© 2023 Jennifer Coopersmith
Global Warming is a difficult idea in so many ways.
Planet Earth doesn’t have ‘a temperature’, one figure that says it all. There are oceans, landmasses, ice, the atmosphere, day and night, and seasons. Also, the temperature of Earth never gets to perfect equilibrium: just as it’s starting to warm up on the sunny-side, the sun gets ‘turned off’; and just as it’s starting to cool down on the night-side, the sun gets ‘turned on’. The ‘temperature of Earth’ is therefore as much of a contrived statistic as the GDP of a country. Also, ‘the climate’ is difficult to define: is it a trend over one decade, century, or millennium? What sized region is it defined for?
Even so, climate change, more specifically human-induced climate change, is a surprisingly simple idea.
The mathematician and philosopher, Bertrand Russell, summed up humankind’s activities as nothing more than the rearrangement of matter on or very near the Earth’s crust. Russell’s words need refining. The rearranging of matter is done in two different ways: by macroscopic mechanical devices (such as levers), or by ‘heat-engines’ (such as muscle-power, or combustion engines). Loosely speaking, anything that ‘farts’ is some sort of heat-engine. Now here’s the thing: even a mechanical device, such as a lever, is actually a heat engine of sorts (the lever is an idealization, and besides somebody still has to operate that lever). In short, every device is a heat-engine and, by the Second Law of Thermodynamics, it always puts out some waste heat. Therefore, Russell’s summary should more accurately say: the activities of humankind can be summed up as the rearrangement of matter and the generation of heat.
There is still the question: is this generation of heat enough to cause climate change? Sceptics claim that the activities of people are completely swamped by the immense power of volcanoes, the variability of the Sun’s output, and other ‘natural’ effects. These effects are indeed immense, but note that life forms have critically affected Earth’s climate in the past (cf. cyanobacteria). Also, while the consequences of the behaviour of any one person are tiny, cumulatively there can be an influence. In fact, monetarist economics demands this – supermarket chains compete for each shopper’s dollar. Sceptics also argue that natural ‘buffering’ mechanisms keep the Earth’s climate stable – yes, but not if pushed too far. How else has climate change happened in the past (Ice Ages, etc.)? An analogy comes from dieting. Go on a weight-loss diet and your body thinks, “Aha, you’re on a fast, switch on the fasting-metabolism” – a buffering mechanism. But if you go too far you’ll die of starvation.
The consensus amongst everyone (scientists and sceptics alike) is that human activities do at least affect the microclimate – for example, cities are hotter than the surrounding areas. But what is a climate if not a lot of microclimates joined together?
Therefore, the consensus is that human activities do result in Global Warming.
An older version of this blog is on Oxford Scholarship Online.
Last update 15/11/2023
Jennifer Coopersmith 