Scientists and activists warning of catastrophic man-made global warming should look at Earth’s long climate history, according to a co-founder of the environmental group Greenpeace. As it turns out, Earth is currently experiencing one of the coldest climates in its history.
“A well-documented record of global temperature over the past 65 million years shows that we have been in a major cooling period since the Eocene Thermal Maximum 50 million years ago,” Dr. Patrick Moore said at a lecture Wednesday hosted by the U.K.-based Global Warming Policy Foundation.
“The Earth was an average 16C warmer then, with most of the increased warmth at the higher latitudes,” said Moore, who helped found Greenpeace in the 1970s. “The entire planet, including the Arctic and Antarctica were ice-free and the land there was covered in forest.”
Moore, an ecologist, left Greenpeace in the 1980s because he thought the group had become too radical in its demands. Greenpeace disowned Moore, who is renowned by conservatives for skepticism over claims that humankind is causing catastrophic global warming.
Moore argues that manmade carbon dioxide emissions have been good for the planet, providing plants with nutrients they need to grow. In fact, scientists have observed a “greening” of the planet over the last couple decades because of higher CO2 levels.
More importantly, Moore argues the Earth was much warmer in its past and life thrived. Today’s climate by comparison is much colder, he argues.
“Glaciers began to form in Antarctica 30 million years ago and in the northern hemisphere 3 million years ago,” Moore said in his lecture. “Today, even in this interglacial period of the Pleistocene Ice Age, we are experiencing one of the coldest climates in the Earth’s history.
“The ancestors of every species on Earth today survived through what may have been the warmest time in the history of life,” Moore said. “It makes one wonder about dire predictions that even a 2C rise in temperature from pre-industrial times would cause mass extinctions and the destruction of civilization.”
While scientists today warn about rising global temperatures since the 1970s, a look at Earth’s climate history reveals a roughly 50 million year cooling trend — based on proxy data derived from oxygen isotope ratios from fossil foraminifera.
Deep ocean temperatures were generally high throughout the Paleocene and Eocene, with a particularly warm spike at the boundary between the two geological epocs around 56 million years ago. Temperatures in the distant past are inferred from proxies (oxygen isotope ratios from fossil foraminifera). “Q” stands ofQuarternary. Graph by Hunter Allen and Michon Scott, using data from the NOAA National Climatic Data Center, courtesy Carrie Morrill. (Credit: Climate.gov)
Ocean core temperature data compiled by NASA shows a cooling trend over roughly the past five million years.
Global temperature relative to peak Holocene temperature, based on ocean cores. (Credit: NASA)
Scientists also argue there was a huge spike in global carbon dioxide levels some 50 million years ago, but it’s not clear if CO2 caused temperature spikes or vice versa.
“It is still uncertain where all the carbon dioxide came from and what the exact sequence of events was,” according to Climate.gov. “Scientists have considered the drying up of large inland seas, volcanic activity, thawing permafrost, release of methane from warming ocean sediments, huge wildfires, and even—briefly—a comet.”
There have of course, been extremely cold periods in the past. Climate.gov notes that between 800 million and 600 million years ago “evidence suggests the Earth underwent an ice age so cold that ice sheets not only capped the polar latitudes, but may have extended all the way to sea level near the equator.”