China’s climate history includes multiple climate warming and cooling fluctuations of 4°C within centuries, with cold periods aligning with declines in solar irradiance.
According to a new study (Zhang et al., 2021), northern China’s coldest temperatures of the last 5000 years occurred 300 calibrated years before present (cal yr BP), coinciding with the Little Ice Age and a decrease in solar irradiance. This frigid period was was followed by a ~4°C warm-up (from about 3.5°C to 7.5°C) within the span of about 150 years during the middle of the Qing Dynasty (1644-1912 CE), which was well before anthropogenic CO2 emissions began sharply rising.
The warmest temperatures of the last millennium occurred during the Medieval Warm Period (Song Dynasty, 960-1279 CE).
Rapid cooling periods of multiple degrees per century also coincided with the collapse of ancient civilizations, or dynasties, as wars and social unrest were often associated with competition for access to natural resources (such as water during droughts).
Image Source: Zhang et al., 2021
The Zhang et al. study above only uses a 30-year (climate-length) sampling resolution to document temperature changes over the last 5000 years.
Another new study (Chen et al., 2021) assigns an annual temperature value for each year since 1200 A.D. in Southern High Asia.
Interestingly, since the end of the Medieval Warm Period there have been 23 total “extremely warm years” in this region. Seven occurred in the 1400s. Six in the 1600s. Five in the 1700s. And there were five “extremely warm” years in the 2000s.
In other words, since 1200 A.D., 18 of the 23 warmest years in Southern High Asia occurred between the 1400s and 1700s A.D.