Yesterday I received a joint press release from a group of renewable energy trade associations. It touted a new report from the UN Intergovernmental Panel on Climate Change (IPCC) on the potential growth of renewable energy by 2050. The report has already garnered an impressive array of headlines, such as "Renewable Energy Can Power the World" and "Renewable Energy Key to Solving Climate Change". The headline from the Financial Times was characteristically more concrete, "World faces $15,000 bn renewable energy bill." Unfortunately, although the final report, rumored to run 1,000 pages, might support all of those conclusions when it is issued at the end of the month, the 25-page "Summary for Policymakers" falls far short of inspiring such confidence. Heaven help those policymakers if the summary is all they actually read.

I'm not even sure if "read" is even the correct verb to apply to this document. Once I got beyond the introductory paragraphs it seemed to degenerate into jargon and bureaucratese that was very hard to parse into plain meaning. The report's genesis as the product of pure consensus is readily apparent. Or as Andy Revkin of the New York Times' Dot Earth blog kindly put it, "it doesn't take readers much beyond what is already well established." That's a shame, because we don't need yet another report telling us that we are swimming in enough renewable energy to power our civilization umpteen times over, if we can merely muster the willpower to reach out and tap it. What we urgently need is a roadmap that describes a path--or preferably several possible paths--through the brambles that separate the energy status quo of 2011 from its ideal low-carbon state of 2050.

For example, we need to understand just how renewables will supplant the petroleum that currently provides around 94% of all transportation energy, at least in the US. That demand might be met by biofuels, although the report points out that the first-generation biofuels that supply nearly 3% of global road transport fuel today, but are still the only kind available on a commercial scale, have serious shortcomings. Closing the gap between 3% and 94% would require a true revolution in next-generation biofuels from sources such as cellulose and algae, yet after reading the Summary for Policymakers we are no wiser about when and how this will occur. I might note that such developments are rarely amenable to precise timetables, as the EPA is learning to its chagrin.

Alternatively, or in combination with biofuels, renewables might replace petroleum in transportation via the potentially more robust pathway of vehicle electrification, matching improved batteries with rapidly expanding supplies of intermittent renewables (wind, solar, tidal, etc.) delivered via increasingly intelligent power grids. But if that's the scenario, its crucial details are barely hinted at here.

The basic message of the summary appears to be that with enough investment, supported by the right policies, the currently identified renewable energy sources could expand by enough that in the very best case (out of 164 scenarios they considered) they could supply roughly as much energy by mid-century as we currently get from fossil fuels. That corresponds to 77% of total expected energy consumption in 2050 and may be the source of the headlines I saw. Of course the median level of those 164 scenarios is quite a bit lower, and the determination of the share of renewables in total energy relies on a projection implying that total global energy consumption will grow by an average of just 0.25% per year over the next 40 years. That suggests either a massive energy efficiency effort or minimal further economic uplift in the developing world. On a more reasonable track of 1% annual energy growth, the top scenario in the scatter chart on page 19 would meet 58% of total 2050 demand, while the median result would cover just a third of global energy needs. That's still impressive, compared to where we are today, but not quite as headline-grabbing.

I will be keenly interested to see what sort of scenarios the IPCC looked at in putting together the report on which this summary is based. Something tells me that they are likelier to fall into the category of what I would call projections or "cases" than true scenarios, which dig deeply into underlying trends and uncertainties and are not merely the output of a mechanistic model. That's not just a technical quibble, because I'm not aware of a single model-type forecast from 1970 that accurately projected the economic and sociopolitical conditions in which we find ourselves today. The intervening improvements in computing power and econometric sophistication still seem insufficient to conquer the fundamental unpredictability of looking that far into the future. But then the IPCC has a built-in bias to accept the results of such work, since long-term climate models underpin its entire effort. I hope I'm not alone in thinking that the expenditure of up to $15 trillion requires a much more rigorous justification than anything provided in this document. Whether or not Saint-Exupery really said it, a goal without a plan is just a wish.

If it seems that I'm being overly critical of a 1,000 page report that I haven't even seen on the basis of the horse-by-committee summary that I have seen, I plead guilty. But isn't that the same sin that the journalists and industry spokespeople are committing when they use this summary as the basis of glowing claims about the potential of renewables? And then there are the politicians and bureaucrats who will attempt to commit vast sums without ever reading any more than summaries such as this--at best--and without questioning the host of assumptions that went into them. If anything, this Summary for Policymakers reinforces my concern that the UN climate process has become so unwieldy and unresponsive that we must look elsewhere for leadership on this complex challenge. Meanwhile, we deserve a clearer articulation of how renewables can overcome the considerable obstacles that stand between their recent impressive performance and the achievement of the milestones this report suggests lie ahead.

Photo by Danilo Rizzuti.