Sunday, January 15, 2006

Global Warming

This week has been a fairly spectacular one in the scientific realm of Climate Change. Two quite impressive articles in Nature are likely to have a significant impact in both our understanding of the climate change phenomenon, as well as its effects on biodiversity. I'll address these articles soon, but first!

I've always been incredibly wary of commenting on this issue, for a number of reasons. Firstly, I don't know a huge amount about it. I mean, I understand the most basic principles, but I'm certainly no climatologist. As opinionated as some people consider me to be, I do try to avoid expressing said opinions until I know what I'm talking about. I guess I've always been a bit old fashioned in that regard; a firm believer in the adage of "read up or shut up". I'm afraid, though, that not many pundits or commentators follow this line. From the debates and commentry I've browsed on the issue, I'd say there was statistically significant correlation between the loudness of one's voice and one's ignorance on the matter at hand. But what's new, huh?

Secondly, global warming is an irrationally emotive topic. I've seen and been involved in some pretty heavy debates, mainly around evolutionary biology, but nothing compares to the astounding level of name-calling, labelling, character assassination and hysteria around global warming. Simply offering up an opinion or a dissenting voice, or perhaps a piece of research, opens one up to the most disturbing amount of lazy ad hominems, from both sides of the alleged 'controversy'.

I need to get a bit of a bug bear off my chest: I hate the term 'global warming'. It can be an incredibly misleading term. While the climate change discourse is grounded in the concept of average global temperatures increasing, on the level of many local, regional, latitudinal and continental systems, temperatures could be predicted to drop as a result of an overall global increase. An oft-cited example of this regional cooling as a result of global warming is the predicted effect of increased global temperatures on Continental Europe due to the slowing of the North Atlantic Drift. Normally, Continental Europe and Britain are kept comparatively warm for their latitude due to the energy that this current brings from the tropical and subtropical areas of the Atlantic. When it meets the cooler waters of the Arctic, the current cools, energy is released from the ocean to the atmosphere in the from of heat, and the water sinks and travels back south again, setting up a kind of energy 'conveyor belt'. With an increase in global temperatures, particularly in the polar regions due to a process known as 'Polar Amplification', a substantial amount of colder fresh water is predicted to emerge into the North Atlantic. Normally, you would expect that because it's colder water it would sink, and thus not affect the warmer currents in the surface layers of the ocean. However, fresh water is lighter than salt water, so it stays on top. This would mean that the North Atlantic Drift is essentially swamped with cooler water much further south, energy is not released into the North Atlantic atmosphere, and the temperatures of Western Europe and Britain essentially drop to match those of Moscow, NewFoundland et cetera. The orange trail of water up the coast of North America in the picture below illustrates the warm temperatures of the Gulf Stream/North Atlantic Drift system:

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So while "global warming" as a phenomenon is a valid term overall, the effects of such a process on smaller scale, essentially the effects that you and I would experience in our own reference frame, are more accurately defined as "climate change". As a superficial paradox, global warming often means locally the opposite.

I am a global warming skeptic. Now, before anyone fires up the flame thrower, let me explain that particular statement; it's time for true skeptics to reclaim that word.

Global warming/climate change is happening. There is too much data clearly showing an increase in global temperatures, both atmospheric and sea, to draw any other rational conclusion. To those who deny the very existence of a warming planet, I have two words: Wilful Ignorance.

There is a lot of data that indicates that, over the last 4.5 billion years, the earth has experienced many global warming and cooling cycles. Many variables have been implicated in these processes: changes in the Earth's planetary orbit, rotation and position of the poles; continental drift and its effects on global ocean currents, meteoric impacts and associated atmospheric distortion and of course the 'Greenhouse Effect', where certain gasses in the atmosphere act as insulators of radiant heat - namely carbon dioxide, methane, sulphur compounds and water vapour. The physico-chemical mechanisms by which these particular substances act has also been elucidated and test quite conclusively.

Further, there is a substantial amount of data which supports the "Anthropogenic Global Warming" hypothesis, namely that the current warming trend our planet is facing is the result, at least in part, of an increased emmission of 'greenhouse gasses' due to the processes of large scale agricultural production and industrialisation.

What the three statements above essentially amount to is this:

*Two statements of fact: (1) the Earth is getting warmer, and (2) greenhouse gasses do lead to increased global temperatures (just look at Venus).

*One reasonably strong correlation: Increases in the Earth's temperature correlated with increases in global greenhouse gasses over the last 160 years.

*One reasonably well supported hypothesis: That the increases in the greenhouse gas emissions and ergo global temperatures are the result of human activity, in particular industrialisation.

It is important to realise that, when you strip away the crap, these data are very compelling. They are presented, as they should be, as a scientific rather than political exercise in the very good book: Climate Change 2001, The Scientific Basis. I would highly recommend at least having a browse.

On the face it then, it seems reasonable and rational to at least tentatively conclude that this idea of anthropogenic global warming is something more substantial than just the rantings of "enviro whacker, Bush hating, anti globalisation, gorse munching, chardonay[sic] slurping (unoaked) Lefties". As you can see, the name calling does get quite absurd.

Of course, the situation just isn't this simple. Along with the two statements of fact, the correlation and the hypothesis come many many many confounding variables. It's these confounding variables that limit our ability to gain much confidence in drawing our conclusions about human involvement in global warming.

Firstly: How good is our data? We are discussing incredibly complex global systems - do our research methods do justice to these complexities? Are our data presenting an oversimplification of what is really happening? Are we properly controlling for other variables that affect our results?

Secondly: What do we know about the relationship, if any, between our current warming cycle and other periods of cooling and warming that have occured in the past? Is the global warming trend that we are observing associated with the Pleistocene/Pliocene Ice Age and glaciations? We know that global temperatures have oscillated wildly in the last 2 million years, especially in the last 200 000 years - could it just be that what we see happening is just the tail end of these processes?

Thirdly: How much do we actually understand about the processes of greenhouse gas production? This particular question has become especially pertinent recently, with an article in this week's Nature that shows that methane (PDF available on request as per usual), probably the most potent greenhouse gas, is possibly being produced by plants under aerobic conditions. Prevailing theory in methane geochemistry holds that the majority of methane in the atmosphere is the result of microbial ecology and leaking natural gas. The recent article, however, hypothesises that between 10 and 30% of the 500-600million tonnes of methane that enters the atmosphere annually is produced by plants - the very organisms that are expected to decrease atmospheric greenhouse gas (carbon dioxide) .

This research underscores how much more we have to learn. We didn't even know that plants could produce any methane aerobically, let alone on such a scale. If it is supported by subsequent research, it will in the words of Christian Frankenburg "shake the methane community"*.

The myriad variables surrounding global warming, as well as our limited understanding of the processes involved mean that any inferences and conclusions that we draw are forever tentative. Our knowledge of the processes is burdened with caveats that always need to be considered. when we are aware of the variables, we are able to refine our methodologies and theories in an effort to increase the confidence we have in our results and conclusions.

So why, then, am I a skeptic? The term is a dirty one, in the world of global warming. It brings with it undertones of libertarians and neo-conservatives who are not so much skeptical about global warming, in the true sense of the word, but rather madly and rabidly opposed to it. The term has been hijacked, or in many cases abused, by those who seek to add legitimacy to a position that is rationally and reasonably untenable.

An essay on global warming skepticism at RealClimate shows that true skepticism is the most justifiable position to hold: an unwillingness to form a position or support a proposition until that position is supported by evidence. As we've seen, anthropogenic global warming does have at least some evidence in support of it. It is supported by a generally broad consensus of scientific opinion. There are flaws with the model, and they need to be considered and tested before we can increase our confidence in our position.

It seems that this middle ground, this skepticism, has been lost between an increasingly polarised slinging match. On one side we have the global warming deniers who have disguised themselves as reasonable skeptics, in order to either somehow justify and protect a global energy economy that is potentially causing significant environmental damage, or to fall in line with a political idealogy, or in most cases a mix of the two. On the other we have truly hysterical environmentalists that refuse to accept the plain truth that there are problems with the anthropogenic model, who claim that every climate related issue is the result of global warming, and that Bush is actually to blame. As a skeptic I reject that proposition that Hurricane Katrina is the direct result of global warming, or that the increased hurricane season witnessed in the North Atlantic this year is the result of global warming. I reject them not because they are necessarily wrong, but because they are not based on any real evidence.

It is an increasingly unfortunate situation: One half of the divide place their fingers in their ears and refuse to accept the evidence, the other half place their fingers in their ears and refuse to accept the problems with the evidence. Those that do try to be rational and reasonable about the evidence, the real skeptics, are labelled as the enemy by both.

As heartening as it is that the global community is, at least in part, beginning to listen to the more sane voices, our attempts to 'solve' the 'problem' will always be damned by the conditionality of our knowledge. If it does turn out (and it is still a big if, at this point) that plants are a large contributor of atmospheric methane, then the Kyoto Protocol in its current form is a lame duck. This, combined with the irrational polarisation of worldwide opinion on global warming, means that coming up with an alternative will become increasingly more difficult.

I mentioned there were two articles in Nature on global warming. The one about plants and methane understandably got the most press, largely due to the gloating from pseudo-skeptics about the its implications for our understanding of the process.

The other article, in my opinion, has far greater implications. Its about frogs. Or more accurately, its about the increasingly threatened status of a particular genus of frogs, Atelopus (of which one is shown below), and how the loss of many of its species potentially is the result of global warming. It's not that the temperatures themselves are killing the frogs, but rather the effects that changes in temperatures have implications for the pathogens that cause disease in these animals.

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In Central and Southern America, a single fungus Batrachochytrium dendrobatidis has been identified as the main cause of decline for species within the Atelopus genus. What is particularly baffling is that the conditions that normally favour the spread of the fungus (cold, moist climates) are the opposite of current climate trends the so-called "Chytrid-Climate Paradox"

The authors were able to explain why the frogs were disappearing after the hottest years, and why that rate of decline was accelerating, as well propose a mechanism for that decline, thereby resolving the paradox. The paper was able to show to a statistically significant margin that climate change in the area has led to far warmer nights and considerably cooler days due to the insulation-effect of increasing cloud cover. This stabilisation of the climate, it seems, is preventing a thermal 'refuge' for the frogs, where hot and cold extremes suppress the disease causing abilities of the fungus.

Even more worrying is the data that shows these effects are the greatest at the altitudinal level where the biodiversity of the frogs is the highest, essentially forming an even greater threat to biodiversity.

The frog example is pertinent because it underscores the potential of global warming and climate change to have far-reaching effects on biodiversity, epidemiology and disease and regional eco-systems. It's not just the frogs that are potentially being 'diseased' out by global warming: the nematode parasite of arctic musk oxen is now, thanks to warmer temperatures, able to reproduce in 1 instead of 2 years, throwing the entire parasite-host system out of kilter. The Pine Beetle, which carries the pine blister rust between trees, is also growing and reproducing in half the time.

The global warming phenomenon has fundamental implications for global ecosystems, and not just through the direct effect of changing temperatures on organisms, but also on the relationships between organisms from all niches within those systems. Whether or not humans are the cause of the warming, and a reasonable interpretation of the evidence suggests we at least in part could be, we need to wake up quickly to these implications: the spread of diseases like malaria and cholera could be affected, as well as many bacterial, fungal and protozoan diseases that infect our livestock and crops.

Even more urgent, however, is the need for a resurgence in the true global warming skeptic: a body of people other than scientists who base their convictions on the evidence. The pundits who either ignore the evidence altogether, or positively leak hysteria into every climate related event are not helping. They are producing too much noise, masking the message that we all need to start hearing.*Science Vol 311 (13 January 2006):p159