The Anthropocene is here: Scientists recommend naming a new geological epoch as humans ‘permanently reconfigure Earth’s biological trajectory’Posted by Jim at Monday, August 29, 2016
29 August 2016 (AFP) – The human impact on Earth's chemistry and climate has cut short the 11,700-year-old geological epoch known as the Holocene and ushered in a new one, scientists said Monday.
The Anthropocene, or "new age of man," would start from the mid-20th century if their recommendation—submitted Monday to the International Geological Congress in Cape Town, South Africa—is adopted.
That approval process is likely to take at least two years and requires ratification by three other academic bodies.
But after seven years of deliberation, the 35-strong Working Group has unanimously recognised the Anthropocene as a reality, and voted 30-to-three (with two abstentions) for the transition to be officially registered.
"Our working model is that the optimal boundary is the mid-20th century," said Jan Zalasiewicz, a geologist at the University of Leicester.
"If adopted—and we're a long way from that—the Holocene would finish and the Anthropocene would formally be held to have begun."
Scientists refer to the period starting from 1950 as the "Great Acceleration", and a glance at graphs tracking a number of chemical and socio-economic changes make it obvious why.
Concentrations in the air of carbon dioxide, methane and stratospheric ozone; surface temperatures, ocean acidification, marine fish harvesting, and tropical forest loss; population growth, construction of large dams, international tourism—all of them take off from about mid-century.
One of the main culprits is global warming driven by the burning of fossil fuels.
A telltale surge in the spread of invasive plant and animal species is also a legacy of our species.
But the working group is not allowed to take any of these measures into consideration unless they show up in the geological record.
If it can't be measured in rocks, lake sediments, ice cores, or other such formations—the criteria used to determine dozens of distinct eons, era, periods and ages going back four billion years—it doesn't count.
This, however, is not a problem when it comes to the Anthropocene, said Zalasiewicz.
"We are spoiled for choice," he told AFP. "There's a whole array of potential signals out there."
Micro-plastics, for example—a synthetic, man-made substance—"are now components of sediment around the world, both in land and in the sea." [more]
By Paul Voosen
24 August 2016
(Science) – Just after World War II, when the atomic bombs fell and our thirst for coal and oil became a full-blown addiction, Earth entered the Anthropocene, a new geologic time when humanity’s environmental reach left a mark in sediments worldwide. That’s the majority conclusion of the Anthropocene Working Group, a collection of researchers that has spent the past 7 years quietly studying whether the term, already popular, should be submitted as a formal span of geologic time.
After tallying votes this month, the group has decided to propose the postwar boom of the late 1940s and early 1950s as the Anthropocene’s start date. The group will ask the International Commission on Stratigraphy (ICS), the bureaucracy that governs geologic time, to recognize the Anthropocene as a series, the stratigraphic equivalent of an epoch, on par with the Holocene and Pleistocene that preceded it. Colin Waters, the group’s secretary and a geologist at the British Geological Survey in Keyworth, will reveal the group’s recommendations on 29 August at the International Geological Congress in Cape Town, South Africa.
The group won’t submit a formal proposal yet. To do so, it must gather multiple cores of sediment from around the planet and show that they contain a sharp transition in geochemical tracers that is likely to persist as a permanent part of the rock record; the core with the best example of the transition would then serve as a “golden spike,” marking the Anthropocene’s start. These cores could come from lakebeds, ocean floors, ice sheets—or even corals or tree rings. But they must capture the “Great Acceleration”: the postwar period when fossil fuel combustion took off, says Jan Zalasiewicz, a geologist at the University of Leicester in the United Kingdom who convened the group. “We’ll go and get our hands dirty, beginning to look for sections that we can formally propose.”
Those sections will have to be rich with multiple signatures, as the Anthropocene proposal faces deep skepticism from stratigraphers. “The voting members of the International Commission on Stratigraphy look at these things critically,” says Stan Finney, chair of ICS and a geologist at California State University, Long Beach.
He and other stratigraphers doubt that their standards can be properly applied to decades-old mud and silt rather than the solid rock that records older stratigraphic boundaries. They question the value of the Anthropocene for their science, which seeks to draw coherent chronologies out of sedimentary rocks. Some also resent the role that scientists from other disciplines such as climate science have played in driving the proposal and see it as a political statement.
Should ICS decide against the Anthropocene, some stratigraphers fear, they could be swamped with bad press. “I feel like a lighthouse with a huge tsunami wave coming at it,” Finney says. Phil Gibbard, a stratigrapher at the University of Cambridge in the United Kingdom and a working group member who voted against the proposal, also worries about a backlash. “We’re nervous,” he says.
The working group, a mix of 35 geologists, climate scientists, archaeologists, and others, considered multiple dates. There were votes for an early start to the Anthropocene, 7000 years ago, when humanity began converting forests en masse to pastures and cropland, perhaps causing carbon dioxide (CO2) to spike, and also for 3000 years ago, when lead smelting tainted the ground. More recently, they considered 1610, when pollen from the New World appeared in Europe, and the early 1800s, the start of the Industrial Revolution. But the most votes went to the Great Acceleration.
The group’s decision to go for a single, recent start date for the Anthropocene disappoints Bill Ruddiman, an emeritus professor of environmental science at the University of Virginia in Charlottesville. “It is a mistake to formalize the term by rigidly affixing it to a single time,” he says, “especially one that misses most of the history of the major transformation of Earth’s surface.” Many archaeologists also favor the 7000-year-old date, when early humans began to alter the planet’s surface. But the working group was looking for a signature of global, human-driven change that would wind up in the rock record, not the first traces of human influence on the local landscape. [more]
Humans are altering the planet, including long-term global geologic processes, at an increasing rate. Any formal recognition of an Anthropocene epoch in the geological time scale hinges on whether humans have changed the Earth system sufficiently to produce a stratigraphic signature in sediments and ice that is distinct from that of the Holocene epoch. Proposals for marking the start of the Anthropocene include an “early Anthropocene” beginning with the spread of agriculture and deforestation; the Columbian Exchange of Old World and New World species; the Industrial Revolution at ~1800 CE; and the mid-20th century “Great Acceleration” of population growth and industrialization.
Recent anthropogenic deposits contain new minerals and rock types, reflecting rapid global dissemination of novel materials including elemental aluminum, concrete, and plastics that form abundant, rapidly evolving “technofossils.” Fossil fuel combustion has disseminated black carbon, inorganic ash spheres, and spherical carbonaceous particles worldwide, with a near-synchronous global increase around 1950. Anthropogenic sedimentary fluxes have intensified, including enhanced erosion caused by deforestation and road construction. Widespread sediment retention behind dams has amplified delta subsidence.
Geochemical signatures include elevated levels of polyaromatic hydrocarbons, polychlorinated biphenyls, and pesticide residues, as well as increased 207/206Pb ratios from leaded gasoline, starting between ~1945 and 1950. Soil nitrogen and phosphorus inventories have doubled in the past century because of increased fertilizer use, generating widespread signatures in lake strata and nitrate levels in Greenland ice that are higher than at any time during the previous 100,000 years.
Detonation of the Trinity atomic device at Alamogordo, New Mexico, on 16 July 1945 initiated local nuclear fallout from 1945 to 1951, whereas thermonuclear weapons tests generated a clear global signal from 1952 to 1980, the so-called “bomb spike” of excess 14C, 239Pu, and other artificial radionuclides that peaks in 1964.
Atmospheric CO2 and CH4 concentrations depart from Holocene and even Quaternary patterns starting at ~1850, and more markedly at ~1950, with an associated steep fall in δ13C that is captured by tree rings and calcareous fossils. An average global temperature increase of 0.6o to 0.9oC from 1900 to the present, occurring predominantly in the past 50 years, is now rising beyond the Holocene variation of the past 1400 years, accompanied by a modest enrichment of δ18O in Greenland ice starting at ~1900. Global sea levels increased at 3.2 ± 0.4 mm/year from 1993 to 2010 and are now rising above Late Holocene rates. Depending on the trajectory of future anthropogenic forcing, these trends may reach or exceed the envelope of Quaternary interglacial conditions.
Biologic changes also have been pronounced. Extinction rates have been far above background rates since 1500 and increased further in the 19th century and later; in addition, species assemblages have been altered worldwide by geologically unprecedented transglobal species invasions and changes associated with farming and fishing, permanently reconfiguring Earth’s biological trajectory.
These novel stratigraphic signatures support the formalization of the Anthropocene at the epoch level, with a lower boundary (still to be formally identified) suitably placed in the mid-20th century. Formalization is a complex question because, unlike with prior subdivisions of geological time, the potential utility of a formal Anthropocene reaches well beyond the geological community. It also expresses the extent to which humanity is driving rapid and widespread changes to the Earth system that will variously persist and potentially intensify into the future.