Wednesday, January 3, 2018
I picked this up with some interest over the Christmas break as family conversations turned to the nature of our cold weather, and the recollection of winters past when the Thames froze – actually something I recall from my childhood although the river did not freeze as far down as London and the tidal sections of the river. The debate was around the possibility of a temporary reversal of global warming, even a mini ice age, perhaps allowing for time for us to find solutions to the greenhouse gas problem and to adapt to change. The idea seemed interesting and prima facie credible, but further investigation emphasised the need for more caution and slightly less optimism. We all agreed this was no reason to reduce concerns over climate.
A model of the Sun's magnetic activity suggests the River Thames may freeze over within two decades, experts say.
Global Warming Overridden by “mini ice age” that will plunge UK temperature in 2030, claim mathematicians.
According to research from universities in the UK and Russia, we could be skating on the Thames in just over a decade.
A flurry of headlines on climate science, including Sky News , the Mirror, the Sun, illustrate the difficulties of reporting serious science and the temptations of sensational headlines. The fake news sits in the exaggerated headlines, and in this instance there is an important kernel of real fact which, if the solar activity projections are correct, may be relevant both to expectations about climate and potentially to climate policy.
The story is not actually new, but has resurfaced with some particular publications by scientists working in the field of astrophysics who believe they have identified some interesting and potentially important features in the solar cycle. Solar activity, popularly known as “sunspots”, has often been suggested as a credible explanation of variations in climate over relatively short periods of a few years, with lower activity reducing the amount of energy reaching Earth from the sun. The current story discusses a projected downturn in solar activity over the next 20 – 30 years, starting as early as 2020. One figure quoted has been the expectation of a 60% downturn in solar activity over this period, although this translates into a reduction in the energy we receive from the sun that is an order of magnitude smaller.
Press reports had quickly transformed this story into the prospect of a mini Ice Age, with the Thames expected to freeze over by 2023, and the possibility that this would save the world from the devastation of climate change I was perfectly prepared, perhaps being of a gullible or over-optimistic disposition, to accept the reporting at its face value, and to treat the story as mildly encouraging. If it was correct, then at a minimum it implied more time to put in place measures to adapt to climate change, and possibly even to develop the technologies that might allow us to manage or even reverse dangerous concentrations of greenhouse gases (GHG).
A reality check followed. This is what emerged.
The sunspot story. There is serious research (Professor Zharkova et al) which forecasts coincidence of cycles in the sun’s activity, resulting in reduced solar activity. This will result in less energy reaching Earth, though the reduction is quite small. Their work presents a model for the sun's magnetic field and sunspots, which predicting a 60% fall in sunspot numbers when extrapolated to the 2030s. Crucially, the paper makes no mention of climate. A first failure of science communication was the Royal Astronomical Society press release from July 9. This stated that "solar activity will fall by 60 per cent during the 2030s" without clarifying that this "solar activity" refers to a fall in the number of sunspots, not a dramatic fall in the life-sustaining light emitted by the sun. A 60% fall in solar energy would most likely extinguish most life on the planet.
Comparison with earlier “mini ice ages”. This relates to a previous period of "prolonged sunspot minimum", the so-called Maunder Minimum, between about 1645 and 1715, which coincided with unusually cold weather believed to have a significant influence on climate. There is therefore some historical evidence, even after allowing for the more limited nature of observation and measurement in that period, of low solar activity being associated with significant cooling.
However even this assertion must be qualified. That mini ice age began before the Maunder minimum and may have had multiple causes, including the incidence of volcanic eruptions. Moreover the previous mini-ice age will almost certainly have built gradually, with ice cover an important part of the mechanism. Whether that mechanism can be relied on in the immediate future, with shrinking ice caps, is more debatable.
Will it reverse global warming? The warming effect from more CO2 greatly outstrips the influence from changes in the Earth's orbit or solar activity, even if solar levels were to drop to Maunder Minimum levels. There is 40 percent more carbon dioxide in the air now than during the 17th century. A new Maunder Minimum might slow climate change, but it is not enough to stop it. Some estimates however suggest an effect on global temperatures of about a 0.3oC reduction. If correct, this is a substantial and welcome effect.
Should we relax our efforts to reduce emissions? The answer is clearly not. A Maunder Minimum may conceal some of the underlying warming trend for a period, but the solar cycle will of course revert at some point, with an acceleration of warming. Reacting to a short term movement in what is now a well established trend would be dangerous or even disastrous on a longer term perspective.
Conclusions. This is an interesting and important element in the science, although it is still imperfectly understood. We may well see a Maunder Minimum effect, although it seems unlikely to freeze the Thames in any of its tidal range. What is important is that we are able to interpret the effect as accurately as possible as we observe global climate in the years ahead.