A third side in the climate change debate

Our corporate media system will often present climate change as an active scientific controversy by framing the issue as a “debate” between two sides, environmentalists and skeptics, each with valid points supported by scientific data (e.g. are temperature increases due to increased atmospheric CO2  or increased solar activity?) This approach purposely doesn’t communicate to the public two important “inconvenient truths” about the “debate”:

1. That the vast majority of climate scientists accept anthropogenic global warming and are very worried about the latest data. Meanwhile, most skeptics have no background in climate science and are in the employ of those with an obvious vested interest in playing down anthropogenic global warming.
2. That there is a significant “third side” in the debate; climate scientists of the opinion that the IPCC (Inter-Governmental Panel on Climate Change) “consensus” is far too optimistic and the reality of climate change may be far more dangerous to human survival.

I want to explore the second point, which I don’t think gets enough coverage. The impression one gets from IPCC recommendations is that there will be a nice linear rise in global temperatures, faithfully tracking a rise in CO2 emissions. The “consensus” communicated to policy makers is that the natural Carbon Cycle, with its annual carbon fluxes and carbon sinks shown in the picture below, will over time correct for the excess CO2 we have put into the atmosphere; once governments pull their finger out and act to reduce global emissions, temperature will continue to rise for a little bit before settling down to a new stable level, with a “safe” overall global average temperature rise of around 2 degrees.

There is a problem with the previous paragraph however. Climate systems are not “nice linear” systems, but contain feedbacks. Lots of them. Both positive and negative. An example of a negative feedback is increased plant growth on land resulting from a CO2 enriched environment; more plant biomass will mean more carbon taken out the air and stored. An example of a positive feedback is the possible melting of polar permafrost, which can have multiple dangerous effects; pockets of trapped methane (a much more potent greenhouse gas than CO2) can be released and also the Earth’s Albedo (the fraction of heat energy reflected back into space, with white ice reflecting much more than tundra) will be reduced, triggering further warming.

The danger with positive feedbacks is that they are self-reinforcing. Imagine a little bit of polar ice melts. The Earth’s Albedo goes down a little. So there is a little bit more warming. So a little more ice melts. And so on. These positive feedback loops can lead to sudden collapses of climates, with dramatic changes in temperature. What about the IPCC’s climate models? The IPCC’s models do not take most of these feedbacks into account. James Lovelock has expressed serious concern over this tendency in his latest book The Vanishing Face of Gaia:

Climate models based on atmospheric physics have their own peculiar dogma: almost all of them forecast a smooth, steady rise in temperature as carbon dioxide abundance increases. They seem to assume that nothing in the next thirty years will alter the course of global warming because our changes to the Earth’s land surface and emissions so far have committed the system to warm by about 2 degrees and its response time is slow. This is the basis of the IPCC recommendations to reduce emissions by 60 per cent by 2050 to avoid ‘dangerous’ climate change…

[However] If the many apparently separate positive and negative feedbacks on climate synchronise coherently then the whole Earth system could heat or cool rapidly by as much as 5 degrees. I find it extraordinary that, given the depth of our ignorance, scientists are willing to put their names to predictions of climates up to fifty years from now and let them become the basis of policy. Surely they are not predictions, just speculations to assuage the fear of the dark clouds that loom on the climate horizon.

So the IPCC recommendations may represent “a convenient lie”, but for a very different set of reasons to those the oil lobby might have you believe! IPCC models are principally models of atmospheric physics and as such should accurately predict how the atmosphere responds to increased CO2 emissions to the extent that the atmosphere functions as an isolated system. But the real atmosphere does not function as an isolated system! Instead it is coupled to many other systems, both organic and inorganic, in ways we are only beginning to understand, many with the potential for dangerous runaway positive feedbacks. The message to take away is both that there might be sudden and dangerous increases in global temperature and that these are precisely the effects the IPCC’s linear models are unlikely to warn us about.

In light of positive feedbacks via melting arctic permafrost, the latest climate data about polar temperature rises is particularly worrying. Remember that a “safe” 2 degree rise refers to a global average – local temperature rises may deviate significantly from this average. This animation from the NASA Earth Observatory shows that there are polar regions consistently warmer than the global average by around 10 degrees. While a 2 degree average rise sounds “safe”, if it implies a 10 degree rise in some critical region (a polar methane sink say) it will be far from safe.

In the past, mass extinctions might have been caused by rising polar temperatures. The most severe extinction in the planet’s history “The Great Dying” is probably one example. 70% of land and 95% of ocean life was wiped out. One theory on how this happened was that an increase in polar temperature unleashed a methane induced positive feedback loop, with ocean temperatures at the poles increasing so much that important ocean currents were shut down. The reduced circulation in oceans allowed massive growths of surface ocean algae (like with a stagnant pond), leading to an anoxic ocean in which hydrogen sulphate producing bacteria thrived, poisoning 95% of ocean life in the process. It goes without saying we would prefer to avoid such a chain of events today! Perhaps it is unlikely our actions will trigger a similarly deadly outcome. But we should bear in mind that we may be setting in motion powerful natural processes we currently have very little understanding of or control over.

Another feedback loop worthy of concern is the stability of the rainforest system. Rainforests might play an important role in global cooling, one we are only just beginning to understand. Rain falling on them enters the system through tree roots and exists via canopy evapo-transpiration; water vapour emission from the surface of leaves. This water vapour forms clouds, which help to lower the Earth’s temperature by reflecting back into space more sunlight. Hence the rainforests might be an important negative feedback system, one which we are currently busy eliminating while at the same time we increase atmospheric CO2 levels. And of course the rainforest is also an important carbon sink.

What is the future of the rainforest system? Much has already been destroyed and if its size falls below some critical threshold the system may be unable to maintain the water falling as rain within its water table; this will simply leech back out to the oceans. It is unknown what this critical threshold is; indeed it may have been passed already. Crossing this threshold will start another positive feedback cycle and the rain forests might “melt away” within a few decades, just as the polar ice-caps might. Global rainfall patterns will also be dramatically affected and many human harvests might fail for want of the rainfall directed to them via the rainforest system. The impact on the 3rd world could be devastating. Many people see the rainforests as merely a hobby horse of environmentalists and not an issue of potential human survival. I hope this attitude begins to change.

The potential causes of an environmental crisis are strongly analogous to the causes of the financial crisis; this involved the simultaneous dismantling of all corrective regulation (negative feedbacks) accompanied by the incentivising of speculative bubbles (positive feedbacks). However the analogy with the financial system does not apply in one critical respect: if we cause natural systems to collapse, they cannot be bailed out. Such natural systems are critical to our own survival. As responsible citizens who care about the futures of our children and grandchildren, we should all endeavor to bear this in mind and act accordingly.

~ by freedomthistime on August 1, 2011.