Day Two: Climate Change 101


Delegates are beginning to arrive in Lima, including UN chief negotiator Christiana Figueres (pictured above).  Before the negotiations begin tomorrow, some 9,000 individuals will descend. Climate change negotiation is quite an industry.  Today the Peruvian army barracks where the talks will take place was quiet. The key negotiators have already pitched their tents (literally; the delegate village is composed of a series of marquees).

Slight issue: the company hired to build the village went bust before air conditioning could be installed in several of the venues. Whilst this does reduce the COP20 carbon footprint somewhat, the generation of hot air may become something of a problem as the week progresses.

Strolling through the conference village got me to thinking about climate change more generally.  So I thought I might offer a short primer before the negotiations begin in earnest tomorrow.  Why are carbon dioxide, methane, water vapour and other greenhouse gasses in the atmosphere such a problem?

The primary greenhouse gases in the Earth’s atmosphere are water vapour, carbon dioxide (CO2) methane, nitrous oxide and ozone.  Without them, the Earth’s surface temperature would be some 33 °C colder; a bit nippy, as we say in Scotland.

A great revolution

We date man’s influence on the atmosphere to the Industrial Revolution, when King Coal changed the globe (although it could be argued that clear felling the world’s forests and the advent of farming probably began the process earlier).  Since the end of the 18th Century, there has been a 40% increase in the atmospheric concentration of CO2. How do we know? Mostly through examination of polar ice.  I might come back to that in a later blog, because it is fascinating.

The globe is awash with carbon sinks - conjures up images of a great bathroom showroom - which store carbon and prevent it escaping into the atmosphere.  Peat is a sink; so is coal. We are carbon-based life forms, so we too are sinks. The greatest sink of all is the life in our oceans (which later dies and literally sinks).  Burning fossil fuels releases the carbon, hence the impact of the Industrial Revolution. Clear felling of trees removes a major sink, and if the land is used for cattle rearing (as in large tracts of South America, just over the Andes from here) then the methane farted out by the cows contributes too.  Just over 25% of global methane is emitted from the arse of cows.

Carbon dioxide is the most frequently cited as everyone knows, greenhouse gasses, (principally CO2) are released into the atmosphere by man, principally through the burning of fossil fuels, the destruction of trees or other forms of vegetation which act as carbon sinks, and more generally the advent of the internal combustion engine.

And then it all went up in the air

In the upper atmosphere, greenhouse gases absorb heat, causing the atmosphere to warm up.  (I may have simplified things a little there, so for a full understanding, try:

Water vapour is the most prolific greenhouse gas.  The higher the atmospheric temperature, the more water the atmosphere can absorb.  It is amplified by a water vapour feedback process, where water vapour increases with temperature and temperature increases with water vapour (it explains why dew forms at night when its cool and evaporates as temperatures rise).  Importantly, the average residence time of a water molecule in the atmosphere is only about nine days, compared to years or centuries for other greenhouse gases.

Carbon dioxide is the most significant of the greenhouse gases in the atmosphere, since it makes up the biggest share, and is also the one growing fastest.  Methane (principally released the burning of fossil fuels and by cattle) is more damaging than carbon dioxide but less common. Its ‘direct radiative effect’ (its ability to retain heat) is about 72 times stronger than the same mass of carbon dioxide over a 20-year time frame. Methane also has an indirect radiative effect because it contributes to ozone formation, another important greenhouse gas.

And now its time for breakfast.  The serious work of COP20 begins tomorrow. So I will report back then.