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Scientists warned US president about global warming 50 years ago

By Dana Nuccitelli  /  The Guardian, LONDON

Fifty years ago today, as the American Association for the Advancement of Science highlighted, then-US president Lyndon Johnson’s Science Advisory Committee sent him a report titled Restoring the Quality of Our Environment.

The introduction to the report noted: Pollutants have altered on a global scale the carbon dioxide content of the air and the lead concentrations in ocean waters and human populations.

The report included a section on atmospheric carbon dioxide and climate change, written by prominent climate scientists Roger Revelle, Wallace Broecker, Charles Keeling, Harmon Craig and J. Smagorisnky.

Reviewing the document today, one cannot help but be struck by how well these scientists understood the mechanisms of Earth’s climate change 50 years ago.

The report said that within a few years, climate models would be able to reasonably project future global surface temperature changes.

In 1974, one of its authors, Wallace Broecker, did just that in a paper titled Climatic Change: Are We on the Brink of a Pronounced Global Warming?

His model only included the effects of carbon dioxide and his best estimates of natural climate cycles. It did not include the warming effects of other greenhouse gases, or the cooling effects of human aerosol pollution, but fortunately for Broecker, those two effects have roughly canceled each other out over the past 40 years.

Broecker’s model predicted the global warming anticipated by this year both from carbon pollution alone, and when including his best estimate of natural climate cycles. The climate model predictions from more than 40 years ago turned out to be remarkably accurate.

The 1965 report also debunked a number of myths that climate contrarians continue to repeat to this day. For example, the first section of the climate chapter is titled Carbon Dioxide from Fossil Fuels — the Invisible Pollutant.

Although the US Supreme Court ruled that carbon dioxide is a pollutant in a landmark 2007 case, many contrarians object to this description. Nevertheless, climate scientists realized a half century ago that human carbon emissions qualify as pollution due to the dangers they pose via climate change.

The report said that although carbon dioxide is an invisible “trace gas” — meaning it comprises a small percentage of the Earth’s atmosphere as a whole — it can nevertheless have significant impacts on the climate at these seemingly low levels.

As the scientists wrote: “Only about one two-thousandth of the atmosphere and one ten-thousandth of the ocean are carbon dioxide. Yet to living creatures, these small fractions are of vital importance Within a few short centuries, we are returning to the air a significant part of the carbon that was slowly extracted by plants and buried in the sediments during half a billion years.”

Contrarians today often repeat the myths that because carbon dioxide is invisible and only a trace gas, it cannot possibly cause significant climate change. This report demonstrates that scientists understood the greenhouse effect better 50 years ago than these contrarians do today.

The report documented the several different lines of evidence that prove the increase in atmospheric carbon dioxide is entirely human-caused.

“We can conclude with fair assurance that at the present time, fossil fuels are the only source of CO2 being added to the ocean-atmosphere-biosphere system,” the report said.

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