A5079971003- Geology and Paleoclimatology Research
- Climate variability and models
- Isotope Analysis in Ecology
- Atmospheric and Environmental Gas Dynamics
- Cryospheric studies and observations
- Methane Hydrates and Related Phenomena
- Oceanographic and Atmospheric Processes
- Meteorological Phenomena and Simulations
- Marine and coastal ecosystems
- Paleontology and Stratigraphy of Fossils
- Groundwater and Isotope Geochemistry
- Tree-ring climate responses
- Atmospheric aerosols and clouds
- Climate change and permafrost
- Ecosystem dynamics and resilience
- Evolution and Paleontology Studies
- Marine and environmental studies
- Geological formations and processes
- Atmospheric chemistry and aerosols
- Plant Water Relations and Carbon Dynamics
- Arctic and Antarctic ice dynamics
- Tropical and Extratropical Cyclones Research
- Geological and Geochemical Analysis
- Marine Biology and Ecology Research
- Reservoir Engineering and Simulation Methods
NSF NCAR Climate and Global Dynamics Laboratory
2020-2025
NSF National Center for Atmospheric Research
2020-2025
Goethe University Frankfurt
2023
Sun Yat-sen University
2023
Purdue University West Lafayette
2022
University of Bergen
2022
Bjerknes Centre for Climate Research
2022
University of Southampton
2022
University of Michigan
2017-2021
University of Wisconsin–Madison
2012-2017
Significance Marine and terrestrial proxy records suggest global cooling during the Late Holocene, following peak warming of Holocene Thermal Maximum (∼10 to 6 ka) until rapid induced by increasing anthropogenic greenhouses gases. However, physical mechanism responsible for this has remained elusive. Here, we show that climate models simulate a robust annual mean in mainly response rising CO 2 retreat ice sheets. This model-data inconsistency demands critical reexamination both data models.
Changes in the Atlantic Meridional Overturning Circulation (AMOC) are moderate most climate model projections under increasing greenhouse gas forcing. This intermodel consensus may be an artifact of common biases that favor a stable AMOC. Observationally based freshwater budget analyses suggest AMOC is unstable regime susceptible for large changes response to perturbations. By correcting biases, we show collapses 300 years after atmospheric CO2 concentration abruptly doubled from 1990 level....
Abstract. The Last Glacial Maximum (LGM, ∼ 21 000 years ago) has been a major focus for evaluating how well state-of-the-art climate models simulate changes as large those expected in the future using paleoclimate reconstructions. A new generation of used to generate LGM simulations part Paleoclimate Modelling Intercomparison Project (PMIP) contribution Coupled Model (CMIP). Here, we provide preliminary analysis and evaluation results these experiments (PMIP4, most which are PMIP4-CMIP6)...
Abstract Because of the pervasive role water in Earth system, relative abundances stable isotopologues are valuable for understanding atmospheric, oceanic, and biospheric processes, interpreting paleoclimate proxy reconstructions. Isotopologues transported by both large‐scale turbulent flows, ratio heavy to light changes due fractionation that can accompany condensation evaporation processes. Correctly predicting isotopic distributions requires resolving relationships between ocean...
Antarctic paleotemperatures It has been widely thought that East Antarctica was ∼9°C cooler during the Last Glacial Maximum, close to ∼10°C difference between then and now determined independently for West Antarctica. Buizert et al. used borehole thermometry, firn density reconstructions, climate modeling show temperature in actually only ∼4° 7°C Maximum. This result important consequences our understanding of climate, polar amplification, global change. Science , abd2897, this issue p. 1097
A state-of-the-art climate model successfully simulates Early Eocene extreme warmth and high sensitivity during the PETM.
Pan-Asian monsoon water isotope variability is found accompanied by a continental-scale hydroclimate footprint.
Abstract. We present results from an ensemble of eight climate models, each which has carried out simulations the early Eocene optimum (EECO, ∼ 50 million years ago). These have been in framework Deep-Time Model Intercomparison Project (DeepMIP; http://www.deepmip.org, last access: 10 January 2021); thus, all models configured with same paleogeographic and vegetation boundary conditions. The indicate that these non-CO2 conditions contribute between 3 5 ∘C to warmth. Compared previous...
The Paleocene–Eocene Thermal Maximum (PETM; 56 Ma) is one of our best geological analogs for understanding climate dynamics in a “greenhouse” world. However, proxy data representing the event are only available from select marine and terrestrial sedimentary sequences that unevenly distributed across Earth’s surface, limiting view spatial patterns change. Here, we use paleoclimate assimilation (DA) to combine model information create spatially complete reconstruction PETM state precedes it...
The Holocene thermal maximum, a period of global warmth evident in early to mid-Holocene proxy reconstructions, is controversial. Most model simulations the have not reproduced this warming, leading disagreement known as Temperature Conundrum. Pollen records document expansion vegetation and African Sahara Northern Hemisphere mid- high latitudes, which has been overlooked previous modeling studies. Here, we use time slice Community Earth System Model assess impact change on annual mean...
Abstract The Community Earth System Model version 2 (CESM2) simulates a high equilibrium climate sensitivity (ECS > 5°C) and Last Glacial Maximum (LGM) that is substantially colder than proxy temperatures. In this study, we examine the role of cloud parameterizations in simulating LGM cooling CESM2. Through substituting different versions schemes atmosphere model, attribute excessive to new CESM2 microphysics ice nucleation. Further exploration suggests removing an inappropriate limiter...
Abstract Understanding the past significant changes of East Asia Summer Monsoon (EASM) and Winter (EAWM) is critical for improving projections future climate over Asia. One key issue that has remained outstanding from paleo-climatic records whether evolution EASM EAWM are correlated. Here, using a set long-term transient simulations last 21,000 years, we show positively correlated on orbital timescale in response to precessional forcing, but anti-correlated millennial timescales North...
Abstract Studying the El Niño–Southern Oscillation (ENSO) in past can help us better understand its dynamics and improve future projections. However, both paleoclimate reconstructions model simulations of ENSO strength at Last Glacial Maximum (LGM; 21 ka B.P.) have led to contradicting results. Here we perform using recently developed water isotope‐enabled Community Earth System Model (iCESM). For first time, model‐simulated oxygen isotopes are directly compared with those from individual...
Abstract The upper end of the equilibrium climate sensitivity (ECS) has increased substantially in latest Coupled Model Intercomparison Projects phase 6 with eight models (as this writing) reporting an ECS > 5°C. Community Earth System version 2 (CESM2) is one such high‐ECS model. Here we perform paleoclimate simulations Last Glacial Maximum (LGM) using CESM2 to examine whether its high realistic. We find that simulated LGM global mean temperature decrease exceeds 11°C, greater than both...
Abstract Earth's hydrological cycle is expected to intensify in response global warming, with a “wet‐gets‐wetter, dry‐gets‐drier” anticipated over the ocean. Subtropical regions (∼15°–30°N/S) are predicted become drier, yet proxy evidence from past warm climates suggests these may be characterized by wetter conditions. Here we use an integrated data‐modeling approach reconstruct and zonal‐mean rainfall patterns during early Eocene (∼56–48 million years ago). The Deep‐Time Model...
Here, we show that the Last Glacial Maximum (LGM) provides a stronger constraint on equilibrium climate sensitivity (ECS), global warming from increasing greenhouse gases, after accounting for temperature patterns. Feedbacks governing ECS depend spatial patterns of surface ("pattern effects"); hence, using LGM to constrain future requires quantifying how produce different feedbacks during cooling versus modern-day warming. Combining data assimilation reconstructions with atmospheric models,...
Greenland ice-core δ 18 O-temperature reconstructions suggest a dramatic cooling during the Younger Dryas (YD; 12.9–11.7 ka), with temperatures being as cold earlier Oldest (OD; 18.0–14.6 ka) despite an approximately 50 ppm rise in atmospheric CO 2 . Such YD implies muted climate response to , contrary physical predictions of enhanced high-latitude future increases Here we show that North Atlantic sea surface temperature well transient model simulations over should be substantially warmer...
Vedolizumab is an effective therapy for ulcerative colitis (UC), but costly and slow to work. New clinical responses occur after 30 weeks of therapy.To enable physicians, patients, insurers predict whether a patient with UC will respond vedolizumab at early time point starting therapy.The study data request website provided the phase 3 trial vedolizumab. Random forest models were trained on 70% tested 30% corticosteroid-free endoscopic remission week 52. Models constructed using baseline...
Abstract The transient response of the Atlantic Meridional Overturning Circulation (AMOC) to a deglacial ice sheet retreat is studied using Community Climate System Model version 3 (CCSM3), with focus on orographic effects rather than meltwater discharge. It found that AMOC weakens significantly (41%) in retreat. weakening follows decrease Northern Hemisphere volume linearly, no evidence abrupt thresholds. A wind‐driven mechanism proposed explain AMOC: lowering sheets induces northward shift...