WGIII is out - Mitigation options and societal impacts

The IPCC AR5 WGIII Summary for Policy Makers is now available for download. Without making a recommendation for any particular option, it assesses "the scientific, technological, environmental, economic and social aspects of mitigation of climate change".  It also assesses societal implications of different mitigation policies.

For this assessment, about 900 mitigation scenarios have been collected in a database based on published integrated models.

That's a lot of mitigation scenarios to work through! I'm still reading the report as I write this. It looks as if the main report will be chock full of facts and figures as well as emphasising what will probably seem obvious to most readers.

One item that fits in the "facts and figures" category is this one, about how if we don't do something, we're stuffed:

Without additional efforts to reduce GHG emissions beyond those in place today, emissions growth is expected to persist driven by growth in global population and economic activities. Baseline scenarios, those without additional mitigation, result in global mean surface temperature increases in 2100 from 3.7 to 4.8°C compared to pre‐industrial levels 10 (median values; the range is 2.5°C to 7.8°C when including climate uncertainty, see Table SPM.1)

Yep, the report comes right out and says we could be heading for a temperature rise of 7.8°C.

We've not done enough to stay safe.  We've not promised to do enough to stay below 2°C of warming. But we can get there if we put our collective mind to it.

Estimated global GHG emissions levels in 2020 based on the Cancún Pledges are not consistent with cost‐effective long‐term mitigation trajectories that are at least as likely as not to limit temperature change to 2°C relative to pre‐industrial levels (2100 concentrations of about 450 and about 500 ppm CO2eq), but they do not preclude the option to meet that goal (high confidence). Meeting this goal would require further substantial reductions beyond 2020. The Cancún Pledges are broadly consistent with cost‐effective scenarios that are likely to keep temperature change below 3°C relative to preindustrial levels. [6.4, 13.13, Figures TS.11, TS.13]

The more we delay the more dangerous and costly it becomes and the fewer choices we'll have.

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

The report includes some pie-in-the-sky scenarios for comparison, such as everywhere on earth starting to mitigate immediately and there is a global price on carbon. It's not all bad news. If we act properly, there will be lots of associated benefits such as clean air (which some parts of the world haven't seen in a while).

The SPM touches on different sectors: transport, buildings, and industry as well as agriculture, forestry and other land use (which has its own acronym AFOLU). It also discusses what actions have been taken around the world to mitigate, in a broader policy context. The final (short) section covers international cooperation.

The main report should also be out shortly.  Meanwhile, you can read the Summary for Policy Makers.


By the way, the only mention of this at WUWT so far is a dig at ClimateProgress (archived here), although for some reason Anthony Watts neglected to mention that the ClimateProgress article was about WGIII.

Anthony probably didn't realise what Joe Romm's article was about, even though it's mentioned in the snapshot he took.  He was too busy trying to make a "funny" out of Joe Romm writing:

You read that right, the annual growth loss to preserve a livable climate is 0.06% — and that’s “relative to annualized consumption growth in the baseline that is between 1.6% and 3% per year.” So we’re talking annual growth of, say 2.24% rather than 2.30% to save billions and billions of people from needless suffering for decades if not centuries. As always, every word of the report was signed off on by every major government in the world.