Last weekend, I just read through this topic and found it very interesting. It started like this:
"When air pollution hurts people's health and heats up the climate it makes sense to do something about it. But what about pollution that cools the planet?"
Whoa! My heart was beating hard. Is it possible to have pollution that cools the planet? That means I don't need to have air-conditioner at home and yet, I can enjoy the cool temperature in tropical countries such as in Malaysia. HEHE!!! What a nice solution to global temperature! This was what I thought at that moment.
However, after reading all the article, I realise the downside of this pollution. It actually reduces the amount of rainfall and worsens the air quality~ What a waste! Sigh~
There are two short-lived climate "forcings" which contribute to the change of amount of energy the atmosphere absorbs, black carbon and ozone, which are crucial in blocking UV rays in stratosphere but dangerous in atmosphere where plants live and people have to breathe. [1]
According to United Nations Environment Programme (UNEP) report, implementing measures against the two pollutants would have immediate and lots of benefits. For black carbon, the measures are largely in the form of more efficient ways of burning things. For ozone, mostly involve reducing emissions of methane, which encourages reactions in the atmosphere that make ozone.
Well, let's come back to what I mention just now - pollution that cools the planet. It is actually called "Nuclear Winter". It is caused by the sulphur aerosol in the atmosphere. These aerosols can form less-black particles that reflect, rather than absorb, the sun's energy. It also provides sites for water to condense. That promotes the formation of clouds, which reflects sunlight back into space. Since black carbon absorb sunlight in the atmosphere and it is emitted together with sulphur, it explains why, though the black carbon in brown clouds has a warming effect, the clouds' net effect is to cool the planet beneath them.
Now, the surface is cool and the air above it, warm, there is less tendency for air from near the surface to rise. Reduced convection will tend to lead to fewer clouds and reduced rainfall. That's why this pollution, although it cools the planet, leads to a serious problem to the Earth.
It is evident that ABCs, the regional effects of which are far greater than global averages, have depressed rainfall in the Indian monsoon over the past decades.
Other than that, black carbon has a pernicious effect on frozen regions. When it falls on snow it greatly increases the amount of sunlight absorbed. Ice core analysis showed that the black carbon rose threefold from 1975 to 2000. [2]
Sulphur, as a reflecting aerosols, provides a cooling effect to the Earth, but it lets the Earth prone to depressed rainfall and affects the monsoon seasons of different regions. The cooling effect of sulphur is so obvious and predominant. Gregory Faluvegi suggests that a typical coal-fired power station in China will take three decades to produce enough carbon dioxide to overpower the initial cooling effects of its sulphates. [3]
Another scientist, Dr Crutzen, said: "If you were to inject a comparatively small amount of sulphate into the stratosphere while phasing out all industrial emissions lower down, you could keep today's cooling levels while getting huge health benefits." [4]
Hence, even though pollution can cool down the planet, which makes everyone happy, still, pollution is pollution! There is no way to say that pollution has no bad effects on Earth. As long as there is pollution, there is always a need to fend for our Earth by solving it! =)
[1], [2], [3] and [4] are the data and citation from "The Economist" ^^
(P/S: Hope you guys like this article)
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