The last of the three IPCC 5thAssessment Reports has now been published, but with a final Synthesis Report to come towards the end of the year. The “Mitigation of Climate Change” details the various emission pathways that are open to us, the technologies required to move along them and most importantly, some feeling for the relative costs of doing so.

As had been the case with the Science and Impacts reports, a flurry of media reporting followed the release, but with little sustained discussion. Hyperbole and histrionics also filled the airwaves. For example, the Guardian newspaper reported:

The cheapest and least risky route to dealing with global warming is to abandon all dirty fossil fuels in coming decades, the report found. Gas – including that from the global fracking boom – could be important during the transition, but only if it replaced coal burning.

This is representative of the general tone of the reporting, with numerous outlets taking a similar line. The BBC stated under the heading “World must end ‘dirty’ fuel use – UN”:

A long-awaited UN report on how to curb climate change says the world must rapidly move away from carbon-intensive fuels. There must be a “massive shift” to renewable energy, says the study released in Berlin.

While it is a given that emissions must fall and for resolution of the climate issue at some level, anthropogenic emissions should be returned to the near net zero state that has prevailed for all of human history barring the last 300 or so years, nowhere in the Summary Report do words such as “abandon” and “dirty” actually appear. Rather, a carefully constructed economic and risk based argument is presented and it isn’t even until page 18 of 33 that the tradeoff between various technologies is actually explored. Up until that point there is quite a deep discussion on pathways, emission levels, scenarios and temperature ranges.

Then comes the economic crux of the report on page 18 in Table SPM.2. For scenarios ranging from 450ppm CO2eq up to 650 ppm CO2eq, consumption losses and mitigation costs are given through to 2100, with variations in the availability of technologies and the timing (i.e. delay) of mitigation actions. The centre section of this table is given below;


Particularly for the lower concentration scenario (430-480 ppm) the table highlights the importance of carbon capture and storage. For the “No CCS” mitigation pathway, i.e. a pathway in which CCS isn’t available as a mitigation option, the costs are significantly higher than the base case which has a full range of technologies available. This is still true for higher end concentrations, but not to the same extent. This underpins the argument that the energy system will take decades to see significant change and that therefore, in the interim at least, CCS becomes a key technology for delivering something that approaches the 2°C goal. For the higher concentration outcomes, immediate mitigation action is not so pressing and therefore the energy system has more time to evolve to much lower emissions without CCS – but of course with the consequence of elevated global temperatures. A similar story is seen in the Shell New Lens Scenarios.

Subtleties such as this were lost in the short media frenzy following the publication of the report and only appear later as people actually sit down and read the document. By then it is difficult for these stories to surface and the initial sound bites make their way into the long list of urban myths we must then deal with on the issue of climate change.