Dry cold  

Posted by Big Gav in ,

The Economist has a look at developments in the atmosphere, noting "a drying out of the stratosphere may help explain recent temperature trends at the Earth’s surface" - Dry cold.

THE stratosphere—specifically, the lower stratosphere—has, it seems, been drying out. Water vapour is a greenhouse gas, and the cooling effect on the Earth’s climate due to this desiccation may account for a fair bit of the slowdown in the rise of global temperatures seen over the past ten years. These are the somewhat surprising conclusions of a paper by Susan Solomon of America’s National Oceanic and Atmospheric Administration and her colleagues, which was published online by Science on January 28th. Whether the trend will continue, stop or reverse itself, though, is at present unknown.

The stratosphere sits on top of the troposphere, the lowest, densest layer of the atmosphere. The boundary between the two, the tropopause, is about 18km above your head, if you are in the tropics, and a few kilometres lower if you are at higher latitudes (or up a mountain). The tropopause separates a rowdy below from a sedate above. In the troposphere, the air at higher altitudes is in general cooler than the air below it, an unstable situation in which warm and often moist air below is endlessly buoying up into cooler air above. The resultant commotion creates clouds, storms and much of the rest of the world’s weather. In the stratosphere, the air gets warmer at higher altitudes, which provides stability.

The stratosphere—which extends up to about 55km, where the mesosphere begins—is made even less weather-prone by the absence of water vapour, and thus of the clouds and precipitation to which it leads. This is because the top of the troposphere is normally very cold, causing ascending water vapour to freeze into ice crystals that drift and fall, rather than continuing up into the stratosphere.

A little water manages to get past this cold trap. But as Dr Solomon and her colleagues note, satellite measurements show that rather less has been doing so over the past ten years than was the case previously. Plugging the changes in water vapour into a climate model that looks at the way different substances absorb and emit infrared radiation, they conclude that between 2000 and 2009 a drop in stratospheric water vapour of less than one part per million slowed the rate of warming at the Earth’s surface by about 25%.

Such a small change in stratospheric water vapour can have such a large effect precisely because the stratosphere is already dry. It is the relative change in the amount of a greenhouse gas, not its absolute level, which determines how much warming it can produce, and this change was about 10% of the total.

By comparison with the greenhouse effect caused by increases in carbon dioxide, the stratospheric drying is hardly massive. Dr Solomon and her colleagues peg the 2000-2009 cooling effect at about a third of the opposite effect they would expect from the carbon dioxide added over the same decade, and only a bit more than a twentieth of the warming expected from the rise in carbon dioxide since the industrial revolution. But it is surprising, nonetheless.

The Economist also has a riff on Bruce Sterling's "Involuntary Parks" concept - Conflict conservation: Biodiversity down the barrel of a gun. Somewhat unsettlingly they are also echoing some of his recent comments about environmental problems and depopulation.
THERE was a time when conservation meant keeping people away from nature. America’s system of national parks, a model for similar set-ups around the world, was based on the idea of limiting human presence to passing visits, rather than permanent habitation.

In recent years this way of doing things has come under suspicion. To fence off large areas of parkland is often impractical and can also be immoral—in that it leads to local people being booted out. These days, the consensus among conservationists is to try to manage nature with humans in situ. But there are still “involuntary parks”, to borrow a phrase from the writer and futurist Bruce Sterling, that serve to illustrate just how spectacularly well nature can do when humans are removed from the equation.

Some such “parks” are accidents of settlement, or its absence. Nature is preserved in those rare places that people just have not got round to overrunning—for example the Foja Mountains in western New Guinea, an area of rainforest that teems with an astonishingly rich variety of plants and animals. Others are accidents of conflict: places from which people have fled and where the fauna and flora have thrived as a result.

The demilitarised zone (DMZ) between North and South Korea is a good example. Over the past six decades this narrow and dangerous strip of land running 248km (155 miles) across the Korean peninsula has become a de facto nature reserve. As agriculture and industrialisation have moved ahead elsewhere, the thousand-square-kilometre DMZ, uninhabited and heavily mined, has been a refuge for two endangered birds: the white-naped and the red-crowned crane. It also contains Asiatic black bears, egrets and, according to some, an extremely rare subspecies of the Siberian tiger. The biggest threat to all this biodiversity is probably peace. There are already calls for the DMZ to be turned into a park in the event of reunification. ...

A little to the west of the Chagos, the Scotsman recently reported, the sea off Kenya’s northern coast currently has a profusion of fish because Somali pirates are keeping out all the big foreign fishing boats. Since the collapse of Somalia’s government in 1991, this part of the world has reportedly been plagued by illegal fishing. Now, goes the story, such boats are too afraid to enter the area because of the pirates.

The illegal dumping in the region of barrels of radioactive waste from European hospitals and factories, which has also been reported, has probably been similarly deterred, if it was taking place. This, though, is unlikely to bother the fish either way. Perhaps the most famous of the Earth’s involuntary parks is the evacuated area around Chernobyl, in Ukraine, where the burgeoning wildlife has been little affected by the risks of radiation.

Military conflict and the preparations that surround it are not, in themselves, good for the environment: far from it. Animals big enough to be eaten, or with body parts that can be sold for a profit, are well advised to stay out of war zones. It is depopulation that matters. Armed conflict and its knock-on effects simply happen to be one of the few forces on the planet that can cause quick and thorough depopulation. These areas struggle to survive when peace arrives. The nasty truth is that the likelihood of random and violent death is the cheapest form of conservation yet invented.


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