message in a bottle

Here's how you can show your sceptical friends that CO2 contributes to global warming - without even leaving your kitchen.

(This experiment comes courtesy of Dr Maggie Aderin-Pocock, left, space scientist, who demonstrated this on Newsnight last week.)

All you need are two plastic water bottles, two lamps, two thermometers, bicarbonate of soda, vinegar and tissues.

First pour a little vinegar on some bicarbonate of soda. This produces carbon dioxide. Dab the tissue in the mix and put that tissue in one of the bottles. Now one bottle contains atmospheric air and the other bottle contains atmospheric air with a greater concentration of CO2.

Then switch on the lamps facing each bottle (these act as sunlight) to warm up the jars. Leave for a few minutes and then read the temperatures inside each bottle.

The result: the bottle with the greater concentration of CO2 has a considerably higher temperature reading than the other one.