Lecture 9: The Anthropocene PDF

Lecture 9: The Anthropocene The anthropocene — a geological epoch where humans are the dominant influence on Earth’s climate and environment Effects humans have had on the earth system: 1. Climate forcing from greenhouse gas emissions ● The “hockey stick” graph ○ “Increase in atmospheric carbon diox...

Lecture 9: The Anthropocene The anthropocene — a geological epoch where humans are the dominant influence on Earth’s climate and environment Effects humans have had on the earth system: 1. Climate forcing from greenhouse gas emissions ● The “hockey stick” graph ○ “Increase in atmospheric carbon dioxide over the past 60 years is about 100 times faster than previous natural increases” ● Current global warming is happening much faster than it did compared to the warming interglacial events over the past million years ○ Humans could witness a warming of 4 degrees C over 110 years; normally this warming would take 5000 years according to climate controls ○ Greenhouse gas concentration left natural trend about 8,000 years ago (time of onset of cattle and wet rice farming) ○ Warming may have started ~15,000 yrs ago 2. Ocean acidification and heating ● “The ocean has absorbed enough carbon dioxide to lower its pH by 0.1 units a 30% increase in acidity 3. Current extinction ● Although extinction is a natural phenomenon, it occurs at a natural ‘background’ rate of about one to five species per year ● Losing species ~1,000 times the background rate 4. Garbage and plastic in oceans ● Pollution of groundwater and surface waters 5. Engineering and agriculture ● Agriculture and excavations shape the landscape more than rivers and glaciers How geologists may define the “Anthropocene”: ● Geological boundaries ratified based on one specific location GSSP (global stratotype section and point = “golden spike”) ○ 65 ratified, most based on fossils Arguments for defining the Anthropocene as a new geological period ● Philosophical arguments ○ Human history v.s. Geologic history ○ Uniting different disciplines ○ Irreversibility: loss of biodiversity, climate stability ● Ethical arguments ○ Societal context for geosciences ○ Difficult situation for geoscientists if this new division would be rejected ● Paradigm shift ○ Stratigraphy linked with huma history ■ Still, stratigraphic determination of ‘Anthropocene’ requires something unique in the sedimentary record ■ Likely candidate: Plutonium 239 from above-ground nuclear tests starting in 1952 (detectable world-wide)