Climate Robustness

Past behaviour can give very strong indications of just how robust systems are to perturbations and forcings. Applying this to climate, we will take a view on how believable are the UKCP09 projections of warming in the UK over the next 45 years (see the post Met Office Fraudcast). The UKCP09 projections are based on computer modelling. Below are UKCP09 ‘central estimate’ projections for changes in Summer Mean Temperatures (medium emissions scenario) for the UK.

Note that in Northern Ireland the central estimate is for a rise of 2.1 to 3.0 degrees in Mean Summer Temperature in the 2050s (and up to 4 degrees by the 2080s). Temperatures in Northern Ireland have been recorded for over 200 years, and we have a fairly good record covering the last 160 years, see below.

Credit:Junkscience

It is clear that summer temperatures in the 1840s and 1850s at the beginning of the record were more consistently warm from year to year and averaged higher maximum temperatures than those over the supposedly sizzling last 20 years – maximum summer temperatures never fell below 18 degrees from 1844-1860. The upper red trace represents the daily maximum temperatures during the day (averaged across June, July and August each year), the lower blue trace represents the minimum temperature (at night), and the central purple trace is the mean of the red and blue traces, this being the Mean Summer Temperature. The straight lines through the traces are the trend lines from the values from 1844 to 2004, 160 years. It will be seen that there is practically no trend in the maximum summer temperatures – on average, summers now are not warmer than they were 160 years ago. There is a slight trend in the minimum temperatures – the nights have been getting a little warmer over the period, and who is going to worry about that? Because of the averaging between the max and min traces, this creates a slight trend also in the Mean Temperature, but it is still an extremely minor effect over the 160 year record. Although there have been periods when the mean temperature has been a little higher (the 1840s and 1850s, for example) there have also been periods when it has been a little lower (e.g. the 1870s to 1920s). A definite period is evident when there was a noticeable short-term cooling trend (1859-1884) yet there is no significant long-term trend when considered over the full 160 years (this accords with the observations in 130-year datasets from other parts of the world as indicated in the post Crops and 130 Years of Climate Records).

Yet the Met Office and Defra are now trying to make us believe that a trend line will suddenly ‘kick up’ and take off as shown in the extended part on the right because of mankind’s carbon emissions. It certainly does look fanciful.