Dominic - Now, a paper which really caught my eye came out in the journal of Climate this week, looking at the environmental impact of chlorofluorocarbons or CFCs. Now, if you were following the news about 25 years ago, you may remember hearing quite a lot about the damaging effect that CFCs have on a layer of the atmosphere called the ozone layer, which is a layer of the atmosphere in the stratosphere which is opaque to the sun’s ultraviolet radiation. It means that we on the surface of the earth are exposed to much less of this damaging radiation. So, it makes it possible to go sunbathing without getting sunburnt. Potentially in the past, might actually have made life possible by making sure that complex chemistry needed for life was able to occur without being broken apart by those ultraviolet rays.
Hannah - And I remember when I was a child that the refrigerators suddenly, they weren’t allowed to emit these CFCs that were damaging the ozone layer. There was a big call to make sure that refrigerators complied with the new CFC legislation.
Dominic - That's right. What happened in 1980s was that people realised that CFCs were used as a refrigerant in fridges in people’s homes. In 1987, the Montreal Treaty banned the use of those because they had this damaging environmental impact. That was ratified by 200 countries, although it has taken a very long time for the CFCs that had already been emitted in the atmosphere to breakdown.
Now this is often held up as being a great triumph of international legislation in solving environmental problems. But what this paper in the journal Climate is saying this week is that CFCs are also really very strong greenhouse gases. Now, we hear about CO2, carbon dioxide and the effect that that has in causing global warming. But CFCs are actually 10,000 times more powerful as a greenhouse gas than CO2. And so, what this paper is saying is that because we had this spike of CFCs in the atmosphere in the 1980s, that was causing a strong greenhouse effect historically, and over the past 20 years or so, that's tailed off.
So in fact, the global warming that may have been caused by carbon dioxide in the last 20 years, we may not have seen the effect of that in full because it’s been offset by this diminishment in the number of CFCs in the atmosphere. So, the argument is really that we mustn’t just look at carbon dioxide,we need to look at the full suite of molecules that can cause global warming to really understand the effect that these gases can have.
Hannah - So, there's no cause to celebrate yet about decreasing CO2 levels because actually, we’re measuring CFC effects on global warming.
Dominic - That's right. I mean, in the 1980s, we has this wonderful success with the Montreal Treaty that really does seem to have solve the problem with CFCs, we haven’t had a similar treaty with carbon dioxide, the Kyoto protocol was not ratified in the end. The data is extremely complicated to analyse because there's all of these different molecules, all causing the greenhouse effect and it’s not just carbon dioxide.
"So, there's no cause to celebrate yet about decreasing CO2 levels because actually, we’re measuring CFC effects on global warming. "
This may shed some light on the question. Nuccitelli et al. (2012) Show that Global Warming Continues.
The problem with all the predictions is that when one looks at the temperature charts, there has been little or no warming from about 1998, or 2001 to present.
Yeah, a sweet illusion, before that war that will come, assuming we keep up this stupidity. Either a war or a slow decline into poverty. But I think that will lead to a war too, between those that have and those that are without. yor_on, Thu, 22nd Aug 2013
"Prediction is very difficult. Especially about the future." (Niels Bohr)
If you're referring to climate models Alan I totally agree, they're just as good as the programming and the assumptions made will make them. And climate science is not a settled field in any way. But you have models that attacks the problem statistically too, as that British one using simpler models, on home computers, tweaking them somewhat differently to then look at outcomes getting probable statistics. You can naturally question those models too, but they are interesting to me. As for my pessimism that has to do not only with global warming, it's about the way we're naturally 'set up', looking at way we behave, and have behaved, historically. Global warming is only the icing on the cake there. Doesn't mean I will be right though, I hope I'm not. yor_on, Fri, 23rd Aug 2013
AFAIK most climate models are self-serving.
You seem very sure on your assumptions here Alan :)
No suggestion that climate doesn't change. I'm sitting in a part of East Anglia that used to be a hot swamp, if the hippopotamus bones in the Sedgwick Museum are to be believed.
I agree, it is important to realize that CO2 levels, and temperatures have varied significantly over the life of the planet. We may be approaching a local high temperature for the Holocene, but it certainly isn't close to the Eocene maximum temperatures.
The rediscovery of viable bryophytes under a retreating Canadian glacier reminds us that things were a lot hotter in the pre-industrial Holocene, never mind the Eocene. 400 years ago my old school was celebrating its 40th anniversary, homo sapiens walked upright, the woolly mammoth had left the building, and there was a flourishing sub-arctic flora in what is now a frozen wasteland.
There's a general problem about the definition of sea level anyway. Where do you measure it in order to determine the global value, and why should it remain constant if, as we know, the seabed and continents are all moving anyway? Within 100 miles of each other, and in recent history, Dunwich has disappeared beneath the North Sea whilst once-thriving ports on the north Norfolk coast are now high and dry, five miles inland from the beach - nothing to do with intentional reclamation, just natural forces. So try to define sea level around East Anglia! Nevertheless, if we ignore all we know about tides, winds and geology, let us assume that the icecaps are melting in an otherwise static world.
That's a interesting take on sea levels Alan, and one I haven't considered. It should have a impact assuming that continents are wandering away form each other, but then you would need more water to measure a same sea rise, as it seems to me? To measure a sea rise from continents wandering we then need to assume that they either press up the sea bottoms, although leaving dry land at a same elevation, or that the continents are coming closer together creating a smaller volume for the same amount of water to exist in. yor_on, Wed, 28th Aug 2013
Clifford, myself I think the problem isn't one in where we don't know that we have a global warming. We can prove a global warming statistically, also excluding external sources as the suns variations, that as we know them too statistically. What we don't know, and can't predict though, is all the ways a earth can react to it. That's what climate models are to me, 'best predictions' based on what people think are most important 'forcing's' of a climate at the moment they present it.