Josh
My source is figure 2b of Jones Hayward Boucher Kravtitz and Robock of
June 2010 in Atmospheric Chemistry and Physics They reckon 5 million
tonnes year will do a general world-wide coolling of 1.1 watt/m2 but
will work the wrong way over the Arctic giving a warming of 4 to10
watts/m2 above the methane releasing areas where last year there was a
step up by a factor of 20. I was caeful to say 10 watts not 10 C but
other speakers had been talking in temperature which are already scary
enough. Jon Egil Kristjansson at Oslo has some confirming results. Can
anyone predict the effects of a spike of methane lasting two years? I
will put figure 2b in my next email incase your spam filters disapprove
of it.
The reason for intense Arctic warming might be that in the summer
stratospheric aerosol scatters energy from solar rays that might just
have missed the earth and half the scattering is downwards. At the
summer solstice there is more solar energy hitting the North pole than
the equator.
In winter there could be about 200 watts per square metre of longwave
radiation trying to get out from the Arctic to deep space. Aerosol at
any height cannot tell up from down and will reflect some back like a
blanket. Low level cloud brightening would have exactly the same
blanketing effect but the shorter life means that we have a much better
chance of not getting any salt residues that far north. Intercepting
heat going from the tropics to the poles can be done anywhere along the
route. Cloud brightening anywhere away from the Arctic will cool it.
Short life and local control is a very attractive feature. Patchy and
quick good, promiscuous and slow bad.
The cloud brightening community would greatly appreciate some
distinction between our own low-level highly controlled activities and
higher level, uncontrolled more acidic ones.
See if there is anything in your spam tray.
Stephen
Josh Horton wrote:
"The idea of putting dust particles into the stratosphere to reflect
sunlight, mimicking the cooling effect of volcanic eruptions, would in fact
be disastrous for the Arctic, said Prof Salter, with models showing it
would increase temperatures at the pole by perhaps 10C."
That's a pretty strong statement--what's the evidence for this?
Josh Horton
On Saturday, March 17, 2012 6:25:22 AM UTC-4, Andrew Lockley wrote:
http://www.bbc.co.uk/news/science-environment-17400804
Climate 'tech fixes' urged for Arctic methane
By Richard Black Environment correspondent, BBC News
An eminent UK engineer is suggesting building cloud-whitening towers in
the Faroe Islands as a "technical fix" for warming across the Arctic.
Scientists told UK MPs this week that the possibility of a major methane
release triggered by melting Arctic ice constitutes a "planetary emergency".
The Arctic could be sea-ice free each September within a few years.
Wave energy pioneer Stephen Salter has shown that pumping seawater sprays
into the atmosphere could cool the planet.
The Edinburgh University academic has previously suggested whitening
clouds using specially-built ships.
At a meeting in Westminster organised by the Arctic Methane Emergency
Group (Ameg), Prof Salter told MPs that the situation in the Arctic was so
serious that ships might take too long.
"I don't think there's time to do ships for the Arctic now," he said.
"We'd need a bit of land, in clean air and the right distance north...
where you can cool water flowing into the Arctic."
Favoured locations would be the Faroes and islands in the Bering Strait,
he said.
Towers would be constructed, simplified versions of what has been planned
for ships.
In summer, seawater would be pumped up to the top using some kind of
renewable energy, and out through the nozzles that are now being developed
at Edinburgh University, which achieve incredibly fine droplet size.
In an idea first proposed by US physicist John Latham, the fine droplets
of seawater provide nuclei around which water vapour can condense.
This makes the average droplet size in the clouds smaller, meaning they
appear whiter and reflect more of the Sun's incoming energy back into
space, cooling the Earth.
On melting ice
The area of Arctic Ocean covered by ice each summer has declined
significantly over the last few decades as air and sea temperatures have
risen.
For each of the last four years, the September minimum has seen about
two-thirds of the average cover for the years 1979-2000, which is used a
baseline. The extent covered at other times of the year has also been
shrinking.
What more concerns some scientists is the falling volume of ice.
Analysis from the University of Washington, in Seattle, using ice
thickness data from submarines and satellites, suggests that Septembers
could be ice-free within just a few years.
Data for September suggests the Arctic Ocean could be free of sea ice in a
few years
"In 2007, the water [off northern Siberia] warmed up to about 5C (41F) in
summer, and this extends down to the sea bed, melting the offshore
permafrost," said Peter Wadhams, professor of ocean physics at Cambridge
University.
Among the issues this raises is whether the ice-free conditions will
quicken release of methane currently trapped in the sea bed, especially in
the shallow waters along the northern coast of Siberia, Canada and Alaska.
Methane is a much more potent greenhouse gas than carbon dioxide, though
it does not last as long in the atmosphere.
Several teams of scientists trying to measure how much methane is actually
being released have reported seeing vast bubbles coming up through the
water - although analysing how much this matters is complicated by the
absence of similar measurements from previous decades.
Nevertheless, Prof Wadhams told MPs, the release could be expected to get
stronger over time.
"With 'business-as-usual' greenhouse gas emissions, we might have warming
of 9-10C in the Arctic.
"That will cement in place the ice-free nature of the Arctic Ocean - it
will release methane from offshore, and a lot of the methane on land as
well."
This would - in turn - exacerbate warming, across the Arctic and the rest
of the world.
Abrupt methane releases from frozen regions may have played a major role
in two events, 55 and 251 million years ago, that extinguished much of the
life then on Earth.
Meteorologist Lord (Julian) Hunt, who chaired the meeting of the All Party
Parliamentary Group on Climate Change, clarified that an abrupt methane
release from the current warming was not inevitable, describing that as "an
issue for scientific debate".
But he also said that some in the scientific community had been reluctant
to discuss the possibility.
"There is quite a lot of suppression and non-discussion of issues that are
difficult, and one of those is in fact methane," he said, recalling a
reluctance on the part of at least one senior scientists involved in the
Arctic Climate Impact Assessment to discuss the impact that a methane
release might have.
Reluctant solutions
The field of implementing technical climate fixes, or geo-engineering, is
full of controversy, and even those involved in researching the issue see
it as a last-ditch option, a lot less desirable than constraining
greenhouse gas emissions.
"Everybody working in geo-engineering hopes it won't be needed - but we
fear it will be," said Prof Salter.
Adding to the controversy is that some of the techniques proposed could do
more harm than good.
The idea of putting dust particles into the stratosphere to reflect
sunlight, mimicking the cooling effect of volcanic eruptions, would in fact
be disastrous for the Arctic, said Prof Salter, with models showing it
would increase temperatures at the pole by perhaps 10C.
And last year, the cloud-whitening idea was also criticised by scientists
who calculated that using the wrong droplet size could lead to warming -
though Prof Salter says this can be eliminated through experimentation.
He has not so far embarked on a full costing of the land-based towers, but
suggests Ł200,000 as a ballpark figure.
Depending on the size and location, Prof Salter said that in the order of
100 towers would be needed to counteract Arctic warming.
However, no funding is currently on the table for cloud-whitening. A
proposal to build a prototype ship for about Ł20m found no takers, and
currently development work is limited to the lab.
--
The University of Edinburgh is a charitable body, registered in
Scotland, with registration number SC005336.
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