Otto in this case is Alexander Otto, a scientist at something called the “Environmental Change Institute” at Oxford University. And the “et al” here is quite the list: 16 climate scientists, many of them heavily involved in the IPCC, although one of them (Nicholas Lewis) is technically not a climate scientist but a statistician who had recently wandered in and begun showing the scientists how to do their jobs. The paper these 17 wrote was published in Nature Geoscience and was remarkably short, only 7 paragraphs in which they got right to the point. There hadn’t been much warming thus far during the 21st century despite all the extra CO2 in the air and it was time to revisit the question of ECS. So they got the data together from the usual places and did the usual calculations and determined the most likely value of ECS is 2.0C.
What with uncertainties, the “error bars” so often missing in alarmist climate science, they said it could be between 1.2 and 3.9C, but the best estimate was 2.0C. And one of the most remarkable points they made was that the flat temperatures of the 2000-2012 interval only slightly reduced the estimate. Had they estimated it using pretty much any data interval since the 1970s they’d get about the same answer, roughly 2.0C.
This number is not zero, so if you’re looking for evidence that CO2 has no effect on the climate, you won’t find it here. But as we’ve said elsewhere, if ECS is around 2.0, then according to economists the Social Cost of Carbon, the amount of harm inflicted by an additional tonne of the stuff, is basically zero because at that level of warming impact the benefits of extra CO2 cancel out any hypothetical problems from warming. So if the climate activists out there really want to follow the science, they should explain why all these scientists keep finding ECS is too low to justify expensive climate policies.