As world leaders prepare for the COP26 climate summit on October 31, AFP Fact Check examines some common claims that question the existence of man-made global warming.
It’s a hoax / a conspiracy
Some are calling the crisis a hoax by scientists to justify their research grants – or even a government plot to control people. If this were the case, it would have to be a project of extraordinary complexity, coordinated by successive governments in dozens of countries with large numbers of scientists. Tens of thousands of peer-reviewed studies in the public domain have led to an overwhelming scientific consensus that man-made climate change is real. The most comprehensive source of this type is the Intergovernmental Panel on Climate Change (IPCC). Far from being a secret operation, its evidence and methods are published on www.ipcc.ch.
Its latest 3,500-page report, published this year, was approved by delegates from 195 states. It lists 234 authors from 66 countries as contributors.
The panel was founded under a UN resolution, which fuels conspiracy theorists but offers proof of its good faith to others.
The climate has always changed
Scientists know that the Earth has long alternated between ice ages and periods of warming – roughly one ice age every 100,000 years over the past million years. Is the current heating just another step in this cycle? No – the speed, relative brutality, and global extent of warming over the past 50 years makes it different this time around.
“The world’s surface temperature has risen faster since 1970 than in any other 50-year period in at least the past 2,000 years,” says the IPCC, with charts to show it.
This is based on several forms of data: paleological analysis of sediment, ice and tree rings for the period before the industrial revolution, and temperatures recorded since 1850.
No evidence of human cause
While the evidence for an unusual warming has grown indisputable, some skeptics admit it’s happening but deny it’s caused by carbon emissions from humans burning fossil fuels. The IPCC has developed a climate model that measures the impact of different factors. It calculates the extent of heating with and without the effect of human activity.
“It is unequivocal that human influence has warmed the atmosphere, the oceans and the land,” concluded this year’s IPCC report.
A summary of this result, with graphics, can be found on page eight of this document: http://u.afp.com/wZ6N
A little warming up is good
âLarge parts of the country suffer from enormous amounts of snow and almost record coldâ¦. It wouldn’t hurt to have some of that good ol ‘global warming right now! “
Donald Trump’s January 20 tweet mixed a common climate myth – that cold is evidence against global warming – with the assumption that even if there is warming, not everything is bad.
Climate is a measure of average weather variations over time. A day or a week of snow is therefore not enough to prove that average temperatures do not increase over decades.
Could a âlittle global warmingâ be nice? Parts of Siberia could become arable and increase food resources – but melting permafrost in the same region threatens to create more problems.
A two-degree rise might sound nice enough – but the IPCC calculates that raising sea levels by half a meter or more is enough to drown coastal towns.
Scientists question climate change
Specialists often express their skepticism, signing joint declarations and editorials. But a review of their credentials in many cases revealed that they were rarely climatologists.
Among scientists’ criteria for measuring the legitimacy of claims, one of the most important is consensus – and consensus on climate change is now overwhelming.
A recent Cornell University survey of thousands of peer-reviewed studies on climate change found that in over 99% of them, the authors agreed that climate change was caused by humans ( http://u.afp.com/wZ6p).
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