Starting this post is a poll of readers view’s on a CO2 emissions target for Australia, announced recently by the Prime Minister. Please take a moment to respond, before moving on to the rest of the post.
This was prompted by a bad article in The Australian newspaper called Climate change: 2008 is world’s 10th hottest year. I put aside the subtext of the article, such as abundant references to phenomena of La Nina, droughts, and Arctic Ice, where global warming is the usual explanation of convenience, and take exception to the statement that:
Australia is on track for its 15th warmest year on record, with a temperature 0.37Â°C above average, according to the World Meteorological Organisation.
The average, according to wikipedia, is the central tendency of a data set, a measure of the “middle” or “expected” value of the data set. That is, an average is the value to be expected with a sufficiently long run of observations. How long? In the case of climate, 10,000 years would only represent a sample of an exceptionally warm period called the holocene; 100,000 would capture the fluctuation of a single ice age cycle while a million years would be needed to represent a long term expected value, or average.
But with only 100 to 150 years of global temperatures on record, how could the temperature be 0.37Â°C above average? Based on the multi-ice age ice core data from Vostok Antarctica, the earth is usually much colder, perhaps an average of 8Â°C colder than the present.
The correct terminology would be to say the temperature is 0.37Â°C above the mean temperature over whatever period the baseline is calculated. The arithmetic mean (or simply the mean) of a list of numbers is the sum of all of the list divided by the number of items in the list.
Update: For fun, try clicking the link on The Australian exclusive poll “POLL: Is the target too high or too low?” right hand side. Follow the link in Pollnet to get to The Australian article.