Understanding Climate Change: Bite 1.2 – The Basic Science.
Our weather defines our local atmospheric conditions. But it is the climate that dictates what the weather might be and sets our long term living conditions.
The Earth’s climate is dictated by:
– the sun and how much of its energy gets to us
– the atmosphere, oceans, land and icesheets
– the regional physical, chemical and biological conditions.
They all interact in complex ways, and create the weather that we feel. And all this happens in our incredibly thin atmosphere: 80% of it is in a 10 mile layer above the surface. If the earth was a bowling ball, this layer would be the thickness of its surface paint.
Since the Earth’s formation, the climate has been changing, with hotter or colder periods lasting thousands or millions of years. The changing earth’s orbit, activity of the sun and those factors above caused these changes.
But in the past 8,000 years our climate has been quite stable. In that time, human population has grown from just a few million to almost 8 billion people today, and has colonized every corner of the globe. The climate conditions have been fairly constant, including the make-up of the atmosphere, up until recently.
About 200 years ago the atmospheric Green House Effect (GHE) was discovered. It is when the atmosphere reflects radiating heat back from the earth’s surface causing it to be 33C warmer than it would be otherwise. See image.
Whilst the main gases (N2, O2, Ar) comprise 99% of our atmosphere, only trace gases (H2O, CO2, CH4, N2O….) contribute to the GHE. If those trace gases change in concentration, as what has happened these past 150 years, we would expect to see a change in temperature and hence climate.
Tony Mitchell
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