Is China behind California’s 2017 catastrophic rain? New study finds a surprising ‘climate teleconnection’ linking the Rocky Mountains and Tibetan Plateau

California’s catastrophic rainfall in early 2017 and 2023 may have had an unexpected connection thousands of miles away. A new study has identified a climate teleconnection linking unusually warm temperatures over the Tibetan Plateau with extreme precipitation across California and neighboring western states. The research suggests that warming over the high-altitude plateau helped create an atmospheric disturbance that traveled eastward along the jet stream before strengthening weather systems near the US West Coast. The finding does not mean China ’caused’ California’s rain in a direct sense. Instead, it reveals how changes in one distant part of the atmosphere can influence weather patterns far away. According to Live Science, this is the first time researchers have identified the link, known as a ‘climate teleconnection’. The findings could help improve forecasts of extreme weather across the western US, potentially giving coastal communities earlier warnings and helping save lives while reducing billions of dollars in property damage.

WHAT HAPPENED IN CALIFORNIA IN 2017 and 2023?

In December 2016 and February 2023, the Tibetan Plateau was unusually warm for that time of year. About a month later, California, Nevada, Oregon, Utah and Arizona experienced record-breaking precipitation. The 2017 event was particularly surprising because it occurred during a La Niña year. La Niña conditions are typically associated with drier weather in California and nearby regions. Existing forecasting systems, which rely heavily on ocean conditions such as El Niño and La Niña, failed to predict the extreme rainfall accurately.

HOW DID THE TIBETAN PLATEAU AFFECT CALIFORNIA?

Researchers say the unusually high temperatures over the Tibetan Plateau created a strong temperature gradient between the plateau and surrounding regions. That disturbance then propagated eastward through the atmosphere along the jet stream. The process involved Rossby waves, enormous atmospheric waves that can travel thousands of miles. The researchers identified a Rossby wave train stretching between the Tibetan Plateau and the Rocky Mountains. As these waves reached the northeastern Pacific, they broke and intensified atmospheric conditions over California and surrounding states.

ATMOSPHERIC RIVERS MADE THE RAINFALL WORSE

The atmospheric disturbance strengthened atmospheric rivers along the US Pacific Coast. These narrow, elongated corridors transport huge amounts of water vapor and are major drivers of precipitation and flooding in the western United States. According to the study, the interaction between atmospheric rivers and Rossby waves helped produce the extraordinary rainfall during the winters of 2017 and 2023. Together, the events caused around $6.6 billion in damage and killed at least nine people.WHAT THE NEW STUDY FOUND

The study, titled “Extraordinary Tibetan Plateau early-winter heating drove record-breaking winter precipitation in California and adjacent regions,” was published in Science Advances on September 9, 2026. Researchers combined precipitation and surface-temperature observations with advanced climate modeling to investigate the atmospheric connection behind the extreme rainfall. The models were able to reproduce the extreme weather with surprising accuracy. The study was led by UCLA atmospheric and oceanic sciences professor Yongkang Xue, with co-authors Qian Li, William K.-M. Lau, J. David Neelin, Xubin Zeng, Yang Zhang, Shuting Li, Xianghui Kong, Bin Guan, Aaron Boone, Zhijiong Cao, Aihui Wang, Yan Pan, Qi Tang and Hara Prasad Nayak.

“This study provides the first evidence from observational data analysis and model simulations that abnormally high early-winter temperatures on the Tibetan Plateau led to stronger atmospheric rivers along the US Pacific Coast, driving heavy regional precipitation,” Xue told the outlet in an email.

The researchers say recognizing this teleconnection could improve early-warning systems for extreme weather in the western United States. If forecasters monitor unusual warming over the Tibetan Plateau, they may gain an additional clue about potentially dangerous weather weeks later. Purdue University professor Matthew Huber, who was not involved in the research, described the findings as a ‘specific and impactful case study’, according to Live Science. He noted that weather in the US West can be sensitive to very small changes occurring far upstream.

The new research reveals a remarkable atmospheric connection between the Tibetan Plateau and the western United States. Unusually warm conditions over the plateau appear to have helped trigger Rossby waves that traveled along the jet stream, eventually intensifying atmospheric rivers near California. The finding is important because traditional forecasting systems missed these events. By recognizing this distant climate signal, scientists may be able to improve warnings for future extreme rainfall, potentially giving communities more time to prepare for floods and other dangerous weather.