Follow the Trail

Saturday 9th of May 2020
Sunset with high-level clouds

Through the middle of April most of the UK enjoyed very settled weather with a great deal of sunshine and pure, blue sky. This has probably been a mixed blessing as far as the lockdown has been concerned. On the one hand, we have had the opportunity to go out and exercise without needing to worry too much about the weather forecast. On the other, the temptation to make use of the weather by ignoring restrictions has been significant.
However, there is one connection between current restrictions and the weather which has been very striking for me and I’m not sure how many people have noticed it. Normally when we have clear and sunny weather, the sky fairly rapidly becomes criss-crossed by vapour trails (sometimes also referred to as condensation trails or even shortened to contrails). Because of the negligible air traffic in the sky at present, this just hasn’t happened.
The other set of thoughts that I have had in relation to this is that I am sure that the output from our solar panels has benefited from the lack of high-level clouds over this period. Obviously, I can’t say what the readings would have been if the normal impact of aircraft had been at play, but I have done a brief Internet survey to see if anyone has attempted to research this.
The answer is “yes”. I found a research paper in an open source journal called Atmospheric Measurement Techniques published by the European Geosciences Union. This paper attempts to give a figure for the impact on solar panel output of contrails. There is an immediate difficulty in doing this because clouds can both block out the sun and hence reduce solar power readings and increase them, because clouds can also reflect light. The balance between this will be affected by the type of cloud, not least by its thickness, and the same applies to contrails. Another part of the difficulty of assigning a figure to this is that there isn’t consistency in whether vapour trails persist or not on a given day. I am sure there are other factors in the atmosphere besides the aircraft themselves which affect that. It does seem that on some days this type of cloud disperses and some days it doesn’t. (The study just mentioned suggests that persistence is more likely in the winter months than in summer). In the latter case, it may then go on to produce actual cirrus clouds. Any research into this phenomenon therefore has to look at averages over a period of time.
The figures given in the paper cover a range, but can approach a 5% loss in solar output. That doesn’t seem like a large amount, but, if this phenomenon happens consistently, this could be significant.
If I am honest, part of my interest in these figures is that lockdown is giving us an opportunity to look specifically at air travel and consider whether we want to return to the same volume of air traffic as during the late 2010s once we come out of lockdown. (It may be worth saying that during the time I have been working on this blog, various companies in both the aviation manufacture and air travel sectors have been talking about reducing staff, so representatives of both these parts of the economy obviously consider it a strong possibility that volumes will be lower).
There are various reasons that I have heard advanced as to why air travel should be reduced from an environmental point of view. Most of them look at reducing carbon emissions in one form or another. Considering the figures above, however approximate they may be, makes me wonder as to whether we could find something we can gain from this as well as cutting emissions. Reducing contrails from air traffic could enable us to have a higher yield from solar power. The more solar installations there are, the greater this effect becomes. However, this also means that unless we continue to make greater use of solar power, this won’t be a huge argument in favour of this reduction in air journeys. I’ll come back later to the question of the motivation behind air travel, but I want first of all to look at the question of energy production worldwide.
In relation to overall output, the production of energy through solar power is relatively small, significantly less than 5% of total output. Even within the renewables sector, solar has been a minor player. However, it has been growing significantly. Over the last ten years the increase has been over 20% each year, some years well over that.
There may be many other reasons for reducing air travel, but there is a part of me that wants to include increasing the energy gain from solar power. Although I’ve set out a case for this above, if I am honest, this has as much to do with the symbolism as it does with the figures. For me there is something about the idea that contrails make it harder for us to see the sun clearly. There is something about the climate change crisis which is about our struggles to see matters “in clear light”. Some of that is because of the complexity of the issues involved. That is no doubt related to the way the climate works, but it is also very much affected by the complexities of human society.
Part of this is definitely a need that we have to step away from the familiar. I would link this again to what Iain McGilchrist says about the right and left hemispheres of our brain. It is the left hemisphere that prefers to stick with what it already knows. In the next of these pieces I want to continue to look at the question of air travel from the point of view of what we have become used to and how we will need to move away from that if we are to reduce the amount we fly.
That brings me back to the idea of the trail. Whilst vapour trails may make it harder to see the sun, they are themselves clear to see. When we think about making changes in life, whether on an individual or group level, we are often dealing with the difficulty of entering an area where the path is far from clear and that is where I want to start next time.