Gary Null, PhD., and Jeremy Stillman - The 12 Tipping Points

The 12 Tipping Points
By Gary Null, PhD., and Jeremy Stillman 

Currently, more than half of the population of the United States does not believe that Global Warming is real or that it is man-made. Most discussions involving our environment rest upon Global Warming as a single issue, however, we are confronted today with multiple environmental crises. Any one of these issues can cause extreme suffering and in some cases, cataclysmic devastation if they were to go so far as to tip. Hence, we present an exploration of these tipping points to better understand the dangers that we face and how to limit their negative consequences.

The Disruption of the Antarctic Circumpolar Current (Not yet tipped)

Linking together the southern Pacific, Atlantic and Indian oceans is the Antarctic circumpolar current (ACC). The current moves west to east around the continent, displacing 34 billion gallons of water per second. Importantly, the ACC circulates nutrients to sustain trillions of phytoplankton near the water’s surface which absorb large amounts of carbon dioxide from the atmosphere. After soaking up the CO2, the phytoplankton sink to the cold ocean depths, creating what is known as a “carbon sink”. This process helps compensate for excess CO2 levels caused by the burning of fossil fuels and deforestation.  Many suspect that Global Warming could disrupt this sensitive cycle, weakening the current’s intensity and leading to an increase in carbon dioxide levels.  Research from 2008 indicated that, while the circumpolar current has shifted farther south over the course of a decade, its strength remains the same.

The Release of Methane Clathrates   (Not yet tipped)

Methane Clathrates refers to the huge supply of frozen methane found below the ocean floor and Arctic permafrost. Holding anywhere from 1- to 2.5-trillion tons of methane, these underground gas chambers continuously release methane into the atmosphere. As Global Warming causes permafrost to melt, the clathrates become more vulnerable to destabilization. Consequently, there is an increased risk of a significant methane discharge being sent into the atmosphere. Models predict that just one good-sized gaseous ejection could accelerate Global Warming by up to 25%.  The signs are there: methane released into the atmosphere has doubled over the last 150 years and recent measurements in clathrate hotspots including Alaska and Siberia showed that levels of the gas were 5 times greater than expected. What makes the situation even more concerning is the fact that methane is 20 times more powerful than carbon dioxide as a greenhouse gas.  

The Disruption of the Monsoon Season (Not yet tipped)

Global warming-induced changes to the monsoon season could cause dramatic decreases to the food supply for billions of Earth’s inhabitants. As the planet’s temperature rises, many scientists are predicting a shift in the course of monsoons and their accompanying rains.  Scientists predict that such a shift could mean much less rainfall in the Indian subcontinent as well as parts of Africa and Southwest Asia.  Since the agriculture of these areas is largely dependent on monsoon patterns, a disruption to this cycle could have a devastating effect food production. Experts also foresee an increased risk of wildfires as a result of this phenomenon.

El Niño (Not yet tipped)

El Niño refers to the increase in sea-surface temperatures that occurs in the Pacific Ocean approximately every five years.  This rise in sea temperatures has contributed to greater rainfall and flooding in South American nations such Peru and Ecuador and a higher risk of drought in the western Pacific countries including Indonesia and Ausralia.  Since 1976, the magnitude of this phenomenon has been observed to increase in scale, leading many to attribute El Niño to greenhouse warming.  Models indicate that El Niño may eventually become a more severe and persistent event, triggering record floods and blistering droughts year-round.  

The Shrinking of the Sahara Desert (Not yet tipped)

While the notion of the Sahara Desert transforming into a fertile, green territory does have its appeal, scientists warn that such a development – which could be a consequence of Global Warming- could dramatically alter world weather patterns. Transported thousands of miles by wind currents, the mineral-rich sand from Africa’s Sahara Desert is an important fertilizer of phytoplankton in the Atlantic as well as trees located in the Amazon rainforest.  Deprived of the Saharan sand, the phytoplankton and trees would be less efficient at soaking up carbon dioxide from the atmosphere. In addition, a portion of the sand that is swept up from the desert serves to reflect the sun’s rays and in effect, shields the Earth from the effects of Global Warming.  This airborne sand also works to curb the formation of hurricanes over the Atlantic. Strangely, a Sahara with less sand and more vegetation may in fact catalyze Climate Change, setting off more intense hurricanes and fostering more carbon dioxide in the atmosphere. Recent investigations using satellite imagery show that the Sahara has become greener over the last few decades. In 2009, a National Geographic article explained that in parts of Egypt and Sudan, trees such as acacias are beginning to thrive.  The report also mentions that nomads in the region have reported unprecedented rainfall in recent years.    

The Collapse of the Atlantic Thermohaline Circulation (Not yet tipped)

The Atlantic Thermohaline Circulation (THC) is another significant oceanographic phenomenon threatened by Climate Change.  Also known as the “conveyor belt”, the THC involves the exchange of dense, cold water from the polar north and warmer water flowing up from the tropics.  It is this circuit that moderates air and water temperatures in Northwestern Europe.  Some scientific models tell us that a collapse of this current due to rising sea temps related to Global Warming is real possibility. A significant THC slowdown could bring more extreme winter weather to England and Scandinavia.   A study from 2005 noted an abrupt 30% decrease in the speed of a central component of the THC.

The Collapse of the West Antarctic Ice Sheet (Tipping)

Spanning nearly 14 million square kilometers, the Antarctic Ice Sheet holds more than 90% of the world's surface freshwater. Many experts consider the status of the West Antarctic Ice Sheet (WAIS), a segment of the ice cap which accounts for 10% for about its mass, as one of the foremost harbingers of Climate Change. Over the last half-century, the WAIS has experienced  an increase in temperature of 0.9 degrees Fahrenheit per decade- the biggest temperature increase on earth during that period. One key ice stream of the WAIS is known as the Pine Island Glacier.  Studies show the glacier at has melted at an accelerated rate over the last four decades.   In late 2011, researchers discovered that a 300 square mile chunk of the Pine Island Glacier is close to breaking off, raising more concern over the stability of the thinning ice sheet. A study published in January 2012 in the journal Nature Geoscience stated that even if all CO2 emissions were to come to a halt by 2100 and the planet's temperatures were to stabilize, regions such as Antarctica would continue to be affected for thousands of years by the circulation of warmer water currents. Another analysis by researchers at the University of Maryland published in 2011 determined that a rise in sea levels by just one tenth of a meter would result in over $2 billion dollars in damage to property and directly affect 68,000 in Washington D.C alone.

The Melting of Greenland’s Ice Sheet (Tipping)

The Greenland ice sheet accounts for 6% of all freshwater on the planet's surface.  If it were to melt entirely- which many scientists see as a real possibility-sea levels worldwide would rise by 23 feet, wreaking havoc on coastal populations around the globe.  As the effects of Global Warming have accelerated, so too has the melting of the ice sheet; one study observed that between 1996-2005, the rate of its disintegration doubled. It is thought that it would take a minimum of 60,000 years for the ice sheet to redevelop if it dissolves completely. A recent study utilizing satellite imagery to chart the loss of global ice mass shed light on the scale how Global Warming affects the planet's ice.  Undertaken by researchers at the University of Colorado-Boulder, the study found that approximately 4.3 trillion tons, or 1000 cubic miles of ice mass was lost between 2003 and 2010. Roughly 75% of this loss could be attributed to the Greenland Ice Sheet and Antarctica. This tipping point is highly interconnected with the Atlantic Thermohaline Circulation, as the water from this dwindling mass of ice could likely weaken the THC.

The Death of the Amazon Rainforest (Tipping)

Covering more than a billion acres with its lush, tropical vegetation, the Amazon rainforest plays a key role in regulating carbon dioxide levels by absorbing about one fifth of all the CO2 produced from the burning of fossil fuels. The compound effects of deforestation and Global Warming pose a major threat to the viability of the rainforest. As temperatures rise, the Amazon could morph into a vastly different landscape defined by much drier, savanna-like climes. Not only would the Amazon no longer absorb CO2, but the dead, rotting trees would release prodigious quantities of carbon into the air and contribute to more environmental upheavals.  The past decade has witnessed some of the driest years on record for the rainforest and one major drought that gripped the Amazon in 2005 resulted in the forest releasing more CO2 into the Earth’s atmosphere than it absorbed.

Deforestation stands out as the other major factor in this tipping point scenario. Models tell us that 20% deforestation could send the Amazon on an irreversible path to destruction. In 2011, the Brazilian Ministry of Science and Technology estimated that more than 18% of the rainforest has already succumbed to deforestation.  Even if humanity were to cease cutting down vast swaths of Amazon, the effects of Climate Change are likely to significantly transform the Amazon within this century.

The Disintegration of the Ozone Layer (Tipping)

In the 1980s, the widespread use of chlorofluorocarbons (CFCs) was identified as a major culprit in the depletion of the ozone layer. But more than twenty years after the phase-out of CFC’s began in many countries, humanity faces the formidable task of minimizing ozone layer damage to prevent potential calamity.  A depleted ozone layer is leading to an uptick in patterns associated with Global Warming.  As the layer thins, more ultraviolet radiation from the sun’s rays hit Earth’s surface.  Aside from raising temperatures worldwide, the increase in UV radiation damages or kills off the vitally important phytoplankton which act as CO2 storehouses.   
In 1985, researchers identified the massive Antarctic ozone hole as the layer’s most significant vulnerability. Thinning of the hole has been measured to be as much as 65% in some places yet the recent discovery of an even more significant hole in the ozone layer late last year, this time above the Arctic Circle, has raised more concerns.  Scientists found an 80% reduction of the ozone in an area located above the North Pole. They attribute the loss to a colder-than-usual winter which promoted ozone damage by chlorine-based chemicals in the stratosphere.  
Today, it is estimated that the ozone layer is diminishing at about 3% per decade. Researchers with NASA and the NOAA have projected that it will take until 2018 for the protective layer to just begin to repair itself.  


The Decline of Glaciers on the Tibetan Plateau (Tipping)

Covering 1 million square miles across western China, the Tibetan Plateau is a considerable factor in the world’s climate patterns. Blanketed by glaciers and snow, the plateau’s icy surface reflects the sun’s rays back toward space.  This phenomenon has worked to mitigate the effects of Global Warming, but as planetary temperatures continue to rise, the Tibetan plateau may accelerate Climate Change. As more of the plateau’s ice recedes, the exposed dark soil readily soaks up the sunlight and warms the Earth’s surface.  Experts warn that this process is picking up momentum. One study from 2010 revealed that the Tibetan Plateau is warming three times the global average.  Another analysis noted that from 2003-2010, the plateau lost an average of 4 billion tons of ice annually. This process will also present huge challenges to populations that depend on glacial runoff to to cultivate crops.  

The Diminishing of Ocean Salinity (Tipping)

Research indicates that Global Warming may result in significant changes to the salinity content of Earth’s oceans.  Such a phenomenon is predicted to have extensive ramifications on ocean currents and marine life.  As higher global temperatures translate to greater rainfall across the world, more freshwater is being dumped into oceans in a process that dilutes salinity.  Also adding to this dilution is freshwater runoff from melting glaciers.  Reductions in water salinity can interfere with “salinity valves”, or chemically-unique pockets of sea water which serve to buffer two disparate marine ecosystems. One such valve is the Strait of Gibraltar which separates the Atlantic Ocean and Mediterranean Sea. A sudden change in the salinity could overwhelm the delicate balance between different bodies of water and potentially devastate marine life that have adapted to a particular salinity content. Furthermore, fluctuations in salinity have the potential to disrupt major water currents such the Atlantic Thermohaline Circulation.  A 2010 study undertaken by scientists at Australia’s Commonwealth Scientific and Industrial Research Organisation assessing the oceans’ salinity showed ample evidence that Climate Change has triggered obvious shifts in the salinity of not only surface water, but deep sea water as well. These findings suggest that Global Warming has triggered profound shifts in the planet’s oceans that will become more clearly manifest in the years to come.



______________________
Sources used in this article:
http://brazilportal.wordpress.com/2011/01/27/the-amazon-at-the-tipping-point/
http://voices.yahoo.com/humans-push-earth-tipping-point-small-changes-could-880963.html?cat=7
http://www.jpl.nasa.gov/m/news/index.cfm?release=2012-036
http://insideclimatenews.org/news/20110712/climate-tipping-points-Atlantic-circulation-catastrophic-warming
http://www.enn.com/climate/article/38712
http://www.guardian.co.uk/education/2004/oct/14/research.highereducation
http://motherjones.com/environment/2006/11/thirteenth-tipping-point
http://insideclimatenews.org/news/20110712/climate-tipping-points-Atlantic-circulation-catastrophic-warming?page=2
http://researchpages.net/ESMG/people/tim-lenton/tipping-points/
http://www.csmonitor.com/Environment/2011/1104/Huge-chunk-of-Antarctic-ice-sheet-set-to-break-free
http://www.huffingtonpost.com/al-gore/al-gore-antarctica_b_1245165.html
http://www.agu.org/pubs/crossref/2008/2008GL033365.shtml
http://nsidc.org/news/press/20080325_Wilkins.html
http://www.obt.inpe.br/prodes/
http://www.npr.org/templates/story/story.php?storyId=101422948
http://news.nationalgeographic.com/news/2009/07/090731-green-sahara.html
http://www.bbc.co.uk/news/science-environment-15105747
http://www.igsd.org/documents/TibetanPlateauGlaciersNote_10August2010.pdf
http://summitcountyvoice.com/2010/04/16/global-warming-driving-ocean-salinity-changes/