Photo Credit: NASA
Those who know me well will also know that one of my long-running "hobby-horses" is Climate Change. This dates back to the old days when it tended to be referred to simply as the "Greenhouse Effect". In fact, I have a claim-to-fame in having asked a question on the subject in a BBC Gardeners' Question Time edition way back in 1990 - and here's my trophy to prove it:
I became increasingly curious about what would later be known as "Global Warming" (a bizarre term, suggesting that thus far the Earth had been a frozen lump of rock!). That interest, alongside my life-long fascination with contraptions of all kinds - and the idea of getting something for nothing - very quickly led me to build a "Micky-Mouse" wind turbine from bits and pieces as long ago as the early 90s. Here's the present-day model:
Still pretty tatty, what! The generator is an old bicycle hub alternator, and the blades are made from plastic guttering (thanks to an article I found on the internet). It produces about 5W in a howling gale - IF the wind catches it right. But, as you no doubt have observed, it is somewhat sheltered! More recently I've added a ramshackle collection of small solar panels.
Now I fully appreciate the fact that - in common with such measures as switching to low-energy light bulbs - the direct impact of this is effectively zero, given the enormous scale of the problem being faced; but there are essentially two principles at stake here. Firstly: if we are not prepared to do our bit, then we have no moral authority to "preach" to the rest of the world. Second: if you believe in something then tell people about it. By myself I can do very little, but with luck others will see what I have done, and maybe some of them will think about it and ... you get the picture. But I digress: that was not to have been my main focus for today. What I had intended to write about was some nagging questions I've had in my mind for a while about the likely severity of climate change and - more importantly - some of the measures that are being explored to cope with it. Now I don't doubt for one moment that the problem is real, and happening now, and that urgent action is needed to tackle it. Quite the contrary, in fact. However, there are three areas I'd like to explore.
1. The latent heat of fusion (of ice) in respect of moderating temerature rise.
Photo Credit: US National Oceanic and Atmospheric Administration
One aspect which is discussed in the climate-change debate is the moderating influence of polar- and other ice. What is generally being referred to here, it seems to me, is the fact that snow and ice are very good at reflecting solar radiation back out into space, thus limiting the warming effect on the ecosphere. This means that while there is still plenty of ice around, the temperature rise is pegged back relative to what it will eventually be, once most of the ice has disappeared. In actual fact, the melting process is driven mostly by the warming influence of the surrounding ocean - or underlying rock in the case of land-based ice - rather than by the sun's radiation directly. Be that as it may, I do agree with this point of view by and large; but there is, surely, yet a further factor: ie the latent heat of fusion of ice which, as every school child used to know, is about 80 calories per g.
Now having lectured to undergraduates on the subject of thermodynamics for many years, I'm keenly aware of just how mind-bogglingly complicated these things are - particularly when it comes to questions of heat-transfer under non-equilibrium conditions (which certainly apply in this case). Nevertheless, I reckon I do have a little knowledge of the subject. Now I may simply have missed it, but I don't seem to recall seeing this aspect mentioned. Am I being naïve in suggesting that once all the ice has gone the situation will be even worse than predicted, for the additional reason that the proportion of solar energy which would otherwise have gone into melting ice (thus merely increasing the overall entropy) will instead contribute directly to temperature rise?
Of course, in a hypothetical "steady-state", where the total amount of planetary ice is constant, there would be no net latent-heat effect. This is because while heat would be absorbed in the melting of ice in one place, the exact same amount would be released as new ice forms elsewhere (eg melting in the northern hemisphere - during its summer - would be balanced by freezing in the southern hemisphere). This might well cause local variations, but no global effect.
However, the fact is that the ice is gradually disappearing. Thus, more heat is currently being secreted away in melting ice than is being evloved in the freezing process. So, are we currently being protected to some extent? And will the rate of rise in temperature increase markedly at some point in the not-too-distant future?
2. Carbon-capture ... or oxygen-depletion?
Here's another one that bothers me a bit - carbon-capture ('sequestration'). The idea sounds simple enough: when coal, oil, gas and other fuels are burned, they release carbon dioxide. (Actually, they also produce compounds based on nitrogen, sulphur and other elements which are equally, if not more, damaging than carbon dioxide; but that's another story.) If one can remove this greenhouse gas at source, and store it permanently in, for example, the subterranean rock, then it cannot contribute to the greenhouse effect. Problem solved. But is it? As far as I recall from my school chemistry lessons, combustion requires two components: the fuel itself ... and oxygen. When carbon dioxide is produced from combustion, the carbon part does indeed come from the coal, oil, or whatever, but the oxygen does not. Ironically, it is produced mainly as a byproduct of photosynthesis, in which a certain gas going by the name of carbon dioxide is imbibed by plants and tranformed into sugars etc. In the absence of carbon-capture, atmospheric oxygen is cycled and recycled indefinitely; but what about with it?
Now OK, oxygen is clearly abundant in the atmosphere, for now. But will it always be if we keep storing it underground?
3. The "neutral" influence of nuclear power on global warming.
Photo Credit: US National Oceanic and Atmospheric Administration
Now for my third niggle: it seems to me that those who are opposed to the expansion of nuclear power may have overlooked a rather basic factor which could potentially strengthen their argument further - at least, I have not so far seen this point made: a recurring claim by the pro-nuclear lobby is that it is not a net contributor to global warming. As far as I can discern, what is generally meant by this is that nuclear power has a neutral carbon footprint. For the moment let's leave aside the contribution made by mining (of the ore), transportation and the other myriad operations surrounding the nuclear industry, and suppose that there is indeed no net emission of carbon dioxide.
In the Great Climate Change Debate, the assumption is always that the sole cause of additional global warming is the emission of greenhouse gases. But is this necessarily the case? Could even nuclear power-generation contribute to global warming? I think so, and in a very direct way. This is because - like coal, gas and oil - nuclear material is non-renewable. Just as with the burning of coal and oil, generating power using nuclear fuels not only puts out huge anounts of water vapour into the atmosphere (and water vapour is acknowledged to be a particularly potent greenhouse polutant - albeit it is at its worst at high altitudes), but also kicks out considerable quantities of something pretty obvious: HEAT.
Now, I accept that nuclear is a better option (if you ignore the rather compelling health- safety- and security issues) than burning fossil fuels in that it entails no significant greenhouse gas-emission, but all of these technologies clearly do produce heat which is additional to that provided by the sun. The only energy-conversion technologies that do not involve extra heat input into the ecosystem are those based on the sun itself - ie the renewables: wind-, tidal-, solar-, biomass-, etc.
Well, I guess you might say compared to the daily solar heat-input, that produced by non-renewable power-sources is insignificant. You could be right. I just don't know what the numbers look like, unfortunately.
Maybe I'm missing something blindingly obvious with these three issues. At any rate, it makes you think, doesn't it? If you have any thoughts or comments on this, I'd be very interested to hear - even if it proves me wildly off-beam!
Bye
M
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