Another side of the future-consequences-in-the-pipeline argument that Hansen makes is this.
The closest thing the naysayers have to a substantive argument is the suggestion that global albedo (how reflective the planet is) might increase; only a small such increase would cancel out the warming tendency, and we could live happily ever after. Of course, nothing in the paleoclimate record gives any cause for believing in such a thing – if anything the system seems surprisingly more “tippy” than one would expect, especially in the geologically recent past.
The fact is that the easiest global climate signal to measure is the surface temperature, which has not gone up as sharply in the past decade as might have been anticipated. Could this be the result of the calming negative feedback that Spencer and Lindzen are always invoking. Have clouds increased in such a way as to reduce global warming? Can we presume that this makes climate risks small?
There are several alternatives to the albedo effect. Hansen refers to one of them – anthropogenic aerosol cooling the surface. This is similar to the cloud albedo suggestion except for two things – first, it is accompanied by many direct health and safety issues, and second, it only grows with new coal plants coming online, while the greenhouse forcing grows as long as those plants stay in business.
Another is that there is a radiative imbalance, and that the extra heat is going somewhere besides the surface. The obvious candidate is the ocean. Until recently the ocean warming signal seemed small, but most of the data were confined near the surface, to the top 700 meters. Actually there was little expectation of warming the abyss.
An important new paper by Balmaseda, Trenberth and Kallen “Distinctive climate signals in reanalysis of global ocean heat content” looks through the entire column, concluding “in the last decade, about 30% of the warming has occurred below 700 m. contriubuting significantly to an acceleration of the warming trend.
Apparently the new (and I’d venture unexpected) involvement of the deep ocean in global warming is attributable to shifts in wind patterns. A whole new range of fluid dynamics questions is suddenly exposed, offering something for the best mathematicians to really sink their teeth into.
“Global warming” construed as global mean surface temperature will certainly speed up again, but it may take some time. Allowing the climate disruption problem to be called “global warming” has always been a misnomer, and the focus on the mean surfce temperature has been overvalued. We are perturbing the system much harder than the natural forcing that times the ice ages. To expect a small result is wishful thinking.
Other reports on the Balmaseda et al paper via Kevin Trenberth (I haven’t read them yet):
Roz Pidcock, Science Communication Officer, The Carbon Brief
Mike Lemonick: Why the Globe Hasn’t Warmed Much for the Past Decade
Andy Extance: Diving deep into ocean data uncovers ‘missing heat’ treasure