We now know that the expression in the emails referred unambiguously to the decision not to use data derived from measuring the width of recent tree rings in part of a graph of temperatures. The tree data suggested that a decline in temperatures in recent decades but we know from thermometer records that the rings were giving false information. To ‘hide the decline’ wrongly indicated by the information from trees, the University of East Anglia scientists replaced the data with instrumental records.

The investigative report by Sir Muir Russell and others examined the phrase and while they criticise the failure of the scientists to provide details of their technique when the chart was published, they seem to accept the explanation of Phil Jones, the head of the Climatic Research Unit at UEA, that the word can ‘mean for example a mathematical approach brought to bear to solve a problem’ when used by scientists. The impression given by Sir Muir’s report is that this sense of the word ‘trick’ is a specialist term, a jargon word that would be understood by other scientists but not necessarily by ordinary people. It is as though the word is an artifice, only used as a sort of internal language in communications between experts, perhaps in order to confuse the wider public.

This interpretation of the meaning of the word is wrong. In conventional English, as used by men and women in ordinary life, the expression has had two sets of meanings for several hundred years,  as well as many other subsidiary connotations. The first of these main meanings revolves around deception or fraud.  The second refers to the use of a skill and has no overtones of malpractice whatsoever. In fact it suggests admiration and appropriateness. It is a great pity that Sir Muir and the journalists that covered Climategate have not made more efforts to demonstrate this point. As a result, the impression among non-experts is still that the CRU scientists behaved wrongly.

Here are the definitions from the full Oxford English Dictionary, the language’s most important record of the history and meanings of words.

Meanings implying deception

 A crafty or fraudulent device of a mean or base kind; an artifice to deceive or cheat; a stratagem, ruse, wile; esp. in phrase to play (show) one a trick, to put a trick or tricks upon. (+ three closely related senses)

A freakish or mischievous act; a roguish prank; a frolic: a piece of roguery of foolery; a hoax, practical joke. (+ two closely related senses)

Meanings implying skill

A clever or adroit expedient, device or contrivance; a ‘dexterous artifice’; a ‘dodge’. bag of tricks.

The art, knack, or faculty or doing something skilfully or successfully.

The OED also gives many other meanings to the word, such as a particular habit (‘up to his old tricks’) or a prostitute’s customer. Because the OED entry for ‘trick’ was finished in 1914, most of the quotations used to support the definitions offered in the dictionary are several hundred hears old. The Shorter Oxford Dictionary, an offshoot of the main OED, gives more modern quotations to illustrate what a word means. Here is one example from the writer and broadcaster Clive James: ‘I learned the trick of carrying nothing much except hand baggage’. No sense of deception or artifice there.

The Shorter Oxford also provides a useful definition of this sense of the word ‘A clever or skilful expedient; a knack or special way of doing something’. Those writing and commenting on Climategate should now specify that this sense of the word was almost certainly what the CRU scientists meant rather than continuing to imply some form of disingenuous or dishonourable behaviour.

(1)    At a meeting at the Royal Institution in London to discuss Fred Pearce’s extremely thorough and illuminating new book, The Climate Files, published by Guardian Books, May 2010.

The IPCC’s most recent report (in 2007) provided an estimate of what is often called the ‘climate sensitivity’, the guess – and it is likely more than a guess –  at how fast temperature is likely to change as CO2 rises. Assessment Report 4 concluded that temperatures were ‘likely’ to rise between 1.5 and 4.5 degrees as a long-term consequence of a doubling of pre-industrial levels of carbon dioxide. (‘Likely’ in the IPCC’s language means a probability of between 66% and 90%).  More precisely, the 2007 IPCC document suggested that the median estimate of ‘climate sensitivity’ is about 3 degrees, exactly half way between 1.5 and 4.5 degrees.

This 3 degree figure has assumed a central importance in the discussions of policymakers. We can make reasonably accurate guesses about the tonnage of fossil fuels we can burn before we double the 280 parts per million of CO2 in the atmosphere. So scientists and others can then use the ‘climate sensitivity’ figure to estimate the impact of various scenarios for cutting the growth of emissions on the likely temperature change in the future.

Bodies such as the UK’s Committee on Climate Change have given a crucial role to the 3 degree number. The Committee’s extremely impressive first report in late 2008 carefully calculated how much global emissions needed to decline by 2050 for the most likely temperature increase to be about 2 degrees by the end of the century and it relied on the key figure for ‘climate sensitivity’. It also used the 3 degree number as a crucial input in its calculation of what emissions could be permitted if the world is to have a less than 1% chance of exceeding an extremely dangerous 4 degree rise. The Committee’s world-leading carbon budgets are largely reliant on the reasonableness of the 3 degree estimate. If the figure is too low, then world emissions would have to be cut even faster if we are to avoid temperature rising more than the Committee’s targets.

Zickfeld’s paper suggests that climate scientists now believe that the 3 degree figure  is too low.  The IPCC’s 2007 report used seven scientific papers to provide a consensus figure for climate sensitivity. Only three of this reports suggested a median figure of 3 degrees or above. The lowest was below 2 degrees. Zickfeld says that the current estimate of the experts interviewed for the paper is now not 3 degrees but nearly 3.5 degrees.  No-one in the survey believed that climate sensitivity was less than 3 degrees. Interestingly, four of the fourteen scientists had participated in a similar survey in 1995 and all their estimates of ‘climate sensitivity’ had risen, in one case by a very substantial amount. The increase from 3 to 3.5 degrees may seem a small change, but it actually suggests a substantial upward revision in the expected global response to increased levels of climate changing gases.

Perhaps even more importantly, the climate experts suggested that they were no more confident about the accuracy of their predictions than the IPCC was in its assessment of pre-2007 research. The money and time going into climate prediction isn’t yet giving scientists a sense that uncertainty about the speed of global warming  is improving. Moreover, the interviewees were pessimistic that we would know much more even in twenty years time. These conclusions are very worrying: not only are some of the world’s top climate scientists increasing their estimate of ‘climate sensitivity’, they are also no more certain about the distribution of probabilities than they were. As an aside, it remains extremely difficult to convey to policymakers that the width of the distributions of probability of temperature change matters as much as the central estimate.

We now have a possibility that a cherished figure – 3 degrees as the central estimate of ‘climate sensitivity’ – is too low. What are the implications? Let’s take just the UK Climate Change Committee’s target of assuring that the risk of a more than 4 degree rise by 2100 is less than 1%.  It produced its recommendation that UK emissions should peak by 2030 and then fall at 3% a year in order to achieve this result. (Global emissions, not just the UK, will have to fall by about 50% by 2050 in the same package). If the true ‘climate sensitivity’ is 3.5 degrees, my rough calculations suggest that even if the globe meets the targets the chance of a 4 degree temperature rise by 2100 is about 3%, not the less than 1% that the Committee targets. In order to reduce the risk back down to 1% – which already seems an unacceptably high figure to me – the rate of decline in UK emissions from 2016 needs to be about 4%, not the 3% currently specified.

It is an unhappy truth that the news about the climate always seems to be worsening. The Climate Change Committee would do us all a service if it now assessed whether it needs to revise its projections in the light of higher expectations of temperature rises from future greenhouse gas emissions.  

(1)    Kirsten Zickfeld, M. Granger Morgan, David J. Frame and David W. Keith, Expert judgments about transient climate response to alternative future trajectories of radiative forcing, Proceedings of the National Academy of Sciences, online edition, 28^th June 2010.

The finances of the Aldi store demonstrate the returns available to investors in PV installations under the new feed-in tariffs. 281 solar panels have been placed on the newly constructed store. The roof is almost south-facing but not quite steep enough for maximum production. Joe Michaels of JoJu, the company that carried out the work , told me that the site would produce about 44,200 kilowatt hours a year, about 90% of the absolute maximum achievable in Oxford for 52kW array, pointing due south and tilted at 41% to the horizontal.

The electricity production creates two streams of income for WOCR. First, the power generated will achieve feed in payments of 31.4 pence per kWh. Second, the store owner pays WOCR for the electricity supplied to the store. All the power produced will be used by Aldi, so there will be no third source of income from the export tariff set up under the feed-in system.

For obvious reasons,WOCR was reluctant to give me a firm estimate of the full cost of the whole system. Today’s small domestic PV installations cost about £5,000 per kilowatt of peak capacity. My guess is that the Aldi installation probably cost about £4,000 per kilowatt, or about £208,000 for the full installation. The lower cost is because of the benefits of installing large numbers of panels on a single roof, helping keep down labour costs. The actual price may have been even lower because the Aldi roof was initially designed and constructed to easily accept the PV array. Joe Michaels told me that about 50% of the total cost was the panels themselves, supplied by Amerisolar, a US company, but made in China. About half the rest of the cost was labour and overhead and the remainder is the electronics necessary to convert low voltage DC into grid-compatible AC current.  

The streams of income will be

The 8.6% return is inflation-linked and the guaranteed feed in income will continue for 25 years. After the point, returns are likely only to come from the value of the electricity sold to Aldi. Most panels will last over 30 years with some degradation in performance in later years. WOCR may choose to replace the PV at some point, meaning the installation may continue to produce income for many decades.  While these levels return are not likely to excite commercial investors, they will provide a good income for people saving for pensions or other long-term savings needs.

Joe commented that the planning process had been simple and well handled by Oxford City Council, taking about 8 weeks. He was similarly complimentary about the actions of Scottish and Southern, the local electricity network company. The negotiations between Aldi and WOCR had taken about fourteen months, principally because of the newness of the concept. This is a pathbreaking installation and we will see many more similar arrays.