A fascinating picture, and blog post, comes my way, ht CR. There are various ways of looking at the same numbers; I've picked solar PV additions on a log scale, but you can also look on a linear scale, or look at total installations; see the post for more.
What we're seeing is that "official" forecasts of solar PV have lagged waay behind actual installations, and have done so with remarkable consistency. Despite repeated failure they have learnt nothing year on year. There's some discussion of just why the forecasts have been so bad, up to and including capture by Evil Fossil Fuel Barons, even though it isn't clear how that would make sense. Greenpeace also don't do a very good job, as the post notes. I tried to trawl back through GP's reports. But I got stuck because the 2005 report has ~70,000 PJ/a total energy baseline for 2000, whereas the 2010 one has 400,000; and that's illogical, captain. Also unpresciently, 2005 lumps solar PV, hydra and wind together; and the 2010 report is lead by pix of shiny mirrors.
The blog post quotes the IEA as pointing out that its reports are not supposed to be forecasts; this is probably about as useful as the IPCC saying the same about its projections. The IEA claims not to take into account new policies or "major new technologies" and that second point gets closest to the problem. Which I take to be not, really, any major new technologies but just steady technological improvements. Wiki has a nice pic showing growth by region; you can see the overall exponential growth continues, but Europe has clearly tailed off.
Although this is somehow news to me - clearly I've been asleep - others have noticed. The linked blog post provides examples, one of which is David Roberts at Vox. And, delightfully, I find myself able once again to disagree with him. He quotes GP saying Everything beyond projections for the next 10 years is simply a political statement from us, indicating what we want to see happen. This also becomes a work plan for us. If we see a renewable energy market isn’t performing as we want it to, we’ll try to jump in with campaigns—against fossil and nuclear fuels and in favor of renewables. And he likes this; because, effectively, he's a campaigner; and campaigners need something to campaign for. And I disagree because I wonder...
What are the consequences of this mis-forecast? Off in the real world, as opposed to scenario-land, solar PV keeps getting cheaper and people keep installing more of it. We can assume this is likely to continue, regardless of who campaigns for what and, probably, by this stage, largely regardless of government policies. Carbon taxes would help it, of course, but carbon taxes (or anything vaguely equivalent) are moving so sloowly that it seems solar PV will likely leap straight past that hurdle. I'm speculating here, of course. So a possible consequence of all this is that CO2 becomes less of a problem than we thought. Could it be that John McCarthy's semi-magical techno-optimism was actually right?