Planetary Boundaries: Defining Our Critical Limits for Survival

We now are much more aware of the fact that humans can't do anything they want to their home planet and survive. Beyond certain critical limits, humans "pushing the envelopes" of any of nine critical physical boundaries - and we get flushed into extinction.

Before the fall of 2009, virtually no one other than an elite core of environmental and climate scientists too the notion of natural boundaries seriously. Even now very few in the general population are informed about them and the consequences if humans play the fool.

But in the run-up to the 2009 Copenhagen Climate Conference, a group of concerned scientists working under the auspices of the 'Stockholm Resilience Center' in Sweden, published a paper in Nature that got on their peers' radar. The paper essentially spelled out nine areas of concern which one might say "parameterized" the safe operating and living space for human development: nine limits beyond which humans ought not push their luck or their planet.  These nine areas are:

-climate change

- ocean acidification

- intervention in the nitrogen and phosphate cycles (crucial to plant growth)

- the conversion of wilderness areas to farms and cities

- extinctions of fauna with which humans share planetary space

- accumulation of chemical pollutants

- the level of particulate pollutants in the atmosphere

Though nine critical boundary areas were given, the authors felt confident enough to actually put numbered limits on seven areas for which they believed incursions and excesses were most critical. They deferre judgment for the chemical pollutants and level of particulates (though we now know the latter have played a role in masking about one third of actual global warming, in a phenomenon we refer to as "global dimming'. )

Since the Resilience Group's breakthrough paper, the notion of planetary boundaries has taken root, as it were. For example, it repeatedly crops up in the UN's Environment Program's GEO-5 assessments of the world. Pride of place actually was conferred by the high level Panel on Global Sustainability which reported recently to the UN Secretary General Ban Ki-Moon. Meanwhile, a group called 'Plan Under Pressure' (a powerful scientific conference held recently in London) made the boundary concept central to the message it conveyed to the Rio+20 Earth summit that opened on June 20th.

Though there have been the inevitable criticisms (i.e. from the likes of the "Breakthrough Institute" - a contrarian think tank), to the effect the limits pay too much attention to effects during the Holocene - or the epoch since the last Ice Age- defenders note it really only takes one critical arena for human life to unspool on this planet. Many also argue for a more concerted effort to constrain the Anthropocene (the truly human-domiated era) within the norms of the Holocene.

Climate change immediately comes to mind, what with more than 9,000 heat extreme records broken in the U.S. this summer alone. Then add to that the apparent total melting of Greenland's ice cover - recently captured in satellite photos by NASA and the next phase of ther elevant  tipping point (ice sheet collapse, melting of permafrost ) becomes easier to process.

Note that skeptics (as usual) have pounced on the NASA "unprecedented melting" claims and trotted out a number of "glaciologists" and "climatologists" who've insisted the massive melt is part of a "natural 150-year cycle". Even if so, these "experts" have not properly factored the melt into the Jökulhlaup phenomenon of massive glacial outbursts in the Greenland ice which are NOT part of any natural cycles and which lead to a forcing event. (See, e.g. 'Jökulhlaup Observed in Greenland Ice Sheet', in Eos Transactions of the American Geophysical Union', Vol. 89, No. 35, 26 August, 2008).

Indeed, the boundary research groups note that of the nine putative boundaries, three apply to systems where there is a clear global threshold: the aciditiy of the oceans (now 30% more acidic than at the outset of the Industrial Revolution),  the climate and the ozone layer. Some of the other six surely have local effects but for the most part the "global" ones are just aggregations of the local effects.

One thing we do know is that there isn't much more leeway in pushing the CO2 concentration (now at just above 390 ppm) before a "runaway greenhouse" effect sets in which will truly destabilize the planet. Currently at the rate we're consuming carbon based fuels, we are adding about 2 ppm per year and enhancing the solar insolation at the same time as a result of radiative forcing (because of the vibrational properties of the CO2 molecule - contributing to its heat -trapping propensity).  Thus, if the threshold for the onset of the runaway greenhouse effect is 470 ppm, then we may be only 40 years away. Once it begins, all bets are off and we'll be on the way to becoming a second Venus.

Optimists - for which we always have a surfeit- insist (as in the book Superfreakonomics) that "practical solutions" can always be found, such as reining in the greenhouse gases' effect on radiative forcing. But this is easier said than done. 'Solutions" like injecting massive SO2 (sulphur dioxide) clouds into the atmosphere, or injecting 12 quadrillion reflecting particles into low Earth oribt,  create more problems than they actually solve.

The simplest solution - to avoid the imminent runaway boundary - may simply be to stop using so much carbon based fuel. To do that, of course, we shall first have to get the expanding human population to "plateau" - since the more people the more CO2 generated. Once we can stabilize the population, we can perhaps entice the existing population to impose less of a carbon footprint!

Stay tuned.