The central fact is that there exists great uncertainty about the long-term dynamics of the global climate system. This fact, however, is not reflected in the partisan positions of either side in the highly-charged political debate over climate change.
The recently published IPCC report (AR5) raised a host of questions relating to how AR5 dealt with changes in the its ECS/TSR estimates from those of preceding report (AR4). Attached below is a very informative, critical analysis of these questions. It was prepared by Nic Lewis, an independent climate scientist, based in the UK, and a well known but respected skeptic of the consensus position.
The Lewis analysis was prepared in response to questions asked by UK House of Commons Energy and Climate Change Committee. While a Parliamentary request is a political request, Lewis’s response in grounded in science and is apolitical. His reasoning and assumptions of open to critical examination by anyone who chooses to do so. If Lewis is correct, his is a devastating critique of the state of art understanding of sensitivity question — which I reiterate, is at the heart of the entire debate of mankind’s effect on the global climate.
Attached for your review is Lewis’s analysis in PDF format; the highlights are mine. If you find them distracting, a clean version can be found at this link. Lewis also has an extended discussion of his all important Figure 1, which quantifies the degree to which the GCMs are running hot, at this link at Steve McIntyre’s Climate Audit website.
It is not easy reading, but it is well organized and well written. Anyone can understand the main points of this paper, if they make the effort.
PDF (9 Pages): Nic Lewis Submission to Parliament on Global Warming
If TCR really is 1.35°C then under RCP8.5 – the worst-case, business-as-usual scenario – the end of the 21st century will be approximately 2°C warmer than today.