Back in November 2019, I blogged about plate tectonics and, in particular, how we live - and die -with the earthquakes, tsunamis and volcanoes that result from us living on an unstable planetary surface. It set me thinking more about the more general risks we face and how we can categorise them.
Plate tectonics covers the below-ground risk. But what about things dropping on our heads from outer space? These could be solid, like meteorites or asteroids, but they could also be unwelcome rays from the Sun or elsewhere. We don't see much evidence of these risks but they do happen and very occasionally they can be very deadly. A single huge collision with another heavenly body 65 billion years ago is believed to have been responsible for the extinction of the dinosaurs.
The third field of risk is atmospheric. The Earth's surface is surrounded by a relatively thin layer of gases which we depend on for life. As the Earth both rotates and tilts on its access, the resulting winds and weather patterns cause all manner of mayhem at the surface. Think Droughts. Storms and Hurricanes. Monsoons. Flooding. Extreme temperatures. Fog. Snow. Ice. Fires (albeit at one stage removed but remember that oxygen is an essential component of fire).
The atmosphere also dictates which life forms, if any, will occupy the surface. No rain = dessert. Frozen rain = snow = Arctic like conditions and glaciers. Lots of heat and rain = jungles. Lots of rain and coolish temperatures = Manchester.
We interact with our atmosphere in ways we don't with the ground beneath or space above. For instance, we can turn fog into smog by adding burnt carbon to the atmosphere. And we can alter the characteristics of the atmosphere itself by tinkering with its component gases. In particular, with carbon dioxide which, despite being only a trace gas making up just 0.04% of the Earth's atmosphere, is known to act as a thermostat for global temperatures.
A more nuanced example of this was our production of CFCs, a 20th century phenomenon, which then drifted into the upper atmosphere and reacted with ozone. This resulted in large holes in the ozone layer which acted as a dampening layer for incoming solar radiation. This made sunshine a far more dangerous factor for those outdoors and led to increases in skin cancer. The Montreal Protocol, in 1987, was a fine example of nations working together to ban the use of CFCs and to bring about a gradual repair of the ozone layer.
An even more nuanced example would be the current fear about the spread of the cornonavirus from China. The atmosphere carries with it not just the threat of challenging external weather conditions, but also as a carrier of communicable diseases.
So there you have it. We live on a Planet with an unstable surface, subject to bombardment by things from outer space and dependent on a thin zone of gases which behave in a somewhat chaotic manner, and which we have started to use as a waste dump.
Having said that, it's a beautiful morning here in Cambridge and it's good to sometimes feel that Earth is not such a bad place to be posited on for a while.