Lecture 2: Are we living in the anthropocene?

## Lecture 2: Are we living in the anthropocene? (Jo Browse)

General information:

* Earth is 5.4 billion years old.
* The spiral of time (figure). Currently in the Panaerozoic Eon (Visable life).
* We are in the Cenozoic era (New life)
* Ice age is defined as when there is permanent ice on the ground, some say we are in an ice age now.

What is a geological 'epoch'?

* They are periods of time spanning millions of years.
* Dates with fossils.
* Beginning and end of these periods are measured by golden spikes.
* Transitions in the GEs are often long (10,000 years) and can be redefined. We can now use other methods to date the geological epoch, such as through ice cores.

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Can life be a geological force?

* At the beginning of time Stromatolites were the only life- they began oxygenation. It took them a billion years to get the oxygen levels we have.
* 2 billion years ago we reached oxygen levels to support us.

What is 'Anthropocene'?

* A term from Paul Crutzen
* We drive the climate in the Anthropocene- it is a period.
* It has now been tacitly accepted and the international commission on stratigraphy, who have now put on a  worldwide hunt for the golden spike to mark the beginning of the new Anthropocene epoch.

Starts with CO2:

* Keeling curve: NOAA- CO2 graph
* 1960 CO2= 316pm
* 1700s = 230ppm
* Measurements above 400ppm in 2015.
* Strong correlation between high sea levels and high CO2.

​Arctic ice melt:

* 1979= satellite observations began to measure sea ice
* nsidc.org= excellent source of information.
* Last time that the Arctic was ice free was most likely between 5000 and 8000 years ago.
* An ice free Arctic is not unprecedented.

Ice melt and sea level rise:

* Sea levels rise from the melting of land ice- Greenland and Antarctic ice sheets.
* When Greenland melts is will probably rise sea levels by 6m- Antarctica = 60m. West Antarctica could melt within 100 years and cause 3 m sea level rise.
* Sea level rise is already happening.
* Sea level rise is not uniform, as tides are not uniform. Some places could see 3 or 4 times higher sea levels than others.

Ocean acidification:

* Ocean is a carbon sink- also absorbs a lot of heat.
* Significant acidification occurring.
* Majority of marine life requite carbonate to build shells.
* 93% of coral reefs have been damages on great barrier reefs by rising temperatures and sea level rise.
* Highest rate of acidification was 65 million years ago- when a super volcano erupted.

Has the Earth’s 6th mass extinction arrived?

* Mass extinction is 75% of all species lost in a geologically short period of time.
* Current extinction rates are between 1000 and 1000 than fossil background.
* We don't know how many species are on the planet
* We have an extinction rate of 0.01%, almost entirely down to humans. E.g climate change.
* At least 10,000 species of extinct each year.
* Casabayo in New Zealand- 40 left in wild due to aline species (rats).
* 95% of mammals are either us or ones that we have bred such as cattle.
* Before it was 40% wild animals.

xkcd = Geography comic (in case anyone wants to read it).

Deforestation:

* 25% of deforestation in last 50 years.
* 30% of world is covered in forest.
* Greenpeace say only 10% ‘intact’ forest.
* Current rates all rainforests will be lost in 100 years.
* Canada is deforesting at current rates- mainly due to tar sand extraction.

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Desertification:

* Occurring everywhere, but Africa is one of the main.
* Aral sea- mismanagement of water. Was one of the 4 largest lakes in the world.

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Freshwater management:

* Very little freshwater on the world- 0.0007% of water (1% of all freshwater) is available to sustain 6.8 billion people.
* By building dams and storing water on land we have reduced sea levels by around 3cm.
* Glaciers in Nepal have almost completely disappeared. They have build artificial glaciers, but this will not last long due to climate change.
* Sediment flows are about how sediment flows around the worlds rivers.
* For the last 100 years sediment loads have decreased- riverbank hardening/ logging etc.

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The human footprint:

* Since 1950s we have been significantly increasing human made objects such as plastics- have not been disposing of this properly.
* Plasticite = plastic rocks. Think are being produced in volcanic processes in oceans before being washed up onto the shore.

A radioactive world:

* First atomic bomb test in 1945
* First nuclear power plant in 1954
* Worst nuclear accident in Chernobyl in 1986
* Multiple anthropogenic isotopes now exist in the world.
* Radiocarbon dating no longer works post 1950.

No reputable scientist will deny that we are in the anthropocene, but they do argeu about when this period started!

When did the Anthropocene start?

* 3,000-11,000 years: Anthropogenic signature in river sediments and emergence of agricultural pollen species. River sediments were changing, and possibly change sea levels due to mismanagement of water.
* The industrial revolution (1800s). Started to produce manmade materials e.g fly ash and black carbon. Black carbon causes snow to melt quicker. Large scale water management started e.g Suez canal- large effects on sediments.
* The great acceleration (1950s).- Increase in trends of everything- Social economic e.g world population/ Real GDP/ Tourism/ Paper production/ Transportation. Earth system trends- Methane/ CO2/ NO2/ Surface temps/ Marine fish capture.
* It was agreed that the Great accelaration wwas when this started (30/3 votes) by international geographic congress. Started when nuclear bombs caused increased nitrates.

Humans as stewards of the natural world:

* Due to the Montreal Protocol ratified by 193 nations in 1989, the ozone hole is predicted to ‘heal’ by 2050. It banned CFCs.
* Ozone hole was found in 1980s- However, no-one believed it, they thought that the data was faulty.

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