985, the IPCC was established by the UN in 1988 to look into human changes to climate, and the Kyoto Protocol was negotiated in 1997 to limit carbon emissions. By 1999 the western political class were doing something, the western media were rallying behind “saving the planet”, and scientists were being paid by governments to research the effects of human-caused global warming.

But then the evidence took science off in a different direction: the new ice core data in 2003, the missing hotspot in 2007, and the global temperature has stopped trending up since 2001 [6]. Governments, the media, and many scientists did not notice.

The remainder of the answer for the current belief in AGW is darker and more political. An offbeat theory in the 1970s, AGW was adopted by a group of about 45 atmospheric modelers and physicists. That group dominated climate science journals, peer reviewed each others papers, and hindered competing ideas by underhand methods [7]. AGW gained political support from proponents of nuclear power, and vice-president Gore appointed AGW supporters to science positions in the USA.

AGW grabbed control of climate funding in key western countries. Lack of diversity in science funding has been a major problem since government took over funding science in World War II. Science is like a courtroom - protagonists put forward their best cases, and out of the argument some truth emerges. But if only one side is funded and heard, then truth tends not to emerge. This happened in climate science, which is almost completely government funded and has been dominated by AGW for two decades. Sceptics are mainly scientists who are retired or who have moved on to other areas - their funding no longer depends on allegiance to AGW. The alarmists are full time, well funded, and hog the megaphone.

AGW was always promoted as being supported by nearly all scientists (though polls and history do not support this). Counting numbers of supporters and creating a bandwagon effect by announcing you are in the majority is a political tactic.

AGW always advanced principally by political means; as a scientific theory it was always weak, and now the evidence contradicts it. It’s like a return to medieval times, where authority rules and evidence is ignored. Notice how the proponents of AGW don’t want to talk about evidence of the causes? Anything but evidence of cause - attack people’s motives, someone else “has the evidence”, theoretical models, evidence that global warming is occurring, how important they are, what credentials they have, how worthy they are, the dog ate my evidence, “the science is settled”, polar bears, anything. Talking about the evidence of the cause of global warming does not advance their cause. Politics says AGW is correct; science says it is wrong.