Intensifying spatially compound heatwaves: Global implications to crop production and human population.

Recent research has provided crucial insights on regional heatwaves, including their causal mechanisms and changes under global warming. However, detailed research on global-scale spatially compound heatwaves (SCHs) (concurrent heatwaves over multiple regions) is lacking. Here, we find statistically significant teleconnections in heatwaves and show that the frequency of global-scale SCHs and their areal extent have increased significantly, which has led to 50 % increase in the population exposed to extreme heat stresses in the two most recent decades. Crop yields were reduced in most of the years of anomalous heatwaves, which often happen during El-Niños. The internal climate variability appears to significantly influence the inter-annual variability of regional and global heatwave extents. Insights gained here are critical in better quantifying heat stress risks inflicted on socioecological systems.

Glaciohydrology of the Himalaya-Karakoram.

Understanding the response of Himalayan-Karakoram (HK) rivers to climate change is crucial for ~1 billion people who partly depend on these water resources. Policy-makers tasked with sustainable water resources management require an assessment of the rivers' current status and potential future changes. We show that glacier and snow melt are important components of HK rivers, with greater hydrological importance for the Indus basin than for the Ganges and Brahmaputra basins. Total river runoff, glacier melt, and seasonality of flow are projected to increase until the 2050s, with some exceptions and large uncertainties. Critical knowledge gaps severely affect modeled contributions of different runoff components, future runoff volumes, and seasonality. Therefore, comprehensive field observation-based and remote sensing-based methods and models are needed.

Snowfall Variability Dictates Glacier Mass Balance Variability in Himalaya-Karakoram.

Glaciers in the Himalaya-Karakoram (HK) are critical for ensuring water-security of a large fraction of world's population that is vulnerable to climate impacts. However, the sensitivity of HK glaciers to changes in meteorological forcing remains largely unknown. We analyzed modelled interannual variability of mass balance (MB) that is validated against available observations, to quantify the sensitivity of MB to meteorological factors over the HK. Within the model, snowfall variability (0.06 m/yr) explains ~60% of the MB variability (0.28 m/yr), implying a sensitivity of MB on snowfall to the tune of several hundreds of percent. This stunningly high sensitivity of MB to snowfall offers crucial insights into the mechanism of the recent divergent glacier response over the HK. Our findings underscore the need for sustained measurements and model representations of the spatiotemporal variability of snowfall, one of the least-studied factors over the glacierized HK, for capturing the large-scale and yet region-specific glacier changes taking place over the HK.