Global warming

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Topical Science

Issue No. 5

May 2017

TOPICAL SCIENCE : GLOBAL WARMING Much has been written in the media about global warming, but the physico-chemical mechanisms involved are seldom explained.

This issue of Topical Science attempts to explain these mechanisms.

May 2017 In this issue, I try to explain the way the gases in our air interact with electromagnetic radiation. Carbon dioxide and water vapour are transparent to visible light, but absorb infrared radiation and therefore can trap heat energy.

The composition of our atmosphere, coupled with the way in which the different gases in the air interact with electromagnetic radiation, plays a crucial role in determining the temperature of our planet. The table on page 2 shows the main gases present in the air we breathe.

Carbon dioxide is essential to life. It keeps our planet warm and is needed for photosynthesis.

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But too much CO2, in the air, causes global warming!

Our Atmosphere: The layer of gases enveloping our planet Earth. The main constituent of our atmosphere is the gas

nitrogen, which makes up almost 80%, by volume, of the air around us. At normal ambient temperatures, this gas is chemically unreactive and serves to dilute the oxygen, which accounts for most of the remaining 20%(approx.) The third most abundant gas in the atmosphere is the inert gas argon, which accounts for about 0.9% of air. 1

We need oxygen to sustain life. With every breath we take, oxygen is drawn into our lungs and goes into our bloodstream, where it is pumped, by the action of our heart, to every part of our body. We derive energy from our food when it combines with the oxygen we breathe. We exhale carbon dioxide (CO2) as a waste product, but green plants use this CO2. 1


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