<p>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.</p>.<p>Some brand the crisis a hoax by scientists to justify their research grants -- or even a conspiracy by governments to control people. If so, it would have to be one of extraordinary complexity, coordinated by successive governments in scores of countries with vast numbers of scientists.</p>.<p>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.</p>.<p>Its latest report, 3,500 pages long released this year, was approved by delegates from 195 states. It lists 234 authors from 66 countries as contributors.</p>.<p><strong>Also Read — <a href="https://www.deccanherald.com/science-and-environment/how-to-make-climate-action-popular-1042345.html" target="_blank">How to make climate action popular</a></strong></p>.<p>The panel was founded under a UN resolution, which provides fuel for conspiracy theorists but offers proof of its bona fides for other people.</p>.<p>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?</p>.<p>No -- the speed, relative abruptness and global extent of the heating over the past 50 years make it different this time.</p>.<p>"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.</p>.<p>This is based on several forms of data: palaeological analysis of sediment, ice and tree rings for the period before the Industrial Revolution, and recorded temperatures since 1850.</p>.<p>As evidence of unusual warming has become incontrovertible, some sceptics concede it is happening but deny it is caused by the carbon emissions from humans burning fossil fuels.</p>.<p>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.</p>.<p>"It is unequivocal that human influence has warmed the atmosphere, ocean and land," this year's IPCC report concluded.</p>.<p>A summary of this finding, with graphs, is on <a href="http://u.afp.com/wZ6N" target="_blank">page eight</a> of this document.</p>.<p>"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!"</p>.<p>Donald Trump's tweet on January 20 blended a common climate myth -- that cold weather is evidence against climate heating -- with the assumption that even if warming is happening, it isn't all bad.</p>.<p>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.</p>.<p>Could "a little global warming" be nice? Parts of Siberia could become arable, expanding food resources -- but the melting of permafrost in the same region threatens to create more problems.</p>.<p>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.</p>.<p>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.</p>.<p>Among scientists' criteria for measuring the legitimacy of claims, one of the most important is consensus -- and the consensus on climate change is now overwhelming.</p>.<p>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.</p>.<p><strong>Watch the latest DH Videos here:</strong></p>
<p>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.</p>.<p>Some brand the crisis a hoax by scientists to justify their research grants -- or even a conspiracy by governments to control people. If so, it would have to be one of extraordinary complexity, coordinated by successive governments in scores of countries with vast numbers of scientists.</p>.<p>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.</p>.<p>Its latest report, 3,500 pages long released this year, was approved by delegates from 195 states. It lists 234 authors from 66 countries as contributors.</p>.<p><strong>Also Read — <a href="https://www.deccanherald.com/science-and-environment/how-to-make-climate-action-popular-1042345.html" target="_blank">How to make climate action popular</a></strong></p>.<p>The panel was founded under a UN resolution, which provides fuel for conspiracy theorists but offers proof of its bona fides for other people.</p>.<p>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?</p>.<p>No -- the speed, relative abruptness and global extent of the heating over the past 50 years make it different this time.</p>.<p>"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.</p>.<p>This is based on several forms of data: palaeological analysis of sediment, ice and tree rings for the period before the Industrial Revolution, and recorded temperatures since 1850.</p>.<p>As evidence of unusual warming has become incontrovertible, some sceptics concede it is happening but deny it is caused by the carbon emissions from humans burning fossil fuels.</p>.<p>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.</p>.<p>"It is unequivocal that human influence has warmed the atmosphere, ocean and land," this year's IPCC report concluded.</p>.<p>A summary of this finding, with graphs, is on <a href="http://u.afp.com/wZ6N" target="_blank">page eight</a> of this document.</p>.<p>"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!"</p>.<p>Donald Trump's tweet on January 20 blended a common climate myth -- that cold weather is evidence against climate heating -- with the assumption that even if warming is happening, it isn't all bad.</p>.<p>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.</p>.<p>Could "a little global warming" be nice? Parts of Siberia could become arable, expanding food resources -- but the melting of permafrost in the same region threatens to create more problems.</p>.<p>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.</p>.<p>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.</p>.<p>Among scientists' criteria for measuring the legitimacy of claims, one of the most important is consensus -- and the consensus on climate change is now overwhelming.</p>.<p>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.</p>.<p><strong>Watch the latest DH Videos here:</strong></p>