Plainly Speaking: How Much Time Do We Really Have Left?

Global Warming ThermometerAlas, most people can be ‘jolted' to their senses only if the eventuality of disaster is quantified in cold, hard numbers. This is the strategy employed by a UK think tank, the New Economics Foundation (NEF), to trigger a much needed sense of crisis for action to tackle climate change, when it launched the 100 Months Campaign last month.

According to NEF's policy director, Andrew Simms, the world will reach a dangerous level of climate change 100 months from August 2008. In other words, NEF has calculated that in about 8 years' time, atmospheric concentrations of greenhouse gases will begin to exceed a point whereby it is no longer likely for humans to avert potentially irreversible climate change, the so-called ‘tipping point', that many scientists have been warning about in recent years.

Specifically, by taking into account a 3.3% annual growth rate of CO2 and other greenhouse gases (GHG) covered under the Kyoto Protocol, a constant level of warming impact of those gases, and other relevant factors such as climactic feedback loops, NEF predicts that by the end of December 2016 we will not only reach but exceed an atmospheric GHG concentration of 400ppm (parts per million), up from the current 377ppm. Details of the analysis can be found in NEF's Technical Note (PDF).

So what's the deal about exceeding ‘400ppm'? Well apparently once this concentration level is breached, there is a high risk that global mean temperature would shoot up by more than 2°C (3.6 in Fahrenheit) when 2°C is generally considered by experts and the European Union to be the ‘safe' level of warming. Such abrupt heating will cause large-scale environmental changes, for example dramatic sea level rises that wipe out populations on low-lying coastal areas and islands.

That's not all. In a study about climate change tipping points, Professor Tim Lenton of the University of East Anglia has outlined nine tipping elements based on key geographical features and the time expected for them to materialize if warming continues:

  • Melting of Arctic sea-ice (approx 10 years)
  • Decay of the Greenland ice sheet (more than 300 years)
  • Collapse of the West Antarctic ice sheet (more than 300 years)
  • Collapse of the Atlantic thermohaline circulation (approx 100 years)
  • Increase in the El Nino Southern Oscillation (approx 100 years)
  • Collapse of the Indian summer monsoon (approx 1 year)
  • Greening of the Sahara/Sahel and disruption of the West African monsoon (approx 10 years)
  • Dieback of the Amazon rainforest (approx 50 years)
  • Dieback of the Boreal Forest (approx 50 years)

Therefore, according to Lenton's predictions, we have a slightly longer time, but not much more, (10 years) to stabilize atmospheric concentrations and prevent the first tipping point from transpiring.                 

Alternatively, to some people like leading U.S. climate scientist James Hansen, head of the NASA Goddard Institute for Space Studies, we may already have crossed the threshold point. In his recent statement to the U.S. Congress, he warned: 

"The disturbing conclusion, documented in paper that I have written with several of the world's leading climate experts, is that the safe level of atmospheric carbon dioxide is no more than 350ppm and it may be less. Carbon dioxide amount is already 385ppm and rising about 2ppm per year. Stunning corollary: the oft-stated goal to keep global warming less than 2°C is a recipe for global disaster, not salvation."

Skeptics will no doubt decry the NEP's ‘prophetic doom' approach as scare-mongering, dismiss Hansen's distress calls as alarmist propaganda, and pick on the inconsistencies between estimates of sea level rise with corresponding temperature increases -  for example, the IPCC Fourth Assessment Report's ‘worst case scenario' anticipates a 7-meter rise assuming the complete meltdown of the Greenland ice sheet after the 21st century, when global mean temperature overshoots the range of 1.9 to 4.6°C (relative to pre-industrial levels). In contrast, Hansen anticipates from historical data that 25-meter rise is possible with only 2 to 3°C warming, at merely atmospheric concentrations of between 350ppm to 450ppm.

So then, what is the ‘acceptable warming level' and do we have 8 years, 10 years or half a century to ‘safely' steer off the path towards irreparable ruin? Why can't scientists agree on what temperature rise and atmospheric concentration of greenhouse gases corresponds with how much the sea will rise?

The truth is, the dynamics of climate change is so complicated that projections are, at best, educated guesses by the scientific community (which is still much better than arbitrary, un-scientific predictions). They are based on models that are being constantly updated as new knowledge is discovered. The BBC has a pretty good article that explains the factors behind sea level rise. Therefore, as much as we crave certainty and verifiability to act rationally, we ought to acknowledge the limits of science, while not using it to justify inaction and indifference.

On the other hand, ‘safety' and ‘tipping' points are value decisions like ‘what is good or bad' which is relative depending on who you are. For people living in sinking islands like Tuvalu, Kiribati and the Carteret Islands, we've obviously gone way past their ‘tipping point'. Whose tipping points will be crossed next? Most likely those who live in vulnerable coastal areas or who love polar bears and coral reefs to bits. We are free to draw our red lines, but they are meaningless if we don't have the courage and willpower to defend them.

How much time do we really have left? One month, 100 months or a century and does it really matter? To wring our hands over probabilistic uncertainties, is to overlook the larger message - that we don't have all the time in the world to, in Simms' words, ‘curdle in complacency'. Better late then never, but when so much is at stake, isn't it better early than late? Consider the signs that confirm the reality of tipping points - it was recently reported that Artic ice loss is set to exceed last year's, and Antarctica's ice is melting faster than predicted.

Let's instead focus and build on things that we've spent nearly two decades to arrive at:  First, global warning is real; second, humans are the major culprits; third, we have the technology and ideas to redeem the situation; and finally; a low-carbon society is simultaneously a solution to prevent dangerous climate change and an evolutionary strategy to wean ourselves off an unsustainable fossil fuel-addicted civilization. Since we're still lucky to be able to carry on with our normal lives, it is still not ‘too late', and definitely not ‘too soon' to act now, knowing full well that with each passing day, every single action matters even more.

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  • Posted on Sept. 16, 2008.

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