Science speaks on climate change

By CHRIS WOOD 

The Intergovernmental Panel on Climate Change released a summary of its fifth periodic report on what’s happening to our planet’s climate on Friday, Sept. 27. The balance of the report, collecting the findings of more than 2,000 researchers over the past half-decade, will be released in stages over the next several months. 

But the bottom line is already clear: “Multiple lines of independent evidence [show that] warming in the climate system is unequivocal. It is extremely likely [ie: above a 90% probability] that human influence has been the dominant cause of the observed warming since the mid-20th century. The evidence for this has grown, thanks to more and better observations, an improved understanding of the climate system response and improved climate models.”

Most of the heat collecting in the planet’s climate system is going into the oceans—expanding their volumes—while all of the globe’s ice sheets have dwindled.

The report is equally clear about what’s causing these changes: “It is extremely likely [again, a greater than 90% likelihood] that human influence has been the dominant cause of the observed warming since the mid-20th century.” The more alarming message may be that we are unleashing natural feedback loops that may push the pace of climate change beyond any human influence. “Climate change,” the scientists warn, “will affect carbon cycle processes in a way that will exacerbate the increase of CO2 in the atmosphere.”

The report was targeted before it appeared by climate-change skeptics who argue that global average atmospheric (air) temperature has not increased in the last decade. Observations show, however, that the last decade was the hottest on record—and the third in succession to be hotter than all previous recorded decades. 

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