Climate Change over the past 4000 Years

 I last wrote about  Climate Change and Civilization for the past 4,000 Years in 2016. Since then, a lot has changed, and I’ve learned a lot more about the subject. First, we learned that various air and sea temperature proxies are different, with different accuracies and sensitivities to seasonal temperature variations. Because of this, they cannot be combined into a global average effectively. The global average surface temperature reconstruction relied upon in the IPCC report was created by Kaufman and others. They admit the average spacing of each temperature is 164 years. To validly compare the global instrumental temperature record to the proxies, we must average all daily readings since 1860 into one point. This means that the rate of warming since 1860 is not detectable by the proxy record due to its limitations.

Most proxies focus on one season, and seasonal temperatures do not necessarily reflect yearly averages. Mixing different proxy types is problematic, and most proxies are influenced by factors like precipitation and CO2 levels, which complicate the data further. While combining proxies into one composite record is difficult, we can analyze high-quality, local proxies individually to gain insights into climate trends. Two valuable records are the Greenland ice core record and the Indonesian Throughflow record from the Makassar Strait, both having a good resolution over the 4,000-year period. However, combining Northern and Southern Hemisphere proxies may not yield accurate results due to differing temperature trends.

The Vinther record and Rosenthal record both provide key insights into temperature changes over time. They show that the Neoglacial climatic period was primarily a Northern Hemisphere event, with significant temperature declines occurring during the Little Ice Age, which started around 1300 but intensified in the late 1400s. This epoch featured severe cold periods, droughts, and significant social and political upheaval in various civilizations.

Historically, around 2000 BC, advanced cultures like the Egyptian and Harappan civilizations faced turmoil, with significant changes in power dynamics and climatic conditions affecting their stability. The Little Ice Age coincided with notable historical events, including the collapse of major civilizations and widespread suffering due to colder climates, plagues, and socio-political strife.

Some scholars suggest that fluctuations in solar activity correlate with climate change, indicating that humans tend to thrive in warmer periods. It is necessary to confront historical and archaeological evidence regarding climate effects on civilization, emphasizing that cold periods pose greater challenges to humanity than warmer times.

https://wattsupwiththat.com/2024/12/03/climate-change-over-the-past-4000-years/