Integrated carbonate dating and thermometry revealed deep-to-surface structurally controlled fluid circulation over the past ∼575 kyr Long-term hydraulic connectivity sustains meteoric-fluid circ...

Open access notables Are Modern Droughts Unprecedented?, Helpap et al., AGU Advances Global drought variability of past centuries remains poorly understood due to sparse instrumental records and limited paleoclimate reconstructions. Yet, quantifying long-term forced and unforced variability is key for assessing the extremeness of modern (2000–2024) drought events. Here, we combine 20 ensemble members from a 600-year climate simulation (ModE-Sim, 1420–2009) and modern reanalysis data (ERA5-Land, 1950–2024) to place recent droughts in a multi-century context. Drought magnitude and timing are measured using the annual maximum potential cumulative water deficit (PCWD), which integrates atmospheric moisture demand and supply, the daily timing of precipitation events, snow melt, and radiation. We analyze the deviation of modern annual, multi-year mean, and 30-year extreme PCWD from alternative reference periods that sample forced and unforced variability to a variable extent. We find a strong decline in the number of regions with unprecedented modern (2000–2024) single-year and 25-year mean PCWD as the reference is extended into the past and with the additional consideration of unforced atmospheric variability. This is not the case for extreme droughts. 30-year extreme PCWD has increased beyond the range of variability of the last 600 years in over half of all regions globally...

Open access notables Are Modern Droughts Unprecedented?, Helpap et al., AGU Advances Global drought variability of past centuries remains poorly understood due to sparse instrumental records and limited paleoclimate reconstructions. Yet, quantifying long-term forced and unforced variability is key for assessing the extremeness of modern (2000–2024) drought events. Here, we combine 20 ensemble members from a 600-year climate simulation (ModE-Sim, 1420–2009) and modern reanalysis data (ERA5-Land, 1950–2024) to place recent droughts in a multi-century context. Drought magnitude and timing are measured using the annual maximum potential cumulative water deficit (PCWD), which integrates atmospheric moisture demand and supply, the daily timing of precipitation events, snow melt, and radiation. We analyze the deviation of modern annual, multi-year mean, and 30-year extreme PCWD from alternative reference periods that sample forced and unforced variability to a variable extent. We find a strong decline in the number of regions with unprecedented modern (2000–2024) single-year and 25-year mean PCWD as the reference is extended into the past and with the additional consideration of unforced atmospheric variability. This is not the case for extreme droughts. 30-year extreme PCWD has increased beyond the range of variability of the last 600 years in over half of all regions globally...

RealClimate: Guest post from Bill Ruddiman, University of Virginia For over a decade, paleoclimate scientists have argued whether the warmth of the last several thousand years was natural or anthropog...

INSTAAR fellow Giff Miller and collaborators document the remnants of a “failed ice age” in a new investigation for Science. The researchers found that Arctic

Land snail shells serve as valuable paleoclimate archives, with their isotopic compositions recording past changes in regional ecology and hydrology. …

Researchers are still puzzling through what happened to the ancient Maya civilization, which mysteriously dwindled. New answers have parallels in the present.

The world's driest desert has its long dry streak called into question. An 8.8-million-year-old capybara relative points to persistent freshwater habitats in this hyperarid landscape.

Abstract. Dust deposits in ice cores provide a valuable archive of past atmospheric circulation, offering insights into climate dynamics during key climate transitions such as the last glacial termina...

Scientific Reports - Palaeocene climate warming as a catalyst for wildfire intensification

Paired IP25-brassicasterol and IP25-dinosterol down-core measurements are compiled from recent literature, including the site location (latitude, longitude and water depth) and biomarker concentrations normalized to gram of sediment (μg gSed−1) and/or total organic carbon (μg gTOC−1) (Extended Data Table 1). Only Holocene records with direct age constraints are retained. For consistency, new age-depth models based on published radiocarbon ages and/or chronostratigraphic markers (and associated regional reservoir age corrections, ΔR) are produced for all cores using the Marine20 radiocarbon age calibration curve57 with the Bacon software58 (see Supplementary Table 1 for details). The ages of all biomarker measurements are subsequently updated with the new age-depth models. The full ensemble of age-depth models obtained from Bacon is used for sensitivity analyses, which show that our results are robust to the associated age uncertainties (see Supplementary Information section 3 for details). We select paired IP25-brassicasterol concentrations with median ages between 5 and 7 ka and supply them to BaySIC, which calculates the ln(PBIP25) index by the following equation: $$\,\text{ln}\,({{\rm{P}}}_{{\rm{B}}}{{\rm{IP}}}_{25})=\,\text{ln}\,\left(\dfrac{[{{\rm{IP}}}_{25}]}{[{{\rm{IP}}}_{25}]+[\,\text{brassicasterol}\,]}\right),$$ (1) with the appropriate detection limit treatment as described by ref. 34. Measurements reported in μg gTOC−1 are prioritized to minimize the effect of changing sedimentation rates35, but the ln(PBIP25) values derived from measurements...