Skip to content
Apr 20 / Jonathan

Global warming disaster scenarios

Deep Antarctic waters freshening
April 18, 2008
Sydney Daily Telegraph

Scientists studying the icy depths of the sea around Antarctica have detected changes in salinity that could have profound effects on the world’s climate and ocean currents. . . Voyage leader Steve Rintoul said his team found that salty, dense water that sinks near the edge of Antarctica to the bottom of the ocean about 5 km down was becoming fresher and more buoyant. So-called Antarctic bottom water helps power the great ocean conveyor belt, a system of currents spanning the Southern, Pacific, Indian and Atlantic Oceans that shifts heat around the globe.

“The main reason we’re paying attention to this is because it is one of the switches in the climate system and we need to know if we are about to flip that switch or not,” said Rintoul of Australia’s government-backed research arm the CSIRO. “If that freshening trend continues for long enough, eventually the water near Antarctica would be too light, too buoyant to sink and that limb of the global-scale circulation would shut down,” he said on Friday.

Cold, salty water also sinks to the depths in the far north Atlantic Ocean near Greenland and, together with the vast amount of water that sinks off Antarctica, this drives the ocean conveyor belt. This system brings warm water into the far north Atlantic, making Europe warmer than it would otherwise be, and also drives the large flow of upper ocean water from the tropical Pacific to the Indian Ocean through the Indonesia Archipelago. If these currents were to slow or stop, the world’s climate would eventually be thrown into chaos.

“We don’t see any evidence yet that the amount of bottom water that’s sinking has declined. But by becoming fresher and less dense it’s moving in the direction of an ultimate shutdown.”

What is the proper response to these disaster scenarios? As even the Bush administration begins to concede that global warming is not only real but anthropogenic, the next debate becomes one over potential consequences and justified responses.

To the extent that these disaster scenarios are plausible, adaptationist responses are not. And “plausible” clearly need not mean “provable”; we have a strong motivation to prevent a low-probability outcome if that outcome is sufficiently bad. Adaptationism assumes a gradual and continous process: slow warming, slow ocean rise, etc. But the prospect of a chaotic catastrophe requires prevention, not adaptation.

Via Sam Smith

3 Comments

leave a comment
  1. Mick / Apr 20 2008

    The Argo probes looked at the oceand and they didn’t find anything dramatic happening.

  2. Jonathan / Apr 20 2008

    I’m not a domain expert here by any means, and my point is a more general one (how do we respond to plausible chaotic catastrophes, or tipping points).

    But as I read this piece, if the scenario plays out, by the time the Argo probes notice it, it will be too late.

  3. Mark / Apr 24 2008

    “To the extent that these disaster scenarios are plausible, adaptationist responses are not. And “plausible” clearly need not mean “provable”; we have a strong motivation to prevent a low-probability outcome if that outcome is sufficiently bad.” That’s a good argument for accelerating “star wars”-type missile defense development, not to mention the following:

    “This is where SOHO comes in. The sunspot number follows a cycle of somewhat variable length, averaging 11 years. The most recent minimum was in March last year. The new cycle, No.24, was supposed to start soon after that, with a gradual build-up in sunspot numbers.

    It didn’t happen. The first sunspot appeared in January this year and lasted only two days. A tiny spot appeared last Monday but vanished within 24 hours. Another little spot appeared this Monday. Pray that there will be many more, and soon.

    The reason this matters is that there is a close correlation between variations in the sunspot cycle and Earth’s climate. The previous time a cycle was delayed like this was in the Dalton Minimum, an especially cold period that lasted several decades from 1790.

    Northern winters became ferocious: in particular, the rout of Napoleon’s Grand Army during the retreat from Moscow in 1812 was at least partly due to the lack of sunspots.

    That the rapid temperature decline in 2007 coincided with the failure of cycle No.24 to begin on schedule is not proof of a causal connection but it is cause for concern.

    It is time to put aside the global warming dogma, at least to begin contingency planning about what to do if we are moving into another little ice age, similar to the one that lasted from 1100 to 1850.

    There is no doubt that the next little ice age would be much worse than the previous one and much more harmful than anything warming may do. There are many more people now and we have become dependent on a few temperate agricultural areas, especially in the US and Canada. Global warming would increase agricultural output, but global cooling will decrease it.

    Millions will starve if we do nothing to prepare for it (such as planning changes in agriculture to compensate), and millions more will die from cold-related diseases.

    There is also another possibility, remote but much more serious. The Greenland and Antarctic ice cores and other evidence show that for the past several million years, severe glaciation has almost always afflicted our planet.

    The bleak truth is that, under normal conditions, most of North America and Europe are buried under about 1.5km of ice. This bitterly frigid climate is interrupted occasionally by brief warm interglacials, typically lasting less than 10,000 years.

    The interglacial we have enjoyed throughout recorded human history, called the Holocene, began 11,000 years ago, so the ice is overdue. We also know that glaciation can occur quickly: the required decline in global temperature is about 12C and it can happen in 20 years.

    The next descent into an ice age is inevitable but may not happen for another 1000 years. On the other hand, it must be noted that the cooling in 2007 was even faster than in typical glacial transitions. If it continued for 20 years, the temperature would be 14C cooler in 2027.

    By then, most of the advanced nations would have ceased to exist, vanishing under the ice, and the rest of the world would be faced with a catastrophe beyond imagining.

    Australia may escape total annihilation but would surely be overrun by millions of refugees. Once the glaciation starts, it will last 1000 centuries, an incomprehensible stretch of time.

    If the ice age is coming, there is a small chance that we could prevent or at least delay the transition, if we are prepared to take action soon enough and on a large enough scale.”

Leave a Comment