 In 2009, a number of leading experts, including one Nobel laureate, concluded that the graphs of Friis-Christensen and Svensmark showing apparent correlations between global warming, sunspots and cosmic rays were deeply flawed.Friis-Christensen agreed that any correlation between sunspots and global warming that he may have identified in the 1991 study has since broken down.There is, he said, a clear "divergence" between the sunspots and global temperatures after 1986, which shows that the present warming period cannot be explained by solar activity alone.