The ‘Dangerous Threshold’ – a Destination, or a Milestone?

I’ve often expressed my concern (here & here for example) that scientists, and, in particular, the politicians that have the greatest power to incentivise change in the world, have been rather arbitrary in settling on a politically correct (read – economically barely palatable) target of reining in the world’s emissions just shy of 450 parts per million (ppm: that’s 450 parts of CO2 for every million parts of atmosphere). 450 ppm would be a 60% increase in CO2 concentration over pre-industrial levels (approx. 280 ppm), and this was accepted by many — even if uncomfortably in some quarters — as the point where we would hit the red zone on our climate system’s tachometer.

A couple of the reports I recently highlighted (3 & 4: The Big Melt, and Target Practice) sought to cut through the political/economic hype and motivational factors to determine a safe concentration target — one that is expedient, rather than merely politically acceptable. If the figures in these reports are correct, then we need to hit the rewind button on emissions real fast. Standing at 387 ppm today, we have already passed the 350 ppm point that has sent the arctic ice sheets into dramatic decline and weather patterns into disarray (also see here & here). The conclusion is that 350 ppm is the point we need to endeavour to pull back beyond — a point we overtook a couple of decades ago….

James Hansen, head of the Earth Sciences Division of NASA’s Goddard Space Institute and one of the earliest scientists to agitate global warming issues before the U.S. congress two decades ago, recently ‘confirmed’ these figures:

The CO2 tipping point for many parts of the climate is around 300 to 350 parts per million, Hansen estimated. — National Geographic

Our climatic systems, those that have supported human existence with relative stability for millennia, may well be a lot less flexible to human/fossil fuel interventions than many have supposed.

Ignoring the ultra-discouraging figures from 300-349 ppm, Bill McKibben, world renowned environmental author and activist, adds to the discussion in a recent Washington Post Op-Ed:

The news this fall that Arctic sea ice was melting at an off-the-charts pace and data from Greenland suggesting that its giant ice sheet was starting to slide into the ocean make even 450 look too high. Consider: We’re already at 383 parts per million, and it’s knocking the planet off kilter in substantial ways. So, what does that mean?

It means, Hansen says, that we’ve gone too far. “The evidence indicates we’ve aimed too high — that the safe upper limit for atmospheric CO2 is no more than 350 ppm,” he said after his presentation. Hansen has reams of paleo-climatic data to support his statements (as do other scientists who presented papers at the American Geophysical Union conference in San Francisco this month). The last time the Earth warmed two or three degrees Celsius — which is what 450 parts per million implies — sea levels rose by tens of meters, something that would shake the foundations of the human enterprise should it happen again. — Washington Post

Humans always find it hard to assimilate inconvenient information. In the political realm, we seem to be stuck in a kind of ‘wait and see’ limbo. Nobody wants to rock the boat and upset economies unnecessarily – understandably – but this way of thinking is setting us up for a major fall.

Many fear government oppression and interference in business activities and even personal freedoms. I share these fears. To be candid, however, I feel present inaction due to economic and libertarian concerns may merely delay far more oppressive measures bluntly applied due to increasingly desperate governments being forced into sudden action further down the track. What’s worse is that those delayed and likely poorly planned actions will be followed by an even more delayed response from climate systems. In other words, if delayed too long, even seriously draconian measures will have no perceivable effect for decades afterwards:

Public attitudes about climate change reveal a contradiction. Surveys show most Americans believe climate change poses serious risks but also that reductions in greenhouse gas (GHG) emissions sufficient to stabilize atmospheric GHG concentrations can be deferred until there is greater evidence that climate change is harmful. US policymakers likewise argue it is prudent to wait and see whether climate change will cause substantial economic harm before undertaking policies to reduce emissions. Such wait-and-see policies erroneously presume climate change can be reversed quickly should harm become evident, underestimating substantial delays in the climate’s response to anthropogenic forcing.We report experiments with highly educated adults – graduate students at MIT – showing widespread misunderstanding of the fundamental stock and flow relationships, including mass balance principles, that lead to long response delays. GHG emissions are now about twice the rate of GHG removal from the atmosphere. GHG concentrations will therefore continue to rise even if emissions fall, stabilizing only when emissions equal removal. In contrast, most subjects believe atmospheric GHG concentrations can be stabilized while emissions into the atmosphere continuously exceed the removal of GHGs from it. These beliefs – analogous to arguing a bathtub filled faster than it drains will never overflow – support wait-and-see policies but violate conservation of matter. Low public support for mitigation policies may arise from misconceptions of climate dynamics rather than high discount rates or uncertainty about the impact of climate change. – Understanding public complacency about climate change (PDF)

It is true that to aim for a 350 ppm target, in the face of present realities of energy consumption, embedded infrastructure, population and economic growth would seem to be wholly unrealistic. But at the same time we cannot afford to ignore the science. Aiming for the lowest possible target will serve to minimise economic costs and social shocks from the huge climate change bill that is accruing. The longer we delay deep cuts in emissions, the more intense will be our problems in the years ahead — and our ability to do anything about it will diminish with every passing year.

Bill put it well:

The gentle measures bandied about at Bali, themselves way too much for the Bush administration, don’t come close. Hansen called for an immediate ban on new coal-fired power plants that don’t capture carbon, the phaseout of old coal-fired generators, and a tax on carbon high enough to make sure that we leave tar sands and oil shale in the ground. To use the medical analogy, we’re not talking statins to drop your cholesterol; we’re talking huge changes in every aspect of your daily life.

Maybe too huge. The problems of global equity alone may be too much — the Chinese aren’t going to stop burning coal unless we give them some other way to pull people out of poverty. And we simply may have waited too long.

But at least we’re homing in on the right number. Three hundred and fifty is the number every person needs to know. — Washington Post

Waiting for technological fixes so we can continue our present scale of consumption should be seen for what it is – shooting ourselves in the foot.

We have been at war with nature – whether we’ve realised it or not. Now we need to mobilise, similar to the way nations have mobilised in the past to defeat a common foe. Unlike the sound of civil defense sirens and overhead bomber craft, the offensive that climate change is bringing upon us is deceptively subtle in its tactics, but likely to be far more catastrophic. Doing nothing is not a defense.

Giving Dr. Hansen the last word:

“We have to figure out how to live without fossil fuels someday,” Hansen said. “Why not sooner?” — National Geographic




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