When it comes to the consensus all is not what it seems. In the last four posts I explored the consensus position and the polls that were used to provide proof of its existence. In every one of them the conclusion seemed to be that this consensus position was rather uncontroversial.
It goes like this: humans increased the level of CO2 in the atmosphere. CO2 being a greenhouse causes warming. The thermometer record shows the earth has warmed in the last century and a half and at least some of this warming is very likely a consequence of the CO2.
Nothing controversial here. It didn’t lay bare the difference between skeptics and alarmists.
The message from the opinion polls was only in favor for anthropogenic global warming because of clever framing of the questions and misinterpretation of the results. It is not because scientists agree that there is a warming that it is automatically dangerous or catastrophically.
But there is more to it. Looking behind that consensus we could ask ourselves the big question: why do we need to rely on the opinion of scientists in the first place? Why even do the effort to poll scientists when there is clear evidence?
The real inconvenient truth is that there is no direct evidence that unequivocally proves the extent of human influence on climate. There aren’t instruments that shows us how much of the warming is due to humans and how much is due to natural variation. There is not much historical data, so there is hardly a base line. The high quality measurements we have now started when the human influence was already assumed to be in process. More, climate is changing all the time. Our climate was different in the Little Ice Age, the Medivial Warm Period, the Roman Warm Period, the previous Ice Age,… How could changes introduced by humans be distinguished from the changes that would have occurred without humans?
When looking at the evidence we don’t know whether that influence is negligible or significant. Therefor, in the absence of hard evidence, that opinion is deemed so important.