Mr Solomon Greens letter of 11 November (The Actuary, December 2015, bit.ly/1RUVcJo) casts doubt on the competence of all those men and women working in the complex and important field of climate modelling.
While it is entirely proper that good actuaries can offer some level of impartial critical interrogation in fields in which they claim no expertise, it cannot be right that this can then morph into outright condemnation and ridicule of an entire profession.
It has taken considerable effort to restrain my language, so I will restrict my remarks to commenting on the seemingly widely held misapprehensions concerning the apparent undershoot in the rate of warming since approximately 2000 - the so-called 'global pause' or 'hiatus'. I emphasise rate, because the absolute temperatures tell us that most of the hottest years ever recorded have happened this century (see, for example, NASA data). It is not getting any cooler. But it may be true that the rate of increase since 2000 has flattened off.
As far as I understand it (see the National Oceanic and Atmospheric Administration), there are always going to be temporary (decadal) variabilities. In recent years, this has been due primarily to a series of negative El Niño years together with a phenomenon known as the Pacific Decadal Oscillation. There have also been a number of volcanic eruptions and other similar variable effects (Scripps Institution of Oceanography provides evidence for the El Niño effect).
But the energy imbalance caused by the greenhouse gases covering the planet is still in effect. Just because the surface temperatures 'only' increased at a reduced rate since 2000 doesn't mean that global warming did not continue. Excess energy doesn't just vanish. It melts ice, it causes evaporations and, in particular, it warms the deep oceans. This last is significant. Measurements down to 2,000m, 700m and 300m below sea level show a marked increase in oceanic warming since 2000, particularly at the deeper levels (Balmaseda et al, 2013).
Finally, the rate of increase may have flattened off. This was indeed what the Intergovernmental Panel on Climate Change (IPCC) concluded in its fifth assessment report. However, in recent years, scientists have been looking hard at the data used by the IPCC (TR Karl et al, Science, 2015). The network of the observation points used to collect this data are expanding and changing, particularly sea-surface temperatures, which rely in part on thousands of commercial ships. There has also been an increase in land-station data. In summary, to quote from the paper in Science, "newly corrected and updated global surface temperature data do not support the notion of a global warming 'hiatus' Indeed, based on our new analysis, the IPCC's statement is no longer valid."
As actuaries, we know all models are wrong, but we can still conclude that some are still useful. However, it casts us in an appalling light if we start issuing blanket condemnations in ignorance of all the facts.
(Although I sit on the IFoA's Resource and Environment Board, and chair the IAA's Resource and Environment Working Group, this letter is written in a personal capacity and the views are my own.)
Kenneth Donaldson, Fellow
13 January 2016
