Climate Change Week 2

So it's week 2 of the Climate Change MOOC (Massive Open Online Course) and it's continuing to live up to my expectations.  Before I get into my reflections for this week, it is worth making a few comments on the MOOC process, which is new to me.  I had concerns that because MOOC is MASSIVE, with unlimited participation and open access via the web, it would be unmanageable.  But my concerns were certainly unfounded.  In fact, far from being unmanageable, it actually seems to manage itself, rather like Facebook, LinkedIn, Twitter, et al.  So although there are obviously many participants with different backgrounds, skill levels, aspirations, etc., the way in which each participant 'tailors' the course to suit his or her requirements, results in an individual learning experience.  So well done FutureLearn, I'm impressed!

This week we have been studying past climate change starting at around 4.5 billion years ago.  The Earth has been habitable for all that period but has seen a tremendous range of climatic conditions.  Interestingly, 4.5 billion years ago the sun was about 25% to 30% less bright than now and yet if today's sun was 'turned down' to that level, the planet would freeze.  But it didn't.  The reason it was warmer than expected, was because of a thicker layer of warming gases.  OK but as the sun warmed up over the years, why didn't the planet get much hotter?  The continents weathered as a result of rain water and carbon dioxide forming a weak acid, which dissolved rocks and the carbon washed into the oceans where it was used by organisms to form shells.  These ultimately were deposited on the ocean floor to form carbonate rocks.  This is how the carbon was taken out of the atmosphere and the climate self regulated.  Clever isn't it?!

There were two notable periods in the planet's history, 2.2 billion and 700 million years ago, when the planet froze and became a giant snowball.  The theory is that on both occasions something happened to cool the planet so the ice caps expanded.  As they grew they reflected more sunlight, causing more cooling and more ice cap growth until the whole world was covered in ice.  The freeze was broken by volcanic activity, which is not affected by the big freeze, this pumped carbon dioxide into the atmosphere, thus creating atmospheric warming, and so on.

We learnt about more recent climate change in the past 2 million years.  Some of the changes in the past thousands of years have been totally predictable and are as a result of variations in the shape of the Earth's orbit and the angle and location of its axis.  The three factors affecting the sun and therefore the Earth's climate, are eccentricity (change from circular to elliptical orbit), obliquity (change of tilt of the Earth's axis and precession (wobble of the Earth's axis).  Evidence of climate change was explained and particularly before modern times when measurements were (and are) taken under carefully controlled conditions.  Methods that are employed include tree rings and ice cores.

Finally we discussed the relevance of the fact that on 9 May 2013, carbon dioxide levels in the atmosphere reached 400 parts per million.  This level has not been reached since the Pliocene period, three to five million years ago.  The temperature then was about 2-3 degrees C higher than now.  Are there any conclusions that can be drawn from that?  Well many participants think there are, but my own view is that it is too simplistic to relate the Earth's temperature solely to the increase of man-made CO2.  That said, I am still a strong advocate of the need to reduce significantly man-made CO2 emissions.

I was less hasty this week before doing the course test and it paid off with a better result!  I am looking forward to week 3.