It is becoming a trend in the journal Science – that of publishing articles stating that there is no ‘hiatus’ in annual average global surface temperature. The latest such article is written by Kevin Trenberth of the National Center for Atmospheric Research in Boulder, Colorado. He’s well-known for two things. Firstly, saying in the 2009 Climategate emails that it was a travesty that scientists could not explain the recent lack of global surface warming, and secondly for finding said missing heat in the deep oceans even though given the observations and their uncertainties that requires something of a leap of faith.
He starts his opinion piece with obvious obfuscation. He states that every recent decade has been warmer than the last and that there has been a reduced increase in global surface temperatures since 1998. He adds that the upward trend resumed in 2014 that was the warmest year on record.
Firstly 1998 is not a good point to start as has been said so many times in these columns and elsewhere. The ‘hiatus’ actually extends back to 1997 and if one starts from El Nino year 1998 or even the following cool La Nina years one can get very different results. Decadal averages are also something to be careful about and should, in my view, always include analysis of start dates and durations, as nature knows nothing of arbitrary decadal start points and using only one such analysis can be misleading. Also Trenberth says the upward trend resumed in 2014. That year was two hundredths of a degree (with an error of plus or minus ten hundredths of a degree) warmer than the previous record holder, 2010, and did not mark the resumption of an upward trend. Precision in scientific writing of this sort is important because the comments made in the first paragraph of an article like this are bound to be repeated and portrayed as “settled science.”
Which Comes First, The Model Or The Data?
There is no mention that the recent Karl et al (2015) paper in science that showed there is no hiatus is in any way disputed. Trenberth then adds that another reason to think there has been a hiatus comes from model-data comparisons. To me this is putting the argument backwards. Model outputs are not more reliable than actual data yet suggesting there has been a hiatus because the models run hotter than reality gives the models too much credibility. A first order look implies that the model-data comparison gives one reason to think the model is wrong not that the data is in some way deficient for not living up to the man-made construct.
Trenberth is correct in saying that the current conditions in the Pacific – the El Nino and the so-called ‘blob’ of abnormally warm water – are the cause of 2015 being warmer that 2014. These are of course weather not climatic events, and it will be interesting when 2015 is finished and is a record year for global surface temperature many other scientists continue to attribute it to weather and not a resumption of long-term global warming.
Trenberth considers the great oceanic temperature cycles and concludes that natural variations can at anytime overwhelm long-term climatic change, and that natural fluctuations are larger than commonly appreciated. This is exactly what many so-called sceptics have been saying for years and in the past were heavily ridiculed for so doing.
Behind the article is an obvious question unaddressed by it. The post-late 90s “hiatus” is due to natural climatic variability, it says. It seems that this hitherto “underappreciated” effect has kept global annual average surface temperatures below what they would have been if the planetary warming of the 90s had continued. But what if that warming was the natural climatic variability, which presumably can cause temperatures to increase as well as decrease. Didn’t somebody raise that very point in the Climategate emails?