Posted: Jan 17, 2015 6:03 am
Clive Durdle wrote:Why the repetition of linear?
Because I'm making the basis of my calculation explicit.
Clive Durdle wrote:I thought there are loads of positive feedback effects, like melting of permafrost releasing methane, therefore exponential?
And are not changes in living systems exponential?
As I said, assumptions of a linear rise may not be justified, but even if there are feedbacks, you need to quantify them. Exponential feedbacks could add 0.1C or less or an extra 2C or more; exponential doesn't mean "huge", especially over what is in climate terms a very short timescale of 85 years. We're on track for 2C by 2100. We may overshoot if there are significant feedbacks before then. Either scenario is not good in terms of impacts, and it's clear that the warming is primarily anthropogenic.
I have no beef with climate science, but you asked:
Clive Durdle wrote:I am correct in stating that is a third of 2 and that we are already on course for a major over shoot of 2?
and the answer is that no, you're not particularly correct that we're on course for a major overshoot of 2C by 2100. It might happen, but 0.68C by 2014 isn't evidence that we will overshoot, but evidence that the 2C prediction is ballpark correct.