Before we forget: IPCC working group 3 report published

In case you have not noticed, the IPCC has published the report of Working Group 3, the last in the trilogy of its state-of-the-art Fifth Assessment. There seems to be an established routine in media coverage which goes by the rule that most attention should be paid to working group 'number one' (covering the physical science basis), less to 'number two' (impacts, adaptation, vulnerability), and well you guessed it, even less to 'number three' (mitigation). But the last one, published last week, seems to have led to some behind the
scenes wrangling between scientists and government representatives which ended with the latter carrying the day. According to one of the scientists on the panel, David Victor, some governments didn't like the inclusion of information which attributes emissions to countries (see also here for an assessment of the episode). This may be understandable but makes a mockery of the principle of the IPCC's slogan that it provides policy-relevant, yet policy neutral information to governments. In this instance governments simply got rid of information which did not suit them.

Another aspect caught my attention. This is the shift of emphasis (or lack thereof) from AR4 to AR5. Below I show two word clouds, taken form the Summary for Policymakers documents. On top is the latest report, below the previous:

The top frequency words are much the same in both SPM documents: emissions, mitigation, energy.

In contrast, both WG1 and WG2 have seen a shift in emphasis. WG1 in the 2007 report emphasised sea level, ice, and warming but in 2013 gave more prominence to the words confidence, mean and surface. Likewise, WG2 shifted from a focus on projected, impacts, and increased to adaptation, risks and confidence. Confidence has gained in both Working groups.

What does this tell us? Perhaps not much. Simple frequency lists are too crude to convey nuanced meaning. However, they are often a good indication of what is emphasised in a text (provided it is of sufficient length). Assuming this is the case I would venture the idea that WG1 and WG2 have re-assessed their previous reports (without explicitly saying so) whereas WG3 has not. It sticks to the same message as before.

If we believe the Economist, the message of WG3 is that massive reductions of CO2 emissions are needed if the world wants to stay within the 'safe' boundary of 2 degrees Celsius of warming. Because of rapidly increasing rates of emissions over the past decade, this goal seems difficult to achieve. However, and this is where it gets interesting, the report sees a chance of achieving the target by reinforcing the efforts of expanding renewables and nuclear for energy generation, up to 80% (and by developing carbon capture and storage). The costs of doing so are projected to be moderate, costing just 0.06% of annual GDP worldwide by the year 2100. 'These numbers are preposterous', says the Economist: 'Germany and Spain have gone further than most in using public subsidies to boost the share of renewable energy (though to nothing like 80%) and their bills have been enormous: 0.6% of GDP a year in Germany and 0.8% in Spain. The costs of emission-reduction measures have routinely proved much higher than expected.'

Should Working Group 3 have known better? After all, 13 of its 113 drafting authors are from Germany, the highest proportion. 9 come from the USA, 5 from India, 3 from China, Brazil, and the UK.