I haven’t, yet, written anything about 2016 becoming the warmest year in record. That’s partly because it appears to have been virtually certain that it would be for a few months now, and partly because it’s been extensively covered elsewhere. There’s Realclimate, Sou, Stoat, Tamino and Carbon Brief, to name but a few. Essentially, 2016 is a record in all of the major surface temperature datasets, NASA, NOAA, Berkeley, and HadCRUT. This is also the third year in a row in which global surface temperatures have broken the record, something that has not happened since records began.
By adjusting for ENSO events, it can be shown that 2016 would still be a record in the NASA and Berkeley datasets, but not in the HAdCRUT and NOAA datasets. This is, however, mainly because the latter two datasets don’t cover the Arctic as well as the former two datasets, and the Arctic has been particularly warm. There seems to be a bit of a fuss about the role played by the recent ENSO events, but I think that rather misses the point; the last 3 years have each been records. Removing the effect of ENSO (and, in some cases, solar and volcanoes) doesn’t change this, it simply illustrates the likely underlying anthropogenic trend. As this Realclimate post illustrates, that we’re continuing to break records is itself indicative of an underlying trend; if the climate were stationary, we’d expect the number of records to decrease with time, not increase.
It seems to me that there is also a chance that we could well be heading for a period of accelerated warming. I might regret suggesting this, but Gavin Schmidt seems to suggest the same in this article. We appear to have had a period of slower than expected warming, and we can’t simply build an ever increasing planetary energy imbalance; surface temperatures will eventually have to increase to close the energy gap. I guess it’s possible that the recent warm years might have closed the energy gap enough that we won’t see much additional acceleration. On the other hand, there are indications that the pattern of sea surface warming, in particular differential warming across the Pacific, has lead to more negative cloud feedbacks and, potentially contributed to the slower surface warming. Maybe this can continue, but I don’t know how long one can sustain differential warming across a major ocean basin. It will be interesting to see what the ocean heat content does in the coming years.
Anyway, that’s about all I was going to say. I suspect the next few years are going to be interesting, for many different reasons. It will be intriguing (although, probably also rather frustrating) to see all the various different ways in which these recent records will be dismissed and what will be promoted when 2017 fails to be another record, which seems quite likely.