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Archive for May 2011

Atlantic_Shiptrack.jpgCombating the effects of man-made climate change is seen as one of the greatest challenges facing us in the 21st century. Most ideas focus upon stabilising and then reducing the amount of carbon dioxide and other greenhouse gases in our atmosphere. We could achieve this by decreasing the amount of oil, coal and natural gas that we use by replacing these fuel sources with alternatives. In addition, we could also simply change our behaviour to facilitate less fossil fuel use. However, the pace at which we can make these changes is a topic of great debate. Scientists are now actively considering whether we need to take a more drastic route, where we artificially control the Earth's climate using something called geoengineering. The aim of such an intervention would be to cool the Earth's climate, in order to offset some of the warming caused by human activity. However, such techniques are not without their own risks and are highly controversial!Join us in this episode to find out whether this idea is simply some science fiction writer's failed plot-line, or something that could actually be used in the future to mitigate our continued fossil fuel use. We'll discuss exactly what geoengineering is, why we might do it and the ethics surrounding it. We will also discuss a specific example, where natural clouds are modified so that they appear whiter, which potentially could cool the Earth.Here is a picture of glass beads of different sizes. As we explained in the podcast, smaller beads are made of equally transparent material but the scatter light more, meaning they appear whiter. The same thing happens when particles are added to a cloud - more cloud droplets form and the cloud appears whiter, reflecting more sunlight to space and cooling the Earth. This is what is happening of the picture at the top of this post. The particles emitted by ships are causing clouds to form, leaving a trail along the ship's track.glassBeads.jpgYou can find out more about this idea on the BBC website and at the Royal Society website, which includes information on other geoengineering schemes also.Below is a video discussion by two of the pioneers of the cloud whitening idea, John Latham and Stephen Salter.Here is a picture that (is meant to) demonstrate the "Kelvin Effect" that Niall and Prof McFiggans were talking about. This the effect that gases find it easier to condense on a less curved surface (bigger particle) than a more curved surface The left hand particle is small and a molecule at the surface has less other molecules next to it. This means there are less bonds (three from its nearest neighbours) holding it there. The right hand molecule is larger and a particle at the surface has more bonds (four from its nearest neighbours this time). The molecule is bound more tightly so it is less likely to leave the particle and enter the gas phase.kelvinEffect.jpgFeaturing: Niall Robinson, Jennifer Muller, Nicky Young and Grant AllenInterviewee: Prof. Gordon McFiggansProduction: Will Morgan

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