Global temperature data for the last 12 months refutes the idea that the warmth of 2017 was due to a resurgence of global warming. In fact, the world has been cooling.
It is clear that 2017 was a very warm year. Tomorrow, NOAA, NASA and the UK Met Office will announce by how much. It won’t be a record-breaker, but it will be in the top five, and that has already started comments about why it has been so hot. After all, the record-setting El Niño temperatures of the 2015-16 are over – so why did it remain so hot? The reason, according to some, is clear: the resurgence of global warming. The year 2017 is the hottest non-El Niño year ever and therefore signifies a dramatic increase of global warming after 20-years or so when the global temperature hasn’t done very much.
The Guardian says that climate scientists predicted the rapid rise in global surface temperatures that we saw in 2017.
Unfortunately for the Guardian it’s not that simple. Firstly, it is rather suspicious that immediately after a record-setting year due to an El Niño there is a record-setting year for other reasons. There are questions about how much of the heat from the 2015-2016 El Niño has been dispersed, especially since the event was unique in many ways. We have relatively little understanding of such extreme events. The year 2017 was a complicated year involving the interplay of a small La Niña cooling event and a manifest attempt by El Niño to rise again. That is its story and the answer to why it was so warm. The reason lies in the strange decay of a monster El Niño, and not in a dramatic upsurge of global warming. For that we need more than one year’s data following an unusual event.
Prediction of El Niños and La Niñas is at an early stage, and it is fair to say that scientists have had limited success. Looking back to the boreal summer of 2012, an El Niño event was predicted to arise only to see the already warmed ocean in the eastern equatorial Pacific suddenly revert to a neutral condition. A similar thing occurred in the boreal summer of 2014. An exceptionally strong El Niño event was predicted but the rapid growth of the anomalous warming in the central-eastern equatorial Pacific dramatically paused during the summer, and no El Niño event formed until the end of that year.
Unsurprisingly predicting what would happen after the 2015-1016 monster has also been a problem. Since April 2016, the National Oceanic and Atmospheric Administration (NOAA) Climate Prediction Center (CPC) repeatedly said that a La Niña event would occur the following winter. However, this La Niña event failed to reach its expected strength and was short-lived. It did not dissipated the heat left over by the El Niño.
El Nino Comeback?
Following this weak La Niña in late 2016 something remarkable happened. There were good signs that another El Niño was on its way. National forecasters said that there was up to a 50% chance of it happening as the global temperature started to rise once more. NOAA said it was 50-60% probable. It was said at the time that if another El Niño did materialise, it would be only the second time in the records that the Pacific went from the hot phase of an El Niño to the cold phase of a La Niña and then back to an El Niño again within three years. It was also noted that the relatively limited nature of those records, though, means researchers couldn’t be certain that such a combination is all that rare.
But the rise stopped just a fraction short of the increase required to technically declare an El Niño, although some Japanese scientists said we did have one and using conditions in one El Nino reference region certainly shows it. It was this warming event, and the previous La Niña’s weakness that contributed to 2017’s warmth.
Click on image to enlarge. Courtesy @JKempEnergy Link.
We know little about El Niño events concerning their timing and intensity. Scientists classify El Niños into Eastern-Pacific and Central-Pacific types based on the peak region of sea temperatures. Thus the 1982-1983 and 1997-1998 events were strongly of the Eastern Pacific type. All La Niñas and moderate El Niños tend to be classified as Central Pacific events. The 2015-2016 El Niño seems to have been a mixture of the two. This shows that El Niños exhibit a wide range of behaviours. Some scientists postulate that the latest event showed the influence of ocean warming trends. There is some indication that they might be changing in character since we started observing them in detail in the satellite era. For example, more and more El Niño events showed spatial patterns centred in the central Pacific after 2000, different from those classical El Niño events centred in the eastern Pacific. Whether this is significant, cyclic or related to global warming is unknown.
So where are we now? In October, the U.S. Climate Prediction Center declared the presence of La Niña and it is thought it might persist throughout the first half of this year. This La Niña, however, is weak; and some scientists and even Bureau’s of Meteorology don’t recognise it.
The suggestion that the warmth of 2017 being a “non-El Niño” year is due to an increase in global warming doesn’t stand up. The temperature structure of the year doesn’t support that idea. Hadcrut4 shows this quite clearly.
Click on image to enlarge.
Hadcrut4 global temperature data (2014-2017) refutes the idea that the warmth of 2017 was due to a resurgence of global warming. The world has been cooling.
Besides, as I have said, such a claim must be made on data for more than one year. If the global warming resurgence idea is correct we can expect to see its sign in the temperatures of subsequent years. But evidence for this is off to a shaky start. The UK Met Office prediction for 2018 is not a new warming record — due to La Niña. This is consistent with why 2017 was so warm.