Guest opinion by John Hardy (UK)
Abraham Hondius “The Frozen Thames” 1677 (during the Maunder minimum)
Two separate indicators of climate change suggest that there is a risk of substantial cooling from 2017 onward. There is also likely to be a gap in energy production worsened by hasty climate change policies, making it three unrelated problems at the same time. In the worst case we could have rolling blackouts in Europe in the next few years.
Why might we expect the climate to cool? Both sides in the climate change debate (see for example this document from CRU) acknowledge a number of factors which appear to correlate to some degree with global temperature:
1. The concentration of water vapour, methane, carbon dioxide and some other gases (“Greenhouse Gasses” or GHGs) in the atmosphere
2. Solar cycles (specifically sunspot cycles)
3. The El Nino Southern Oscillation (ENSO)
4. Aerosols (from volcanic eruptions and other sources)
5. Milankovitch cycles
[Note – “correlate” i.e. both change in step. There is violent disagreement on “causation”, i.e. whether one actually causes the other. It is possible for example that rising temperatures cause an increase in carbon dioxide rather than the other way around]
Number 4 in our list – Aerosols – are rather unpredictable. Number 5 – Milankovitch cycles – are very long. No one credible on either side of the argument maintains that GHG will cause a step change in climate in the near term.
This leaves number 2 – Solar cycles, and number 3 – ENSO. Historical data and present trends suggest that both may be heading for a strong downturn at more or less the same time.
Whammy 1 – Solar Cycles
There are records of sunspot activity going back hundreds of years. Rather bizarrely there is a historical correlation between low sunspot activity and cooler periods:
Graph of sunspot numbers against year
(from Wikipedia – CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=969067. Downloaded 27 June 2016)
There is an obvious 11 year cycle but with other variations on top of that. The critical point is that levels of sunspot activity correlate strongly with temperatures: in particular the Maunder Minimum coincided with the Little Ice Age and the Dalton Minimum likewise was a cold period.
In 2006 NASA predicted “Solar Cycle 25 peaking around 2022 could be one of the weakest in centuries.” (http://science.nasa.gov/science-news/science-at-nasa/2006/10may_longrange/), and it is shaping up that way. Several recent posts have made a similar point:
Graph of sunspot numbers against year on a shorter timescale
(From ftp://ftp.swpc.noaa.gov/pub/weekly/RecentIndices.txt . Data downloaded 6 June 2016)
This pattern is similar to the cycles at the start of the Dalton minimum above, a period of significant cooling. This suggests the possibility that we might be heading for a similar temperature “minimum”.
Note again that this is only correlation, not causation. It could be coincidence.
Whammy 2 – ENSO
It was well known to peoples living on the Pacific coast that temperatures were cyclic. The warm years were dubbed “El Nino” and the cold ones “La Nina”. The ENSO index attempts to put some numbers on this. Six variables related to the tropical Pacific are combined into a “multivariate ENSO index”.
So what is the evidence that this correlates with global temperature more widely? It has been gleefully and widely reported that 2015 global temperatures were the highest in recent years. This is certainly so in the global temperature data sets we have available, although they are all different and all disputed. The higher temperatures in 2015 have been interpreted in the media as a resumption of CO2 induced warming, but the correlation is far stronger with ENSO. 1998 and 2015 were both strong “el Nino” years. Here is the detail
The graph below is the HADCRUT4 (Met Office and UEA Climate Research Unit) data set with the 1998 and 2015 peaks circled:
UK Met. Office temperature anomaly versus year
(Downloaded from http://www.metoffice.gov.uk/hadobs/hadcrut4/diagnostics.html 27June 2016. Emphasis added)
And here is the University of Alabama satellite data set, again with 1998 and 2015 circled:
University of Alabama temperature anomaly versus year
(Downloaded from http://nsstc.uah.edu/climate/ 27 June 2016. Emphasis added)
These two datasets are different in detail, but both agree that there was a peak around 1998 which was not significantly exceeded until 2015.
The graph below plots the multivariate ENSO index. The positive red peaks are (warm) “el Nino” years and the negative blue peaks are (cold) “la Nina” years. Again, 1998 and 2015 are circled:
Graph of ENSO index against year
Downloaded from http://www.esrl.noaa.gov/psd/enso/mei/ 27 June 2016. Emphasis added
If (and only if) previous patterns are repeated, we are now headed into the “La Nina” part of the cycle. If this occurs we would be likely to see a reduction in global average temperatures, although the correlation with temperature appears to be different in different locations.
Whammy 3 – Power supply
There seems to be a strong possibility of a shortfall in UK energy supply in the coming years, and this reflects a pattern over much of Europe. A report from the UK Institute of Mechanical Engineers noted that it is UK government policy to close all remaining coal-fired generating capacity by 2025. They conclude that “…The loss of coal by 2025, along with growth in demand and the closure of the majority of our nuclear power stations will therefore be significant, leaving a potential supply gap of 40%–55%, depending on wind levels….” And “…we have neither the time, resources, nor the sufficient [Sic] number of skilled people to build enough CCGTs [Combined Cycle Gas Turbines] to plug this gap…”
If this analysis is correct (and they discuss various scenarios) the UK may have a growing power problem, and other western countries may have similar problems in the rush to scrap coal-fired and nuclear power stations.
Relatively sudden temperature changes do occasionally occur. The most extreme in the time scale of human agriculture was the Younger Dryas about 12,000 years ago. In Greenland at that time the temperature is believed to have dropped 10oC in 10 years although the change in global average may have been less. 10oC is the same order as the difference between the mean temperature for January and the mean temperature for May in London.
We would be extremely unfortunate to be hit by a Younger Dryas magnitude event; but two of the main factors correlating to earlier climate changes appear to be heading for a strong downturn at the same time. If we are hit by a combination of a very strong La Nina at the same time as a repeat of something like the Dalton minimum we could be in for some cold winters.
The uncertainty of the power supply, caused in part by green opposition to coal and nuclear, could make it a triple whammy. Rolling blackouts are a possibility, particularly on cold, still, evenings. To some pensioners, alone in the dark on a freezing night with heating inoperative, it would mean a lonely death. Folk with the honourable intention of “saving the planet” may instead be killing their grannies.