New research from a team of scientists with the Institute of Atmospheric Physics (IAP) at the Chinese Academy of Sciences investigate past changes in El Nino diversity and quantify the contribution of anthropogenic forcing and internal variability to the recently observed El Nino diversity. They found that greenhouse warming and internal variability synergistically increase extreme and central Pacific El Nino frequency since 1980.

The research was published in journal Nature Communications on January 24. It is based on multiple pieces of evidence, including multiple long-term observations and the outputs from sixth phases of the Coupled Model Intercomparison Project (CMIP6). The researchers found that there exists another extreme El Nino and CP El Nino epoch, around year 1900, with similar spatial and temporal evolution, dynamic processes, and climate impacts as those that occurred in the last 40 years. They also found that the frequent occurrence of extreme El Nino events and CP El Nino events since 1980 was caused by the combination of anthropogenic forcing and internal variability associated with the Atlantic Multidecadal Oscillation (AMO). Researchers revealed that a positive AMO enhances the zonal sea surface temperature gradient in the CP, which strengthens zonal advective feedback, favoring extreme and CP El Nino development. Moreover, using a statistical model, researchers quantified the contribution of anthropogenic forcing and internal variability to the recently observed El Nino diversity.

"How El Nino will change in the future is a crucial issue, yet model projections remain large uncertainty. Understanding the variation of observed El Nino may help more accurately project El Nino's future change," said Prof. HUANG Gang, corresponding author of the study.

In addition to Huang, Qi Liu from Nanjing University is also the corresponding author of the study. Ruyu Gan from IAP is the first author of the study. Kaiming Hu and Xichen Li from IAP are the coauthors of the study.

Reference:
Gan, R., Liu, Q., Huang, G., Hu, K., Li, X. Greenhouse warming and internal variability increase extreme and central Pacific El Nino frequency since 1980. Nature Communications 14, 394 (2023). https://doi.org/10.1038/s41467-023-36053-7.

Link：https://www.nature.com/articles/s41467-023-36053-7

Contact：LIU Qi，qiliu@nju.edu.cn; HUANG Gang，hg@mail.iap.ac.cn，