Meiyu-Baiu, the distinct rainy season in subtropical East Asia, is characterized by a quasi-stationary Meiyu-Baiu Front (MBF) along which excessive rainfall and mega floods often occur. This study shows that the spatial stationarity of MBF, and thus its potential to generate catastrophic flooding is inherently modulated by synoptic-scale disturbances over northeastern East Asia. The activity of these disturbances is coupled with the Northern Annular Mode (NAM) and the subtropical westerly jet across the subseasosnal timescales. A prominent negative phase of the NAM shifts the jet and its associated Rossby waveguide equatorward, channeling wave energy toward subtropical East Asia instead of northeastern East Asia. This “diversion” of Rossby wave leads to suppressed development of synoptic-scale disturbances and a more stable mid-latitude airmass, ultimately stabilizing the MBF and thus persistent and extreme Meiyu-Baiu rainfall. This mechanism clearly operated in the extreme Meiyu-Baiu season in 2020. Subseasonal hindcasts of the event further confirm that their skills are directly proportional to their capability in predicting the NAM transition to a negative phase. This finding underscores the need to improve the representation of the extratropical atmospheric variability in forecast models to better predict and prepare for extreme rainfall and hydrological hazards typical of Meiyu-Baiu seasons.
Timely and accurate projections of when global warming will exceed the Paris Agreement’s 1.5 °C threshold are essential for effective climate policy. Existing estimates place this exceedance in the early 2030 s but carry substantial uncertainty. Here we analyze the latest observational temperature records through 2025 and identify a statistically significant doubling of the global warming rate during 2011–2025 (0.40 °C per decade) compared to 1971–2025 (0.20 °C per decade). Extrapolating this accelerated rate projects a crossing of the 1.5 °C threshold by 2028, nearly a decade earlier than previous estimates. Regional analyses attribute this acceleration primarily to intensified warming over East Asia–the North Pacific, mid-latitude Eurasia, and the South Atlantic–Antarctic regions. The ensemble mean of 26 climate models fails to capture the observed doubling of the warming rate, simulating a rate of only 0.29 °C per decade. These findings suggest a narrower window remains to limit warming to 1.5 °C, underscoring the urgency for rapid and substantial reductions in greenhouse gas emissions.
A key challenge in semiarid savannas is determining whether ambient isoprene directly traces local biogenic emissions or represents an integrated signal shaped by chemistry and atmospheric dynamics. Here we use hourly measurements of isoprene, methyl vinyl ketone, and methacrolein from August to December 2024 at a savanna site near the Okavango Delta, Botswana, spanning dry to early wet seasons. During the early-wet seasons, daytime isoprene increased with vegetation growth and followed the expected daytime pattern of biogenic emission, suggesting a stronger local contribution. During the dry seasons, isoprene often increased at night, with patterns consistent with stronger atmospheric processing and shallow nighttime boundary-layer influence. Back-trajectory analyses suggested a preferred upwind sector, consistent with possible recent transport. These results suggest that seasonal state affects both isoprene abundance and its representativeness as a proxy for local biogenic emissions in semiarid savannas.
Large tropical volcanic eruptions have been hypothesized to induce surface warming over Eurasia in winter. Recent studies, however, have questioned the robustness of this claim and highlighted the very large internal variability in that season, which can easily overshadow any forced signal caused by such eruptions. To address uncertainties arising from sparse winter proxy data in previous reconstructions, we here examine a recently developed “online” paleo-data assimilation dataset, LMR Seasonal, in which the analysis from one season is propagated forward as the prior for the next season, allowing information from the dense network of summer-sensitive proxies to better constrain winter climate. We examine Eurasian and Northern European temperatures first following the 20 largest tropical eruptions of the last millennium, each exceeding the magnitude of the 1991 Pinatubo event and then, separately, following the largest extra-tropical eruptions over the same period. Irrespective of latitude, we find no evidence of statistically significant wintertime post-eruption warming – or cooling – and correlation analyses show no significant relationship between volcanic stratospheric sulfur injection and subsequent winter temperature anomalies. These findings are corroborated with two additional datasets (WinTEDA and ModE-RA). In addition, analysis of individual eruptions reveals considerable spread across datasets for many events, leading us to question the validity of superposed epoch analysis, which can yield erroneous conclusions even on continental scales.
Vessel Speed Reduction (VSR) lowers ship CO2 emissions, but its aerosol consequences remain poorly constrained. Combining unmanned aerial vehicle (UAV) plume interception, single-particle mass spectrometry (SPMS), and population-balance inversion across 14 ship plumes, we reconstructed ultrafine and coarse modes and identified two marker gaps. Only 35.8% of the reconstructed particle-number population carried detectable V (29.5% at 4.9 versus 39.7% at 13.4 knots in a matched-vessel pair; 0–70.8% across a speed-blind manifold), showing operation-dependent marker coverage. Approximately 20% of analyzed particles met SPMS biomass-burning criteria, indicating potential false positives in ship-influenced samples. Plume-stratified analysis found 2.3–10.7-fold higher median sulfate-related ion signals in V/VO-bearing particles. Independent V–S co-location supports an association potentially arising from V-associated sulfur chemistry during exhaust cooling, pre-existing SO3 uptake, or terminal co-deposition; laser desorption/ionization matrix effects may contribute to the contrast. In the matched-vessel case, VSR’s CO2 benefit coincided with a carbon-rich particle shift, altered V/VO–sulfur signatures, and lower strict detectable-V coverage. This indicates a potential aerosol-composition and marker-reliability trade-off missed by bulk-mass metrics, with implications for hazard-relevant compositional indicators.
