Global Warming: Did it Start in the Stone Age

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Global WarmingDid it Start in the Stone Age?

• Presented by
• Loren Berman, Dana Kresel,
• Shayna Sehayik, and Sam Shaffer

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William Ruddimans Theory

• The combined effects of deforestation and
  agricultural practices in the early Holocene
  period led to increased levels of CO2 and CH4
  about 8000 years ago.
• This stands in contrast to the idea that it was
  the Industrial Revolution that started global
  warming.
• These increased GHG emissions staved off an ice
  age.

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Rice Paddies

• Rice paddies release methane into the atmosphere.
• Ruddiman notes an upward trend of atmospheric
  methane, at a time when it should have decreased,
  corresponding to the new rice irrigation
  techniques used by farmers in Asia about 5000 yrs
  ago.

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Deforestation

• Deforestation leads to CO2 emissions.
• Based on historical documents from the Middle
  Ages, Ruddiman argues that a significant portion
  of Eurasia was already deforested.
• Right as deforestation practices spread across
  Eurasia, CO2 levels rose rapidly, against a
  natural declining trend.

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Staving Off an Ice Age

• Anomalies amounting to 250 ppb of CH4 and 40 ppm
  of CO2 would cause an increase of 0.8 degrees
  Celsius.
• Without this addition, the global temperature
  would have been 1.5-2 degrees cooler.
• This drop in temperature would have allowed for
  ice sheets to form as far south as northern Canada

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Criticisms

• Methane Emissions
• Deforestation
• Coral Reef Calcification
• Role of anthropogenic forces alone
• Provides evidence for skeptics
• He offers no solution for GW today
• Current Implications
• Water management and rice cultivation practices
• Deforestation vs. forest conservation