Saturday, August 21, 2010

global warming

I'm referring to news articles rather than scientific articles, and avoiding technical discussions in order to keep this article readable to everybody.)

If I told you that the Ganges and the Brahmaputra will both dry up by the year 2035, how hard would you laugh at me? Now, what if it was the world's leading scientific authority on climate change that told you?

I'm sure every one of us knows at least a little bit about global warming: that it is primarily caused by the greenhouse effect, and that greenhouse gas levels in the atmosphere have been rising because of industrialization and deforestation, that rising global temperatures will melt polar ice caps thus causing sea levels to rise, and so on. However, until recently, we've all been led to believe that we have a century or two to cut greenhouse emissions and quell the problem. The key phrase there is "until recently", because climate science has now progressed enough to tell us how bad the situation really is.

How bad will India be hit?
The first sentence of this article must have sent alarm bells ringing in your head. But a little thought will tell you why the Ganges will dry up, if not when: the Ganges, and indeed all perennial rivers in North India, are fed by glaciers in the Himalayas. As global temperatures rise, the glaciers receive snow later and start melting earlier, causing them to gradually fall back to the colder regions. This news article [1] in the Hindu has a detailed discussion about the effect of global warming on glaciers. The world's leading authority on climate change, the Intergovernmental Panel on Climate Change (IPCC), believes that all North Indian rivers will turn seasonal, and ultimately dry up by the year 2035 itself if global warming remains unchecked.

But there's more. Another news article [2] confirms our worst fears: inundation of low-lying areas along the coastline owing to rising sea levels; drastic increase in heat-related deaths; dropping water tables; decreased crop productivity are some of the horrors outlined for us. Falling crop productivity due to the change in the length of the seasons is of particular concern, because there is an acute shortage of arable land in our country. With the population still growing rapidly, and crop productivity dropping, combined with the fact that we are already facing a grain shortage this year and have been forced to procure from abroad, the situation appears dire.

Is it fair? The major contributors to the greenhouse effect thus far are the developed nations, and even on an absolute basis (let us not even go into a per-capita basis), India's contribution to global warming is very little. And yet, we will be among the first to suffer its effects, as the change in climate will decrease crop productivity near the equator but actually increase it in the temperate regions. Effectively, the third world has been offered a very raw deal: suffer for something you didn't do, and still bear the yoke of cutting emissions because, frankly, at this point our planet needs all the help it can get.

How high is safe?
Let us leave India's concerns aside for now, take a step back and look at the global picture. Global temperatures have risen about 0.6 C on an average in the past century. There is a worldwide consensus among scientific circles that the adverse effects of global warming will probably be manageable for a rise in temperature upto 2 C, but beyond that, melting ice caps, unbalanced ecosystems, drastically reduced crop yields, etc. will cause worldwide disaster of monstrous proportions. If I haven't painted the picture clearly enough for you, read this article [3] and this article [4] detailing exactly what countries like Canada and Australia can expect in terms of "disaster".

But, is this where you heave a sigh and think, if it takes a century for the temperature to rise 0.6 C, then we have plenty of time to remedy the situation before the rise reaches 2 C? Wrong. You see, there is a lag between the rise in greenhouse gases and the rise in global temperatures. Scientists give the analogy of heating a metal plate directly, and then indirectly, by placing a metal block between the plate and the heat source: when you place the block, it takes some time before an increase in temperature at the heat source affects the plate; at the same time, if the heat source stabilizes or drops in temperature, the plate will continue to increase in temperature for a while before stabilizing or dropping. Thus, the increase in temperature now is a direct effect of rising greenhouse gas levels sometime in the 20th century. We are yet to reap the effect of the carbon dioxide we are currently dumping into the atmosphere! And the fact is, the amount of greenhouse gases that have been going into the atmosphere has been steadily accelerating over the past century.

So, where should we hold greenhouse gas levels in order to hold the global temperature rise to 2 C? The answer cannot be explained in one sentence, because there is some statistics involved. We cannot accurately predict the temperature rise from carbon dioxide levels yet; we have to talk in terms of probabilities. A recent study by Meinshausen et al. [5] gives some startling numbers. This is actually explained in much simpler terms in this press article [6]. The gist of it is that, we are already past the safe limit! You see, the current level of greenhouse gases in the atmosphere stands at 459 ppm of carbon dioxide equivalent (the actual concentration of CO2, corrected to include the effect of other greenhouse gases). According to the Meinshausen study, if atmospheric greenhouse concentrations are maintained at 450 ppm, the probability of global temperature rise crossing 2 C reaches unacceptable levels (> 50%). The current EU target is 550 ppm - at that level, we will be looking at a rise of around 3 C! In other words, emissions across the world should already be decreasing, not increasing at an accelerating pace. Countries around the world should be spending a significant percentage of their GDPs to save the planet, but everyone seems reluctant to move.

Panels and Reports
I had mentioned the IPCC earlier. The IPCC was formed by the UN and has actually been around since 1988. Over the years, it has established itself as the world's leading authority on climate change. It publishes its findings periodically, the assessment reports published this year being the fourth set, and the most controversial one because it reads more like a disaster movie script than a scientific report. Actually, there had been protests over the previous report that the IPCC is being alarmist, and the UK government ordered an independent study be made (a committee was appointed, led by Nicholas Stern), and its findings were released at the end of October 2006. The Stern Review actually reported that the IPCC had understated the situation in the third assessment report. You see, climate science is far from exact, and the IPCC tends to err on the conservative side. There are already publications that say that the IPCC has been conservative even in the fourth report - read this news article [7].

Perhaps the most important thing that the fourth assessment report has accomplished is that it has finally laid to rest claims that global warming is a myth. Yes, until a few years ago, there wasn't even a global consensus on whether global warming is the fault of man, because the waters got muddied by studies that showed that greenhouse gases, while absorbing heat radiated by the earth, happened to reflect sunlight coming in, thus reducing temperatures. Further, it is believed that geologically, the world is headed towards an ice age. Increasing global temperatures were attributed to periodic properties of the Sun! Now, at last, all these speculations have been laid to rest, and IPCC has stated that there is a 90% probability that the phenomenon of increasing global temperatures is anthropogenic (caused by man), and primarily because of greenhouse gases - what we've suspected all along. India, too, has finally woken up to the threat, and has set up a panel [Citation needed] to investigate the specific effects of global warming on India over the next few decades, and what remedial measures are feasible. The panel is to be headed by Mr. Pachauri himself, the current head of the IPCC.

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