This is the latest piece of evidence which at the very least puts the cosmic ray theory, developed by Danish scientist Henrik Svensmark at the Danish National Space Center (DNSC), under very heavy pressure.

The Svensmark hypothesis is that when the solar wind is weak, more cosmic rays penetrate to Earth.

That creates more charged particles in the atmosphere, which in turn induces more clouds to form, cooling the climate.

The planet warms up when the Sun's output is strong.

Professor Sloan's team investigated the link by looking for periods in time and for places on the Earth which had documented weak or strong cosmic ray arrivals, and seeing if that affected the cloudiness observed in those locations or at those times.

"For example; sometimes the Sun 'burps' - it throws out a huge burst of charged particles," he explained to BBC News.

"So we looked to see whether cloud cover increased after one of these bursts of rays from the Sun; we saw nothing."

Over the course of one of the Sun's natural 11-year cycles, there was a weak correlation between cosmic ray intensity and cloud cover - but cosmic ray variability could at the very most explain only a quarter of the changes in cloudiness.

And for the following cycle, no correlation was found.