Cold Cold Christmas?

Scientists have discovered evidence that climate change is killing polar bears. The bears inhabit the edges of polar ice, where it is thinnest, hunting seals when they break holes in the ice to breath. As the ice retreats north in the Artic summer, between June and October, they are forced to travel between ice floes in order to continue hunting in the food-rich shallow waters of the continental waters off the Alaskan coast. Last summer, as an apparent consequence of global warming, the ice caps receded about 200 miles further north than the average of twenty years ago, requiring the bears to undertake much longer and more arduous journies between floes.

The US Minerals Management Service (MMS) report that in a quarter-century of aerial studies of the Alaskan coastline prior to 2004 they typically spotted a lone polar bear swimming in the ocean far from ice only once every two-years. Polar bear drownings were so rare they have never been documented in surveys. In September 2004, however, when the ice had retreated a record 160 miles north of the northern coast of Alaska, researchers counted 10 polar bears (20% of those spotted) swimming as far as 60 miles offshore

Steve Amstrup, a wildlife biologist with the US Geological Survey (USGS) explains why this is a problem:

We know short swims up to 15 miles are no problem, and we know that one or two may have swum up to 100 miles. But that is the extent of their ability, and if they are trying to make such a long swim and they encounter rough seas they could get into trouble.

This seems to have been what happened to many of the bears spotted in September 2004. According to the Sunday Times:

The researchers returned to the vicinity a few days later after a fierce storm and found four dead bears floating in the water. “We estimate that of the order of 40 bears may have been swimming and that many of those probably drowned as a result of rough seas caused by high winds,” said the report.

This may not be a unique event. A study by the USGS in conjunction with the Canadian Wildlife Service (CWS) which is due to be published next year examined polar bear populations in Hudson Bay, Canada, the site of the most southerlu polar bears, concluded that the population fell by 22% from 1,194 in 1987 to 935 last year.

Paradoxically, while climate change may be turning up the heat on polar bears it may have quite the opposite effect on those of us in blighty. The UK is on the same latitude as Labrador on Canada's east coast. We are warmed, however, by the Gulf Stream which forms part of the North Atlantic thermohaline circulation. This is a system of ocean currents which functions kind of like a giant conveyor belt, carrying warm water from the tropics. The Times explains:

The Gulf Stream begins in the Gulf of Mexico and carries warm water north and east, through the straits of Florida and across the North Atlantic. Halfway across the ocean, it branches into two, with one current flowing south towards Africa and another drifting towards northern Europe.

By the time the northern current reaches the Arctic, its waters have become colder and more saline, causing them to sink. A vast undersea river of cold water then flows back towards the Gulf of Mexico, where the process begins again.

This is obviously a good thing. I don't mind the cold half as much as some people, but even I might find permafrost hardgoing. Those of you uninterested in my discomfort might care to consider the fact that 25,000 elderly people die from cold-related illnesses every winter, that's 8 an hour. Imagine how much worse that would be if winter temperatures routinely dropped to -25C. It seems to me therefore, that screwing with the Gulf Stream probably isn't a very good idea, which is unfortunate because that's exactly what we seem to be doing.

Scientists have predicted for sometime that melting ice caps could disrupt these currents as the melting ice increases the amount of freshwater and reduces the salinity of the Arctic waters, stopping it from sinking. A study by the National Oceanography Centre (NOC) based in Southampton suggests that this may already be happening as the Times explains:

To assess whether this is already happening, the Southampton team measured current flow across a latitude of 25 degrees north. The original Gulf Stream, cold water returning from the Arctic, and the southern branch of warm water all cross this line stretching from north Africa to the Bahamas. Measurements taken in 2004 were compared with data collected in 1957, 1981, 1992 and 1998.

The results, published today in the journal Nature, show that while the outward flow of the Gulf Stream has not changed, the strength of the cold water returning from the Arctic has fallen by 30 per cent since 1992.

Over the same period, the flow of warm water branching off the Gulf Stream towards Africa has increased by 30 per cent. This suggests that the current’s warm waters are being diverted to the south and away from Europe, with potentially serious consequences for the continent’s climate.

The report, of course, is couched in the requisite scientific caveats and there is no question that we can't be sure this isn't a transient phenomenon. A project to monitor Atlantic currents continuously over the next four years is currently underway to determine if the 1992 and 2004 readings are merely aberrations or indicative of a real change. Nevertheless, it's clear that this is something we ought to be concerned about.

Similarly, the kind of temperature drops we can expect to see is a point of some debate. We're unlikely (to put it lightly) to see a drop comparable to that depicted in disaster film The Day After Tomorrow (which I've never bothered to watch, but have heard much about), but Meric Srokosz of the Natural Environment Research Council, which funded the NOC study suggests a fairly minor drop of 1C over a decade or two if the decline in currents remains persistent, although a total shutdown would entail a drop of 4-6C and a German study suggests a 50% shutdown would lead to a 2c drop. Others point to the possibility of harsher drops, Rahul Mahajan notes, "During the Younger Dryas, a period roughly 12-11,000 years ago, the NATC was disrupted, lowering average summer temperatures in New England by 5-7 degrees in a few decades."

As depressing as all this sounds, Rahul suggests that there may actually be good reason to view the decline of the Gulf Stream not just as a problem, but also as an opportunity:

This terrible threat also, paradoxically, gives reason for hope. So far, the victims of global warming (it’s estimated that hundreds of thousands die every year from it) have been primarily the poor from the Global South, who don’t count in the calculations of the globally powerful. The worst projections of short and medium-term future effects were also confined to the Global South.

This rapid climate change scenario changes all of that – we now know there is a good chance of major effects in the eastern United States and northwestern Europe, which just happen to be the seats of global power and influence. So far, although the Pentagon recognized rapid climate change as a potential national security threat, it has not really gotten attention outside of scientific circles; now, it can be used to lend a greater urgency to the whole debate on global warming.

[snip]

The next 20 years are the crucial period and, outside of the United States, everybody seems to know it. We have a genuine, though slight, chance to eliminate or mitigate some of the numerous catastrophes that lie in wait for us. All the political conditions are ripe for a real movement against climate change. We will have to take on not just rampant energy inefficiency and use of fossil fuels, but, sooner or later, the cult of growth itself. In doing so, we will have to take on some of the fundamental tenets of capitalism. It won’t be easy, but it is, for the first time, eminently possible.

I hope he's right. For my sake as much as the bears'.