IPCC WGIII report on mitigation is out and since it is long I suspect that it will make sense to split my commentary in small pieces. Everybody cherry picks from these reports and I will be no different. I will cherry pick from the parts that I feel are most relevant, interesting (for me), or most target rich. The report is kind of long and I have made no attempt to read every single line of it. So lets get going..
Magnitude of the challenge
To grasp the main point see the Fig. 6.18 from the report. The figure shows a large collection of fantasies of what might happen and how the story relates to concentrations of greenhouse gases and thus to global warming. Scenarios with estimated CO2 concentrations in the range between 430-480 ppm are the blue dots and the rest imply stronger heating than the political goal of roughly 2 ℃. Note, however, that in most scenarios concentrations actually overshoot 450 ppm and rely on negative emissions technologies to ride to the rescue in the later part of the century. (I wonder if anyone making decisions at 2050 reads are cares about reports written in 2014? I certainly wont.) On the x-axis we have the global final energy use and on the y-axis we have low-carbon (nuclear, renewables, CCS) primary energy supply.
The first thing to note is that bulk of those pretty blue dots correspond to final energy use of about 500EJ which is about 40% higher than today. Therefore, the blue dots implicitly assume a growth rate of around 0.8%. This is much lower than our recent past would suggest and if we were to use perhaps more realistic growth rate of 2%, the final energy use would grow 120% from 2010-2050 so that the final energy use would rise to almost 790 EJ, a value that is almost off-scale in the figure. This suggests that not only do most of those blue dots rely on non-existing negative emission technologies, but they also rely on very radical assumptions about consumption growth.
To illustrate the 2nd point, I added to the figure few line to make trends clearer. The green line shows estimated trend for the addition of low carbon energy 1970-2000, the red line shows the progress 2000-2010, and the blue line shows what is needed to get to those blue points. Ironically enough as public expressions of climate concerns have escalated, the actual effort to decarbonize has been reduced (see also here). Even with the low estimates of consumption growth, the current low carbon additions to energy supply are too low by more than a factor of ten.
Let me illustrate the gap between talk and substance by a simple numerical example. Wind resource is huge and can (so we are told) power the entire planet many times over. So let us just build wind turbines to cover most of that low carbon energy needs. Let us say 400EJ of wind energy by 2050 and ignore all integration, cost, and land use issues. (Since at this level wind electricity would also be transformed to other forms of energy such as heat, I will ignore the distinction between primary energy and electricity here. 1kWh of electricity is no more than 1kWh of heat. If you object you can divide the relevant numbers by about 3, but it will not change anything of relevance.) If the turbines have a 20 year lifetime and they run at 25% capacity factors we will need about 51TW of wind power capacity at 2050. Taking into account that 20 year lifetime maintaining this level requires a construction rate of around 51000GW/20 year=2500GW/year. Last year 27 GW of wind power capacity was installed in the world. The amount needed is therefore off by about a factor of 100. (If you add that factor of three…”just” a factor of 30 or so.)
I find it troubling that in addition to supposedly avoiding telling countries what policies to pursue, IPCC also declines from comparing past policies with respect to their success at mitigating emissions. This is largely an empirical question with obvious relevance for mitigation and responsible governments should welcome critical evaluation of their policies by outside experts. However, I guess the keyword here is “responsible” and suspect that honest comparison cannot be made since it would be politically too inconvenient for many countries. The fact remains that to date countries most successful in reducing their GHG emissions, were countries like Sweden and France in the 80’s without any climate policies whatsoever (see here, here, and here for a Global Carbon Project presentation on page 12, for example). The politics in the past few decades has been heavy on rhetoric and ever lighter on substance. In conclusion I find it very unlikely that we will stay below 2 ℃ warming. The goal is too demanding and is not made any easier by the woefully inadequate response demonstrated by every single country on the planet.