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Landmark climate study thoroughly debunks one of deniers’ go-to talking points

IPCC study finds human-caused warming since 1850 is "indistinguishable from ... total observed warming."

Human-caused warming for the 2006–2015
decade relative to 1850–1900. CREDIT: IPCC
Human-caused warming for the 2006–2015 decade relative to 1850–1900. CREDIT: IPCC

The Trump administration wants Americans to believe that we don’t know how much of global warming is due to human causes, such as the burning of fossil fuels.

But the landmark climate report released Sunday says that we do know. Indeed, while the world’s foremost scientific panel on climate change (the IPCC) had concluded back in 2013 that humans are responsible for all of the warming we have suffered since 1950 — now they have extended that back to 1850.

These findings are so uncontroversial that every major country, including the United States, literally approved them line-by-line.

Yet, while these conclusions are not in dispute among scientists or the world’s leading governments, they have been repeatedly disputed by President Donald Trump’s team of climate science deniers.

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In April 2017, for example, when former Environmental Protection Agency administrator Scott Pruitt defended his claim that carbon dioxide is not “a primary contributor to the global warming that we see,” even outlets like Fox News felt compelled to debunk him. As anchor Chris Wallace said at the time, “Mr. Pruitt, there are all kinds of studies that contradict you.”

Then, during June 2017 Senate hearings, Energy Secretary Rick Perry pushed the same science denial. But he lost his cool when he was informed that scientists — including skeptics funded by conservative petrochemical billionaires Charles and David Koch — have concluded “humans are entirely the cause” of recent warming.

Perry raised his voice and said: “To stand up and say that 100 percent of global warming is because of human activity, I think on its face, is just indefensible.”

Ironically, just a few months later, the White House itself approved the National Climate Assessment (NCA) — the work of scientists from 13 federal agencies peer-reviewed by the National Academy of Sciences — which came to the exact same conclusion: humans are responsible for all recent warming.

But the NCA finding didn’t stop Trump’s choice to run the Department of Homeland Security, Kirstjen Nielsen, from repeating the same tired science-denying talking point in her confirmation hearing a few days later.

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In response to repeated questioning by Sen. Tom Carper (D-DE), she hemmed and hawed and finally ended up retreating to “I believe that climate change exists. I’m not prepared to determine causation.”

Nielsen now oversees FEMA disaster planning and preparation, which  requires an understanding of the threat posed by sea level rise and the role humans are playing in speeding it up.

In fact, the causation of global warming is crystal clear. It is entirely “anthropogenic” or human-caused, as this week’s report shows.

The new IPCC report examined the best global temperature data sets going back to the mid-19th century. It then compared all that data with the latest models of both natural causes of temperature change (such as volcanoes and variations in solar radiation) and human causes (such as CO2 emissions from burning fossil fuels and deforestation).

The IPCC concluded that, relative to 1850–1900 temperatures, current “anthropogenic warming is indistinguishable from … the total observed warming.”

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In other words, humans are the cause of global warming, which is why we are the only ones who can stop the impending catastrophe.