As world leaders prepare for the COP26 climate summit from October 31, AFP Fact Check examines some common claims that question the existence of global heating caused by humans.
– ‘It’s a hoax / conspiracy’ –
Tens of thousands of peer-reviewed studies in the public domain have led to an overwhelming scientific consensus that human-made climate change is real. The most comprehensive such source is the Intergovernmental Panel on Climate Change (IPCC). Far from being a covert operation, its evidence and methods are published at www.ipcc.ch.
The panel was founded under a UN resolution, which provides fuel for conspiracy theorists but offers proof of its bona fides for other people.
Scientists know the Earth has long alternated between ice ages and periods of warming — about one ice age every 100,000 years over the past million years. Is the current heating just another stage in this cycle?
“Global surface temperature has increased faster since 1970 than in any other 50-year period over at least the last 2,000 years,” the IPCC says, with graphs to demonstrate.
– ‘No proof of human cause’ –
The IPCC 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.
A summary of this finding, with graphs, is on page eight of this document: http://u.afp.com/wZ6N
“Large parts of the Country are suffering from tremendous amounts of snow and near record-setting cold…. Wouldn’t be bad to have a little of that good old fashioned Global Warming right now!”
Climate is a measure of average weather variations over time. One day or one week of snow is therefore not enough to prove that average temperatures are not rising over decades.
A two-degree rise may sound pleasant enough – but the IPCC calculates that it is enough to drive up the level of the seas by half a metre or more, enough to drown coastal cities.
Specialists often voice scepticism, signing joint statements and editorials. But an examination of their credentials in numerous cases has revealed that these are rarely climate scientists.
A recent survey by Cornell University of thousands of peer-reviewed studies on climate change found that in more than 99 percent of them the authors agreed that climate change was caused by humans (http://u.afp.com/wZ6p).