I thought it would be possible to get students to think about the difference between infra red light and heat by making a lens of water ice and using it as a burning glass. However, I wondered whether this would work if you made a lens of dry ice? I know that carbon dioxide absorbs strongly in the infra-red, so it would be a good way of demonstrating the link between carbon dioxide and global warming (although I guess nearly impossible to do in practice). All the dry ice I have been able to obtain for school is always pearly white.

Obviously there are other experiments I can do to demonstrate this using gaseous carbon dioxide.

Assuming no other action, how many Earth Hours do we need every year in order to avoid dangerous climate change?

One suggestion to combat climate change is that we should become vegetarians as livestock is more environmentally damaging than growing crops.

However, if we stopped eating meat, livestock would still live, so is the suggestion correct? Or are we expected to cull any remaining pigs and cows?

Ella Gribben, London, UK

I look after a pendulum clock at the University of Cambridge which I hope will achieve an accuracy of less than 1 second of error per year (www.trin.cam.ac.uk/clock). It has a temperature-compensated pendulum, but is sensitive to air pressure variation.

If the mean global temperature was to rise by, say, 4 °C, would there be any change to mean air pressure at sea level? Put simply, would global warming cause the clock to speed up or slow down?

Hugh Hunt, Keeper of the Clock, Trinity College, University of Cambridge, UK

For a biology experiment i'm planning on finding out the affect of climate change on algae or marine plants. I'm unsure how heat will affect these two types of organisms.

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A lot of the ideas put forward to stop global warming involve reflecting the suns light back out of the atmosphere. How much difference would it make to global warming if everyone painted their roof white?

During the last 100 years, humans have been burning oil, natural gas, peat and coal. In the next 50 years we will burn even more. Burning hydrocarbons produces carbon dioxide and water. How much has this water added to sea-level rise?

Alfred Jacobsen, The Netherlands