[katieHaylor (OP)]

Michael asks -

If the shrinking of the icecaps is contributing to global warming due to reduced reflection of lift of the ice, could we counteract the effect by painting most of the roofs in the world white?

What do you think?

[alancalverd]

Less than you might think, sadly. Only about 5 - 7 % of the UK surface is artificial - roads and roofs. Very few other large countries exceed this (Singapore, Vatican City etc are tiny) and a good many artificial surfaces are already white. You might affect local microclimates but the ice caps are way bigger than all human habitaition put together. 

[Bored chemist]

More than you might think- a white (or better, silver) painted roof would keep a building cool in Summer and warm in Winter.
The reduction in air conditioning and heating energy might be worthwhile.