Flying to Torino

Water vapour and droplets in the atmosphere

Water vapour and droplets in the atmosphere

I spent last week in Torino discussing experiments which will lead to a new estimate of the Boltzmann constant and eventually lead to a redefinition of the kelvin and the celsius, the units of temperature. I was crazily busy the week before – and most of the weekend before too – writing a paper and a talk. But as I sat on the plane out there, my anxiety was momentarily relieved. I gazed out the window in awe and reflected on what I saw.

Firstly I gazed at England and France and Italy, and reflected that there was not a single a single square centimetre of the land surface of Europe which had not been affected by humanity. Subsequently I have relented and I would acknowledge that there are regions of the Alps where this is not true. But I still contend that anywhere where anything grows, it is true. Broadly speaking, we have cut down all the trees and planted stuff or built houses. The scale of what humans had done to the surface of the Europe was overwhelming. I gazed down from a height of 38,000 feet and could see the hand of humanity writ large beneath me.

Secondly I gazed at the clouds. Their almost unbearable brightness told me about the amount of sunlight they reflected. I imagined how the temperature of the air would vary as one rose up from the ground into the clouds. I imagined the temperature falling and then – as the water vapour condensed, stabilising as the latent heat of the water was released. I imagined the impenetrability of the cloud to the infra red light being radiated from the Earth’s surface. I stared at the clouds fascinated by their endless variety. I saw cascading towers and the wisps of mist. I saw them form at different heights and I saw the gaps. And I felt acutely aware of how the water vapour in the atmosphere totally dominated the radiation balance of the Earth. But I reflected on the impossibility of accurately modeling the complexity that lay beneath me.

And I reflected on the 200 kg or so of carbon dioxide that was being released into the atmosphere as a result of my 650 mile trip. And the 200kg I would release on the way back. Later I travelled in a taxi with my colleagues and thought about just how efficient cars were at delivering people from one point to an exact location where they wanted to be. And I reflected that when four people travelled together in a  car,how little carbon dioxide was produced per person. But that it was just the requirement – or the desire – to travel hundreds or thousands of kilometres in  few hours that caused the carbon emissions. The mode of travel – plane or train or car – made relatively little difference to the amount of carbon emitted. With one exception. If I had travelled across France by TGV powered by electricity generated in a nuclear power station my carbon emissions would have been kilograms rather than hundreds of kilograms. And if the taxi to Torino had been electric and charged by nuclear or renewable energy then  it would have emitted negligible carbon on its journey. And I that imagined journeys such as the one I was making could still be made while emitting a tiny fraction of the carbon I had emitted.

And after my reverie I returned to a week of incredible busy-ness and meetings. But more of that on another evening.


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