Climate change is a hotly debated topic (excuse the pun), this then can make getting to the science of climate change difficult. Those who underplay climate change are compared to people who denied the health effects of smoking. Tobacco companies were behind this misinformation as they were trying to maintain their profits, clearly, they were not concerned about people dying from lung cancer. Are big oil companies doing the same with climate change? Are the lungs of our planet being polluted to such an extent we are headed for climate apocalypse? It must be recognised that unlike smoking, carbon fuels are useful, carbon-based fuels are a good source of cheap energy (petroloeum is also an essential feed stock for many of the materials and pharmaceuticals we take for granted), powering industry and increasing the standard of living for billions. It could then be argued that carbon based fuels are of great benefit to humanity. However, is the purple haired brigade correct, is the earth going to go up in climate flames, is it now pay back time for our overuse of carbon-based fuels. This is not a simple thing to answer, as the physics and chemistry behind the question is very complex and open to analysis. The now famous quote “lies, damned lies, and statistics” can no doubt be applied to the topic of climate change as well as to other domains where money is involved (renewables are also big business)
What for the moment does science teach us about climate change. For a start the climate is changing apparently. i Sea levels are rising by about a few mm each year, according to some source's temperatures have risen by about 0.06oC per decade since 1850ii. The difficulty I suppose from a measurement point of view is how to compare temperatures from the past to the present, we are told this can be done reliably, though if you were a skeptic you might argue the methods of the past ie mercury thermometers could be subject to unreliability, less of a problem with the more sophisticated satellite technology of now a days, however we are told statistical approaches are used to flag up anomalies in the past and compensate for the so called ‘urban islands’ ie the heating up due to urbanization and not climate iii. That been said it must be recognized that recent data, say from the past 50 or 60 years is very convincing, an upward trend in temperature is more than likely been observed, so the planet is getting warmer, though historical data is in my opinion debatable.
Are we heading for an environmental apocalypse then. This is the claim made by many scientists, some of whom don’t even have purple hair (but they do need research money). Inevitably then we have to discuss carbon dioxide, the main greenhouse gas produced by burning carbon fuels. Carbon dioxide is of interest as it can absorb IR radiation. The mechanism of this is well known. Molecules stretch and vibrate, some of these stretches and vibrations can change the dipole moment, when this happens the molecule is able to interact with electromagnetic radiation, carbon dioxide has an asymmetric stretch and a bending vibration shown below resulting in a change of dipole (the symmetric stretch does not result in a change of dipole and is therefore IR inactive iv). Short wavelength radiation mainly in the visible and UV region from the sun reaches the earth, this is absorbed and some irradiated back in the form of longer wavelength IR radiation, this can have two fates radiated back out to space or absorbtion by greenhouse gases and re radiated back to earth. The more carbon dioxide in the atmosphere the greater the greenhouse effect, that is the theory.
The earth can be thought of in terms of a heat engine v. The average surface temperature of the earth is about 288 K and IR is radiated into space at about 255 K. Some of the absorbed heat is used to do work, air turbulence, movement of air flows(for eg winter storms caused by cold air in higher altitudes transferring to warmer lower altitudes) etc. In an ideal engine the so called “Carnot Engine” no work is lost due to an increase in entropy (S), this ideal engine is shown in diagram (a) below. Real heat engines however result in an increase in entropy, energy is conserved but entropy tends to increase (2nd law of thermodynamics) diagram (b). Diagram (c) shows that the earth as a heat engine. Solar energy is the heat source and cooled by emmision of radiation to space, the work done produces wind and ocean currents. The efficiency of this heat engine is less than 1%.vi As previously mentioned, more carbon dioxide means more heat absorbtion, this can cause a positive feedback loop creating more water vapour which in itself is a greenhouse gas.vii
Is water vapour causing the increase in temperature, it is known that water is far more abundant than carbon dioxide in the atmosphere. The latent heat of water can release huge amounts of energy in storms such as hurricanes, should we be fixing the water vapour problem viii(not according to climate scientists who in general evoke the positive feedback loop mentioned above). Some scientists say that increasing carbon dioxide levels are of benefit to plants and food crops, so we shouldn’t worry.ix Global warming could result in less mortality from cold waves, longer growing seasons, the opening of the Northwest passage, so it's not all doom and gloom.x
Is the earth warming, probably, are we headed for climate apocalypse, probably not. For the purple haired brigade who wish to put the poorest into fuel povertyxi, perhaps it‘s time to be balanced and reasonable no need for hysterics, the environment certainly needs protection, overuse of chemicals and toxins (some associated with making batteries) is in my opinion the greatest threat. A move toward cheaper reliable fuel would be welcome of course, for the moment we must use fossil fuels, a reliable source of energy. Nuclear power has been much maligned (it's not cheap to build a nuclear plant but onced they are built they run for a long time making them in the long term economically viable, France unlike the UK had the foresight to see this) this would reduce carbon dioxide, but environmentalists of the past were dead against nuclear energy. Will environmentalists of the future protest against renewable sources of energy or stop eating tofu. Renewables are not without their problems, so future renewable protests are inevitable, tofu is a favourite for those saving the earth from burgers and steaks, so tofu is unfortunately here to stay. My main concern is the toxicity of purple dye, and does it effect your IQ.
i https://climatedata.imf.org/pages/climatechange-data
ii https://www.climate.gov/news-features/understanding-climate/climate-change-globaltemperature#:~:text=The%20roughly%202%2Ddegree%20Fahrenheit,significant%20increase%20in%20
accumulated%20heat.
iii https://science.nasa.gov/earth/climate-change/the-raw-truth-on-global-temperature-records/
iv https://edu.rsc.org/download?ac=11394
v https://pubs.aip.org/physicstoday/article/75/7/30/2848581/Thermodynamics-of-the-climatesystemTo-understand
vi http://www.atmo.arizona.edu/students/courselinks/fall10/atmo551a/CarnotCycle.pdf
vii https://science.nasa.gov/earth/climate-change/steamy-relationships-how-atmospheric-water-vaporamplifies-earths-greenhouse-effect/
viii
ix https://www.scientificamerican.com/article/climate-skeptics-want-more-co2/
x https://www.climate.gov/news-features/climate-qa/are-there-positive-benefits-global-warming
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