Updated 15th July
The most prominent climate science story of the past week was that of Kaufmann et al writing in the PNAS stating that the temperature standstill of the past decade was caused, in part, by China emitting sunlight-reflecting aerosols from its burgeoning coal-fired power stations.
It was saying nothing new about the temperature standstill of the past decade. The scientific literature is full of references to it and suggestions for explanations, even if commentators and the media do not reflect this.
The paper (and the press release) made a mistake in taking 1998 as a start year for recent temperature trends. As this was the warmest year on record because of the strongest El Nino on record this was unwise, and should have been spotted by the paper’s referee. Later in the paper they change the start to 1999 which is again not a good year due to a La Nina. The same caveats apply for ending a run of climate models without allowing for a later El Nino, which may be the case in this paper.
Another point the referee should have picked up is the reference to temperature increases seen between 2009 – 2010. It should have been noted that this was due to an El Nino and it was misleading of Kaufmann et al not to mention that and imply it was due to anthropogenic factors.
The paper says that China doubled coal consumption between 2003 – 2007. It would have been instructive to see a few more figures at this point before being told this increase in consumption translated to a climate forcing factor of 0.06 W per m sq.
My main worry is that whilst the China coal figures were interesting, I was not convinced that they could easily be applied to be a linearly scalable indicator of aerosol pollution. I was puzzled that no aerosol data was mentioned in the paper, as aerosols include sulphur pollution. Aerosols and their effects are one of the biggest uncertainties in climate science, but at least we have good measurements of them to see if there is any correlation with the China coal figures.
Flue Gas Desulphurisation
China is the largest consumer of coal in the world. Soon it will be the largest user of coal-derived electricity.
According to the IPCC AR4: In 2006 69% of its energy came from coal, some 1.95 Trillion KWh. Coal generation capacity was 484 GW and less than 15% of coal power stations had flue gas desulphurisation equipment.
These figures are, however, out of date.
Its coal consumption is increasing, but that is not the only relevant factor. In 2010 China consumed 3.2 billion tonnes of coal, a 10% increase on the previous year. Since 2005 China has had a major effort to install state-of-the-art desulphurisation in its coal-fired plants installing more such units than the rest of the world combined. In the first five months of 2007 alone, China installed 27.6 GW of flue gas desulphurisation equipment.
At the end of 2008 China’s installed capacity of flue gas desulphurisation in power plants totalled 379 GW accounting for 66% of the countries coal-fired capacity, according to its National Development and Reform Commission. Today 75% of all desulphurisation systems are being installed in China.
Looking at the aerosol data it is apparent that the global aerosol burden declined between 1960 – 1980. Remer et al, despite showing strong aerosol forcing over China, shows no trend in global aerosol depth between 2000 – 2006, a period that includes the Kaufmann analysis.
In 2007 Nasa stated that the aerosol burden had reduced, and even said that the “thinning” of the atmosphere had given a push to global warming.
Additionally, the increase in Chinese coal consumption has not shown itself in the global temperature data, either globally or in individual northern and southern hemisphere data. Over the past 12 years there is no sign of it. It would be too much of a coincidence to expect that all of its influence on the annual global temperature was negated by other effects that exactly compensated for it!
I’m not convinced by the arguments set out in this paper and would like to see them proposed and examined in greater depth in a subsequent paper, as they probably should have been in the first place.
The majority of the media parroted the press release associated with the story, with no in depth analysis or indeed counter-opinion, for which one would not have to travel far. The analyses, and the figures, were taken at face value and as obviously unquestionably correct. After all, we all know that China is a polluter on a vast scale, don’t we?
The Carbon Brief (whose stated modus operandi is to ‘fact check’ media stories) did absolutely no fact checking at all, and missed the irony that just recently it was saying that there was no global temperature standstill over the past decade.
The BBC, once again, covered the story mostly using the press release and a quote provided for it by the Science Media Centre (containing only rather vague supportive comments). The BBC showed, again, its irresistible tendency to have a go at climate ‘sceptics’ as early as the second paragraph. Sceptics in this instance are anyone who wonders what the last decade’s temperature standstill means. Presumably Kaufmann et al are sceptics as well!
More amazing were the comments on the story in Richard Black’s subsequent blog. He misrepresents the GWPF by using a quote made by the GWPF about one aspect of the story (the choosing of outputs of climate models) and criticising it using as evidence something completely different (picking 1998 as the start date for measuring temperature trends). As an aside, 1998 was the year mentioned in the research paper and the associated press release by the PNAS. Because of the 1998 strong El Nino it is generally not used as a start point in temperature trends, as the BBC should well know.
Then the blog does something rather amazing in that it performs a crude, statistically meaningless analysis of past temperature trends. This presumably impresses the author of the blog and also contradicts the central premise of the Kaufmann et al paper that prompted it. I wonder if the author had known that Kaufmann et al could be so obviously shown to be based on a false premise, that there was a standstill in global temperatures, he would have written the original report on the paper in such positive and supportive terms.
Richard Black looks at the NasaGiss and Hadcrut data sets and concludes there has been no standstill in the past decade after examining the differences between yearly measurements. He falls into the most rudimentary of statistical traps by neglecting to take into account errors of measurement and noise in the data. He even observes that “the numbers vary a bit from year to year” which is actually the reason why it’s meaningless to just join up datapoints and leave it at that, otherwise you end up with claims that there has been a 0.3 deg C increase since 2000!
I’ve said it before but the coverage of the Kaufmann paper emphasises it. Environment Correspondents should get much closer to the science, and the process and tools of science. This way they would be able to cover developments in climate science more competently, would rely less on passing on press releases, and not see everything in terms of politics.
Added 15th July
We are happy to acknowledge the subsequent assertion of Richard Black that he did not base his article on the PNAS press release.
However, his assertion that he did not use the quotes sent to journalists by the Science Media Centre is less convincing.
These were the Prof Piers Foster quotes sent by the Science Media Centre:
“The masking of CO2-induced global warming by short term sulphur emissions is well known. It is believed that the flattening off of global mean temperatures in the 1950s was due to European/US coal burning and just such a mechanism could be operating today from Chinese coal.”
“Other natural fluctuations in the Sun’s output, volcanoes and water vapour have also been proposed for causing the non-warming naughties, and all may have contributed to an extent. the magnitude of the masking effect is difficult to gage as other short-term emissions, such as soot, warm the climate; and the effect of these short term emissions on clouds is difficult to quantify. This makes it difficult to gage the climate impact of adding scrubbers to Chinese power stations.”
“It needs to be emphasized that any masking is short-lived and the increased CO2 from the very same coal will remain in the atmosphere for many decades and dominate the long-term warming.”
These are the quotes used by Richard Black;
“The masking of CO2-induced global warming by short term sulphur emissions is well known – it’s believed that the flattening off of global mean temperatures in the 1950s was due to European and US coal burning, and just such a mechanism could be operating today from Chinese coal,” he told BBC News.
“Other natural fluctuations in the Sun’s output, volcanoes and water vapour have also been proposed for causing the non-warming ‘noughties’, and may have contributed to a degree.”
“It needs to be emphasised that any masking is short-lived, and the increased CO2 from the very same coal will remain in the atmosphere for many decades and dominate the long-term warming over the next decades.”
It is disappointing that a journalist should have sought out Prof Foster for an individual briefing only to obtain quotes identical (aside from two trivial changes) to those already distributed to the BBC, as well as many other journalists!