快猫短视频

BACK in 2050, the planet was not doing so badly. The ozone layer was healing
fast after the last rogue CFC factories in Asia had been shut down. And global
warming had been moderated by planting a global network of 鈥渟ink鈥� forests to
soak up carbon dioxide. The world population crisis had failed to materialise as
Asians adopted Western family planning habits.

True, Asians had also adopted Western car-driving habits and smogs were
spreading steadily across the northern hemisphere in the warm greenhouse air.
But that had been predicted for so long that nobody paid much attention.

The watchword was wealth. On Indian highways, buffaloes had given way to
sports utility vehicles. Indeed, with a third generation of the Bush family
occupying the White House鈥攁fter the 16-year hegemony of George W. and his
brother Jeb鈥� by 2050 the whole world was beginning to look and feel like
Texas.

And then it hit. The environmental Armageddon nobody had expected. As Bob
Zimmerman, the meteorologist who raised the alarm, remarked: 鈥淭he little
molecules that have cleaned pollution out of the atmosphere since before there
was pollution鈥攖he planetary janitors with mop and detergent鈥攏ever
showed up for work.鈥�

The story came first from Oregon, where for decades Zimmerman and his
colleagues had been sniffing the Pacific air looking for new compounds infecting
the atmosphere. But this time it was what didn鈥檛 show up that worried them. The
hydroxyl radicals, highly reactive molecules which oxidise most common
pollutants, had gone missing.

At first it was hard to spot. Individual hydroxyl molecules, each made from
just a hydrogen and an oxygen atom, don鈥檛 hang around for more than about a
second and there wasn鈥檛 much hydroxyl to start with. It has only ever existed in
the atmosphere at levels of less than one part per trillion鈥攖hat鈥檚 less
than a thimbleful in a volume of air the size of the Great Pyramid of
Cheops.

But as every season passed, the air crossing the Pacific to Oregon contained
less and less hydroxyl and more and more pollution. 鈥淲ithout the hydroxyl, there
is nothing in the air to clean up the effluent from the factories and vehicle
exhaust pipes of Asia,鈥� said Zimmerman. Hydroxyl is the atmosphere鈥檚 detergent.
It oxidises pollutants, making them soluble in water so that they wash away in
the rain. And it was disappearing. Right across the northern hemisphere smogs
were worsening by the month. Human civilisation was being engulfed in its
undigested pollution.

Before 2050, few people outside a small band of atmospheric chemists had even
heard of hydroxyl. But suddenly the obscure molecule was on everyone鈥檚 lips. At
first, the new President Bush had a little trouble getting his tongue around the
word. 鈥淗ydra鈥� hydractyl鈥�hydraulic鈥�?鈥� he had stuttered. But as the smogs
festered, he asked the big question: 鈥淲here the hell has this hydroxee stuff got
to anyway?鈥�

The scientists didn鈥檛 have an immediate answer. They were panicking because,
like the discovery of the ozone hole back in the 1980s, none of them had
predicted what became known as the 鈥渉ydroxyl holocaust鈥�.

There had been a few fears about hydroxyl back in the 1980s, when Joel Levine
of NASA鈥檚 Langley Research Center in Hampton, Virginia, had spotted what looked
like a 25 per cent decline in atmospheric levels between 1950 and 1985. But
nobody took much notice, since measuring the stuff was so difficult. It hardly
featured in the plethora of atmospheric chemistry studies that were carried out
around the turn of the century. True, researchers had predicted that air
pollution would become more and more prevalent. In 2001, the UN鈥檚
Intergovernmental Panel on Climate Change had warned that methane emissions
could soar by 50 per cent in half a century, and that the concentration of smog
chemicals, such as carbon monoxide, nitrogen oxides and ozone, could double or
triple. As it turns out, they were right on target.

They had also forecast a 20 per cent decline in hydroxyl levels by the year
2100, because of the heavy demands being made on the atmosphere鈥檚 limited supply
of oxidising chemicals by the mounting tide of pollution. The IPCC report even
briefly considered 鈥渢he possibility that future emissions might overwhelm the
oxidative capacity of the troposphere鈥�. But that was just one sentence in a
thousand-page report. Few people read it.

In any case, the feared decline didn鈥檛 materialise then. If anything,
hydroxyl levels seemed to be going up at the end of the 20th century, flushing
away pollutants in double-quick time. Hydroxyl radicals are mostly consumed by
methane, carbon dioxide and nitrogen oxides鈥攚hich are themselves destroyed
in the encounter. Thanks to that extra whiff of hydroxyl, methane鈥檚 typical
lifetime in the air went down from 12 years to 10. And the concentration of the
main pollutant that gobbles up hydroxyl鈥攃arbon monoxide鈥攆ell by more
than a fifth in the US between the late 1980s and mid-1990s. 快猫短视频s briefly
marvelled at this 鈥渂reath of fresh air鈥�, without ever properly explaining it. By
2050, of course, their successors were angry at this missed opportunity to
understand hydroxyl chemistry.

Then, Internet archivists turned up a 1993 paper from Sasha Madronich at the
US government鈥檚 National Center for Atmospheric Research in Boulder, Colorado.
Madronich had warned that hydroxyl chemistry carried the seeds for runaway
reactions that could cause levels to collapse. If the atmosphere was forced to
absorb ever more pollutants, he argued, it would lose hydroxyl. That would in
turn reduce the rate at which the pollutants were cleaned out of the air,
causing ever more pollution to build up. His modelling studies showed that
鈥渂eyond certain threshold values, hydroxyl can decrease catastrophically鈥�.
Investigation of this positive feedback should be 鈥渁 major issue in tropospheric
chemistry鈥�, he declared.

Some hope. 快猫短视频 magazine published a whimsical doomsday
scenario based around the hydroxyl holocaust in a supplement in April 2001.
Madronich had told the magazine that 鈥渦nder high pollution, the chemistry of the
atmosphere becomes chaotic and extremely unpredictable.鈥� There was growing
evidence, he said, that many urban areas were already sufficiently polluted for
hydroxyl levels to be locally suppressed. And he gave a stark warning: 鈥淚f, in
future, large parts of the atmosphere are as polluted as cities like Athens and
Mexico City today, then we could anticipate the collapse of hydroxyl on a global
蝉肠补濒别.鈥�

One reason scientists had ignored hydroxyl was that it was so very confusing.
In 1999, Paul Crutzen of the Max Planck Institute for Chemistry in Mainz,
Germany, reported that over the oceans, nitrogen oxide emitted from ships
actually increased the production of hydroxyl. Along major shipping routes,
hydroxyl concentrations were five times as high as the background level. What
received less attention was that this effect only worked in otherwise clean air.
In more polluted areas, nitrogen oxides used up hydroxyl at a prodigious
rate.

What did most to keep hydroxyl鈥檚 profile low, however, was the apparent
harmlessness of CO鈥攖he pollutant that consumed half of all the hydroxyl in
the atmosphere. Emitted mostly from forest fires and fossil fuels, CO had for
many years been the Cinderella pollutant. Its presence in the atmosphere did not
seem troublesome, even though concentrations had tripled between 1800 and 2000
and carried on rising. It wasn鈥檛 very long-lived. It didn鈥檛 cause acid rain or
global warming. It simply didn鈥檛 show up on any major environmental agenda.

Until, that is, the catastrophic hydroxyl collapse of the 2050s. Suddenly the
world was like a washing-up bowl piled high with greasy dishes, when the
detergent runs out and the grease stays congealed on the plates.

Through the 2050s, the smogs got rapidly worse. Japan was choking in sulphur
dioxide fumes from China that resolutely refused to convert into acid rain.
South Pacific islands periodically disappeared beneath palls of smog from the
Philippines. Asthma became the number one killer of the under-30s worldwide. The
wheat fields of Siberia鈥攚hose emergence was one of the more beneficial
results of global warming鈥攚ilted and died, triggering famine across
Russia. Accumulating DDT, which was still in use to fight the growing plagues of
malarial mosquitoes, caused a massive die-off of whales in the Atlantic and
Arctic.

The newly formed World Environment Organization flirted briefly with
manufacturing hydroxyl using lasers, an idea first proposed by Japanese company
Ebara in the 1990s. But even though it worked in the lab, it looked as though it
wouldn鈥檛 do a lot for the wider atmosphere. So in 2058, President Bush IV
accepted the advice of scientists that nitrogen oxides would be the easiest
pollutant to reduce. With American car makers finally ready to mass produce
fuel-cell vehicles, Bush launched a massive effort to cut emissions of nitrogen
oxides from vehicles. He threatened economic isolation鈥攁nd worse鈥攆or
any nation that didn鈥檛 follow suit.

It didn鈥檛 work too well. Bush鈥檚 advisers should have read Madronich鈥檚 1993
paper more carefully. It had warned that, once past the threshold when hydroxyl
levels crash, reducing nitrogen oxide emissions wouldn鈥檛 bring back the
hydroxyl. It wasn鈥檛 enough to go back to the point just below the threshold.
Only something much more drastic would rescue the atmosphere.

In 2060, it looked as if the end was nigh. The huge expanses of carbon-sink
forests planted across the tropics began to die. Foresters had seen nothing like
it since the trees of central Europe succumbed to the sulphurous fumes of
Soviet-built factories in the 1980s. But this time the pollution was travelling
thousands of kilometres and killing hundreds of times more trees. It was coming
from everywhere, and there was nothing to wash it out of the atmosphere locally.
Pollute in any one place and the whole planet now felt the effect.

The dying, rotting forests were releasing huge amounts of greenhouse gases
into the air, accelerating global warming. Then, after an El Ni帽o
drought, the tinder began to burn. All across the tropics in 2062, millions of
people fled their homes and headed for the West, closely followed by the smog
from their burning forests. As gunboats turned back the refugees鈥� boats, world
war loomed.

Then scientists made the most unexpected discovery of all. Most had by now
accepted that Madronich鈥檚 law of runaway hydroxyl loss explained the
atmosphere鈥檚 crisis. But some suspected another factor. They asked: what had
changed most dramatically in the atmosphere in the 2040s? What finally triggered
the hydroxyl meltdown?

False hope

The answer eventually came from a chance display of graphs of environmental
trends in a popular science magazine. A reader wrote to point out that the
timing of hydroxyl decline coincided almost exactly with the recovery of the
ozone layer鈥攁s the last remaining long-lived CFCs finally disappeared. The
penny dropped. It looked as though this successful environmental repair job had
in fact triggered the hydroxyl holocaust.

It was all down to ultraviolet radiation. As almost every late-20th century
schoolchild could have explained, the ozone layer shields the Earth from
ultraviolet radiation. But we also need some UV to fuel the reactions that
create hydroxyl. One of the unnoticed benefits of the thinning ozone layer was
to let in more UV to create more hydroxyl and counter the pollution. This, as a
few scientists pointed out at the time, might have explained the apparent
revival of planetary cleansing processes in the 1990s鈥攖he so-called
鈥渂reath of fresh air鈥�.

But the downside was that once the ozone layer recovered in the 2040s, UV
radiation fell back and hydroxyl production in the atmosphere crashed. The
breath of fresh air had gone. Reduced production of hydroxyl meant the
atmosphere had ever greater difficulty in cleansing itself. Madronich鈥檚 runaway
collapse of hydroxyl and runaway rise in pollution had begun.

And that鈥攆or those of you who have never been outside the city domes
that increasingly house us in the 2070s鈥攊s the truth of what happened to
the Earth鈥檚 natural atmosphere.

I need not remind you of the decade of wars and disease that brought a
billion or so of us here, to the safety of the great air-conditioned domes that
make our environment habitable. Nor remind you that billions more live outside
in the fetid public air, where life expectancy is 30 years at best, where they
have to eat food grown on land exposed to a constant fallout of chemicals that
the atmosphere can no longer neutralise.

In time, the fleets of aircraft that have been spraying the stratosphere with
CFCs will destroy the ozone layer, let through more UV radiation and increase
atmospheric production of hydroxyl. In time, our technological efforts here on
Earth will reduce pollution to the pre-industrial levels that scientists tell us
will be necessary for this most precious molecule to continue doing its work. In
time, clad in sunscreen, we will be able to venture back out into the air.