" />

Just what is this Consensus anyway? En quoi consiste le “Consensus” ?

We’ve used the term “consensus” here a bit recently (see our earlier post on the subject), without ever really defining what we mean by it. In normal practice, there is no great need to define it – no science depends on it. But it’s useful to record the core that most scientists agree on, for public presentation. The consensus that exists is that of the IPCC reports, in particular the working group I report (there are three WG’s. By “IPCC”, people tend to mean WG I). Fortunately that report is available online for all to read at http://www.grida.no/climate/ipcc_tar/wg1/. It’s a good idea to realise that though the IPCC report contains the consensus, it didn’t form it. The IPCC process was supposed to be – and is – a summary of the science (as available at the time). Because they did their job well, it really is a good review/summary/synthesis.

Par William Connolley (traduit par Pierre Allemand)

Nous avons utilisé le terme “consensus” ici très récemment (voir l’ article précédent sur le sujet) sans réellement définir ce que nous entendions par là. Normalement, il n’y a pas vraiment besoin de le définir – rien de scientifique n’en dépend. Mais, il est d’usage de noter le cœur du sujet sur lequel la plupart des scientifiques sont d’accord, pour des présentations publiques. Le consensus existant est celui des rapports du GIEC, en particulier le groupe de travail n°I (il y a trois groupes de travail. Par “GIEC”, on a tendance à vouloir parler du groupe de travail n°I).


The main points that most would agree on as “the consensus” are:

  1. The earth is getting warmer (0.6 +/- 0.2 oC in the past century; 0.1 0.17 oC/decade over the last 30 years (see update)) [ch 2]
  2. People are causing this [ch 12] (see update)
  3. If GHG emissions continue, the warming will continue and indeed accelerate [ch 9]
  4. (This will be a problem and we ought to do something about it)

I’ve put those four points in rough order of certainty. The last one is in brackets because whilst many would agree, many others (who agree with 1-3) would not, at least without qualification. It’s probably not a part of the core consensus in the way 1-3 are. Most (all?) of us here on RealClimate are physical scientists – we can talk sensibly about past, present and future changes in climate, but potential impacts on ecosystems or human society are out of our field. If you want to see the IPCCs own summary, it’s here.

Other things we have mentioned in other posts come in as supporting evidence. That the increase in atmospheric CO2 is anthropogenic is so obvious that few people question it and in consequence few people rebut skepticism of it (though Eric has done so recently here; and the IPCC mention it). That the recent increase in temperature is unprecedented in the last 1000 years (see e.g. posts 64 or 7 by Mike) is one (but by no means the only) line of evidence indicating that recent change is likely to be unnatural (see update).

Page 1 of 3 | Next page