Airlines are reported to be losing £130m a day due to the ash cloud but the effects of climate change will cost a lot more. Photograph: Christian Hartmann/Reuters

As the silence in our skies enters its second week, what will be the effects on our climate? Will the world warm up faster because of the gases spewed from Iceland’s Eyjafjallajokull volcano, or will the drop in emissions from aircraft slow the warming? And are these questions even relevant, or do the really important ones run deeper?

Greenhouse gas emissions from volcanoes equal less than 1% of those generated by human activities; slightly less than half of the emissions from aviation. There is even some evidence that volcanoes have a cooling effect on the planet, because their ash blocks out some of the sun’s rays.

Sea surface temperature from March this year. Illustration: MODIS/Aqua/NASA

Experts need to beef up ways to measure the heat content of oceans as a way to track more reliably the course of global warming, scientists say today.

Kevin Trenberth and John Fasullo, climate scientists at the National Centre for Atmospheric Research in Boulder, Colorado, say that only about half of the heat believed to have built up in the Earth in recent years can be accounted for. New instruments are needed to locate and monitor this missing heat, they say, which could be storing up trouble for the future.