My letter on global warming in The Irish Times (see post below) got a response from an Irish lobby group called Turn 180. The sub-title of their blog is ‘Humans are not causing global warming’, top marks for clarity there. You can read their objections in their own words here.
The Turn 180 blog got me thinking about why there is so much resistance to the whole idea of an enhanced greenhouse effect. Below are some favourite points:
Q1. Why do climate scientists keep banging on about recent changes over the last few decades, when everyone knows that, by definition, it is only meaningful to talk about climate over extremely long timeframes?
A. Studies of past climate changes (yes, climate has certainly changed in the past) suggest that once started, climate change tends to happen quite quickly due to feedbacks – with noticeable effects over decades rather than hundreds of years.
Q2. If climate change has occurred in the past, clearly not linked to human activity, why are the boffins so sure it’s different this time?
A. The fact that climate change has had natural causes in the past doesn’t mean it can’t have a man-made cause now. We know greenhouse gases (GHGs) in the atmosphere such as C02 play a major role in regulating the heat of the earth and we know we have increased the GHG concentration by over 40%. It would be very nice to show that this has had no effect on climate, but the evidence points the other way. In particular, measurements of infra-red radiation emerging from the atmosphere into space show it has been steadily decreasing over recent decades. This matches the rise in temp measurements, ice melt and sea-level rise measured worldwide. At the same time, there is no matchup between the recent temp rise and natural cycles (e.g. studies of sun cycles, earth orbit cycles etc suggest we should be in a cooling cycle).
Q3. Isn’t it true that C02 rise has followed temp rise in past climate change, not vice versa?
A. Yes, but the data also show that once started, a rise in C02 leads in turn to further temp rise. Ouch.
Q4. What’s all this about consensus, hasn’t scientific consensus been wrong in the past?
A. Yes; Scientists like evidence, not ‘he said, she said’. However, if a serious threat to society is perceived (think meteor or alien invasion) the first thing is to find out if the experts are agreed amongst themselves. The IPCC was set up for precisely this purpose, to collate and make sense of the many hundreds of diverse scientific studies of various aspects of global warming. The most striking aspect of the IPCC reports is how closely the studies agree – all this from scientists who like nothing better than proving each other wrong.
On consensus in science, it’s quite hard to find examples in modern science where the consensus was wrong, from the dangers of tobacco to the ozone layer. Examples quoted usually predate the rise of the scientific method.
Q5.Ok, so what is the principle at work in the current climate change?
A. The physics of the greenhouse effect is quite straightforward. The earth’s heat balance is regulated by certain gases in the atmosphere that trap emerging heat, known as greenhouse gases. Given the sensitivity of the earth’s heat balance to greenhouse gases, and given that we have increased their concentration by 40%, one would expect a gradual increase in trapped heat and temperature. This is exactly what we measure, in many different ways.
Q6. Any good news?
A: There’a a Nobel prize waiting for anyone who can show that carbon emissions don’t matter i.e. that greenhouse gases created by human activity quietly disappear instead of clogging up the atmosphere (about 50% currently gets absorbed by the oceans, but that is also causing problems and cannot last). Drinks on me if you do prove this.
There is a reference to a really interesting paper in the comments section, thanks Justin! The paper, by Tony Dorlas of the Dublin Institute of Advanced Studies, takes a most unusual and simple approach; in the complex system that is climate, take the one parameter that is varying in a systematic way (C02), explore from first principles what variation in average temperature this parameter could lead to, and compare the results to the measured warming. The result is pretty thought-provoking, see here