Yesterday Jim Hansen, now with Columbia University, and several of his colleagues released their summary of 2017 global temperatures. Their history, published by the NASA Goddard Institute for Space Studies, has constantly been evolving in ways that make the early years colder and the later years hot. I recently posted on how this can happen, and the differences between these modified datasets and those determined objectively (i.e. without human meddling).
For a couple years I have been pointing out (along with Judith Curry and others) that the latest fad—which puts a lot of warming in recent data—is to extend high-latitude land weather station data far out over the Arctic Ocean. Hansen’s crew takes stations north of 64⁰ latitude and extends them an astounding 1200 kilometers into the ocean.
This, plainly speaking, is a violation of one of the most fundamental principles of thermodynamics, which is that when matter is changing its state (from, say, solid to liquid), a stirred fluid will remain at “freezing” until it is all liquid, whereupon warming will commence.
This also applies in the Arctic, where the fluid is often stirred by strong winds. So if, say, Resolute, one of the northernmost land stations, is 50⁰F, and the Arctic is mixed water-ice (it always is), that 50 degrees will be extended out 1200 kilometers where the air-sea boundary temperature has to be around 30⁰F, the freezing point of seawater up there.
Hansen et al. did pay some attention to this, noting this extension, which they normally apply to their data, was responsible for making 2017 the second-warmest year in their record. If they “only” extended 250km (still dicey), it would drop their “global” temperatures by a tenth of a degree, which would send the year down a rank. The result of all of this is that the big “spike” at the end of their record is in no small part due to the 1200km extension that turns thermodynamics on its head.
There’s another interesting pronouncement in the NASA announcement; many people have noted that the sun is a bit cool in recent years, and that it continues to trend slightly downward. The changes in its radiance are probably good for a tenth of a degree (C) of surface temperature or so. Hansen et al. use this to provide covering fire should warming stall out yet again:
Therefore, because of the combination of the strong 2016 El Niño and the phase of the solar cycle, it is plausible, if not likely, that the next 10 years of global temperature change will leave an impression of a ‘global warming hiatus’.
The significance of this will all fall out in the next year or so. If temperatures head back down all the way to their pre-El Niño levels, that will ultimately bring back the post-1996 “pause.” We’re going to guess they are going to remain a couple of tenths of a degree above that, based on what happened after the big one in 1998, where they settled a small amount above the pre-El Niño of the earlier 1990s.
If the recent warming rate (adjusting for El Niño) continues, we’ll hear that it is doing so “despite” the sun. Given that one year (2018) can have little influence on a recent trendline, that copy may already have been written!
All of this begs the question: Hansen notes in his release that the warming rate since 1970 has been fairly constant, about 0.17⁰C per decade, and didn’t note that the average of the UN’s climate models say it should be about twice that now. More lukewarming.