While climate warming reduces the occurrence of frost events, the warming-induced lengthening of the growing season of plants in the Northern Hemisphere may actually induce more frequent frost days during the growing season (GSFDs, days with minimum temperature < 0 °C). Direct evidence of this hypothesis, however, is limited. Here we investigate the change in the number of GSFDs at latitudes greater than 30° N using remotely-sensed and in situ phenological records and three minimum temperature (T_min) data sets from 1982 to 2012. While decreased GSFDs are found in northern Siberia, the Tibetan Plateau, and northwestern North America (mainly in autumn), ~43% of the hemisphere, especially in Europe, experienced a significant increase in GSFDs between 1982 and 2012 (mainly during spring). Overall, regions with larger increases in growing season length exhibit larger increases in GSFDs. Climate warming thus reduces the total number of frost days per year, but GSFDs nonetheless increase in many areas.

The reported progressive change of vegetation activity along elevational gradients has important aesthetic and conservation values. With climate change, cooler locations are suggested to warm faster than warmer ones, raising concerns of a more homogenized landscape along the elevation. Here, we use global satellite data to investigate the spatio-temporal dynamics of the elevational gradient (EG) in vegetation greenness (NDVI_max3), spring (SOS) and autumn phenology (EOS) during 1982–2015. Although we find clear geographical patterns of the EG in NDVI_max3 and SOS, there are no prevalent trends of vegetation homogenization or phenology synchronization along elevational gradients. Possible mechanisms, including spatially heterogeneous temperature lapse rate changes, different vegetation sensitivities to climate change, and human disturbances, may play diverse roles across different regions. Our finding of mixed EG trends and no general rules controlling EG dynamics poses challenges for mitigating possible adverse impacts of climate change on mountainous biological diversity and ecosystem services.

Amidst the escalating impacts of global warming, the occurrence and severity of compound extreme weather events have risen significantly, presenting substantial threats to both lives and property. Existing response strategies predominantly focus on individual events, often overlooking the cumulative effects rising from their inherent complexity. To address this critical gap, we conducted a thorough examination of sequential extreme precipitation–heatwave compound events (SEPHCE) in China from 1975 to 2020, utilizing data from 1929 meteorological stations. Our investigation revealed a consistent rise in the frequency and duration of SEPHCE, with a particularly notable surge since 1993. Furthermore, shorter interval events disproportionately affected the regions of southwestern and southeast coastal China. Furthermore, SEPHCE onset times exhibited advancement, and the endings were delayed, thereby intensifying the overall trend. These findings underscore the pressing need to prioritize effective planning and adaptation strategies to mitigate the impact of these compound event, while also addressing the potential exacerbation of inequality resulting from climate change.