Could you get your parents to change their driving habits?... and perhaps their car! Why? Cars guzzle fuel, but they use much less if people drive them gently and keep below speed limits. Big SUVs make about six times their own weight in CO₂ each year. A small efficient diesel or hybrid car covering the same distance not only uses much less fuel, it makes less CO₂. For shorter journeys, electric cars are now becoming both cheaper and more popular. And so they should and will in the next few years — along with driverless cars which could be on the roads by 2020.

Apologies, parents, if you already do this!

That means accelerating slowly and driving so that you don't have to keep braking all the time. Most modern cars have instant read-outs of fuel consumption so you can see what a difference 'gentle' driving makes.

Diesel cars use around one third less fuel to travel the same distance as a car which uses gasoline. Less fuel means less carbon dioxide.

Hybrids are electric cars which also have a small engine which runs when the batteries get low on charge when you are on a longer journey. Like an electric car, you can plug a hybrid into the electric power grid and re-charge the batteries.

Electric cars are here and getting both better and cheaper all the time. If recharged from a renewable power source, their emissions are effectively zero.The main problem at present is that the batteries are expensive, heavy and take a long time to recharge. But there is a lot of work going on to develop better batteries – not just for cars but for all kinds of renewables so that energy can be stored efficiently.