Category Archives: Global warming

Climate change, The Economist and The Irish Times

The Irish Times have kindly published an article of mine on climate change today. Two apparently contradictory facts have recently emerged that I thought worth discussing in my regular column on the IT science page:

A. The buildup of greenhouse gases in the atmosphere has increased over the last few decades, despite the warnings of climate scientists (this month, the concentration of carbon dioxide in the atmosphere exceeded a value of 400 parts per million for the first time in millions of years).

B. There has been a slight slowing in the rise in average global surface temperatures in the last ten years in comparison with the preceding decade.

Some commentators have sought to reconcile these two facts by suggesting that scientists may have over-estimated our climate’s sensitivity to greenhouse gases. In particular, a recent article in The Economist making this argument has been widely cited. However, the Economist article makes heavy use of a single Norwegian study that has yet to be published (why?) and I don’t know any physicists who agree with the hypothesis , for several reasons:

(i) Climate sensitivity is a complex issue and measurements of global surface temperatures do not tell the whole story: about 90% of global warming is estimated to occur in the oceans

(ii) Heat and temperature are not the same thing: temperature response to heating can be significantly delayed, particularly in the case of large bodies of water

(iii) Sometimes significant heating can occur without any discernible change in temperature, for example when ice melts to water: just such a ‘change of state’ is happening on a massive scale at the poles and will result in inexorably lead to increased sea levels and reduced reflectivity, causing further warming

GW_Components_1024

Total_Heat_Content_2011

Images from the Skeptical Science website

Some climate scientists fear that we may be entering a new phase of global warming, where a dangerous amount of heat will be stored in the ecosystem without an appreciable change in temperature at first (known as latent heat). Significant temperature rise will eventually follow, but we can expect climate change skeptics to use this delay to deny the reality of climate change.

You can read my full article on the subject on the Irish Times website

Update and correction

In a follow-up letter to The Irish Times, Tony Carey points out that the figures I gave in the article for the increase in greenhouse gas concentrations are actually those for CO2 only.  He is absolutely right in this, the error crept in at the very last draft of the article, aargh. He is also right to point out that while the concentrations of other GHGs are also rising, the rate of increase has in fact slowed for these gases. Well spotted.

However, this doesn’t really affect the argument I make in my article simply because the CO2 concentration is much larger than that of the other long lived greenhouse gases. Indeed, figures for CO2 are often quoted as a proxy for all longlived greenhouse gases for this reason, although this is not strictly accurate.  The diagram below from NOAA illustrates the dominant effect of CO2 very well (turquoise line). Note that ‘radiative forcing’ relates to the effect of GHGs on climate, involving calaculations I won’t go into here. Note also that climate sensitivity is defined in terms of a doubling of CO2, because of its dominance.

aggi_2012.fig4

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No man-made global warming in Ireland, thank you

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:

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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.

Update

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

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Where is the global warming?

A few days ago, the letter below was published in The Irish Times, Ireland’s most respected newspaper:

Sir, – I’ll believe in global warming when I don’t have to turn on my central heating in mid-June. – Yours, etc,

PETER STAPLETON,

Drumshanbo,

Co Leitrim.

As the short statement contains three common misunderstandings, I thought it worthwhile to respond. My response is published in The Irish Times today :

Sir, – Peter Stapleton writes “I’ll believe in global warming when I don’t have to turn on my central heating in mid-June” (June 16th). This short statement contains three classic errors:

1. Weather is not climate. Mr Stapleton has confused a wet summer in Ireland with longterm trends in global climate.

2. There is now a great deal of evidence pointing towards a gradual increase in the average surface temperature of the earth and its oceans, an increase that is strongly linked to carbon emissions. Recent data from MET Éireann show a warming in Ireland in line with this global trend.

3. Climate change is not a question of belief, it is a question of science. The overwhelming consensus among climate scientists is that global warming has the potential to affect the lives of many millions of people, from widespread flooding in some countries to permanent drought in others.

Sadly, one suspects Mr Stapleton’s misapprehensions are shared by a great many political leaders worldwide. – Yours, etc,

CORMAC O’RAIFEARTAIGH,

Lecturer in Physics,

Waterford Institute of Technology.


All in all, I think the two letters sum up the challenges of communicating climate science. Could it be that mankind will one day face devastating cimate change, all because we couldn’t distinguish between weather and climate?

Flooding in Bangladesh: soon to be permanent?

Drought in Africa: more frequent and severe?

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Tyndall conference in Ireland

This weekend, I caught the last day of a climate conference honouring the memory of the great Irish scientist John Tyndall. Born in County Carlow, Tyndall became a key member of the Royal Society around the time of Charles Darwin. He studied under Robert Bunsen in Germany and did much to promote the idea of experimentation in science. Among his many contributions are the discovery of the Tyndall effect (an explanation for the colour of the sky in terms of the scattering of light) and pioneering works in optics.

Tyndall’s most important contribution was his experimental demonstration of the greenhouse effect. He was the first to show that certain gases – notably carbon dioxide and water vapour – absorb radiation of infra-red wavelength, thus trapping heat reflected from the earth. This discovery forms the bedrock of the modern climate science. Today’s phenomenon of global warming (measured as an increase in global temperature, glacier-melt and sea level rise over the last few decades) has been attributed to an increased concentration of greenhouse gases in the atmosphere caused by the burning of fossil fuels.


The 2011 Tyndall climate conference was sponsored by the EPA and the Royal Irish Academy

The conference celebrated the 150th anniversary of the publication of Tyndall’s landmark paper On the Absorption and Radiation of Heat by Gases and Vapours and took place in Dublin castle, a superb venue in the heart of Dublin’s vibrant city center (and the seat of British rule in Ireland only a century ago). Day one was an overview of Tyndall’s life and work, with a keynote lecture by eminent climatologist Richard Sommerville. The next two days featured slightly more technical talks on climate science. You can find the conference program and book of abstracts here.

I caught several excellent talks on Friday, including a talk on climate sensitivity and feedback mechanisms by John Mitchell of the UK Hadley Centre, and a talk on tipping points and their predictability by Peter Ditlevensen of the Center for Ice and Climate at the Niels Bohr Institute in Copenhagen. Another talk, by George Moore of the University of Toronto, suggested that we may already have passed such a tipping point. The lecture  ’20 years of IPCC projections’ by Ulrich Cubasch of the Free University of Berlin, demonstrated how well IPCC projections have stood the test of time. This is a point often overlooked in discussions of climate science in the media. The public are wary of theoretical models, and climate scientists sometimes forget to point out that we have had twenty years to test predictions – so far, the projections have turned out to be all too accurate.

Possibly the most advanced talk of the day was by Professor Ray Bates of the Meteorology and Climate Centre at University College Dublin, a former professor of meteorology at the Neils Bohr Institute. In his talk, Ray presented a new global climate model, contrasting it with the recent model of Dick Lindzen. The Lindzen model is quite controversial as it suggests that conventional climate models overestimate the contribution of an enhanced greenhouse effect on climate. In good scientific fashion, Ray outlined the basic physics underpinning the two models, steering clear of polemics and concentrating on the science. You can Ray’s paper on his, and other, models here .

All in all, a great conference, I was sorry to miss the first two days. One of the aspects the increased teaching workload in the Institute of Technology sector is that there is almost no time left over for conferences – someone’s idea of increased productivity.

Update

Richard Sommerville did a very nice interview on the Pat Kenny show, a flagship radio show on RTE radio 1. Pat raised almost every point favoured by climate skeptics, while Richard provided clear and cogent answers to each. Well worth a listen, you can download a podcast here.

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Climate change: the tv briefing

There was a chat program on the Irish channel TV3 last week that perfectly illustrated the difficulty of discussing complex scientific issues in a public forum (see last week’s post).  It consisted of a tv panel debate on climate change, where two respected scientists and a member of Friends of the Earth debated climate issues with two members of a new Irish political lobby group. It quickly became clear that neither the Chair nor the lobbyists knew (or accepted) anything of the basic facts of climate science. Faced with a blank rebuttal of basic physics, the scientists had an uphill struggle tryng to communicate the issue of climate change.

I thought this a fairly typical example of the problems of such media discussions. The lobbyists were clear, passionate and articulate, stating their views as if they were established facts, uncluttered by equivocation. (The first sentence uttered was “the earth is not warming” and there were many other such statements). The scientists, by comparison, sounded rather uncertain and unclear. As so often, completely uninformed opinion, unweakened by any sort of balanced view, sounded much more convincing.

It’s very hard to know what to do when one encounters such resistance to basic science. I suppose all we can do is keep repeating the basics, as clearly as we can, and hope the public and politicians can discern the difference between established facts and random opinion. As an exercise, I decided to write down the main points I myself would hope to make during the course of such a debate. This is what I would like to have said:

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1. GLOBAL WARMING

There are now multiple lines of evidence that show clearly that, over the last 50 years, the average surface temperature of the earth and its oceans has been steadily increasing. This rise (about 0.75 °C) may seem small compared with the normal background variation in day-to-day and seasonal temperatures. However, a gradual increase in average represents a significant physical effect; for example, the difference in the average global temperature of the last ice-age and the present is only a few degrees Celcius.

2. PART OF A NATURAL CYCLE?
Those who study past climate cycles have considered this question in great detail and their conclusion is that the temperature rise cannot be attributed to a natural cycle, for a number of reasons. The most obvious is the rate of change; the rise in average temperature we are seeing over the last few decades corresponds to a rise  seen over thousands of years in past climate cycles. Obvious external causes, such as solar cycles or changes in solar activity, have been specifically ruled out (we are currently in a cooling part of the dominant solar cycle). Most tellingly, it has been discovered that while the lower atmosphere is steadily heating up, the top of the atmosphere (the stratosphere) is cooling down – an observation that strongly suggests a cause closer to home.

3. THE ENHANCED GREENHOUSE EFFECT
Physicists have long known that the temperature of the earth is regulated by certain gases in the atmosphere. These gases trap heat radiated from the warm earth’s surface, stopping the globe from radiating all of its heat to space (the greenhouse effect). The ‘greenhouse gases’ only account for a tiny percentage of the atmosphere but they play a vital role in regulating the planet’s temperature.  Hence global climate is highly sensitive to the concentration of greenhouse gases in the atmosphere and one can expect any change to this concentration to have a significant effect on climate. (The Irish scientist John Tyndall established that the most important greenhouse gases are water vapour, carbon dioxide and methane, while major gases such as oxygen and nitrogen do not block the earth’s heat).

We now know that, since the advent of the industrial revolution, mankind has been increasing the concentration of atmospheric greenhouse gases. In particular, the burning of fossil fuels such as oil, coal and gas all release extra CO2 into the atmosphere. Direct measurements of the CO2 content of the atmosphere have been made since the 1950s and there is no doubt that there has been a steady rise since measurements began; in general, it is estimated that the current concentration of CO2 in the atmosphere is over 35% higher than that of pre-industrial times. At first, it was thought that this extra CO2 would be absorbed by the oceans. Some of it is, and this causes its own problems. However, it is now known that much of the extra CO2 remains in the atmosphere.

Putting two and two together, scientists believe that the global warming we have observed in recent decades is almost certainly caused by man-made greenhouse gases released into the atmosphere, a phenomenon known as the enhanced greenhouse effect.There are now muliple lines of evidence for this hypothesis (not least direct satellite measurements of the heat radiated from earth into space that show an increasing dip in the region of the spectrum where CO2 absorbs).

4. THE FUTURE PROGNOSIS
Studies of past cycles suggest that as time goes on, the warming will accelerate because of feedback loops. For example, the melting of large areas of ice at the poles will significantly reduce the ability of the globe to reflect heat, causing additional warming. The oceans will lose their ability to absorb CO2 as they acidify, also causing further warming. Studies of past cycles also suggest that the rising temperature will itself lead directly to an increase in greenhouse gases such as CO2 and water vapour in the atmosphere, and eventually to the release of methane from deep sea vents and the permafrost.

For human populations, the main consequences of a warming earth will be increasing desertification and drought in the hotter regions, and an increase in sea level around the globe (the latter is because water expands when heated and because of glacier melt). The former could render large parts of Africa and Australia uninhabitable, while the latter could cause widespread and permanent flooding in low-lying countries such as Holland and Bangladesh (pop 55 and 25 million respectively).

5. THE SOLUTION?
We can certainly reduce the enhanced greenhouse effect by replacing the use of fossil fuels with renewable energy technologies such as wind, wave and solar energy that do not cause carbon emissions. Since there is a time lag associated with the effect, we need to do this as soon as possible. However, this is economically difficult as the Western standard of living is built on the cost-effectiveness of fossil fuels. Most importantly, action to curb fossil fuel use will only be effective if it is global and it is hard to persuade developing countries to curb fossil-fuel use essential for their development. So far, attempts to reach international agreement on binding targets for carbon emissions have failed. Yet is estimated that China alone has coal deposits that if fully used, could tip us into irreversible climate change within one century.

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All of the above is basic, well-established science that is accepted by almost the entire scientific community. However, much debate on the topic occurs in the media. This is simply a facet of a modern media that does not distinguish between informed and random opinion (not to mention vested interest). Uniquely among scientific theories, the theory of man-made global warming also faces great political resistance from conservatives who oppose regulation in almost any form. Lobbying by conservative interests can be heavily influential, in politics and in the media , particularly in the USA. The result is a continuing confusion and lack of public engagement with the issue, a state of affairs that is making it very difficult for world governments to put in place any sort of co-ordinated mitigating action.

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Climate change: a burning question on tv

This week, RTE (the national broadcasting authority of Ireland) aired a program on climate change. ‘A burning question was an hour-long TV documentary on climate science, climate scepticism and the role of the media in this debate. The program was produced by Earth Horizon Productions, directed by Paula Kehoe and edited by Dónal Ó Céilleachair. I watched the program out of general interest and was intrigued to see my name listed in the credits (I think this arose from several discussions I had with Dónal).

I thought the program very good overall, with some reservations. It’s hard to cover such a topic in an hour, so the producers employed some media tricks that few scientists enjoy. I’m not sure cutting to a vox pop every few minutes throughout the program casts much light on the subject matter (besides, are the opinions of random individuals stopped on the street a reliable gauge of the view of the general poulation?). Secondly, the constant switching from expert to expert in a cyclic merry-go-round of byte-sized interviews tends to confuse rather than elucidate. Thirdly, I thought the program could have had more on climate skepticism (see below).

That said, the core of the program was solid. The main presenter was Duncan Stewart, an award-winning architect and environmentalist well-known for his excellent TV series Eco-Eye. There were some very good interviews, notably with heavy hitters such as former UN High Commision Mary Robinson, UN Secretary General Ban Ki-Moon and IPCC Chairman RK Pachauri.

Duncan Stewart of Earth Horizon Productions

The key scientist of the program was superb; Peter Lynch, a leading climatologist at University College Dublin, gave the lie to the old media adage that experts make poor communicators. Professor Lynch explained the basic principles of the enhanced greenhouse effect in exemplary fashion, starting with the work of pioneers such as Fourier, Tyndall and Arrhenius, and finishing with modern measurements of carbon dioxide emissions and surface temperatures. Interesting that the best way to explain science is often to describe it in chronological order of discovery!

Prof Peter Lynch of UCD

There were many other good contributions in the program; in particular from the environmental writer John Gibbons (on the societal impacts of climate), from Professor John Sweeney (Professor of Geography at UC Maynooth and member of the IPCC) and from economist and boadcaster David McWilliams (on the economics of climate change). One of the most lucid summaries was given by former UN High Commisioner Mary Robinson – describing the expected impacts of climate change on the poorest societies in the world, and the importance but difficulty of concerted international action, she left one wishing other politicians had as good a grasp of the subject.

Prof Mary Robinson, former UN High Comissioner

Justin Lewis, a Professor of Journalism and Media Studies at Cardiff University, talked a little about the role of the media in the public perception of climate science. He explained the basic problem clearly; that in the media’s attempt to present a balanced debate view, the observer is left with the impression of a great 50/50 debate between experts, rather than the overwhelming consensus that exists. This is the familiar problem of a ‘balanced debate’ in the media that pays no attention to weightings. Lewis also touched on ‘climategate’, contrasting the great publicity afforded to the hacked East Anglia emails with the minimal media attention given to the results of the subsequent enquiry (the ‘perpetrators’ have since been exonerated).

Prof Justin Lewis of Cardiff University

I thought this section very interesting, but there could have been more: for example, there was no mention of the obvious point that “Scientists Right!” is not much of a media story, while “Scientists Wrong!” is. By definition, the minority viewpoint will always get more publicity, a fact the public should be made aware of. I also thought that more time could have been spent on the analysis of the role of journalists. Given the dominance of the media in our lives, this is a key issue in the pubic perception of science (and of anything else). In particular, there was no mention of the issue of political bias. Much of the climate scepticism in the US media is driven not by business interests, but by journalists of a particular political viewpoint: the viewpoint of right-wing conservatives who oppose government regulation and taxation in all forms.

In general, I thought the program could have had more on climate skepticism, rather than simply dismissing it as ‘vested interest’. In my opinion, there are at least five distinct categories of skepticism (with many overlaps):

(i) A tiny minority of genuine scientists with no links to industry or politics (such as Freeman Dyson or Richard Lindzen), who remain unconvinced of the scale or extent of man-made warming. Such minority opinion is important, but exists for almost every scientific theory (an obvious fact that is almost never stated in the media).

(ii) A larger group of economists, political scientists and intellectuals such as Bjorn Lomborg who remain unconvinced. This community are strong on economics but they are not scientists and rarely understand the reliability (and limitations) of experimental measurements – another fact that is rarely highlighted in the media.

(iii)A huge community of commentators, journalists and bloggers who seem to have almost no appreciation of the difference between random, informed, and expert opinion. A great deal of these reject the opinion of the majority of scientists as biased and subscribe to all sorts of ‘rent-seeker’ conspiracy theories.

(iv)The vested interests of big business; as in the case of the tobacco lobby, there are still climate scientists who are paid to believe what they believe

(v)The political viewpoint of conservatives and anti-regulation interests; I suspect this last sector is much more influential than is generally realised.

Overall, I enjoyed the program very much – it’s hard to cover everything in one hour. I nearly fell off the couch when I saw my name in the credits!

Update

Justin Lewis has a book out on climate science and the media - ‘Climate Change and the Media’ looks well worth a read

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