All global temperature data sets confirm that global temperature has fallen rapidly in recent months as the recent El Nino ended.
HadCrut4 global land and ocean data
Over the last couple of years there have been many articles about how they have been record-breakers in global temperature. It’s often sold as a simple ‘the planet is getting warmer only because of us’ story. As I have discussed before the concurrent El Nino was dismissed by some climate scientists as having an insignificant contribution to that record. However, there is a great deal of confusion and diversity in the assessment of its contribution. Some scientists maintain that it was the recent very strong El Nino that elevated the temperature to record levels.
Nevertheless some maintain that warm records would have been broken without the El Nino (although the significant contribution made by the highly unusual warm “Pacific Blob” is usually ignored).
As the 2015/16 El Nino started to wane wiser heads said the records would fade along with it, “No El Nino, no record,” they said, showing that the El Nino was responsible for edging the years to be records.
It is obvious that the world is cooling after the El Nino and nobody knows how much it will as global temperatures bottom out. So the time is right, one would have thought, to monitor that cooling process and see what can be deduced to set the recent record warm years into their proper context.
In doing so it seems that you can write a straightforward article, clearly one that can be revisited in the coming months with new data, present some current data, discuss the caveats surrounding it, and still get criticised, especially about what the article did not say. Cut and paste comments and quotes blossomed in many blogs, sloppy statistics are bandied about, along with not a little hubris wrapped up in ignorance and gratuitous use of the ‘denier’ label.
David Rose’s article in the Mail on Sunday simply reported what has happened recently to the Lower Tropospheric temperature over land. This data set responds more quickly to temperature changes that other sets which follow suit later. Land temperatures heat up and cool down quicker. They show the El Nino spike very clearly and the possible return to pre El Nino temperatures.
Some have said the article is flawed because it has cherry-picked the particular data used, some have even said “extreme cherry-picking,” implying it is the only data set that shows the global temperature drop. This is nonsense.
Firstly the graph is not an outlier as critics could have seen if some had bothered to look. Other temperature data sets show something similar – that the global temperature has fallen a lot in recent months as a result of the ending of the El Nino. Here are a selection of them showing that the lower tropospheric temperature is not unusual but typical. The same story could have been written using any of these graphs. We have discussed this data frequently in these pages and shown that prior to the latest El Nino the gradient of the data, post 1997 is statistically insignificant if one is careful about starting trend analysis during an El Nino or La Nina year. The Nasa data is definitely not an upward trend with a lot of variation.
Nasa global land and ocean data
Hadcrut4 global land and ocean data
Hadcrut4 northern hemisphere data (mostly land)
As has been said, the temperature of the lower troposphere over land has the quickest response to such changes and should be looked at first to provide an indication of what might happen in the future to the data sets shown above. It has been done many times before without revolt. The graph used is an example of what is happening, and data that should not be ignored because some find it inconvenient.
Some have even dismissed the data because it’s land only, ignoring how useful land only data can be. After all, why would all the temperature data sets produce them? Obviously data should be used carefully and it is encouraging to see the other data sets in collaboration with the land-only tropospheric data.
Secondly, even if it had been unusual it would still have been worth talking about in a responsible manner. The thing we teach young scientists – because it is at the very heart of science – is to keep their eyes open for the unusual, the unexpected and the outlier. The most important words in science are, I contend, “that’s strange,” used when seeing something that attracts intention. Perhaps Alexander Fleming in 1928 should have ignored the single petri dish among many that showed a fungus growing on staphylococci as he would be cherry-picking his results!
Some argue that all the atmospheric land data should be displayed as it starts in 1979. This was one gist of one frequently quoted response to the Mail on Sunday article.
The anonymous analyst ignores what the article says, builds a straw man case and deliberately misses the point. He says the article wants “you to think that the worldwide heating we’ve seen for decades now has somehow, magically, come to an end … that it has shown some kind of “pause.” ” He also maintains that one can draw a straight line through the 1979 -2016 lower tropospheric data that shows there is no pause or hiatus.
The blogger shows the lower tropospheric data back to the start of the data set in 1979 and says showing the post-1997 “hiatus” data on its own is misleading as there is a clear trend from 1979 upwards. Except that there isn’t.
There is no way to reliably reproduce the trend observed either during the period 1979 – 1997 or 1979 – 2016 in the post 1997-data (ie half the data set) because a straight line does not represent the data over its entirety. It is obvious that a straight line doesn’t work when one examines the residuals (the difference between observed and predicted data) which are not randomly distributed. One could only obtain a positive trend by using the recent powerful El Nino to skew the trendline upwards, but that would be using a short-term effect to deduce a long-term trend which is comparing apples and oranges. Because the El Nino has risen and fallen back to pre El Nino levels it should not be part of the long term trend, as has been the case for the El Ninos of 2007 and 2010. Treat with suspicion any analysis that simply draws a straight line through this data that is raised by the temporary uptick of the latest El Nino data! Even more so if the El Nino in question is not yet fully over. If such analysis ignores the large body of evidence for the hiatus be doubly suspicious. Ponder the trend in Hadcrut4 global data after the 1998-2000 El Nino and La Ninas up to the start of the latest El Nino.
Carbon Brief’s “Factcheck” commits all of the above sins. It gets itself into a muddle right from the start saying that without the El Nino we would have had recent record years when in fact they would probably have been what it was like before the El Nino in being all statistically identical to one another. Then it says that temperatures are dropping “modestly” to where they were before the El Nino started. To Carbon Brief the satellite data published by the Mail on Sunday is an “obscure” data set which disagrees with other data sets. See above.
The proof of the claim that the recent El Nino had a minimal effect on recent record temperatures will be found next year. If it is true 2017 would be another record warm year.
So let’s summarise. As the El Nino has faded global temperatures are dropping, not just in lower tropospheric land data (where it has been seen the strongest so far) but in the other data sets as well. Without the El Nino (probably the strongest on record) and the Pacific Warm Blob there will be no new record next year, or probably the year after if the la Nina sets in. Temperatures are more likely to return to pre-El Nino levels. If so, the 2015/16 El Nino would be shown to be a temporary blip in a continuous “hiatus” period which, nethertheless remains the warmest period of the instrumental temperature era. For all we know, at the end of next year we could see the global warming “hiatus” approach its third decade.