Mr Guy Caruana (Coast Community News Forum, June 3) should perhaps stick to playing marbles with his bucket of marbles.
Straightforward physics demonstrates that a bare rock at Earth’s distance from the sun should be far colder than the Earth is, and it is greenhouse gases which make earth warm enough for life as we know it to exist. Greenhouse gases are those which trap heat, resulting in an increase in the average temperature of the Earth.
The major constituents of the atmosphere, nitrogen and oxygen, are not greenhouse gases. Only molecules composed of at least three atoms are able to absorb infrared radiation. Although greenhouse gases constitute less than 1% of the atmosphere, they have an enormous effect on the global environment.
The ‘small quantity’ argument is spurious. Ingesting one millionth of a gram of polonium 210 will kill you. It was John Tyndall who, in 1859, discovered that not all gases are infrared transparent, identifying carbon dioxide (CO2) and water vapour (H2O) as gases able to trap infrared energy.
Water vapour is the most abundant gas in the atmosphere with three or more atoms, but its presence is dependent upon atmospheric temperature, rather than surface emissions. It is factored into climate models. Other greenhouse gases include methane, ozone, nitrous oxide, hydrofluorocarbons and sulphur hexaflouride.
During the 1950s, Charles David Keeling developed the first instrument which could accurately measure CO2 levels in the atmosphere. Prior to his discovery, CO2 levels were measured using techniques based on titration with limewater or baryta (the Pettenkofer process), which was finicky and required the regular use of a CO2 standard to ensure the accuracy of readings, something most users skipped.
Nearly all of the early samples were taken in locations convenient to the operator but subject to periods of heavy industrial pollution, so they did not reflect wider atmospheric conditions. Thus, pre-industrial CO2 levels had to be determined using correctly conducted readings from isolated locations and through other means, such as ice cores.
In March this year, the worldwide average concentration of atmospheric CO2 was 400.83 parts per million (ppm), the first time in recorded history that the entire planet has averaged more than 400ppm for an entire month. This is a huge increase on the 280ppm pre-industrial level, which had remained steady for thousands of years.
Atmospheric CO2 levels are measured by hundreds of stations in isolated locations, spread across sixty six countries, well away from any sources of local pollution which might otherwise infl uence the results. A natural change of 100ppm normally takes 5,000-20,000 years.
Humanity has achieved it in just 120 years and greenhouse gas emissions continue unabated. Scientists have stated that prolonged atmospheric CO2 concentrations of above 350ppm are likely to cause irreversible damage. Climate scientists’ maths is accurate.
It is denialists of anthropogenic climate change who are losing their marbles over maths and science.
Letter, 10 June 2015
Helen Moss, Melbourne