Solar radiation management[1] (SRM) projects are a largely theoretical type of geoengineering which seek to reflect sunlight and thus reduce global warming.[2] Proposed examples include the creation of stratospheric sulfur aerosols. They would not reduce greenhouse gas concentrations in the atmosphere, and thus do not address problems such as ocean acidification caused by these gases. Their principal advantages as an approach to geoengineering is the speed with which they can be deployed and become fully active, as well as their low financial cost. By comparison, other geoengineering techniques based on greenhouse gas remediation, such as ocean iron fertilization, need to sequester the anthropogenic carbon excess before they can arrest global warming. ugg boots uk sale Solar radiation management projects can therefore be used as a geoengineering 'quick fix' while levels of greenhouse gases can be brought under control by greenhouse gas remediation techniques.
A study by Lenton and Vaughan suggest that marine cloud brightening and stratospheric sulfur aerosols are each capable of reversing the warming effect of a doubling of the level of CO2 in the atmosphere (when compared to preindustrial ugg boots sale levels).[3]The phenomenon of global dimming is widely known, and is not necessarily a geoengineering technique. It occurs in normal conditions, due to aerosols caused by pollution, or caused naturally as a result of volcanoes and major forest fires. ugg boots uk However, its deliberate manipulation is a tool of the geoengineer. The majority of recent global dimming has been in the troposphere, except that resulting from volcanos, which affect mainly the stratosphere.
By intentionally changing the Earth's albedo, or reflectivity, scientists propose that we could reflect more heat back out into space, or intercept sunlight before it reaches ugg uk sale the Earth through a literal shade built in space. A 0.5% albedo increase would roughly halve the effect of CO2 doubling.[4]
These geoengineering projects have been proposed in uggs bailey button order to reduce global warming. The effect of rising greenhouse gas concentrations in the atmosphere on global climate is a warming effect on the planet. By modifying the albedo (whiteness) of the Earth's surface, or by preventing sunlight reaching the Earth by using a solar shade, this warming effect can be cancelled out although the cancellation is imperfect, with regional discrepancies remaining.[5]
The applicability of many techniques listed here has not been comprehensively tested. Even if the effects in computer simulation models or of smallscale interventions are known, there may be ugg boots cheap cumulative problems such as ozone depletion, which only become apparent from large scale experiments.[6]
Various smallscale experiments have been carried out on techniques such as cloud seeding, increasing the volume of stratospheric sulfur aerosols and implementing bailey button uggs uk cool roof technology.
As early as 1974, Russian expert Mikhail Budyko suggested that if global warming became a problem, we could cool down the planet by burning sulfur in the stratosphere, cheap ugg boots which would create a haze. Paul Crutzen suggests that this would cost 25 to 50 billion dollars per year. It would, however, increase the environmental problem of acid rain.[7][8][9] However, this is now believed to be a minor side effect.[10]
A preliminary study by Edward Teller and others in 1997 presented the pros and cons of various relatively "lowtech" proposals to mitigate global warming through scattering/reflecting sunlight away from the Earth via insertion of various materials in the upper stratosphere, low earth orbit, and L1 locations.[11]As well as the imperfect cancellation of the effect of greenhouse gases ugg sale uk on global warming, there are other significant problems with solar radiation management as a form of geoengineering not least of these are effects on the global hydrological cycle[12] and the inability of such techniques to reduce ocean acidification.
Particular to solar radiation management, a risk of abrupt cessation exists. If SRM were to abruptly stop, the climate would rapidly warm.[13] uggs uk This would cause a sudden rise in global temperatures towards levels which would have existed without the use of the geoengineering technique. This would typically be achieved using hydrogen sulfide or sulfur dioxide, delivered using artillery, aircraft (such as the highflying F15C) or balloons.[8][15][16][17] [18] (Alternative approaches using photophoretic particles have been proposed.[19]) Ozone depletion is a risk of such techniques,[20] but only if high enough quantities of aerosols drift to, or are deposited in, polar stratospheric clouds before the levels of CFCs and other ozone destroying gases fall naturally to safe levels because CFCs can settle on larger sulfate particles, increasing their ozone destroying potential.[21] This proposal, not unlike the others, carries with it considerable risks, including increased drought[22] or acid rain.[23]
Broadly speaking, this technique is seen as a credible geoengineering scheme, although not one without major risks, and challenges for its implementation. This technique can give >3.7W/m2 of globally averaged negative forcing,[3] which ugg uk is sufficient to entirely offset the warming caused by a doubling of CO2.
Sulfate is the most commonly proposed aerosol for geoengineering, since there is a good natural analogue with volcanic eruptions. Explosive eruptions inject large amounts of sulfur dioxide gas into the stratosphere, which form sulfate aerosol. Studies of the Earth's climate have shown that such aerosol can achieve significant cooling. Sulfate aerosols have been shown to enhance ozone depletion. However, other aerosol types may be more efficient at cooling the climate or less damaging to the ozone layer. ugg boots sale uk Such aerosols include the highly reflective titanium dioxide.
United States Patent 5003186 suggested that tiny metal flakes could be "added to the fuel of jet airliners, so that the particles would be emitted from the jet engine exhaust ugg boots bailey button while the airliner was at its cruising altitude." Alternative proposals, not known to have been published in peerreviewed journals, include the addition of silicon compounds to jet fuel to make silicon dioxide particles in the exhaust.[24]
A uggs for cheap more sophisticated approach, using multilayered nanoparticles (consisting of aluminum and barium titanate), was published by David Keith in 2010. He suggests utilizing the effects of photophoresis to increase the amount of time the aerosols stay airborne.[25]
Working with Pat Mooney, David Keith has also ugg sale developed an experiment involving the release of sunreflecting sulphate from a balloon more bailey button ugg boots uk than 80,000 feet above Fort Sumner in New Mexico to replicate the cooling effects of volcanoes.[26]
Alleged secret experiments with aircraft exhaust modification are one version of the cheap uggs Chemtrail conspiracy theory.[27]
In 1992, a report by the US National Academy of Sciences (NAS)[28] on geoengineering noted that dust is a better choice compared to sulphur, because dust is from natural soil and so should have no noticeable effect on the bailey button uggs ground as it gradually falls into the troposphere and rains out. It estimated that about 1010 kg dust would be required to mitigate the warming from a doubling of atmospheric CO2 or about 1 kg dust per 100 t of carbon emissions.
An example of the effects of the imposition of aerosol particles in the
atmosphere can be found in history. Comets have been blamed for the dramatic but
brief cooling period which commenced in 1159 BCE, and resulted in widespread
disruption to civilisations at the time.[30] However, this mechanism, and even
www.cheapestbootsuksale.co.uk
the involvement of a comet, is
not universally accepted. If a comet was indeed to blame, the action of its
aerosols could also have been by the mechanism of cloud condensation nuclei.
Other examples bailey button ugg
boots
of climate change events linked to comets include the famines around
536 CE.[31]
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