Over the past 2000 years, these thrilling volcanic eruptions have had a huge impact on the global climate!

Volcanic eruptions have important climate effects. Based on observation, reconstruction, simulation and assimilation data, the research team of Professor Liu Jian from Nanjing Normal University systematically summarized the historical facts of major volcanic eruptions in the past 2000 years, the impact mechanism on the global and Chinese climate, and future research directions. The results were reported in the Chinese and English editions of Science China: Earth Sciences, Issue 1, 2024.

Data from the reconstruction of volcanic activity over the past 2000 years show that cold periods (530-700 AD, 1200-1460 AD, and 1600-1840 AD) occurred during periods of frequent major volcanic eruptions, while warm periods (0-200 AD and 900-1100 AD) occurred during periods of volcanic calm. The Changbaishan eruption in 946 AD was the strongest volcanic eruption in China over the past 2000 years.

The study found that within a few years after a major volcanic eruption, both the world and China experienced significant cooling, but the cooling amplitude shown by the reconstruction data was not completely consistent with the volcanic intensity (Figure 1). However, the cooling simulated by the climate model has a significant linear relationship with the volcanic intensity. On the interdecadal scale, when there are continuous major volcanic eruptions, interdecadal cold events have occurred in both the Northern Hemisphere and China. In the first year after a major volcanic eruption, global monsoon precipitation decreased significantly, while precipitation in the Yangtze River Basin of China increased abnormally. There were inconsistent responses between different data in North China, Northeast China, and the southern Qinghai-Tibet Plateau. Frequent strong volcanic eruptions, volcanoes superimposed on the solar minimum, and the effects of internal variability in the climate system superimposed on volcanoes will lead to interdecadal drought events in the Northern Hemisphere monsoon region and eastern China.

Figure 1 Changes in global average surface temperature over the past millennium

(a) Reconstructed global volcanic external forcing; (b) Reconstructed surface temperature anomaly (°C); (c) Global annual mean surface temperature simulated by climate models

The research team summarized the changes in the El Niño-Southern Oscillation (ENSO) over the past millennium based on tree ring reconstructions and found that when a major tropical volcanic eruption occurs, an El Niño event will occur and then quickly decay into La Niña, causing an abnormal northwest Pacific anticyclone and transporting water vapor to the Yangtze River Basin; however, the coral δ18O records in the central tropical Pacific show that major volcanic eruptions do not cause significant El Niño events, indicating that there are differences between the reconstructed data. Frequent major volcanic eruptions can affect the phase changes of the Atlantic Multidecadal Oscillation (AMO) by triggering changes in the Arctic sea ice expansion process, sea-air interaction, and changes in the dynamic processes within the ocean. The response of ENSO and AMO to volcanoes will further affect the differences in regional climate responses, which may cause divergence between reconstruction and simulation data.

Future research needs to strengthen the in-depth understanding of the impact of internal variability of the climate system on climate under the influence of volcanoes, the changes in weather-seasonal intrascale variability, and climate abrupt changes. This depends on the improvement of volcanic external forcing reconstruction, the development of stratospheric chemistry-aerosol-climate models, and a more comprehensive revelation of major volcanic climate effects.