When speaking of time bombs, frozen tundric dust may seem an unlikely contender at first blush. The bad news is that this particular type of permafrost harbors an estimated 500 gigatons of carbon, which—via a series of complex chemical reactions—is slowly yet at an accelerating clip being released from the thawing soil into the atmosphere as methane, a far more potent greenhouse gas than standard-issue carbon dioxide. Researchers are taken aback by the rate at which lakes with “methane bubbling up out of them” are forming all over a region in northeastern Siberia of roughly one million square kilometers, which (at least for the past 11,000 years) had not been particularly amenable to traversal by boat.
Global warming precipitates a melting of the permafrost, and the subsequent release of methane escalates global warming, which, in turn, hastens the liquefaction of the soil. A positive feedback loop has begun, analogous in principle to what happens when one holds a microphone too close to an amplifier. Squeezing such self-reinforcing climatic chain reactions back into the tube will require efforts quite a few orders of magnitude more elaborate than simply moving a mike away from the speaker. The question arises as to the precise location of that particular point in time after which an undoing of a process already in progress becomes impossible no matter how massive and concerted the remedial actions deployed in response. In other words, how can we predict when a given system will tip or determine whether it has done so already?
Twelve specific environmental tipping points have been identified so far, and mathematical models abound that aim to quantify exactly how disquieted mankind ought to be about each one. Upon studying a number of these models, however, one quickly realizes that, on balance, they are no less chaotic than the systems they seek to describe, and there never appears to be a shortage of game-changing variables that had somehow or other failed to make it into a given calculation. Hence, the arithmetic of climate change has proven inordinately prone to the “oops” factor, as upon being confronted with the most recent set of satellite data which reveal that yet another strapping ice shelve that was scheduled to spring a hairline crack a few centuries down the road has mysteriously disintegrated overnight.
Large ice sheets act like gigantic mirrors, reflecting sunlight back into the cosmos. This process is known as ice-albedo feedback. Any drawdown in surface ice, therefore, results in more light and hence more heat being absorbed by the planet. Antarctica is the largest ice machine on earth, containing more than 90% of its frozen water stores. Aptly nicknamed a “slumbering giant” of climate change, it was upgraded to an “awakening giant” by Chris Rapley of the British Antarctic Survey in 2005. One of its major segments, the West Antarctic Ice Sheet, partially rests on a sloping surface, making it inherently unstable. Once a tipping point is reached, nothing can stop the sheet from disintegrating completely and plunging into the ocean in relatively short order, raising global sea levels by several feet as a result. Subway trains in coastal cities around the world will convert to submarines, and Manhattanites will be hailing yellow gondolas in lieu of cabs.
A further rise in sea levels is to be expected in the wake of the collapse of the Greenland ice sheet, which would be the inescapable result of passing yet another tipping point. Given atmospheric levels of heat-trapping carbon dioxide (CO2) currently at 335ppm, NASA climatologist James Hanson believes that Greenland may have tipped already, although it is often difficult to determine with accuracy the lag time between the silent tipping of a system and its observable effects.
The Tibetan Plateau, spanning a whopping quarter of China’s landmass and harboring the world’s third largest stores of ice, is yet another melting mirror about to tip. Southeast Asia’s large-scale industrial emissions of “black carbon” work towards darkening snow covered Himalayan surfaces, thus impairing the reflection of sunlight. The plateau’s glaciers rapidly receding, the exposed darker soil soaks up even more incoming heat, which makes mischief for atmospheric circulation over virtually half the planet.
Siberia, having clocked an average temperature increase of 3°C over the last 40 years, is the fastest warming area on earth. It also holds more than 25% of terrestrial methane (CO4). When the carbon molecules trapped inside the thawing Arctic permafrost are converted to CO4 and discharged into the atmosphere in quantities that exceed countervailing human efforts at slashing carbon emissions overall, tipping point number three will have been reached.
Slowing ocean currents bode a potential tipping threshold as well. By way of the North Atlantic Conveyor Belt, which belongs to a network of currents known as the Global Ocean Conveyor, warm surface water from the Gulf of Mexico moves north to be cooled down by westerly winds. The cooler layer then gradually sinks to the bottom and travels back south, where it warms and rises once again. This thermohaline circulation, which takes centuries to complete, is a function of aquatic turbulences set off by density variations at different depths.
The density of seawater derives from its temperature as well as its salinity, the latter being roughly ten times higher than that of sea ice. The burgeoning quantities of near-fresh water from melting sea ice that slosh into the Atlantic lower the salinity of its upper layer, thus reducing its density and, in consequence, its proclivity to sink, thereby disrupting the very dynamic which keeps the conveyor going. Moreover, rising atmospheric temperatures bring forth increased rainfalls, which further attenuate surface salinity.
The Atlantic conveyor belt in conjunction with regional wind patterns serves as Europe’s central heating system, and one particularly ironic corollary of a global-warming induced grinding to a halt – or even a significant slowdown – of these ocean currents could be the thrusting of Northwestern Europe into a mini-Ice Age. A few miles of border fence between Texas and Tijuana may repel a few Mexicans but will be of scant utility in keeping millions of shivering Swedes off American shores. Mass migrations of species, hominids included, are another troubling consequence of climatic upheavals.
The world’s largest and perhaps most significant ocean gyre, the Antarctic Circumpolar Current, whirls more than 30 billion gallons of water per second around Antarctica as it blends waters from the Pacific, Indian, and Atlantic Oceans. Once again, cold water descends towards the bottom and warmer water rises as it carries with it vital nutrients from the ocean floor. According to a 2006 Princeton study, the Antarctic Circumpolar Current ranks utmost as far as maintaining Earth’s nutrient and carbon cycles. Phytoplankton in the water absorbs gargantuan amounts of CO2 from the atmosphere. Not only do these critters thrive off nutrients delivered from the ocean floor by the rising layers of warmer water, but once the plankton dies a natural death, it sinks all the way to the bottom, thus safely sequestering its CO2 stores. The ocean’s functioning as the Earth’s most powerful carbon sink, however, weakens drastically once its subtle surface-to-bottom currents are disrupted, leading to progressive starvation of the carbon-guzzling plankton. Therefore, carbon dioxide accumulation in the atmosphere is inversely proportional to the ocean’s capacity to scarf it up, and tipping will occur.
Perhaps surprisingly, plankton also feeds off mineral-rich dust kicked up by sandstorms in the Sahara and carried over large distances by wind currents until settling in the ocean. Covering 3.5 million square miles, the world’s largest sandbox is currently expanding. It stands to reason, however, that increased precipitation due to shifting climate will soon reverse the process and convert its southern reaches into vegetation. While this may sound desirable, the downside will be a decline in peripatetic Sahara dust, which fertilizes not only plankton in the Atlantic but also CO2-consuming trees in the Amazon. In addition, clouds of sand, like ice, reflect significant amounts of sunlight; hence, somewhat counter-intuitively, any shrinking of the Sahara will cause a further warming of the atmosphere. When this happens, some say Africa will tip.
A tipping of the Amazon rainforest would trigger the cascading collapse of some of the world’s most biodiverse ecosystems with direful consequences for the entire planet. Enormous amounts of carbon are stored inside its vegetation, and a large-scale die-off would not only cease absorption of greenhouse gases from the atmosphere, but the subsequent rotting of its trees would in itself unleash amounts of CO2 that may equal the total fossil fuel output of the entire 20th century. In effect, a state of worldwide emphysema is liable to attend any significant malfunction in this major lobe of the global lung. .
Roughly two million years ago, a large-scale extinction of sea plankton coincided with a nearby supernova. Radiation from the cosmic explosion had wreaked havoc to Earth’s ozone layer, and the plankton succumbed to increased UVB rays pelting the ocean. Although the ozone has had plenty of time to recover since, in recent decades atmospheric concentrations of CFCs and other man-made chemicals have triggered a slow-motion supernova from below, leisurely blasting a massive hole in the ozone above the Antarctic and thinning the protective layer worldwide. Dubbed the “mother of all tipping points,” not only will increased levels of ultraviolet radiation hitting the surface boost melanoma rates, but also contribute to global warming via dealing an additional blow to the ocean’s already severely impaired role as a carbon sink by killing off even more phytoplankton.
Virtually all of the climate hazards outlined above conspire to bring about severe disruptions to the Asian and West African monsoon. Much like for millennia Egypt has been called the “gift of the Nile” for the river’s clockwork overflowing of its banks, thus enabling irrigation of farmland and ensuring reliable crop yields, periodic monsoon rains constitute a carefully calibrated water source around which hundreds of millions of people have adapted their lives, and any systemic disturbances, causing either too much rain or too little, would wreak havoc on local food production and trigger massive starvation.
In one of his songs, Elvis Presley once lamented, “Why Can’t Every Day Be Like Christmas?” This question may have sounded rhetorical in the 1960s, but in hindsight is seems eerily prophetic. Every 2-7 years, a warming of the central and Asian Pacific ocean has been known to occur, carrying in its wake major shifts in weather patterns. This warming was dubbed “El Niño,” Spanish for “the little boy” in reference to baby Jesus, as this phenomenon was usually noticed around Christmas time. As global warming progresses, however, El Niño may become the average state of the region’s climate, significantly shifting precipitation patterns around the globe.
In summation, the twelve potential climatic tipping points are these:
The most striking feature of these phenomena is their inherent inter-connectedness, much like a breakdown in one organ system, unless remedied in due time, inevitably leads to multiple organ failure. Nothing happens in isolation.
One major difficulty lies in quantifying with precision the human factor in all of this. After all, systems have tipped in the past without anthropogenic intervention. Needless to say, this argument is being milked to the max by those who, either for political reasons or out of sheer attachment to their merry ways, wish to dismiss environmental concerns as the ramblings of a bunch of tree-hugging maniacs, blithely ignoring the mounting evidence that human activity is indeed a major catalyst in pumping up the Earth’s temperature and all its incident reverberations.
As to the notion that nature will adjust, it is absolutely true. Nature will adapt, and the planet will survive, and if, to this end, it has to emancipate itself of the human race, it will. Make no mistake about it.
But try to explain that to India, Russia, China, and Sean Hannity.
(This essay was composed as a trial assignment for a Gary Null Inc. researcher position.)