Complex decisions are best left to your unconscious mind to work out, according to a new study, and over-thinking a problem could lead to expensive mistakes.

The research suggests the conscious mind should be trusted only with simple decisions, such as selecting a brand of oven glove. Sleeping on a big decision, such as buying a car or house, is more likely to produce a result people remain happy with than consciously weighing up the pros and cons of the problem, the researchers say.

Thinking hard about a complex decision that rests on multiple factors appears to bamboozle the conscious mind so that people only consider a subset of information, which they weight inappropriately, resulting in an unsatisfactory choice. In contrast, the unconscious mind appears able to ponder over all the information and produce a decision that most people remain satisfied with

A satellite study of the Greenland ice cap shows that it is melting far faster than scientists had feared - twice as much ice is going into the sea as it was five years ago. The implications for rising sea levels - and climate change - could be dramatic.

Yet, a few weeks ago, when I - a Nasa climate scientist - tried to talk to the media about these issues following a lecture I had given calling for prompt reductions in the emission of greenhouse gases, the Nasa public affairs team - staffed by political appointees from the Bush administration - tried to stop me doing so. I was not happy with that, and I ignored the restrictions. The first line of Nasa's mission is to understand and protect the planet.

This new satellite data is a remarkable advance. We are seeing for the first time the detailed behaviour of the ice streams that are draining the Greenland ice sheet. They show that Greenland seems to be losing at least 200 cubic kilometres of ice a year. It is different from even two years ago, when people still said the ice sheet was in balance.