Anthropogenic Climate Change P2

what is the anthropocene

A proposed geological epoch representing the period when human activities have significantly impacted Earth's geology and ecosystems, making humans a geological force.

How do humans act as geological agents?

Humans move more rock, soil, and sediment than all natural processes combined, produce enough concrete to cover the globe 2mm thick, and affect the biosphere, atmosphere, and chemosphere.

How have humans altered biogeochemical cycles?

: Carbon, nitrogen, and phosphorus cycles have been altered by fertilization, widespread farming, and burning fossil fuels.

How much has human-induced warming increased?

Approximately 1°C above pre-industrial levels in 2017, increasing ~0.2°C per decade, primarily driven by greenhouse gas concentrations.

how has biodiversity been affected

Wild animals now account for only 3% of global mammal biomass, showing drastic biodiversity loss.

What is the Great Acceleration?

A proposed mid-20th century period marked by rapid human impacts like consumerism, nuclear testing, increased fly ash, microplastics, and shifts in heavy metals.

how many wild mammals have been lost since the start of civilisation

83%

also 80% marine mamals, 50% plants and 155 fish

What proxies define the Great Acceleration?

1) Atmospheric plutonium from nuclear testing
2) Fly ash from fossil fuels
supporting proxies: Microplastics, persistent organic pollutants, heavy metal changes, and fossil assemblage shifts

Why was Crawford Lake rejected as a GSSP for the Anthropocene?

he International Commission on Stratigraphy (ICS) did not accept it as the global reference point for defining the epoch.

What is the Early Anthropogenic Hypothesis?

Proposed by William Ruddiman; suggests pre-industrial deforestation and farming caused CO2 and CH4 increases thousands of years ago.

7000-5000 years ago

• Pre-industrial CO2 increase from deforestation: 21–24 ppm.

• Net terrestrial carbon release from deforestation: ~3.5 ppm CO2.

What is the "Orbis Spike"?

Proposed start of the Anthropocene in 1610, linked to the Columbian Exchange, showing species movement, crop introduction, diseases, and ecological changes.

How did the Orbis Spike affect atmospheric CO2?

Forest regrowth after pandemics(50 mill deaths) decreased CO2 by ~6–10 ppm, removing 13 billion tonnes of co2, causing global cooling from 1594–1677.

What are the main arguments for defining the Anthropocene?

Clarifies human impacts, provides a scientific framework, and draws attention to environmental issues.

What are the main arguments against defining the Anthropocene

Choosing a start date may neglect indigenous history, distract from current impacts, or oversimplify complex environmental changes.

How can the Anthropocene affect predicting future climate?

Human impacts are unprecedented, making historical analogues (like the Mid-Pliocene) less reliable for predicting future conditions.

how much did deforestation and farming contribute to pre-industrial carbon emissions

310–343 Gt

equivalent to 21–24 ppm CO2 increase.

how much mammal biomass do humans and livestock have

over 95%

how did rice paddies and livestock in n. asia contrubute to CH4 emissions 5000-10,000 years ago

70%

Why is the Mid-Pliocene used as an analogue for future climate, and what is the limitation of this approach?

• The Mid-Pliocene (3.3–3 Ma) was 2–3°C warmer than today, so scientists use it to predict potential future warming.

• Limitation: Human activity is now altering climate patterns in unprecedented ways, making past analogues less reliable for forecasting future impacts.