John Gardner, an old schoolfriend, has sent me his reaction to the claims of the “denialists” quoted in my last post, and I append his comments below. As a layman I would not presume to make a definitive judgement on all this, but I do think it is important for us to try to follow what is going on – difficult though it is. After all, we will also suffer whatever consequences there may be and in any case we will be PAYING for and living through any measures taken! There is even a small chance that if we work together we might be able to INFLUENCE what measures are taken …….
This really is one instance where a reaction of “I’m not interested in politics.” or even “I’m not interested in science.” would be just dumb.
Thank you for these fascinating comments, John, who writes ……….
The interesting thing about the arguments from denialists is that they all come from totally different directions. One set say that CO2 doesn’t cause global warming, some say that anthropogenic CO2 doesn’t cause global warming, some say that CO2 does cause global warming but the oceans will sort it out, some say that global warming doesn’t exist, and others that global warming does exist but it’s all the sun’s fault.
They can’t all be right! It reminds me of the variation of arguments put forward by Creationists.
To get to the basic science of Greenhouse Gases:
1. Do you believe that CO2 is a greenhouse gas that serves to warm global temperatures?
Very simple models show that given the solar radiation received from the sun the Earth would have a temperature of 253K without CO2. The same simple model shows that with the current atmospheric CO2 the Earth should have a temperature of 303K. It actually has a temperature of 295K – and that is with a model that just includes solar radiation, a bare Earth with an albedo of 33%, and a layer of CO2.
The science of greenhouse gases is well understood. In essence, the sun’s radiation is absorbed by the Earth and re-emitted as black body radiation with the peak in the infrared. The CO2 absorbs a significant proportion of
this radiation, and re-emits it, much of which reaches the ground again.
2. Do you believe in Anthropogenic CO2 loading of the atmosphere?
There really is no reason not to. We oxidise fossil fuels and make CO2. CO2 levels have risen by 30% since the industrial revolution, and this increase matches the increase in economic production. We supply about 10 Gigatons of carbon to the atmosphere per annum, mainly in the form of CO2, compared to about 0.1-0.2 emitted by volcanoes.
(Incidentally, there are about 700 Gigatons of carbon in the atmosphere, 2,000 Gton on the land, 3,800 Gton in the oceans, and 1,200,000 Gton as limestones and fossil fuels. And it cycles round the four reservoirs.)
3. How can CO2 be such a big factor in all this if it comprises only 0.0405% of the atmosphere?
A good question, but easily answered. Each molecule of CO2 can absorb radiation around the 667 cycles per second waveband, which warms it up. That’s 405 molecules out of one million. Now think how many billions of molecules there are in a column of the atmosphere (90% of them are in the troposphere within the bottom 15 km), and you’ll appreciate that 0.0405% amounts to a significant number.
Interestingly enough, there is a finite amount of energy being emitted by the planet at 667 cycles, so one would think that it would all be absorbed by a certain amount of CO2, and then there will nothing else to absorb. This is true, except that a phenomenon called ‘pressure broadening’ starts to take effect such that the range of IR frequencies absorbed by CO2 becomes broader. This is caused by the gas molecules interacting with each other. The result of this is that the Earth’s temperature rises in proportion to the number of CO2 doublings – i.e. if 4 dollops add 1K to the global temperature, it will take 8 dollops to raise it by 2K, and 16 to raise it by 3K.
4. The Earth has warmed over the last 150 years
The Earth has warmed about 0.5K over the past 150 years. This 0.5K is consistent with climatic models when run with the actual CO2 levels, and then run without the anthropogenic input.
5. Increasing CO2 will continue the trend. -> Commonsense and modelling indicates that it will.
To me, all the above is all very clear and obvious. If it looks like a duck, and quacks like a duck, then it probably is a duck.
FREQUENT OBJECTIONS BY THE DENIALISTS
Some of the objections put forward are easily dismissed, and some of them have actually been withdrawn but are still being recycled.
1. The sea will soak it up.
The sea is actually soaking up about half our emissions. However, there are things to be aware of.
a) Given enough time, the CO2 in the atmosphere will be in equilibrium with that in the sea. The equilibrium used to be a given concentration in the sea, and 300 ppm in the atmosphere. Raise the CO2 in the atmosphere and the concentration in the sea will rise. But because it is in equilibrium it will not take it all.
b) Because there are relatively few windows between the surface and the sea and the depths of the oceans, it takes about 1,000 years to reach equilibrium.
c) Increasing the CO2 in the sea decreases the pH (it has decreased by 0.1 in the last 150 years), which will have a catastrophic effect on the marine ecosystem.
2. Increases in CO2 occur 700 years after the increase in temperatures (Point 2).
This is obviously nonsense as a glance at any graph showing rising temperatures over the past 150 years with CO2 increase will confirm. It is actually referring to the fact that this is observed during the retreat of ice during
the last ice age. The main agent behind the ice ages is the variation of solar flux reaching the northern hemisphere during the course of the Milancovic Cycle. It seems that the retreat of ice from the landscape
results in CO2 being released as the biosphere re-established its hold. This does not stop the CO2 so released having a positive feedback on the rate of the decreasing ice.
3. Satellites show no increase in global temperatures.
This did puzzle climate scientists for some time, until they realised that the temperatures being measured were being affected by the temperature of the stratosphere which has been getting colder. This has now been taken into account, and the measurements now match those of other means.
4. Sea Levels aren’t rising
This is just crap. Sea levels are rising by about 3mm per year, and have risen by about 250 mm in the last 150 years. It does seem, however, that most of the islands currently seen to be at risk are suffering from increased tides due to El Nino, and increased erosion due to more energetic weather, rather than from rising sea-levels.
5. It’s all down to the Sun
There has been no changes in solar radiation measured in the past 150 years apart from that expected from the 11-year solar cycle.
The climate scientists do not know it all. There will always be unknowns which are not being modelled; there will always be errors in the modelling; and there will always be problems with things that can’t be properly modelled.
Having said that, if one accepts the basic science, it is clear that increasing the rate at which we inject CO2 into the atmosphere will be bad for those alive in a 100 years, and even if we steady reduce our CO2 output, it still won’t be good.
The good news, however, is that it will all sort itself out over the next 60 million years. We can’t do anything that will totally screw up the carbon cycle for ever.