28 September 2013

Global warming will be long with us

United Nations Secretary General Ban Ki-moon calls it the "greatest collective challenge we face as a human family.” He is, of course, referring to climate change. The Intergovernmental Panel on Climate Change presented the first installment of its Fifth Assessment Report Friday and it has much of interest to say about the "greatest collective challenge."

This includes the stark warning that "Carbon dioxide induced warming is projected to remain approximately constant for many centuries following a complete cessation of emissions. A large fraction of climate change is thus irreversible on a human timescale, except if net anthropogenic emissions were strongly negative over a sustained period." To put it bluntly, unless we invent some way to suck billions of tons of carbon dioxide out of the atmosphere, we will be stuck with the higher temperatures and all the attendant problems for centuries.

And of course the longer we allow emissions to increase, and we are doing precisely that, the worse those problems will be. Storms and floods will be bigger and more frequent, droughts will be vaster, and sea levels will continue to rise. Indeed sea levels will continue to rise for centuries even if emissions don't increase due to the delayed effects of thermal expansion of the warming oceans and the melting of ice sheets. And then there is the nightmare of global warming becoming irreversible, a very real possibility if we don't soon act proportionate to the "greatest collective challenge."

Considering our procrastination with reducing emissions, developing means of removing them from the atmosphere will be challenging indeed. We may as well accept that we will be living with our increasingly unpleasant new normal for a very long time.

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