London, Feb 10 (IANS): A review of solar activity in the past 400 years has shown that the level of sun activity was not very different in the 18th century as it is now, suggesting that blaming the sun for global warming is simply barking up the wrong tree.

Counting sunspots over time helps in knowing the activity of the sun. The more spots that appear, the more luminous the surrounding areas are, and our star shines brighter.

"It has been a huge surprise to observe that in the 18th century the levels of the Sun's activity were practically the same as they are now," said co-author Jose Vaquero, researcher at the University of Extremadura in Spain.

"A proper estimate of the past and present activity of the Sun, our main source of light and heat, is crucial in understanding numerous phenomena that occur on Earth, especially to rule out the role of the Sun in global warming," Vaquero explained.

Scientists have been counting sunspots since 1610 with small telescopes. The more intense peaks of the Sun's luminosity were produced in the 20th century, which experts have called the 'modern maximum'.

However, reviewing historical data, the new research has verified that there were also elevated values in other periods.

The researchers used information from the catalogue of sunspots from the Observatory of the University of Valencia, created between 1920 and 1928, and data from the Astronomical Observatory of Madrid recorded between 1876 and 1986.

The study appeared in the journal Space Science Reviews.