So Eli has found a revised final draft

So Eli has found a revised final draft submitted by the WGIII working group and there is also a copy on SCRIBD for the bunnies Sunday morning reading pleasure.

There are, of course, any number of take homes.

First that properly done mitigation is low cost, 0.06% of global GDP

Second that nations trying to do it alone will fail, raise costs

Effective mitigation will not be achieved if individual agents advance their own interests independently. Climate change has the characteristics of a collective action problem at the global scale, because most greenhouse gases (GHGs) accumulate over time and mix globally, and emissions by any agent (e.g., individual, community, company, country) affect other agents

Third, that energy systems will have to be substantially altered

Scenarios reaching atmospheric concentration levels of about 450 ppm 1 CO2eq by 2100 (consistent with a likely chance to keep temperature change below 2°C relative to pre‐industrial levels include substantial cuts in anthropogenic GHG emissions by mid‐century through large‐scale changes in energy systems and potentially land use (high confidence).

Fourth that delay is the devil

Delaying mitigation efforts beyond those in place today through 2030 is estimated to substantially increase the difficulty of the transition to low longer‐term emissions levels and narrow the range of options consistent with maintaining temperature change below 2°C relative to pre‐industrial levels (high confidence)

Fifth that costs are not zero, but bearable, very bearable compared to the nothing at all, and even the adaptation only or primarily scenarios.  this is a bit tricky because the 0.06% annualized estimate corresponds (as is the habit for such) of 3-11% total in 2100

Of course, if you think the costs of a 580-650 ppm world are fine, the cost is less.  Good luck with that, and also of course there are some optimistic assumptions

Scenarios in which all countries of the world begin mitigation immediately, there is a single global carbon price, and all key technologies are available, have been used as a cost‐effective benchmark for estimating macroeconomic mitigation costs

and, reading the next section of Table 2 reveals a very very optimistic take on the possibilities of carbon capture which, even including reforestation as it does, depends at least in substantial part on unproven technology.

And making everyone unhappy

Nuclear energy is a mature low‐GHG emission source of baseload power, but its share of global electricity generation has been declining (since 1993). Nuclear energy could make an increasing contribution to low‐carbon energy supply, but a variety of barriers and risks exist (robust evidence, high agreement).

GHG emissions from energy supply can be reduced significantly by replacing current world average coal‐fired power plants with modern, highly efficient natural gas combined‐cycle power plants or combined heat and power plants, provided that natural gas is available and the fugitive emissions associated with extraction and supply are low or mitigated (robust evidence, high agreement).

Carbon dioxide capture and storage (CCS) technologies could reduce the lifecycle GHG emissions of fossil fuel power plants (medium evidence, medium agreement). While all components of integrated CCS systems exist and are in use today by the fossil fuel extraction and refining industry, CCS has not yet been applied at scale to a large, operational commercial fossil fuel power plant.

Finally on various methods of restraining emissions

Since AR4, cap and trade systems for GHGs have been established in a number of countries and regions. Their short‐run environmental effect has been limited as a result of loose caps or caps that have not proved to be constraining (limited evidence, medium agreement).

In some countries, tax‐based policies specifically aimed at reducing GHG emissions–alongside technology and other policies–have helped to weaken the link between GHG emissions and GDP (high confidence).

The reduction of subsidies for GHG‐related activities in various sectors can achieve emission reductions, depending on the social and economic context (high confidence).