export_ofoct.com

[00:00.41] Since the middle of the 20th century, humans have had a very strong effect on planet Earth.

[00:09.18] These effects have included climate change, species loss and pollution.

[00:16.08] Humanity’s impact has been so strong that scientists say a new geological epoch began then.

[00:26.97] The scientists call it the Anthropocene epoch.

[00:31.22] The word comes from the Greek terms for “human” and “new.”

[00:37.06] This epoch started sometime between 1950 and 1954, the scientists say.

[00:45.56] There is evidence worldwide of the harmful impact on the Earth’s health of burning fossil fuels, dropping nuclear weapons and releasing fertilizers and plastics on land and in water.

[01:01.77] “It’s quite clear that the scale of change has intensified unbelievably and that has to be human impact,” said University of Leicester geologist Colin Waters.

[01:16.11] He led the Anthropocene Working Group.

[01:20.63] The scientists say the power of humans is comparable with the meteorite that crashed into Earth 66 million years ago.

[01:31.51] The meteorite killed off the dinosaurs and started the Cenozoic Era, or what is known as the age of mammals.

[01:41.34] While that meteorite started a whole new era, the working group is proposing that humans only started a new epoch.

[01:51.70] An epoch is a much smaller geological time period.

[01:57.01] The scientists are proposing a small but deep lake outside of Toronto, Canada, to place a historic marker.

[02:06.84] The lake is called Crawford Lake.

[02:10.03] The group aims to decide on an exact start date of the Anthropocene by measuring plutonium levels at the bottom of Crawford Lake.

[02:21.72] Crawford Lake is 29 meters deep and 24,000 square meters wide.

[02:29.42] It was chosen over 11 other sites because the yearly effects of human activity on the earth's soil, atmosphere and biology are clearly shown in its layers of sediment.

[02:44.29] That includes everything from the effect of nuclear weapons to pollution to rising temperatures.

[02:52.53] There are clear signs in Crawford Lake showing that, starting in 1950, “the effects of humans overwhelm the Earth system,” said Francine McCarthy.

[03:05.81] She is part of the working group who specializes in that site as an Earth sciences professor at Brock University in Canada.

[03:17.77] The Anthropocene shows the power — and hubris — of humankind, several scientists said.

[03:23.61] Hubris is a great or foolish amount of confidence.

[03:31.05] “The hubris is in imagining that we are in control," said former U.S. White House science adviser John Holdren.

[03:42.20] He was not part of the working group of scientists.

[03:46.46] He disagrees with the group’s proposed start date.

[03:51.76] Instead, he wants one much earlier.

[03:54.95] Holdren said the power of humans to change the environment is far greater than their understanding of the impacts.

[04:04.51] Geologists measure time in eons, eras, periods, epochs and ages, with eons being the longest.

[04:16.20] The scientific working group is proposing that Anthropocene Epoch followed the Holocene Epoch.

[04:23.90] Holocene started about 11,700 years ago at the end of an ice age.

[04:33.20] The proposal still needs to be approved by three different groups of geologists.

[04:39.31] It could be signed at a major conference next year.

[04:44.36] Naomi Oreskes is a science historian with Harvard University and a working group member.

[04:53.13] She said if there is no change to harmful human activities, “we are headed for tragedy.”