Archive for the ‘Scientists’ Category

paul crutzen, nobel prize, ozone layer

Paul Crutzen won the Nobel prize in Chemistry in 1995 for his work on the chemical compounds that were causing the hole in the ozone layer.

In 2000 Paul Crutzen, the Dutch atmospheric chemist and Nobel prize-winner, and American ecologist Eugene F Stoermer, proposed using the term ‘anthropocene’ for the current geological epoch to emphasize the central role of mankind in geology and ecology.

Fifteen years on, several of the papers that were presented at the four-day World Economic Forum in Davos, Switzerland, last week referred to the advent of the Anthropocene era, though it is doubtful if many of the 2,500 attendees paid much attention.

Geological Epochs

So what is a geological epoch, when did the Anthropocene epoch start, and how is the Anthropocene relevant to us?

You will know about the Jurassic period when dinosaurs roamed the earth*. But do you know some of the other periods of geological time: the Cambrian, the Devonian, the Carboniferous, the Triassic, the Cretaceous? The Cambrian period started about 540 million years ago, and the Cretaceous period ended 66 million years ago. This enormous length of time is only 10% of the age of the Earth, which is 4.6 million years old.

(*The dinosaurs actually first appeared in the Triassic period, 231.4 million years ago, and were the dominant terrestrial vertebrates for 135 million years, from the beginning of the Jurassic period until the end of the Cretaceous, 66 million years ago.)

The last 66 million years is also made up of geologic periods: the Paleogene, the Neogene and the Quaternary, and to make it more complicated, the Quaternary period is made up of two epochs, the Pleistocene (2.6 million years ago to 11,700 years ago) and the Holocene (11,700 years ago to the present day). Even though human beings first appeared between 400,000 and 250,000 years ago, the Holocene, the start of which is marked by the end of the last major ice age, encompasses the rise of modern humans, all human written history, the development of major civilizations, and the relatively recent transition toward urban living. The word Holocene means ‘entirely recent’ and comes from the Greek holos, meaning ‘whole’ or ‘entire’, and –cene meaning ‘new’.

geologic time, cambrian, pre-cambrian

In this geological time chart, the time before the Cambrian period, the Pre-Cambrian, which extends for most of the top level, covers seven-eighths of the age of the earth, with the remaining one-eighth expanded into levels below.

The Anthropocene Epoch

But for some time, geologists, climate scientists and ecologists have been debating whether the profound effect that the human species is having on the Earth means that we are moving from the Holocene to a new epoch, the Anthropocene (pronounced an-thropo-scene). The first use of a similar term however goes back to 1873 when the Italian geologist Antonio Stoppani  acknowledged the increasing power and effect of humanity on the Earth’s systems and referred to an ‘anthropozoic era’. Incidentally Eugene Stoermer originally coined the term in the 1980s, but never formalised it until Paul Crutzen, who had started using the term, contacted him. The name Anthropocene is a combination of the Greek roots anthropo- meaning ‘human’ and -cene meaning ‘new’.

Geologic epochs primarily refers to geologic time based on boundaries between different rock strata differentiated by fossils, which is the science of stratigraphy, and any decision on recognising the Anthropocene epoch, which is still an informal term, lies with the International Commission on Stratigraphy (ISC). The ISC set up an international Anthropocene Working Group of scientists which was ‘tasked with developing a proposal for the formal ratification of the Anthropocene as an official unit amending the Geological Time Scale’. The working group, which first met in Berlin last year, has given itself until 2016 to come up with the proposal to submit to the ISC, but this month they put forward their initial view.

The Beginning of the Athropocene

The working group has proposed that if there were to be a single date to mark its beginning of the Anthropocene epoch, it would be 16 July 1945, the date that the first atomic-bomb test took place at the US Army testing range at Alamogordo in New Mexico, as the subsequent nuclear tests left an indelible mark around the Earth due to the release of radioactive isotopes or ‘fallout’ which settled in the soil and land around the world. This event also coincided with a worldwide ‘great acceleration’ of other human activities that ushered in a new geological epoch.

However a significant minority of the working group supported alternative dates, and the group plans to bring forward a formal, evidence based, proposal in 2016. Scientists have argued for a number of different dates that mark the start of this new human epoch. One date is the start of the industrial revolution in England in the 18th century when coal became the main source of fuel, production by hand changed to production by machine, new processes to produce iron were introduced, and the use of steam power increased dramatically. Earlier dates include the invention of agriculture and the clearing of forests about 10,000 years ago, and even further back to 14,000 to 15,000 years ago based on lithospheric evidence, the exposed top layers of the earth. These latter dates would be closely synchronous with the current epoch, the Holocene.

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Joe Farman (left), with Brian Gardiner and Jon Shanklin, discovers of the depletion of the ozone layer

Joe Farman (left), with Brian Gardiner and Jon Shanklin, discovers of the depletion of the ozone layer

Joe Farman died in Cambridge on 11 May 2013. His name is unknown to most people. He was a British physicist who along with fellow researchers, Brian Gardiner and Jon Shanklin, caused a sensation when they published their findings in Nature in May 1985 revealing that the levels of ozone above the Antarctic had fallen by about 40% between 1975 and 1984. This had caused a very large hole  (more correctly a reduction in the concentration of ozone) to appear in the ozone layer, a thin layer in the earth’s stratosphere which absorbs virtually all the ultraviolet rays from the sun which are harmful to life.

The hypothesis of ozone depletion had been put forward in the 1970s but had been dismissed by NASA scientists after satellites failed to substantiate the loss. Since 1957, Farman and his colleagues had been looking at atmospheric data collected by the British Antarctic Survey station at Halley Bay, Antarctica, using old-fashioned devices like weather balloons and a Dobson meter, a rudimentary ozone measuring machine that had to be wrapped in a duvet to work properly. At first the figures were questioned, even by the team. Perhaps the discrepancy was just above Halley Bay? Measurements were taken 1,000 miles further north, but these showed the same result? Why had NASA’s satellites not picked up the anomaly. Much later and to NASA’s embarrassment, the data had been collected by the satellites but had been overlooked.

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