Stern warning from climate change economics report 30 October 06

The headlines have all been optimistic – we can tackle global warming with only a 1% cost to global GDP. A rare good news story on the global warming issue, right?

Wrong. The stabilisation pathway this figure refers to is 550 CO2 equivalent (about 500ppm in CO2 only), which will yield anything between three and four degrees warming. Yet, as I’ve argued in several recent articles, if we pass the two degrees threshold, the chances of runaway global warming impacts kicking in are dangerously high.

Stern suggests that stabilising at 400 ppm CO2 only is well nigh impossible given that we will be there within less than 10 years. But what is impractical for humans may be the only thing which is practical in terms of the planetary biosphere. The report admits that 3-4 degrees would lead to the mass extinction of 50% of species alive today, yet seemingly advocates a stabilisation target that would lead to exactly this outcome. The impact on humanity – especially the poor – would also be catastrophic, a point made very clearly by Christian Aid.

I highly recommend people read the report (the whole thing, not just the Executive Summary) however – it is an excellent review of the latest science, and says very clearly what impacts are likely to arrive with what degree changes. The tables on what stabilisation targets will yield what temperature increases are particularly useful. I do think that the headline figures on both economic damages and climate refugees are major under-estimates, but credit should be given for trying to quantify them at all.

So unlike almost everyone else, the sheer awfulness of our current position made me feel more and more pessimistic the deeper into I got into the Stern review. Evidently the only practically possible course will extinguish half of life on Earth – and even that requires emissions cuts unlikely to be acceptable to the likes of the US and China. The business as usual scenarios, Stern tells us, take the planet into five or more degrees of warming by the end of the century – something my upcoming Six Degrees book suggests will trigger the greatest mass extinction in geological history, one that humanity will be hard-pressed itself to survive.

Make up your own mind. The whole thing is on the web here.