So, what does that mean in a practical sense? Scientists presently estimate that we can pour about 565 additional gigatons (Gtons) of carbon dioxide into the atmosphere by mid-century and still have some reasonable hope of staying below an increase of two degrees. As Bill McKibben writes in Rolling Stone, "'Reasonable,' in this case, means four chances in five, or somewhat worse odds than playing Russian roulette with a six-shooter."
That's a pretty gloomy prediction but what if Dr. Birol is only half right? Let's say the increase over the next fifty years is only three degrees Celsius. At the Copenhagen summit, a spokesman for small island nations warned that many would not survive a two-degree rise: "Some countries will flat-out disappear." Kerry Emanuel of MIT, a leading authority on hurricanes, believes "Any number much above one degree involves a gamble, and the odds become less and less favorable as the temperature goes up." Thomas Lovejoy, once the World Bank's chief biodiversity adviser, contributed this assessment, "If we're seeing what we're seeing today at 0.8 degrees Celsius (the amount we've already warmed over the base year), two degrees is simply too much." NASA scientist James Hansen, the planet's most prominent climatologist, was even blunter: "The target that has been talked about in international negotiations for two degrees of warming is actually a prescription for long-term disaster."
A spokesman representing a number of small island nations said that even a two degree C increase the world's mean temperature would threaten a great many small islands.
Islands that have already disappeared are:
Maldives, a smallisland nation in the Indian Ocean. The high point is only 8 feet. Other places in the island are much lower. It the ocean level rises further, this island will disappear.
Vanuatu Island, also called the Republic of Vanuatu is another island nation in the South Pacific which may be submerged due to rising ocean level.
Tuvalu Islands, located between Australia and Hawaii, is, at its highest point, only 15 feet above sea level. Home to nearly 11,000 people, they have already started evacuating due to the rising waterline. New Zealand has agreed to grant refuge to 75 Tuvaluans every year. It is estimated that this island will disappear in 50 years from now.
Kiribati Island, officially known as the Republic of Kiribati. It is located in the central tropical Pacific Ocean and also experiencing rising water levels.
Marshall Islands, formally called the Republic of Marshall Islands is in the middle of the Pacific Ocean. This island may become another victim of rising ocean levels.
Tonga Island, officially known as the Kingdom of Tonga, is located in the South Pacific Ocean. If ocean levels rise, this island is likely to be at least partially, if not totally, submerged.
The Tyndall report (Environment and Development Challenges: The Imperative to Act) also concludes that the present world's commitments to reduce emissions are consistent with at least a 3 degree C rise (50-50 chance) in temperature: a temperature not seen on the planet for around 3 million years, with serious risks of 5 degree C rise, a temperature not seen for around 30 million years.
Let's look at the potential impact of these numbers from a different angle. One thing we know for certain is that no life on earth is permanent. Some species, in fact some whole genera, become extinct from completely natural processes. Others are helped along by unnatural causes. There have been five major extinction events in the history of our planet but one is particularly pertinent here, the Permian-Triassic extinction. Occurring about 252 million years ago, the extinction at the Permian-Triassic boundary, the most deadly of the five major events, took place with increasing speed over a period of somewhere between 100,000 and 200,000 years. It wiped out over eighty percent of the genera on land, and over 95 percent of those in the oceans. It took ten million years for the planet to restore the level of biodiversity that existed prior to the Permian-Triassic extinction. While its cause and its course are still open to some debate, a widely accepted theory holds that it started with an increase in the earth's mean temperature of about four degrees C precipitated by an eruption of the Siberian Traps. I need to be clear here. I'm not predicting that we are all going to become extinct in the near future. My purpose is to give some perspective on the magnitude and power of the forces of nature with which we are tampering.
Here's another very graphic way of looking at how anthropogenic activities can effect a large land mass very quickly. The unexpectedly rapid melting of the Greenland ice cap provides a dramatic and sobering picture of the problem we face.
Other statistics are equally alarming. A third of summer sea ice in the Arctic is gone and the oceans are thirty percent more acidic. Since warm air holds more water vapor than cold, the atmosphere over the oceans is a shocking five percent wetter than normal, setting the stage for more frequent and stronger hurricanes and more devastating floods. Kerry Emanuel, a highly regarded atmospheric scientist, a hurricane expert, director of MIT's Atmospheres, Oceans and Climate program and a staunch conservative added, " . . . and the odds become less and less favorable as the temperature goes up. "
In June, just a week after the conclusion of the Rio de Janeiro conference, Arctic sea ice hit the lowest level ever observed in any June in recorded history, tropical storm Debbie poured over twenty inches of rain on Florida, the largest fire in New Mexico's history burned on and, in Colorado Springs, the most destructive fire in Colorado's history destroyed 346 homes, breaking a record set only the week before.