Last week a team of researchers from the UK Met Office, the University of East Anglia, the University of Gothenburg, the University of Southern Queensland and the Sorbonne published in the journal Science Advances an interesting paper showing that the recent much debated and researched 21st century “slowdown” in global surface temperatures was real and could be explained by reduced solar activity and increased volcanic counteracting climate forcing from greenhouse gases. It achieved almost no media coverage despite being published in a high profile journal.
Its stated aim was to “place the slowdown in a longer term context.” It chose not to use the words “pause” or “hiatus” because it says warming did not entirely cease on decadal timescales.
That’s where I disagree. It depends upon when you start the decade. All the global databases clearly show that warming did cease between 2001 – 2013 (before the recent very strong El Nino), though I would advise the reader to experiment with trends by altering start and end dates to get a better picture of what is going on.
Over this period HadCRUT4 for example has a trend of -0.005 +/- 0.167 degrees per decade which is statistically equivalent to no trend in any researchers notebook. The krigged HadCRUT4 has 0.051 +/- 0.185 degrees per decade, GISTEMP 0.038 =/- 0.175 degrees per decade, Berkeley 0.050 +/- 0.176, NOAA 0.044 +/- 0.185. The satellites also show the same effect RSSv4.0 TLT 0.001 +/- 0.301, RSSv4.0 TTT -0.069 +/- 0.294, UAH v5.6 TLT 0.044 +/- 0.292 and UAH v5.6 TTT -0.070 +/- 0.291. (click on image to enlarge).
From 2001 to 2013 it is flat and after that period the El Nino takes over. Because of this the post-2001 period contains no information that can be extrapolated backwards to see if it is a continuance of previous warming statistics. It is a true break with the warming before it. Some maintain that you can take the data starting in 1980 (the start of the most recent warming period) and fit a linear trend to it and maintain there is no slowdown whatsoever. They should take up their position with these scientists who say there was a slowdown.
Perhaps it would be interesting to read this paper alongside the famous Karl et al paper in 2015 that removed the slowdown by upgrading an ocean temperature database. It hasn’t stood the test of time, has it?
The science looks different today than it did a decade ago. Back then it was said that greenhouse gas forcing was strong and would in the next decade overwhelm natural climatic variations. It hasn’t. Remember the time when experts told us that all the changes happening to the Earth’s climate were happening faster than the IPCC had predicted! Climate change is still vitally important but the past decade has shown us that the science was not settled then and isn’t now. The BBC said the science was settled in 2005 and led the cry that there was no sun link to climate change. A decade later it seems it does. A decade in science, as any competent reporter who covers science should know, can be humbling.