London, April 3 : Scientists have produced evidence that proves that modern-day climate change is not caused by changes in the Sun's activity.
According to a report by BBC News, the new evidence was found after a research by scientists from Lancaster University in UK.
The research contradicts a favoured theory of climate "skeptics", that changes in cosmic rays coming to Earth determine cloudiness and temperature. The idea is that variations in solar activity affect cosmic ray intensity.
But Lancaster University scientists found there has been no significant link between them in the last 20 years.
The team explained that they used three different ways to search for a correlation, and found virtually none.
This latest piece of evidence puts the cosmic ray theory, developed by Danish scientist Henrik Svensmark at the Danish National Space Center (DNSC), under very heavy pressure.
Cosmic rays are deflected away from Earth by our planet's magnetic field, and by the solar wind - streams of electrically charged particles coming from the Sun.
The Svensmark hypothesis is that when the solar wind is weak, more cosmic rays penetrate to Earth, which creates more charged particles in the atmosphere, which in turn induces more clouds to form, cooling the climate.
Professor Terry Sloan's team from Lancaster University 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," said Sloan.
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.
"We tried to corroborate Svensmark's hypothesis, but we could not; as far as we can see, he has no reason to challenge the IPCC - the IPCC has got it right," said Sloan.
"So we had better carry on trying to cut carbon emissions," he added.