In the previous article, we saw how coal is formed, how much reserves are there in the world, and who the top ten consumers, producers, importers, and exporters of coal were in 2010.
So what happens when you burn coal? The carbon in it combines with the oxygen in the air to produce carbon dioxide (CO2), which is a by-product of our breathing as well; we breathe in oxygen and breathe out CO2. Trees, on the other hand, do the exact opposite; they breathe in CO2 and breathe out oxygen. Therefore, trees are the ones that maintain the right amount of oxygen in the air; without them, we would have run out of oxygen long time back.
Since the beginning of the industrial revolution, we started burning fossil fuels – primarily coal, oil (diesel/petrol), and natural gas – and it has been increasing at an alarming rate for the past several decades. At the same time, we are clearing native forests to increase the amount of land available for agriculture and building houses; this has to be done to accommodate the increasing population of the world. Forests are also cleared since trees take care of needs that are an intrinsic part of our lives today: timber for construction and furniture, fuel for cooking and heating, and paper (for reading, writing, and cleaning).
This has disturbed the delicate balance between the producers and consumers of CO2 and led to a net increase in the amount of CO2 in the air. Compared to the year 1750, the atmospheric concentration of CO2 has increased from 280 parts per million (ppm) to 392.6 ppm, a 40% increase. In the northern hemisphere, the levels have already crossed 400 ppm! Why is that a problem? Well, because CO2 is a greenhouse gas (GHG), and GHGs as you might know cause global warming.
Before we proceed, let us understand what the “greenhouse effect” is. It is the process by which thermal radiation from a planetary surface is absorbed by GHGs and re-radiated in all directions. Since some of it is towards the surface and the lower atmosphere, it increases the average surface temperature as opposed to what it would be in the absence of these gases.
Referring to the above figure, of the 235 W/m2 that is absorbed by the Earth, 168 W/m2 is absorbed by the land and oceans while 67 W/m2 is absorbed by the outer atmosphere. This absorbed radiation is re-radiated by the GHGs, re-absorbed, and re-radiated, with the net effect that another 452 W/m2 is generated. Out of which 195 W/m2 escapes into outer space and 324 W/m2 is absorbed by the lower atmosphere and surface of the Earth. This increases the average surface temperature of the Earth to 14°C. If Earth did not have any GHGs, its average surface temperature would be -18°C, or 32°C lower than what it is!
Essentially, all GHGs act like a blanket around a planet. If they are not enough, it leads to a very low surface temperature as on Mars. On the other hand, if they are too much, it leads to a temperature high enough to melt lead as on Venus. Thankfully, Earth has just the right amount of GHGs that leads to a humane temperature of 14°C, which is what makes life, as we know it, possible!
The four main gases that contribute to the greenhouse effect on Earth are:
1. Water vapour (36 to 70 per cent)
2. CO2 (9 to 26 per cent)
3. Methane (4 to 9 per cent)
4. Ozone (3 to 7 per cent)
As you can see, it is water vapour that contributes the most to the greenhouse effect! However, other gases have started contributing more than they should. CO2 is obviously one of them since its atmospheric concentration is much more than what it was three centuries ago. Methane is the other since – and this may surprise you – the number of cows is increasing! Each cow lets out 30 to 50 gallons of methane in the atmosphere per day through its burps and farts, and since there are around 1.5 billion cattle in the world, it adds up to a significant number. All the other ruminants – sheep, goats, giraffes, and deer – put together also add about the same amount of methane to the atmosphere as all cows. And since methane is 72 times more potent as a GHG over a 20-year period as compared to CO2, it is contributing a lot more to the greenhouse effect.
All of this is leading to global warming. Earth’s average surface temperature increased by around 1°C in the 20th century. The increase per decade in the last 5 decades – 0.13°C – was double that in the first 5 decades – 0.07. So clearly, the situation is worsening at a faster pace and something needs to be done to keep things from going out of hand. According to a study, if emissions are cut drastically and the most stringent mitigation methods are deployed, Earth’s average surface temperature will increase by 0.3°C to 1.7°C in the 21st century. If nothing is done, that rise could be anywhere from 2.6°C to 4.8°C.
Now you may say, “That’s not much. What impact could that marginal increase in temperature have on us?” The short answer is, “A lot.” The immediate effect is that the mean sea level (MSL) will rise by half a meter in the 21st century according to conservative estimates. However, many believe that it will actually rise by as much as 2 meters, which could lead to widespread coastal flooding and eventually submerge large swaths of land. Sustained global warming of only 2°C for millennia can increase MSL by 1 to 4 meters due to thermal expansion. Add to that the melting of glaciers and the situation gets a lot worse.
Climate change is expected to affect ecosystems like the tundras and mangroves in a big way. Most ecosystems will be affected by higher atmospheric CO2, which will result in the extinction of many species, and therefore reduce bio-diversity. Higher atmospheric CO2 means more CO2 will be dissolved in the oceans and make them more acidic, which will threaten coral reefs, fisheries, protected species, and other natural resources of value to society. In general, global warming and climate change, if left unchecked, will affect nearly every ecosystem on Earth and the livelihoods of nearly 3 billion people!
I read a very interesting comment on the internet where someone said, “Global warming is not such a great name because many people wouldn’t mind if it gets a little warmer!” This is especially true in the case of people who live in cold countries. The positive connotation that the word warm has due to phrases like “stay warm, stay dry” may partly be the reason for this. So “global warming” needs to be changed to something else that has a negative connotation and conveys a sense of urgency that something needs to be done about it. Irrespective of what the best term to describe it is, global warming is a serious issue, or a “burning” issue if I may say so, and needs to be addressed ASAP!
In the next article, I will take a look at India’s coal situation.
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