@ Bob Wallace
Well after I had a look at the paper, I think this is not what they are showing and they do not miss "what is currently happening in the world" & "The authors put a ruler on the growth of coal up to 2012 and projected growth going forward" is not what they actually have done. They put it into a well needed perspective (which is not yet possible with the post 2012 years, as the data is not complete).
Fortunately the paper in question is not pay walled and accessible here (
http://iopscience.iop.org/1748-9326/9/8/084018/)
I'll try to give a "short"
summary, but as I usually do miss or misunderstand some things (what happens when laymen like me read scientific papers), please feel free to correct me if I have made some mistakes, because I do want to understand things better & I don't want to misrepresent anything.
In short: I think they provide a valuable insight into how big the task of emission reduction really is. They show that the future emissions of the already existing ff-power-plants are huge, even if we would shot them down quite quickly and would not built new ones. But for a matter of fact we do built news ones - and we still do it with a growing pace, even if the growing is slowing a little bit (as they demonstrate).
Summary: The main target of the paper is the inertia of our socio-economic system (especially our energy system). The authors think that this inertia is not well represented in the RCPs and other emission pathways which leads to an underestimation of the task at hand.
In 2010 (Davis, Future Co2 emissions and climate change from existing energy infrastructure, Science 329 2010) they tried to quantify the inertia with the concept of "committed" emissions for the first time. The paper provided data for the year 2009, but no historical trends for a broader perspective.
The concept of "committed emissions" of the new paper is described as follows (emphasis mine, see also fig 1 bellow):
Note: they only look at the power generation sector, wich did account for ~40% of the total emissions in 2011.
"The general principle of commitment accounting is shown schematically in figure 1. Two views are contrasted for the case where a new device, when built, is expected to run for five years and to emit one unit of CO2 each year. Today’s carbon accounting would report annual emissions of one unit of CO 2 in each of the five years of operation. Commitment accounting instead assigns all five units to the year when the device begins to operate (figure 1(a)). We call these anticipated emissions‘ committed emissions ’ or simply ‘ commitments. ’ Figure 1(b) presents the same device three years after it begins to operate and shows (below the line) the initial commitments that have been realized as emissions and those that remain commitments. We depict realized and remaining commitments as negative numbers to re fl ect the fact that net commitments will be zero when fully realized.
‘Committed’ does not mean inevitable. If the device in figure 1 was shut down after operating only four years, its remaining commitment would go to zero, and both committed and realized emissions would be shortened to four units in all subsequent representations. Conversely, if the device continued to operate after fi ve years, both committed emissions and realized emissions would be increased by one unit each year until the device was retired." (p. 2)
For the "commitment accounting" you need at least 4 pieces of information about the ff-burning power plants:
(1) the year the device began operating,
(2) the expected operating lifetime of the device,
(3) the annual emissions from the device, and,
(4) if the device is no longer operating, the year the device ceased operating.
To get this infos, they used two sources:
The Platts World Electric Power Plant database (
http://www.platts.com/products/world-electric-power-plants-database)
Carbon Monitoring for Action (CARMA) database (
http://carma.org/)
(Interesting detail: from the 95.529 fossil-fuel generators included in the Platts list, only 13.000 are retired.)
A lot of data correction is needed for the available date, but in the end they get a estimate of mean lifetime for ff-power-plants:
37 (natural gas),
35 (oil),
and 32 years (coal)
They did a deeper analysis of the lifetimes, but in the end they found no specific regional trends. To make things simple, the choose a mean lifetime for their computations of 40 years. That seems a bit odd as 35 years would seem closer to the mean of all three ffs, but in the end it doesn't matter much as they provide results for lifetimes between 20 and 60 years.
Results see following post.
