Geological History of Earth's Climate

Overview of Climate Changes

• Global Climate Changes: Earth's geological history shows many global climate changes.
  • Effects on Species: Some species went extinct, others evolved.
  • Major Extinctions: Up to 90% species extinction at times; five known in the past 500 million years.
  • Current Extinction: Sixth extinction is ongoing and fastest in known history.

Factors Influencing Climate

• External: Solar activity, planetary orbit deformations.
• Internal: Earth’s own geological and atmospheric activities.
• Graph Analysis: Temperature changes over 500 million years shown via excavation data.

Detailed Periods in Earth's Climate History

Possible Past: 66 Million Years Ago

• Asteroid Impact: 10-km asteroid caused massive extinction.
  • Aftermath: Cooling period, extinction of most large species including non-avian dinosaurs.

Cenozoic Era

• Paleocene Epoch: Earth recovering from asteroid impact.
  • New Species: Flowering plants, mammals, and birds.
• Eocene Epoch: 56-34 million years ago.
  • Temperature Rise: Average up to 28°C.
  • Continental Configuration: Facilitated even heat distribution.
  • Mammalian Evolution: Emergence of primates, cetaceans, and rodents.
• Gradual Cooling: Spread of Azolla decreased CO2.

Oligocene Epoch (34-23 million years ago)

• Important Events:
  • Rise of mountain ranges.
  • Emergence of C4 photosynthesis in plants.
  • Tectonic shifts isolating Antarctica, initiating ice formation.

Miocene Epoch (23-5.3 million years ago)

• Mid-Miocene Disruption (14 million years ago):
  • Milankovitch cycles: Orbital changes causing cooling.

Pleistocene Epoch (2.6 million-11,700 years ago)

• Climate Oscillations: 41,000-year cycles of warming and cooling.
• Middle Pleistocene Transition: Irregular cooling cycles every 100,000 years.
• Human Evolution: Spread and adaptation of ancient humans.

Human Impact and Modern Climate Change

• Industrial Revolution: Increased carbon dioxide and pollutant emissions.
• Current Emissions: 38 billion tonnes of CO2 annually (2022).
• Comparisons with Volcanic Emissions: Human emissions ~150x larger.
• Consequences:
  • Glacier melting.
  • Permafrost melting releasing more CO2 and methane.
  • Sea levels potentially rising 66 meters.
  • Extreme weather, forest fires, habitat loss.
• Species Extinction: 1,000 large species in 500 years; 35,000 currently threatened.
  • Key species at risk: Honeybees, bananas, and others crucial to ecosystems.

Call to Action

• Importance of environmental stewardship to prevent catastrophic climate change.
• Encourage public discourse and awareness.