Climate change – the story locked in ice? Clathrates, clathrates, clathrates!September 22, 2008 at 1:23 pm | Posted in Climate change, Environment, Global warming | 2 Comments
Tags: Clathrates, Climate change, CO2, Gas hydrates, Ice core CO2 measurements, Ice cores
Your comments on the introduction to Zbigniew Jaworowski’s presentation at the Energy Institute next month are welcome. Here it is:
The man-made climate warming hypothesis is based on the assumption that mainly through burning fossil fuels the pre-industrial level of CO2 of about 290 ppmv has increased by about 30%. However this assumption is at odds with direct measurements of CO2 over the past 200 years.
Furthermore recent estimates of pre-industrial levels of CO2 have been largely based on analyses of polar ice cores which do not fulfil the essential closed-system criteria required for reliable reconstruction of the pre-industrial and ancient atmosphere. Prof. Jaworowski will discuss the inconvenient ice core evidence due to analysis problems. These include differential solubility of gases and the formation and decomposition of various clathrates as pressures increase with depth or are released by removal of ice cores.
The first paragraph alone is misleading.
To begin with, ‘The man-made climate warming hypothesis is based on‘ evidence presented in the form of scientific observations:
“Warming of the climate system is unequivocal, as is now evident from observations of increases in global average air and ocean temperatures, widespread melting of snow and ice, and rising global mean sea level.”
~ IPCC AR4 2007
See CRU Information Sheet No. 1: Global Temperature Record.
Then, the ‘assumption that … the pre-industrial level of CO2 of about 290 ppmv has increased by about 30%‘ refers to scientific records—observations of atmospheric carbon dioxide concentrations—obtained and analysed systematically, so hardly a mere ‘supposition‘ as in common parlance. In fact, a hydrocarbon combustion process yields carbon dioxide as one of its products, and the attribution of the increase in CO2 ‘mainly through burning fossil fuels‘ over the industrial period has been studied extensively, leading to this assessment:
“Most of the observed increase in globally averaged temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic greenhouse gas concentrations. … Discernable human influences now extend to other aspects of climate, including ocean warming, continental-average temperatures, temperature extremes and wind patterns.”
~ IPCC AR4 2007
Figures for CO2 concentrations from peer-reviewed scientific publications (such as Implications of ‘‘peak oil’’ for atmospheric CO2 and climate, by climatologist Pushker Kharecha and director James Hansen of NASA GISS in 2008) are given as:
- 1850 preindustrial ~ 280 ppm
- 2007 ~ 385 ppm
This is an increase of 105 ppm, 37.5%, over 157 years: hardly an assumption that ‘is at odds with direct measurements of‘ atmospheric carbon dioxide concentrations. (As a minor point, I note that the time period in question is not ‘over the past 200 years‘ … yet, but it’s clear that continuing with business-as-usual and emissions-as-usual is not a viable option.)
Based on the misconceptions in the first two sentences, I wondered what was left to unravel in the rest of the introduction. Knowing nothing about clathrates, I looked them up, and buried within the Q&As of last year’s NERC online debate is the answer on gas hydrates I was looking for, and I hope it gives you some idea of what we’re up against 😉
Question, Monday, 22 Jan 2007 – 16:08:40 GMT (post 349)
Professor Colin Prentice, in Your answer to my posting 332 you do dismiss the expertise of Jaworowski although he in reality has a very long and impressive record in ice studies and gas analyses. In fact his latest presentation at the climate seminar in Stockholm last September received excellent applause from the majority of participating scientists.
My main point in criticising the ice core data on CO2 has to do with clathrate formation and the dissociation of gases, which you do NOT address at all. The fact that the Antarctic ice cores are consistent is not scientific proof.
Furhtermore the procedure in ice core analysis does not seem to take into account the much greater solubility of CO2 (compared to N2 and O2) in ice and water.
I note that you leave the stomatal evidence to scientific “consensus”, a very questionable attitude. As we all know consensus in science is nonsense.
Boris Winterhalter, Espoo, Finland
Answer, Thursday, 25 Jan 2007 – 09:45:26 GMT
The great advantage of determining CO2 concentrations from ice cores is that the air bubbles trapped in ice do contain a sample of the past atmosphere. One can measure the concentrations of gases in these bubbles directly, without having to translate a “proxy” into a concentration.
It is correct that beyond a certain pressure (and therefore below a certain depth, typically around 1000 metres), the components of air in the bubbles become dissolved into the ice lattice as crystals of gas hydrate. However, the methods used in ice core analysis release these clathrates as well as the bubbles. Some of the molecules form clathrates slightly more easily than others, so that one has to be careful in the transition zone between bubbles and clathrates that one is not releasing only the bubbles (which could cause a small fractionation). The fact that there is no discontinuity in the records of trace gas concentrations across the transition zone is one simple demonstration of the fact that ice core scientists have successfully solved this problem. However there are numerous careful studies of clathrate formation and release that support this statement.
The problem that CO2 is more soluble in water than other gases is well recognised, and is the reason that dry extraction techniques (crushing the ice or subliming from still frozen ice) are always used for CO2, whereas wet extraction techniques can be used for some other gases. Tests with the sublimation extraction techniques confirmed that solubility of CO2 in the ice lattice itself is also not a problem.
To my knowledge, Prof. Jaworowski has not published any peer-reviewed papers about ice core gases since 1992. Since then numerous studies have confirmed the accuracy of ice core CO2 measurements. If physical processes and properties, such as solubility, modified the concentration of CO2 seen in ice core data so as to produce variations over time, then they would also alter it in a different way at sites with different physical parameters (such as temperature). The fact that ice cores from sites with very different temperatures give the same concentrations and the same temporal variations over the last glacial cycle and beyond is very strong evidence against the kind of physical interferences you are worrying about.
Eric Wolff, Glacier Chemist, British Antarctic Survey