I haven’t seen this reported elsewhere (so perhaps I am way off base) but I think the new statement of climate sensitivity in the IPCC AR5 represents some real good news compared with the statement in AR4
Here is the statement from AR5:
Climate sensitivity is likely in the range 1.5°C to 4.5°C, extremely unlikely less than 1°C, and very unlikely greater than 6°C
And here is the statement from AR4:
Climate sensitivity is likely to be in the range of 2 to 4.5°C with a best estimate of about 3°C, and is very unlikely to be less than 1.5°C. Values substantially higher than 4.5°C cannot be excluded, but agreement of models with observations is not as good for those values
The part I put in bold represents the terrifying possibility that climate sensitivity is much higher than we thought. Thankfully research published since the 2007 IPCC AR4 indicates that this terrifying scenario is not likely to be accurate.
Of course this doesn’t mean we are out of the woods. The estimates of climate sensitivity in AR5 are plenty worrisome and even the low-end estimate of 1.5°C is reason for real concern . To stretch the ‘out of the woods’ metaphor in the 2007 AR4 report we were lost in the woods and in real danger (the estimate of climate sensitivity). On top of it all there was a distant howl of hungry wolves (the possibility of climate sensitivity being substantially higher) . Now in 2013 with AR5 we are still lost in the woods, and in real danger but the wolves are gone.
In a field like climate change, where dire news in the norm, I think this qualifies as very good news.