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1. Which benefit of trees has not been mentioned by the speaker?
1) Protection from flooding.
2) Protection from the sun’s rays.
3) Protection from precipitation.
2. The smell of pines in the forest is the result of trees releasing
2) carbon dioxide.
3) other gasses.
3. Scientists want to study how
1) gasses are released by trees into the atmosphere.
2) organic compounds form tiny particles.
3) these particles influence the climate.
4. Cloud droplets are unable to
1) absorb solar radiation.
2) reflect solar radiation.
3) scatter solar radiation.
5. According to scientists, cloud droplets influence
1) the size of the cloud.
2) the colour of the cloud.
3) the movement of the cloud.
6. The actual formation of the clouds is governed
1) only by the formation of cloud droplets.
2) primarily by the formation of cloud droplets.
3) by several different processes.
7. A new way of addressing the problem of global warming is by reducing the amount of
1) greenhouse gasses in the atmosphere.
2) the sun’s radiation getting through the atmosphere.
3) the sun’s radiation reflected by the clouds.
1 – 2
2 – 3
3 – 3
4 – 1
5 – 2
6 – 3
7 – 2
The benefits of planting trees, from improving air quality to providing a habitat for wildlife, are well known. Wind speed and direction can be affected by trees. The more compact the foliage on the tree or group of trees, the greater the influence of the windbreak. The downward fall of rain, sleet, and hail is initially absorbed or deflected by trees, which provides some protection for people, pets, and buildings. Trees intercept water, store some of it, and reduce storm runoff and the possibility of flooding. Now there’s another, much more amazing effect. We’ve found that small particles released by tree leaves can also cause clouds to form.
During its life, the tree 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. What we’re interested in is 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 volatile organic compounds.
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 that scientists are still trying to get a clear idea about, but we know that it happens. So it’s the impact on the climate of these particles that we’re especially interested in.
Well, we know that they have two main effects. Firstly, while they’re present in the atmosphere they are able to interact with incoming solar radiation, the energy from the sun essentially, and block its path so that it doesn’t make it to the earth’s surface, and scatters it. Additionally, and what we’re most interested in here, is the role that these particles play in brightening the clouds that are above the forests. They do this because when they’re in the atmosphere they grow and get to a certain size where they’re able to form cloud droplets. The more of these droplets there are in a cloud, the whiter and brighter it becomes. That means that it will reflect away more of the incoming solar radiation.
So if you’ve got a lot of trees in a forest and they’re producing these volatile organic compounds which produce particles, you’re likely to see the brighter and whiter clouds above them. There’s a number of other processes that govern the actual formation of the clouds but what we’re interested in is just how significant the impact of these particular particles is on the clouds, how much of that effect we can credit to the original compounds that are released by the trees essentially.
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 which means that more of it is 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 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. The more carbon dioxide and other greenhouse gases we have in the atmosphere, the less of this radiation is allowed to escape. So the main way that we’re trying to address this is by reducing greenhouse gasses in the atmosphere, allowing more of the radiation to escape. Something else that we can do is to try and reflect away more of the sun’s radiation so that less of it gets in, in the first place. That’s another way we can address this energy imbalance.
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.