2007 - possibly the tipping year for Arctic meltdown that "stunned experts"; what of 2008?

What were you doing in the summer of 2007? In mid-July, I was speaking at the AR2007 conference in Los Angeles (www.ARConference.org), and I even participated in a plenary on global warming and human population. Then, I spent the next 4 months driving through 30 states working intensely on the deer hunting, bowhunting, urban deer culling and deer immunocontraception issues, as well as forming the Global Wildlife Alliance with member groups in about as many states. But due to my laser-like concentration on the deer and hunting issues, something of enormous global importance slipped right beneath my radar, even though there were newspaper articles and newscasts galore on the subject, and perhaps it did yours too.

I'm talking about the massively record-breaking melting of the Arctic sea ice as well as the Greenland ice sheet.

Now, it is February 2008, and what happened in the summer of 2007 is history. But it is not over, because the summer of 2008 may take it yet to a new height, and no scientist in the world, except those still incredibly in denial, would dare to dismiss the possibility, or even lower its probability.

I have since amassed hundreds of articles on the subject, about 150 of which I present below for your interest. The best way I would suggest that you approach this vast amount of reading is to not to read them, at least not to begin with, but to just read their titles from beginning (1995) to end (2008). There is nothing sacred about 1995; it just happens to be the year of the first article I've included in this list. There is nothing particularly sacred about now either; it just happens to be the time of this writing. There were many relevant articles before 1995 and surely there will be amazing occurrences in the articles to come, especially those publishing in the summer of 2008.

You will notice that the tone of the titles of the earlier articles are more or less tentative, but as time rolled on, from year to year, it became more and more tangible, then definite, then seriously concerned, then surprised, then amazed, then unnerved, then shocked, then stunned, then horrified� Also, you will notice that the estimate of the remaining life-span of the Arctic ice cap and the Greenland icesheet was shortened from -50% by 2040 to a complete meltdown by 2013 the closer the estimators approached the summer of 2007.

Of course, for every alarm sounded, there would be the skeptics who would call the alarm sounder an "alarmist". I have included one such debunking article dated January 28, 2007. Obviously what happened in the summer of 2007 totally exonerated the "alarmist" and demolished the debunker. Still, even after the great plunge of 2007, the skeptics and cynics are again mouthing that it was nothing but an "anomaly", and that the ice was reforming. Well, one of the reasons is called "winter". And the summer of 2008 will likely silence them again.

A general consensus amongst the articles was that the 2007 Arctic meltdown exceeded expectations by three fold. Indeed, the titles below contain phases as "stunned experts" and "shocked scientists". And what was expected was already quite dire.

This is a direct revelation from nature not to be slighted, much less ignored. The same computer models that underestimated the 2007 Arctic ice melting rate are the same models that estimated only 2-4 degree increases in the global temperature by 2100, and a moderate 30% extinction rate. These same models also underestimated the role in global warming of the greenhouse gas called methane.

Methane as a greenhouse gas (GHG) is 20 times more potent than carbon dioxide. The Arctic permafrost contains an immense quantity of methane stored in the solid form of methane clathrate. If the permafrost is melted, the atmospheric GHG would increase by 50%. The current atmospheric GHG concentration is 370 ppm. Scientists say that the maximum should be capped at 400 ppm to prevent "tipping" the system into a runaway greenhouse effect. A 50% GHG concentration rise means 550ppm, deep in the danger zone if not past the point of no return. And we haven't even considered the methane stored in clathrate form on and under the continental shelves around the world.

If methane is release as free gas into the atmosphere, it will raise the global temperature even higher, which will melt even more permafrost which will release more methane� a positive feedback loop that could push the global temperature spirally out of control. And this is only one of several positive feedback loops.

Another is the albedo feedback loop, where less ice reflects less solar heat, causing more heat absorption, temperature increases and ice melting.

In the context of global warming, there is such a thing as "tipping points". And nine "tipping elements" have been identified in which tipping points exist. I believe that no matter what field and discipline we specialize in, we should all know something about global warming, because it involves all life on Earth and for all time. The 9 tipping elements and their possible timeframes are:

1. Melting of Arctic sea-ice (approx 10+ years, small uncertainty). As sea-ice melts, it exposes a much darker ocean surface, which absorbs more radiation than white sea-ice so that the warming is amplified. This causes more rapid melting in summer and decreases ice formation in winter. Over the last 16 years ice cover during summer declined markedly. The critical threshold global mean warming may be between 0.5 to 2 degrees Celsius, but could already have been passed. One model shows a nonlinear transition to a potential new stable state with no arctic sea-ice during summer within a few decades.

2. Decay of the Greenland ice sheet (more than 300 years, small uncertainty). Warming over the ice sheet accelerates ice loss from outlet glaciers and lowers ice altitude at the periphery, which further increases surface temperature and ablation. The exact tipping point for disintegration of the ice sheet is unknown, since current models cannot capture the observed dynamic deglaciation processes accurately. But in a worst case scenario local warming of more than three degrees Celsius could cause the ice sheet to disappear within 300 years. This would result in a rise of sea level of up to seven meters.

3. Collapse of the West Antarctic ice sheet (more than 300 years, large uncertainty). Recent gravity measurements suggest that the ice sheet is losing mass. Since most of the ice sheet is grounded below sea level the intrusion of ocean water could destabilize it. The tipping point could be reached with a local warming of five to eight degrees Celsius in summer. A worst case scenario shows the ice sheet could collapse within 300 years, possibly raising sea level by as much as five meters.

4. Collapse of the Atlantic thermohaline circulation (approx 100 years, intermediate uncertainty). The circulation of sea currents in the Atlantic Ocean is driven by seawater that flows to the North Atlantic , cools and sinks at high latitudes. If the inflow of freshwater increases, e.g. from rivers or melting glaciers, or the seawater is warmed, its density would decrease. A global mean warming of three to five degrees Celsius could push the element past the tipping point so that deep water formation stops. Under these conditions the North Atlantic current would be disrupted, sea level in the North Atlantic region would rise and the tropical rain belt would be shifted.

5. Increase in the El Ni�o Southern Oscillation (approx 100 years, large uncertainty). The variability of this ocean-atmosphere mode is controlled by the layering of water of different temperatures in the Pacific Ocean and the temperature gradient across the equator. During the globally three degrees Celsius warmer early Pliocene ENSO may have been suppressed in favor of persistent El Ni�o or La Ni�a conditions. In response to a warmer stabilized climate, the most realistic models simulate increased El Ni�o amplitude with no clear change in frequency.

6. Collapse of the Indian summer monsoon (approx 1+ year, large uncertainty). The monsoon circulation is driven by a land-to-ocean pressure gradient. Greenhouse warming tends to strengthen the monsoon since warmer air can carry more water. Air pollution and land-use that increases the reflection of sunlight tend to weaken it. The Indian summer monsoon could become erratic and in the worst case start to chaotically change between an active and a weak phase within a few years.

7. Greening of the Sahara/Sahel and disruption of the West African monsoon (approx 10 years, large uncertainty). The amount of rainfall is closely related to vegetation climate feedback and sea surface temperatures of the Atlantic Ocean . Greenhouse gas forcing is expected to increase Sahel rainfall. But a global mean warming of three to five degrees Celsius could cause a collapse of the West African monsoon. This could lead either to drying of the Sahel or to wetting due to increased inflow from the West. A third scenario shows a possible doubling of anomalously dry years by the end of the century.

8. Dieback of the Amazon rainforest (approx 50 years, large uncertainty). Global warming and deforestation will probably reduce rainfall in the region by up to 30 percent. Lengthening of the dry season, and increases in summer temperatures would make it difficult for the forest to re-establish. Models project dieback of the Amazon rainforest to occur under three to four degrees Celsius global warming within fifty years. Even land-use change alone could potentially bring forest cover to a critical threshold.

9. Dieback of the Boreal Forest (approx 50 years, large uncertainty). The northern forests exhibit a complex interplay between tree physiology, permafrost and fire. A global mean warming of three to five degrees Celsius could lead to large-scale dieback of the boreal forests within 50 years. Under climate change the trees would be exposed to increasing water stress and peak summer heat and would be more vulnerable to diseases. Temperate tree species will remain excluded due to frost damage in still very cold winters.

Bear in mind that all of these estimate are uncertain, and some if not all could be gross underestimates. I refer to the time frame as well as the severity. No matter when it comes, a 6 degree global temperature rise is the tipping point of survivability of most life on Earth, and will doom the present-day Earth to the 6th mass extinction (already well in progress). The 3rd mass extinction, the End-Permian 251 million years ago, wiped out 75% of all land species and 95% of all marine species. The agent was indeed global warming.

This is not to say that the world is doomed. It is to say that if we carry on the way we have, which has channeled us into the current predicament to begin with, we would doom all life on Earth, the Earth itself, and us ourselves.

Arctic sea-ice and the Greenland ice sheet are regarded as the most sensitive tipping elements with the smallest uncertainty.