Sir, At the risk of still further muddying the waters of the discussions about the origin of global warming I should like to express my disappointment at the standard of the arguments being used, especially by "believers".
I do not have the technical knowledge necessary to understand the three dimensional fluid-dynamics and thermodynamics of the atmosphere which seems to control our weather, or of the computer modelling which is used to predict future events. I have to rely on the arguments presented by others, and remember the past record of the number of "universally agreed" theories which have been displaced in due course by better knowledge put forward by original thinkers from Galileo onwards.
The response of "believers" to the "sceptics" is, too often, not to address their specific arguments but to dismiss them as (a) flat Earthers or (b) in the pay of the oil industry (to have to rely on this smear is particularly disappointing). Abuse is no argument.
For instance the CO2 concentration appears to have increased more or less linearly in the last 100 years since 1910 but in contrast the temperature rise has been intermittent and non-linear. For half of those 100 years it has been rising and for the other half it has been constant or falling. This appears to weaken the link between cause and effect.
And the archaeologists tell us people in Roman times and the Middle Ages appeared to enjoyed a warmer climate than today before the advent of coal-fired power stations and cheap air travel. And apparently it was both warmer still and colder in the geological past.
The extent to which the variations in the Earth's orbit around the sun has an influence on our climate was discussed as long ago as 1892 by Sir Robert Ball in his book The Cause of an Ice Age.
If the believers can demonstrate that their computer models include and predict these changes we could have more confidence in them.
From Colin Summerhayes* (Rec'd & Pub'd 15 November 2010)
Sir, Robert Freer (Letters, 3 November, above) rightly notes that “people in Roman times and the Middle Ages appeared to enjoyed a warmer climate than today before the advent of coal-fired power stations and cheap air travel”.
The warming of medieval times is known as the Medieval Warm Period (MWP). According to the father of climatology in Britain, Hubert Lamb1, it lasted from around AD 900-1400. It was followed by the Little Ice Age (LIA)1, which lasted from about AD 1400-1750. The cooling of the LIA was not uniform, but focused in certain periods during which there were hardly any sunspots: the Sporer Minimum (1400-1520) and Maunder Minimum (1645-1715). Earth gets less energy from the sun when there are fewer sunspots than when there are many. Some researchers regard the LIA as having extended into the 19th Century in association with a subsequent sunspot minimum - the Dalton Minimum (1790-1830).
That the LIA was a global event related to diminished solar activity has been well established for example by Maasch et al. (2005)2. What many people do not realise is that Lamb recognised that the MWP was not uniform and thus not global: as he said (p.171) “China and Japan evidently missed this warm phase”. He went on to note (p.172) that “the lands where the warmth of the high Middle Ages was most marked” was around the Atlantic – by which he meant the North Atlantic. Indeed, Maasch et al (2005) use geochemical data to show that there is no clear relationship between the MWP and sunspots, which helps to explain Lamb’s observations. Mayewski and Maasch (2006)3 point out, further, that the MWP is absent from Antarctica, where there is a warming event from AD 500-1000. These various lines of evidence concerning the MWP are either ignored or unknown by the so-called climate ‘sceptics’ (a title I object to because as a scientist I am sceptical by training and inclination).
Mr Freer alludes to the fact that our climate is influenced by the Earth’s orbit around the sun and wonders if this has been considered by climate modellers. This influence is discussed in considerable detail in the several books and papers in the reading list attached to the GSL’s climate change statement. The tiny changes in solar radiation received on Earth as the result of predictable changes in the Earth’s orbit recur with frequencies of 20,000, 40,000 and 100,000 years - time scales far longer than the human time scale or than the periods considered by the numerical models used for climate forecasting. Nevertheless, the slight gradual decline in global temperature since the Holocene climatic optimum 8000 years ago is likely to have resulted from these orbitally driven changes. The climate and palaeoclimate science communities do recognise the existence of these tiny variations in the climate background of the past few hundred years and their likely change in the future.
Finally, in response to Mr Freer’s comment about the apparent lack of tight linkage between temperature and CO2 in the atmosphere today, it seems fair to point out that the links of cause and effect between CO2 and temperature are not simple. That is because of the wide variety of feedbacks within the Earth system. CO2 is both absorbed by and emitted from the land surface and the ocean at different times, at different rates and in different places, obscuring a direct connection to temperature. From time to time major volcanic eruptions like that of Mt Pinatubo in 1991 thrust dust into the stratosphere and so change the global temperature for short periods (1-3 years). Temperature is also affected by changes in Earth’s albedo (e.g. the amount of sea ice or land ice reflecting energy to space at any one time).
Climate modellers try as best they can to take all of these feedbacks into consideration (see for example the climate science books by Sir John Houghton or David Archer referred to at the end of the GSL’s climate change statement). But by accounting for all known feedbacks they are unable to replicate the warming since 1970; they can only replicate it by incorporating the effects of anthropogenic emissions of CO2 acting as a greenhouse gas.
References
- Lamb, H.H., 1995, Climate, History and the Modern World. 2nd Edition (first published 1982). Routledge, London, 433pp
- Maasch, K.A., et al., 2005, A 2000-year context for modern climate change. Geografiska Annaler 87 A., 7- 15.
- Mayewski, P.A., and Maasch, K.A., 2006, Recent warming inconsistent with natural associatoion between temperature and atmospheric circulation over the last 2000 years. Climate of the Past Discussions, 2, 1-29: www.clim-past-discuss.net/2/1/2006/
* (GSL Vice President, Emeritus Associate, Scott Polar Research Centre, and Chair of the GSL climate-change statement's drafting group.)
From Peter Whiteside (Rec'd & Pub'd 2 November 2010)
I am writing to express my utter dismay at the articles by yourself and by Bob Ward in the October edition of Geoscientist.
My dismay at Bob Ward's piece, a man who is well known in the media and blogosphere as an ardent promoter of anthropogenic global warming (AGW), is not caused by my disagreement with his views but its unscientific nature, and insinuation about the motives of Joe Brannan. Moreover it was not accompanied by the reply from Joe Brannan which I see is now available on the website.
Geoscientist is a magazine for geoscientists concerned with scientific issues, and in my view the editorials should reflect this. They should be balanced, non-partisan and they should promote geoscience in a rational way. Your article was a call to arms of the worst kind. You address the Fellows of the Society by saying "...the probability of our being responsible for most of the measured warming of the last century ... should be accepted by everyone, everywhere, as fact." This is totally out of order, and I take great exception to being hectored in this way.
Your editorial is emotive, full of unjustified assertions and insinuations that I believe are out of place in Geoscientist. Your statement that the errors in the latest IPCC Assessment Report were "trivial" is highly debatable. Your claim that "...climate-change denyers are...strong in the dark side of...media management...and they are backed by powerful interests.", and that "denialists...being unconstrained by evidence...can construct any number of simple messages whenever they like." is grossly insulting to Fellows who like me maintain that the scientific evidence is far from clear and the theoretical hypotheses far from proven. The term "denyers" is provocatively abusive, recalling Holocaust denyers - and far from being "unconstrained by evidence" most scientists who are seriously sceptical about AGW want an open, scientific discussion of evidence, rather than the closed mentality and bullish assertiveness too frequently displayed by some parts of the AGW establishment.
From John G Gahan (Rec'd 20.10, Pub'd 3.11 2010)
How disappointing to note Ted Nield’s take on climate change (Editorial Vol 20. No 10 Oct 2010) following his previous editorial comment in the June edition. Notwithstanding Ted’s claim, human beings are not responsible for climate change despite the recharged campaign suggesting that they are. So why is Geoscientist attempting to sway us with unscientific critiques that AGW is responsible?
It will be evident to most geologists that atmospheric warming and cooling were the norm over long periods of geological time whereas in recent times empirical research suggests much shorter timeframes. Heinrich Events and D/O Cycles clearly point to rapid climate exchanges and indeed for the period 1979 to 1998 was a time of increased warming. Since then however the warming trend has declined to more ‘normal’ conditions (whatever normal may be). Influential bodies including (shamefully), the Royal Society, the BBC, parliamentarians and ministers aligned themselves with what can only be called ‘noble cause politics’ in support of dubious environmental initiatives rather than traditional scientific rigour.
The Editor is right about one thing though: ‘science consensus changes rarely and slowly’ and so indeed does science itself (as indeed do climates). But Ted’s analogy relating to smoking versus cancer to espouse his conviction is wrong. Quite apart from a lack of rigour in climate science generally, he overlooks the fact that it was the tobacco industry itself that deluded smokers with spurious data, not forgetting smokers themselves were/are hooked on the weed anyway while intuitively understanding the truth of the matter. However, perhaps akin to climate change, cancer is an uncomfortable reality and medical science is extremely assiduous to establish cause. Certainly a cure or powerful hypothesies is desirable and will always pertain, but until that time and unlike AGW conviction, is it not wiser to work with perceived claims rather than circumvent scepticism with dodgy science? It should be noted that temperature records (correlation) are not a measure of cause so geo-engineering projects and precautionary principles (relating to new laws) will prove to be extremely erroneous and costly in the long term as sound science, not speculation, will prevail.
References:
- Costella J.P.-2010, ‘Climategate Analysis’ Science & Public Policy Institute, Vancouver. (http://www.google.co.uk/#hl=en&source=hp&biw=1026&bih=675&q=climategate+analysis+costella&aq=1&aqi=g2&aql=&oq=Climategate+Analysis&gs_rfai=&fp=cee3fafcad61482)
- Thorne, P. W., Parker, D. E., Tett, S. F. B., Jones, P. D., McCarthy, M., Coleman, H., and Brohan, P., 2005, Revisiting radiosonde upper-air temperatures from 1958 to 2002, J. Geophys. Res., 110, D18105, doi: 10.1029/2004JD005753. (PDF file)