Thongchai Thailand

European Colonization of America & the LIA

Posted on: April 23, 2019


  1. According to researchers at University College London, “One surprising effect of European colonization of the Americas was a cooling of the Earth’s climate that explains the Little Ice Age (LIA). The LIA is described in a related post [LINK] . These researchers estimate that the indigenous population of the Americas at the end of the 15th century was 60 million. Over the next century, this population declined by some 90 percent, largely due to epidemics introduced by Europeans. As a result, around 215,000 square miles of cultivated land, roughly the area of France, was left fallow and reverted to forest. This sucked up enough carbon dioxide—a greenhouse gas that traps heat in the atmosphere—to lead to cooling. This process took place amid an extended cold stretch known as the Little Ice Age, which lasted from around 1250 to 1850. Other factors that contributed to cooling during this period included numerous widespread volcanic eruptions and natural fluctuations in solar radiation. But, Koch says, the effects of colonization played a key role in driving temperatures down in the early seventeenth century, adding, “This is thought to be the coolest part of the Little Ice Age.”
  2. This assessment likely derives from a decline in atmospheric CO2 concentration of ≈10 ppm from ≈282 ppm in ≈1580 to ≈271.6 ppm in ≈1612  as seen in the chart below. This drop of 10.4ppm in atmospheric CO2 implies a temperature decline of ≈0.12C over a period of 32 years or 0.00375C/year by way of climate sensitivity to atmospheric CO2 at the Manabe climate sensitivity value of λ=2. lawdomeco2
  3. The paleo temperature record for the Northern Hemisphere in Mann etal 2008 is shown in the chart below. Here we find a correspondingly undetectable change in temperature from 1580 to 1612.      mann2008chart
  4. The data presented above is consistent with the assessment that there was a minor CO2 decline of ≈10 ppm during the time of the European settlement of North America. However, the attribution of the change to European colonization is speculative and its proposed contribution to the the cooling from the Medieval Warm Period (MWP) to the Little Ice Age (LIA) is inconsistent with the minute amount of cooling implied by the climate sensitivity and the absence of cooling in the paleo record shown above.
  5. We note also that the total area of agricultural land that reverted to forest of 556,847 square kilometers represents 0.374% of global land area. Since about 65% of the world’s photosynthesis is in the ocean the net increase in photosynthesis could not have been more than 0.13%. It is unlikely that this insignificant change in photosynthesis caused a significant change in atmospheric CO2 concentration.
  6. CONCLUSION: We find no evidence to support the attribution of the 10 ppm drop in atmospheric CO2 from 1580 to 1612 to the European colonization of North America or for its alleged contribution as a cause of the Little Ice Age. Without the necessary supporting data, the proposed relationship between European colonization of North America, the drop in atmospheric CO2, and its contribution to the Little Ice Age proposed in the research paper appear speculative.
  7. Related posts: [MWP]  [LIA] .

3 Responses to "European Colonization of America & the LIA"

[…] European Colonization of America & the LIA […]


Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

%d bloggers like this: