So the AR4 synthesis is out. You can read the SPM and cherry-pick your favourite bit. The BBC has, and has selected climate change is “unequivocal” – fair enough but boring, because we’ve had that already – and may bring “abrupt and irreversible” impacts which made me sit up and take notice.
There is a headline that sez this, “Anthropogenic warming could lead to some impacts that are abrupt or irreversible, depending upon the rate and magnitude of the climate change.” But what is the supporting text? “Partial loss of ice sheets on polar land could imply metres of sea level rise, major changes in coastlines and inundation of low-lying areas, with greatest effects in river deltas and low-lying islands. Such changes are projected to occur over millennial time scales, but more rapid sea level rise on century time scales cannot be excluded.” Its a looooooooonnnggg jump from “cannot be excluded” to “may”, even if you go via “could”. The next para has “The MOC is very unlikely to undergo a large abrupt transition during the 21stcentury.” so that doesn’t help you either. The factsheet doesn’t mention abrupt.
Conclusion: still no good backing for use of “abrupt”.
A bit lower down they note that One declaration that reportedly caused heated discussion during the week-long talks here states that climate change may bring “abrupt and irreversible” impacts. Well I should hope so too, because that headline seems to be very poorly supported indeed.
Postscript: the beeb further report Mr Ban urged politicians to respond at a UN climate change conference in Bali “Today the world’s scientists have spoken clearly and with one voice,” he said. “In Bali I expect the world’s policymakers to do the same.” which wins him the Nobel prize for naivety (well I don’t suppose he is naive enough to belive it; he’s just jollying people along in a way that chairs are expected to). Mr Ban arrived at the IPCC meeting in Valencia from a fact-finding trip to Antarctic and South America. “I come to you humbled after seeing some of the most precious treasures of our planet threatened by my own GHG emissions” he said. Can you spot the bit that he *didn’t* say ;-)?