Tuesday, December 02, 2008

Climate Change Not Caused by CO2?

I have put a question mark at the end of the title, since that sentence, made as a statement is highly controversial. Indeed, the term "denier" has been accoladed to the still substantial faction, including some serious and respected scientists, who challenge the assertion, based on computer models of the earth's climate that the increase in atmospheric CO2 derived from fossil fuel carbon is causing the planet to warm-up, perhaps by an additional 5 - 6 degrees C by 2100.

Let me emphasise my own perspective here. I am not a climatologist, but I do see that the most immediate impact on human life on earth will be caused by the dearth of cheap oil, then gas, and finally coal. Unless fast-breeder reactors, including thorium-based systems (the simpler liquid fluoride reactors rather than the vastly complex accelerator driven systems) are introduced fast and on a large scale, or other deposits of uranium are found, nuclear too will overrun its energy supply within 40 - 50 years, or sooner if nuclear power is proliferated as most western governments aspire to do.

If the climate models are correct in their predictions, the impact of carbon emissions will be felt later than that, and it is debatable how much we can moderate this, simply by reduced carbon emissions strategies (see yesterday's posting). Once we begin to eliminate fossil fuels, either through new "clean" technologies or by simply running out of them, the anthropogenic burden of CO2 will begin to level off. However, if the oceans are becoming saturated with CO2 in the surface layers and are less able to dissolve more of the gas, the consequences of carbon emissions both past and future may haunt us for millennia.

Since various computer models give different answers, e.g. warming by as little as 1 degree or as much as 5 degrees by the end of the century, it would be handy to have some experimental data to make recourse to. Obviously, we can't know the future, and that will only unfold as time passes. However, there is the geological record which gives some clues as to past behaviour. In a nutshell, according to ice-core samples, rather than the CO2 increasing and then the earth heating up, what may be deduced is the reverse of this; i.e. the planet warms and then, with a lag of around 800 years, the CO2 levels increase in the atmosphere.

The observables are a little less direct than this, since the temperature at a particular time in history is deduced from the ratio of heavy (deuterium) to light (protium) hydrogen isotopes (and O-18/O-16) in water (ice-cores), i.e. the ratio of heavy water to (ordinary) light water. Since the heavy water tends to evaporate more when it is hot, an increase in the heavy/light water ratio is observed, and vice versa for cold periods. There has been some speculation as to the accuracy of such isotopic thermometers, and corrections are proposed that close the gap somewhat between the temperature and CO2 levels suggesting a closer correspondence between the two, but nonetheless the initial heating period cannot be explained as being caused by rising CO2 levels, even though it may well be that once the CO2 concentration increases, its heat-trapping effect does introduce a thermal feedback to the climate.

One might speculate what exactly is the mechanism for that initial warming process if it cannot be simply explained in terms of CO2. Possibly, Milankovich cycles (changes in the amount of solar energy received by the Earth according to changes in the periodicity of its orbit over time) may play some role. For example, the roughly 100,000 year period between ice-ages corresponds to an "orbital forcing factor", between the closest and most distant approach of the Earth to the Sun, following the slightly undulating ellipse of its solar-orbit.

Some recent papers provide evidence that the global climate is subject to variation even over the past few centuries, i.e. before humans began burning up to the present 7 billion tonnes of carbon fuels each year. Global temperatures declined abruptly by around 2 degrees C from the Medieval warm period (1200 AD to 1500 AD) to the little ice-age (1500 AD to 1850 AD), when skaters built fires to roast chestnuts on the frozen surface of the river Thames in London. More detrimentally, there were widespread and frequent crop failures during the latter cold period which led to perhaps a million deaths from famine and disease. After 1850, average temperatures rose by around 4 degrees C, and this was before humans began releasing huge amounts of CO2 into the air. This amount of global warming was about 7 times the temperature increase observed during the past century and cannot be attributed to CO2 emissions since the CO2 levels in the atmosphere were relatively low then.

Since 1977, both the Earth mean temperature and the atmospheric CO2 levels have increased, which is usually taken as causative of the former, and yet during the 30 years prior to then, the temperature actually fell despite the fact that CO2 levels were increasing monotonically year on year. Surely if CO2 levels determine the temperature, the latter should have risen between 1945 and 1977, rather than the converse.

Although some 80% of the total manmade CO2 has been emitted since 1945, more than half of the warming observed in the past century occurred between 1890 and 1945, which could not have been a result of CO2 emissions. Of course, we may have more warming to come from those later emissions of CO2. We don't know yet.

It may be concluded that CO2 does not cause planetary temperature rise, but there are other regulatory systems at work. Now, it is impossible to state that the present unprecedentedly high levels of CO2 will not cause the earth to warm to the extent that the climate models indicate, but there is no direct evidence that recent global warming is caused by rising CO2 levels.

It has been argued that if global warming is not caused by CO2, then mathematical predictions of global catastrophe are meaningless, and we enter the red-zone of an arrogant belief that we can re-engineer the earth systems by curbing our carbon emissions, and hey presto global warming will be switched-off. As noted, the inertia in the system may be far greater than these models indicate if the ocean sinks for CO2 are becoming saturated.

There are however two imperatives. Firstly, we have to use less oil, gas and ultimately coal because these are present only in finite reserves, and so energy efficiency and conservation in relocalised (less transport-intensive) societies appears a must. It becomes arguable just how much of our effort and resource should be spent on actual carbon-remediation schemes (e.g. biochar production and other carbon capture technologies) , if CO2 is not the problem, and the earth has its own agenda irrespective of what we do.

Moreover, if we cannot ameliorate global warming, surely it makes more sense to devise strategies for how to survive under the stresses that it will impose upon us, in terms of sea-level rise, keeping those in vulnerable health comfortable during especially hot periods, and providing enough water for all of us. We need to take realistic and practical action. The rest is theory, untested and probably untestable until nature's own plan is revealed to us in full.

Related Reading.
"CO2 might not be cause of climate change." By Dr Don J. Easterbrook. htt://www.mtexpress.com/story_printer.php?ID=2005114101


Anonymous said...

There a few misconceptions in this post. I'm not someone who knows a great deal about climate change but the IPCC has done sterling work in producing readable reports that summarise as much of the data that is available. The cooling period post-war up to the 70s is dealt with in the third and fourth assessment reports and is attributed to sulphate aerosols from industry, cutting total solar radiation reaching the earth. The people at real climate, a blog actually written by climate scientists, is really good at covering anything you ever wanted to know and goes into it in great detail citing all the papers and posting all the data you could ever want. www.realclimate.org

They've also dealt with some of your other points before such as the lag time between CO2 and temperature increases.

Interestingly part of the reason the Thames froze over during the colder period, sometimes referred to as the little ice age, rests with the bridges over the Thames at the time. Without todays engineering capabilities the bridges had significantly more piers slow the Thames to a crawl making it freezing more likely. I can remember in 86 I think that the see froze down in Kent.

Yorkshireminer said...

There was only one bridge over the Thames at that time and that was London Bridge. the Thames was certainly wider and the flow somewhat constricted by the no of arches but it was simple the colder winter over most of Europe, check out the Dutch painters of that time and you will see the same scenes acted out on the rivers of Holland at exactly the same time. The confinement of the flow of the Thames did not cause the Thames to freeze over it was the cold bloody weather. After that period people went back to rowing on it not roasting chestnuts at the Michalmas fair.

Professor Chris Rhodes said...

I thought this would be contentious. However my understanding is that the temperatures really were colder then, across Europe. Yorkshire miner makes a good point about the paintings.

Maybe that's true about aerosols in the 1970.s and so is the idea now that the air has got cleaner or that the rising CO2 has more than offset the cooling from reflected radiation by aerosols?

Anyway, as you see may point in these last two articles is what is the best course of action to take? If curbing CO2 isn't going to help because of the surface ocean layers becoming saturated with CO2, we need to deal with living in a different climate.

No one argues that the climate is and always has changed - the ice-cores show that - and if CO2 is not the cause of the periodic heating episodes throughout hi9stiry it may provide a forcer (feedback) mechanism.

My contention is that running out of cheap oil, gas and then coal is going to have a greater and more immediate impact on humanity and that is what we should aim for. Cutting the use of fossil fuels for the fact of their ultimately limited supply does at least serve the additional role of cutting CO2 emissions, whatever the veracity of various theories.

So, we save (some of) both humanity and maybe the planet too by energy efficiency, curbing oil-powered transport use etc. etc., and making as much sustainable fuel as is possible albeit on a much smaller scale than we get from oil.. if we want to grow any food that is.



Anonymous said...

You won't get any argument from me that there was a cooler period in the Northern Hemisphere around 1300-1850, although sources seem to disagree on the actual start date. Apparently there was a cooling of around 1degC. As for there being one bridge over the Thames I suppose it depends on when you're talking about. Frost fairs were held up until 1814.

On a different note, I'd be interested in Chris' opinion on this interview with Richard Pike from the RSC. Or perhaps you've already done a post on it and I just missed it...


Professor Chris Rhodes said...

I think what Richard Pike is saying is that there is plenty of oil "down there". Now, he may well be right and I hope he is.

Whether we are close to the actual point of peak or or not matters less than how much oil can be recovered against demand for it.

Thus if a gap appears between the two either through increasing demand or falling supply or both, we are in trouble.

The CEO of Shell is quoted as saying that the gap will appear sometime between 2010 and 2015 so either way we have to use less oil, unless by some rapidly deployable technology we can get more oil out or make a lot of unconventional oil - the latter demands a very high EROEI of other resources, by the way, so I doubt it's possible.

If Dr Pike is right, we may have a bit more time left to devise a lower-energy (lower personalised transport) way of living. The oil and gas and finally coal will run short (the cheap stuff anyway) at some point and so it makes sense to cut our use of these fuels.

Nobody really knows how much petroleum there is down there and how much of it will be extractable at a reasonable rate and cost. So the jury is still out on this one.

Either way, we need to begin to power-down, and use more biomass etc., since this serves all purposes we have referred to.


Professor Chris Rhodes said...

...that should read, EIOER - energy invested (e.g. gas) for a not large return of tar sand oil for example.

You get somewhere near 3 barrels of tar sand oil for every 2 barrels of oil worth of energy you put in. The process also needs a lot of water and is environmentally pretty filthy.

Michelle said...

A number of people are questioning the reliability of ice core data. I have started studying the IPCC documents and one thing I noticed is the very flat line on the graph showing CO2 in ice core samples over the past 1000 years up until just before they started using atmospheric neasurements instead.

Could it be as simple as the ice core evidence of higher CO2 levels during those periods melted?

Professor Chris Rhodes said...

Hi Michelle,

now this is most interesting! I don't think the ice would have actually melted, as to go back 1000 years the cores have to be cut from some depth, but there may be another reason connected with the difference between ice-core and atmospheric sampling? If you have more details of this sceptical view, I would be very pleased to know them.

I know that they have been measuring atmospheric CO2 since about 1950, and that there is a much less fine time-scale on the ice-core data.

It seems to be dangerous territory to dispute anything about the anthropogenic CO2/global warming/climate change link though, doesn't it?! The term "denier" is used with just emphasis!

Personally, I don't think there is any doubt that the problem is complex and there is much that is not understood. The temperature-CO2 "lag" is an annoyance to the simple view and yet it may well indicate forcing mechanisms at work as climate scientists say.



Michelle said...

Hi again Chris. I am not a denier, however I am definately a sceptic (occupational requirement as well as hazard).

I am actually serious in my suggestion that evidence of higher CO2 levels does not exist in the ice core samples because the evidence melted, and therefore there is also no evidence to support my suggestion.

There is overwhelming evidence from a number of sources that polar ice has diminished in recent times. The argument, from what I have read, is by how much and over how long. Now some say that the ice is rebuilding.

The IPCC graph on page 33 of the 2001 Summary for Policymakers http://www.ipcc.ch/ipccreports/tar/vol4/english/pdf/spm.pdf is incredibly flat up until the last 50 years. This struck me as remarkable because every other graph on global warming has ups and downs over this length of time. So I wondered "why?"

Most people agree that over the past 1000 years the earth's temperature has gone up and down from time to time. There are other sources of evidence of CO2 levels during this period which show ups and downs. Why is ice core CO2 data so flat for so long?

If you agree that global temperatures have not been dead flat for 950 of the last 1000 years, you realise that at some times the temperature was higher than others. When the temperature dropped, more ice built up, when temperatures rose, the ice during that time melted a bit, or at least did not build up.

Therefore, when the world was warmer, the ice didn't build up leaving a trace of the CO2 levels which existed at that time and actually melted a little, taking away part of the layer. Next cooling period the ice built up again leaving a trace of the CO2 levels which existed at that time, next warming period the ice either melted or at least did not build up to leave a nice layer of CO2 evidence containing ice.

It doesn't matter how deep the ice core samples are taken from, that is related only to time span. What does matter is that in the time series within the ice core samples, there are gaps in time.

Evidence of higher CO2 levels (if CO2 levels are related to temperature as we are told) isn't there because it melted.

As for dangerous territory to question and reconsider, how dangerous is it if we (people of today's world) get it wrong, or don't study the other elements of the earth's climate and therefore don't take all of the different types of action that may be needed?

As for the time lag, this is making people question which causes which? Questions are good - they lead us to learning more.

Professor Chris Rhodes said...

Hi Michelle,

yes, if we get it wrong and misdirect resources on a massive scale rather than planning to cope with a changed climate that would be a disaster! I quite agree.

There was a Danish academic who brought a book out, saying as much, some years a go and there were calls for him to be sacked etc. etc...

that's what happens when you offend the world of "science"! I believe he has been forgiven now, probably because the voice of GW is so loud that no one really hears any dissenters!

Thanks Al Gore!


Gruff said...

I'm not a climatologist and I don't get the impression that any of the posters on this site are either. So, what to do? Tempting though it is to form our own opinions on CO2 vs global warming, it seems a nonsense to attempt to do so as a hobby. The science of climate is so complex and so awash with masses of data, you have a far, far better chance of being an amateur theoretical physicist and getting to grips with general relativity, quantum theory, string theory etc etc We have no choice (if we are sensible) but to rely on the summaries and models and predictions of the professional climatologists who spend their working lives on this and have access to all the data and the computer resources and colleagues to process and understand it.

If a climatologist has an alternative theory to AGW and has data and a model and the physical theory to make it work, they will for sure get published and listened to - that is how science works! If their theory has no data or model behind it, or is not new, there is no reason why any respectable journal would publish them, there is no reason why colleagues would waste their time on it - that is also (thank God) the way science works.

The way to really make your name to do something new, but *crucially* with evidence/data to back it up. Otherwise the idea is worthless. Nearly all real scientists want to do something new (to be the next Einstein), rather than just follow the herd.

Professor Chris Rhodes said...

Hi Gruff,

I find it interesting that the Earth has apparently not warmed as much as the climate models predicted, which had led to some speculation that e.g. the excess heat is being stored in the deep ocean.

So indeed,modelling climate change is very complex, as indeed is the phenomenon itself. I am in no disagreement that rising CO2 levels in the atmosphere should cause the Earth to warm, which is in line with some calculations from basic physics that I have done with Dr Alexander Koewius. http://www.koewius.de/Website/Climate_Change

However, I remain with my original contention, that the most pressing problem facing humanity is the "liquid fuels crisis" which will result from a declining supply rate of conventional crude oil.