Hi Here's a talk show which discusses trees manipulating cloud albedo. There could be a bit of 'gaia' going on here, with scattered light better for photosynthesis. The MT aerosols were very apparent at Banff workshop, where the whole valley was bluish-hazed.
http://planetearth.nerc.ac.uk/multimedia/story.aspx?id=979 Transcript below A RH:David Tupman with his audio diary from research ship, the James Clark Ross. I've asked David to send us some pictures and as soon as we have them, we'll put them up on our Facebook page. To find our website and join the debate on Facebook search for Planet Earth Online. Back on solid ground now and the benefits of planting trees, from improving air quality to providing a habit to wildlife are well known. But there's also a hidden benefit. Small particles produced by trees in a forest can affect local cloud cover producing whiter brighter clouds. Katherine Scott from the University of Leeds Institute of Climate and Atmospheric Science is studying this phenomena. Sue Nelson went to meet Katherine to find out more. CS:During the life of a tree it will take in a certain amount of carbon from the atmosphere in the form of carbon dioxide. It does that as part of photosynthesis when it also releases oxygen back into the atmosphere. But what we're interested in looking at are other gasses that trees release into the atmosphere. So if you're walking through a forest you can smell a kind of piny odour and that's because of these other compounds, volatile organic compounds. And they're things like isoprene, monoterpenes. SN:What in particular are you interested in about them? CS:These compounds are incredibly important because when they're released into the atmosphere they undergo reactions with a class of compounds called oxidants and that's things like ozone. Following those reactions they're able to form tiny particles in the atmosphere via a number of different mechanisms and that scientists are still trying to get a clear idea about, but we know that that happens. So it's the impact on the climate of these particles that we're really interested in looking at. SN:So what role do these particles play then? CS:Well, we know that they have two main effects. Firstly, while they're present in the atmosphere they can kind of interact with incoming solar radiation - the energy from the sun essentially and kind of perturb its path so that it doesn't make it to the earth's surface and scatters it. But additionally and what we're most interested in looking at here are the role that these particles play in brightening the clouds that are above the forests. And they do this because when they're in the atmosphere they grow and they get to a certain size where they're able to form cloud droplets. And the more of these droplets that there are in a cloud the whiter and brighter that it becomes. And that means that it will reflect away more of the incoming solar radiation that's falling on that particular part of the earth's surface. SN:That's amazing. So if you've got an area where you've got a lot of trees in a forest and they're producing these volatile organic compounds which produces particles, you're likely to see then brighter whiter clouds above them. It's they're sort of producing their own clouds then are they or brighter whiter fluffier clouds? CS:Essentially, yes. There's a number of other processes that govern the actual formation of the clouds but what we're interested in looking at is just how significant the impact of these particular particles are on the clouds, how much of that effect we can credit to the original compounds that are released by the trees essentially. SN:What would a brighter whiter cloud then do for a forest? Because normally nature has a way of, you know, what's in it for them, sort of thing. There's normally a beneficial effect for the forest perhaps, but maybe not necessarily on all climate, or is it beneficial to both the climate and the forest? CS:Well, we think that these particles are beneficial to the forest because of the way they scatter the radiation as it comes in. It's scattered into different directions - it means that more of it's available for the leaves of the trees to use and that's something that we think is really quite important. As for the climate, the problem that we've got at the moment with climate change is that there's an imbalance really in between the amount of solar energy that's coming into the earth's system and the amount of energy that's allowed to escape from the earth's system through the atmosphere. And the more carbon dioxide and other greenhouse gases that we have in the atmosphere the less of this radiation that's allowed to escape. So the main way that we're trying to address this is by reducing greenhouse gases in the atmosphere, allowing more of the radiation to escape. But something else that we can do is try and reflect away more of the sun's radiation so that less of it gets in in the first place. And that's another way we can address this energy imbalance. SN:Because a white cloud will reflect more solar radiation. CS:Yes. Essentially. So what we're trying to do is quantify this effect using computer simulations so that we can understand exactly the impact that forests are having on the earth's system at the moment. SN:Katherine Scott from the University of Leeds chatting to Sue Nelson about the impact of forests on clouds and climate. And that's the Planet Earth Podcast from Planet Earth Online. Do follow us on Facebook. I'm Richard Hollingham from the Norfolk Coast where I'm getting sandblasted by the beach in this wind. Thanks for listening. Bye. -- You received this message because you are subscribed to the Google Groups "geoengineering" group. To post to this group, send email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/geoengineering?hl=en.
