I struggle to to understand certain aspects of the global warming debate. Climate change deniers generally admit that the global temperature is warming as we're coming out of an ice-age. Their denial is that human activity is accelerating that process. This has always seemed silly point of view to me, I mean if you were standing on a railway line with a train coming towards you, you would take action and get out of the way, not stand there arguing about whether the train was accelerating or travelling with constant velocity. Similarly then I don't see why we don't take action to avoid the consequences of a change in climate that is inevitable, rather than bickering about carbon taxes (or even more dangerous IMHO, plans to 'reverse' global warming). Common sense never prevails however, so conservatives will continue to allow folk to build houses on flood plains and crumbling cliff edges!
Anyway, the main point of this post is a modest lightbulb moment I had a few years back that I'd like to share.
My friend Mike works in Seville, Spain as an English teacher. He said he was cycling to work one evening at about 5:30pm and, finding it difficult to breath, noticed the temperature was a staggering 57 degrees Celsius. He explained that Seville is like a cauldron and heat just collects there and sits during the day, which is worse in summer as everyone uses air-conditioning which pumps more hot air in the street.
I live in Spain too, and I learned the trick years ago that to cool myself down, I run my wrists under the tap for a few minutes. Since all the blood passes through the wrist and the veins are near the surface, the cool water takes the heat away quite efficiently. This is the point where the light-bulb went off. It struck me that Seville was on a river and that the river must be acting like the tap water, taking some of the heat away with it as the water flowed through it. Furthermore, apart from a few sparsely populated mining towns, just about every human settlement was built on a river or near the sea. The thought crossed my mind 'what if we humans are acting like radiators for the worlds air and water. Summer and air-conditioning aside, even in the coldest winters our cities are still pumping heat into the environment when we run a bath or turn on our central heating. Billions of humans make heat and we do it by and large in our cities.
The notion might have drifted into obscurity if I hadn't come across an article on climate change which shared the Web address of the NASA GISS database containing records of world surface temperature. Out of curiosity I started to look at the data. I was struck by how temperature increases correlate closely with population density. Where ever I looked, temperatures had been rising in the worlds cities more than anywhere else. In fact, looking in comparison at some sparsely areas, places like Alaska and Mongolia had actually fallen in temperature at the same time temperature in cities had been rising.
Now if the most densely populated areas of the planet are near water, and the temperature is rising more profoundly in these areas, the impact on the worlds weather could be starker than previously imagined. Weather is governed by fluid dynamics of water and air. If these flows were being affected evenly by a global change in temperature by a degree or so, the effect on the world's weather would probably be negligible. The problem is, if that one degree in temperature is concentrated locally in coastal areas, the effect is bound to be more pronounced. Taking this further, we could see a situation where the global temperature of the earth remained stable, or even fell overall, but local heating could continue to have a devastating effect on the worlds weather systems.
Another thought experiment has a chilling consequence. If magically we were able to flip a switch tomorrow that transformed all the energy that powered our heating, lighting, A/C and domestic equipment from a fossil fuel source to solar, heat generated in cities will continue to have a disproportionately large effect on global weather, and the heat in our cities will continue to rise in tandem with population increases.
Up until this point these ideas were the merely the musings of a pretty ignorant layman with no expertise at all in the field. Then a few weeks ago I stumbled across an article from 2016 which went some way to confirm what I'd been thinking.
The article goes on to explain that the effect, know as the Urban Heat Island (UHI) had been know about for a long time, so I was surprised I'd not read about it before.
My point here is that while we mostly talk about man-made or 'Anthropomorphic' global warming, the real killer is the man-made local warming we all contribute to by our never-ending desire to congregate in cities. I'm not claiming that CO2 emissions are irrelevant. These too exacerbate local warming effects, though carbon emissions should not be singled out as the sole culprit here. Man's tendency to aggregate in to ever larger conurbations is a much larger factor than previously thought.