A new study of earthshine, the sunlight reflected back onto the Moon from our planet, suggests that falling cloud cover could explain the warming of the Earth’s lower atmosphere seen over the last 20 years.

The decline suggests fewer clouds, which reflect sunlight, and therefore that more sunlight has been making it into the lower atmosphere (troposphere).

The idea presents a controversial alternative to most scientists’ prime suspect for the warming — rising levels of greenhouse gases.

However, the results are preliminary and inclusive.