Global warming deniers may have just lost another crucial point of recourse in their flagging campaign: according to a new study carried out by an international team of researchers, variations in solar ouput are not to blame for climate change. Indeed, just as the sun's output has been declining over the last two decades, global temperatures have been on the rise.
This directly contradicts the cosmic ray hypothesis, a theory advanced by two scientists from the Danish National Space Center which holds that cosmic rays, through the intermediary of clouds (which they help form), help cool the planet. When the rays are partially blocked by the sun during periods of intense solar activity, fewer clouds are able to form and the Earth warms as a result. While this may have held true in the past, Mike Lockwood from the Rutherford-Appleton Laboratory in the U.K. and Claus Froehlich from the World Radiation Center in Switzerland dismissed its impact on the current episode of climate change, stating their findings "should settle the debate." In fact, their study partially originated from Lockwood's desire to rebut a TV documentary aired earlier this year entitled "The Great Global Warming Swindle" that prominently featured the cosmic ray hypothesis.
They arrived at their conclusion by analyzing solar output and cosmic ray intensity side-by-side with the rising trend in the global average surface temperature over the last 3-4 decades. The sun, whose activity typically fluctuates on a cycle of 11 years between high and low episodes, saw its output begin to steadily decline in early 1985. Contrary to what the cosmic ray hypothesis would've predicted, temperatures continued rising, often at a faster clip than they had over the past century.
"I do think there is a cosmic ray effect on cloud cover. It works in clean maritime air where there isn't much else for water vapour to condense around. It might even have had a significant effect on pre-industrial climate. But you cannot apply it to what we're seeing now, because we're in a completely different ball game," said Lockwood, commenting on the validity of the cosmic ray hypothesis.
Climate change skeptics had often latched onto this hypothesis to argue that anthropogenic influences were not to blame for the trend in global warming. With yet another talking point shot down, it sure looks like they have their work cut out for them now (well, even more so than before).
Via ::BBC News: 'No sun link' to climate change (news website)