Trinity and the dawn of the Anthropocene

Reflecting on the moment the world changed

By David Salt

Seventy four years ago, at 5.29am on Monday 16th of July 1945, the US military detonated the world’s first atomic bomb. Code named Trinity, the test was run out on a lonely New Mexican desert on an air force bombing range. Small by the standards of later tests, Trinity still managed to light up the surrounding mountains brighter than day, fuse the sand underneath it into radioactive green glass and generate a shock wave felt over 160 km away.

Yet the significance of Trinity extends way beyond that New Mexican desert, and even beyond the end of the Second World War which, with the aid of atomic weapons, was now only weeks away.

By some reckonings, 5.29am on Monday 16th of July 1945, marks the beginning of a new geological epoch – the Anthropocene, the age of humans. Seventy four years on, the trajectory of the Anthropocene should be at the fore front of all our thinking.

Written in stone

The Anthropocene is not yet an ‘official’ geological time period. Such decisions require a formal review and proclamation by the International Commission on Stratigraphy (ICS), a fairly conservative scientific panel not keen on mixing their science with fashion and politics (and the ‘Anthropocene’ is jam packed with political ramifications).

According to the ICS, planet Earth is still officially in what’s known as the Holocene Epoch, which began after the last ice age ended some 12,000 years ago.

But many scientists have been unhappy with the title ‘Holocene’ believing human activity is now dominating the Earth system, and this should be reflected in the stratigraphic nomenclature – the Earth’s geological rock strata reflecting the deep history of our planet. The name ‘Anthropocene’ was proposed by the atmospheric chemist (and Nobel laureate) Paul Crutzen back in the year 2000.

For a new geological epoch to be declared the rock strata above a proposed boundary needs to distinctly different from those below, suggesting some major change in the processes that created them. But this difference also needs to be evident all around the world, indicating that the change is global and not merely regional in character.

Can human activity be seen in the geological record? You betcha! Particles of plastics, concrete and aluminium, all of undeniable human origin are now widespread around the planet and found in today’s emerging strata. But possibly the most undeniable material of human origin being found in the strata are radionuclides from atomic bombs, beginning with Trinity in 1945. Nothing like these substances had existed on Earth prior to 1945, but now they coat the planet.

While the radionuclides serve as an easily detectable marker, they only exist in trace quantities. Other artificial materials are so abundant we’re drowning in them. The total amount of concrete that humanity has produced, most of it in the post-1950 period, amounts to about a kilogram for every square metre across the entire surface of the Earth. The amount of plastic wrap produced since 1950 is enough to cover the entire planet in plastic. And enough aluminium foil has been manufactured to wrap the continent of Australia.

All of these stratigraphic markers begin to appear in significant amounts around the middle of the 20th century. This coincides with a time that is now commonly referred to as the Great Acceleration, a period of unparalleled economic growth and development. And it wasn’t just plastic production that skyrocketed; so too did water use, energy use, fertilizer consumption, international tourism, dam construction and paper production. Underpinning it all was a swelling human population and an insatiable drive to grow the economy.

When did the Anthropocene begin?

When Crutzen first began writing about the Anthropocene with colleagues he proposed that it began with the invention of the steam engine and the Industrial Revolution from the second half of the 18th Century. This was because this period coincided with increasing levels of carbon dioxide associated with greater levels of coal consumption.

Other scholars have suggested the Anthropocence began much earlier, back with the Agricultural Revolution some 5-8000 years ago. The spread of agriculture also led to increased greenhouse gas emissions through changes in land management.

Others have suggested even earlier dates with human making their mark through the extinction of mega fauna in areas where they appeared.

Each proposal for the beginning of the Anthropocene has its strengths and weaknesses depending on your frame of reference.

From an Earth systems perspective, however, it is only from 1950s that the cumulative impact of human activity began to distort the Earth system itself. Humanity was changing the very behaviour of our planet. None of the earlier ‘start’ dates can claim this.

And, when you combine this with the crystal clear signal of radionuclides and their sudden appearance, I believe Trinity is the best candidate for the opening of this latest planet-shifting epoch – the Anthropocene. The fact that Trinity also symbolises our ‘mastery’ over matter by unleashing the dangerous power of the atom only reinforces the significance of the 16th of July 1945.

So, 74 years into the Anthropocene, where is it taking us? I don’t think we’ll need another 74 years to find out.

Image: The Anthropocene began with a bang. The Trinity explosion is pictured here 16 milliseconds after the detonation. The highest point of the explosion’s dome in this image is about 200 metres high. (Los Alamos National Laboratory)