The 21st century has witnessed an increase in the frequency and intensity of extreme weather events like heatwaves and heavy rainfall, significantly impacting human lives, ecosystems, economies, and food security. These events often exhibit spatial and temporal associations across the globe, suggesting common underlying circulation patterns. While various non-stationary and inhomogeneous extreme events have been observed since 2000, concurrent extremes are projected to become more frequent due to anthropogenic forcing. The year 2022 saw five record-breaking summer extremes in the inter-hemisphere, prompting investigation into the mechanisms and forcing sources behind these concurrent events. Anthropogenic forcing amplifies both the mean and variability of temperature and precipitation, affecting concurrent extremes through multiple pathways, including increased atmospheric water vapor content, changes in atmospheric circulations (weakened storm tracks, shifted jet streams, amplified waves), and changes in low-latitude circulations (Walker, Hadley, and monsoon circulations). However, anthropogenic forcing alone is insufficient for annual to seasonal extreme predictions. Other factors such as sea surface temperature (SST) anomalies, soil moisture-temperature feedback, and the urban heat island effect play crucial roles. Accelerated warming in the Earth's three Poles, exceeding the global average, also has significant implications, due to ice and snow-albedo feedback and snow-hydrological effects. Arctic amplification (AA) slows westerly jet streams, leading to the formation of double jet streams and amplified planetary waves influencing weather patterns. Snow cover on the Tibetan Plateau and snow/ice melting in Antarctica also impact regional and global climate patterns. This study aims to investigate the concurrent features of record-breaking heatwaves and precipitation extremes in 2022, analyze significant anomalies in ice phase changes in the three Poles, and explore their independent and synergistic effects on these extremes.

The literature review section extensively cites previous research on various aspects related to extreme weather events. It covers studies on the increasing frequency and severity of heatwaves and heavy rainfall (references 1, 2), their impacts on human society and the environment (references 3-11), the spatial and temporal associations between different extreme events (references 12, 13), and the role of anthropogenic forcing in amplifying these extremes (references 14-27). The role of Arctic amplification (references 28-43), the impact of snow cover on the Tibetan Plateau (references 21, 44, 45), and the influence of Antarctic melting (references 46-48) on global climate are also discussed. The review highlights the lack of research focusing on the concurrent occurrence of heatwave and precipitation extremes and the role of ice and snow melting in the Earth's three Poles, which this study addresses.

The study defines a temperature co-occurring index (TCI) to quantify the spatial distribution of concurrent extremes. It analyzes spatial distributions of air temperature anomaly and extreme precipitation in 2022 (Figure 1). Regression analysis was conducted to assess the relationship between surface air temperature and soil moisture with the TCI, identifying key regions in the Arctic, Antarctic, and Tibetan Plateau exhibiting significant hydro-thermal anomalies associated with the extremes (Figure 2). Correlation analysis examined the relationships between heatwaves and precipitation extremes with 2-m air temperature, skin temperature, and soil moisture in these key regions (Figure 3). The analysis also explored the relationship between extremes and atmospheric circulation anomalies (Supplementary Figures 1 and 2), including the South Asia High (SAH), West Pacific Subtropical High (WPSH), North African High (ASH), Asian Summer Monsoon (ASM), and Mascarene High (MH). Sensitivity experiments using the Community Earth System Model (CESM) were conducted to simulate the independent and combined effects of reduced snow depth and ice cover in the Arctic, Antarctic, and Tibetan Plateau (Figures 4 and 5). The CESM model incorporates coupled models for atmosphere, land, sea ice, and ocean, allowing simulation of ice-atmosphere, ocean-atmosphere, and land-atmosphere interactions. Four sensitivity experiments were run: independent forcing from the Arctic, Antarctic, and Tibetan Plateau, and a combined forcing experiment. Control experiments were also run for comparison. The study uses several datasets for analysis, including CPC precipitation data, ERA5 circulation data, HadISST sea surface temperature and sea ice data, and GLDAS soil moisture data (Data Availability section).

The study found that 2022 exhibited an amplified trend of concurrent extreme events, as indicated by a high TCI value. Significant warming anomalies were observed in the Arctic and Antarctic during late spring and summer 2022, along with record-breaking soil moisture increase on the Tibetan Plateau. Heatwaves and precipitation extremes in various regions (Yangtze River, Western Europe, Western North America, Pakistan, South China, Northeast Asia) showed significant positive correlations with hydro-thermal factors in the three Poles and negative correlations with albedo. Analysis of atmospheric circulation anomalies revealed the roles of poleward and amplified westerly Rossby waves, poleward-extending subtropical highs, and southward-weakened Asian monsoon circulations in driving the concurrent extremes. The South Asia High (SAH) showed significant associations with all extremes, suggesting the importance of thermal conditions over the Tibetan Plateau and condensation heating. The study also found interactions between the hydro-thermal conditions in the three Poles. CESM simulation results confirmed that the independent and coupled forcing from reduced snow depth and ice cover in the three Poles led to positive temperature anomalies in various regions (heatwave), and positive precipitation anomalies in Pakistan, South China, and Northeast Asia, consistent with the observed concurrent extremes. The simulated circulation anomalies included poleward jet streams, amplified Rossby waves, and a weakened Asian summer monsoon.

The findings strongly suggest that the warming and hydro-thermal anomalies in the Earth's three Poles played a crucial role in driving the concurrent heatwaves and precipitation extremes observed in 2022. The interactions between the three Poles, acting independently and synergistically, modulated atmospheric circulations, leading to the observed patterns. The study demonstrates the importance of considering the impacts of polar warming on mid-latitude and tropical weather extremes, particularly for sub-seasonal to annual predictions. While long-term mitigation strategies are necessary, improved understanding of the mechanisms linking polar warming to concurrent extremes is critical for enhancing disaster prevention and mitigation efforts.

The study reveals a significant link between warming-induced hydro-thermal anomalies in the Arctic, Antarctic, and Tibetan Plateau, and the amplified concurrent extremes of 2022. The independent and synergistic effects of these three poles modulated atmospheric circulation patterns, leading to intensified heatwaves and precipitation extremes across tropical and extratropical regions. Future research should further investigate the complex interactions between different forcing factors, including ENSO and local land feedback, to improve seasonal prediction capabilities.

The study primarily focuses on the role of three Poles warming, acknowledging the influence of other factors like ENSO and local land processes. The CESM simulations provide valuable insights, but model uncertainties and limitations should be considered when interpreting the results. Further research could explore the impact of different emission scenarios on future concurrent extreme events and refine the model simulations to reduce uncertainties.