A5075466673- Climate variability and models
- Geology and Paleoclimatology Research
- Tree-ring climate responses
- Plant Water Relations and Carbon Dynamics
- Atmospheric and Environmental Gas Dynamics
- Meteorological Phenomena and Simulations
- Cryospheric studies and observations
- Atmospheric Ozone and Climate
- Hydrology and Drought Analysis
- Climate change and permafrost
- Archaeology and ancient environmental studies
- Global Energy and Sustainability Research
- Solar and Space Plasma Dynamics
- Geological and Geochemical Analysis
- Arctic and Antarctic ice dynamics
- Climate Change and Environmental Impact
- Ecosystem dynamics and resilience
- Hydrology and Watershed Management Studies
- Financial Risk and Volatility Modeling
- Inertial Sensor and Navigation
- Environmental, Ecological, and Cultural Studies
- Atmospheric chemistry and aerosols
- Time Series Analysis and Forecasting
- Seismology and Earthquake Studies
- Food Security and Health in Diverse Populations
University Corporation for Atmospheric Research
2005-2019
NSF National Center for Atmospheric Research
2009-2018
Research Applications (United States)
2012-2018
Research Applications Laboratory
2012-2014
NSF NCAR Climate and Global Dynamics Laboratory
2003-2013
NOAA National Centers for Environmental Information
2011
U.S. National Science Foundation
2010
Purdue University West Lafayette
2010
Pennsylvania State University
2009
Scripps Institution of Oceanography
2008
Patterns of Change The global climate record the past 1500 years shows two long intervals anomalous temperatures before obvious anthropogenic warming 20th century: warm Medieval Climate Anomaly between roughly 950 and 1250 A.D. Little Ice Age around 1400 1700 It has become increasingly clear in recent years, however, that changes inevitably involve a complex pattern regional changes, whose inhomogeneities contain valuable insights into mechanisms cause them. Mann et al. (p. 1256 ) analyzed...
Understanding natural causes of climate change is vital to evaluate the relative impacts human pollution and land surface modification on climate. We have investigated one most important change, volcanic eruptions, by using 54 ice core records from both Arctic Antarctica. Our recently collected suite data, more than double number cores ever used before, reduces errors inherent in reconstructions based a single or small cores, which enables us obtain much higher accuracy detection events...
The temperature history of the first millennium C.E. is sparsely documented, especially in Arctic. We present a synthesis decadally resolved proxy records from poleward 60 degrees N covering past 2000 years, which indicates that pervasive cooling progress years ago continued through Middle Ages and into Little Ice Age. A 2000-year transient climate simulation with Community Climate System Model shows same sensitivity to changes insolation as does our reconstruction, supporting inference this...
Abstract. Simulations of climate over the Last Millennium (850–1850 CE) have been incorporated into third phase Paleoclimate Modelling Intercomparison Project (PMIP3). The drivers this period are chiefly orbital, solar, volcanic, changes in land use/land cover and some variation greenhouse gas levels. While these effects can be easily defined, reconstructions volcanic use-related forcing more uncertain. We describe here approach taken defining scenarios used PMIP3, document discuss likely...
Observations indicate that the height of tropopause-the boundary between stratosphere and troposphere-has increased by several hundred meters since 1979. Comparable increases are evident in climate model experiments. The latter show human-induced changes ozone well-mixed greenhouse gases account for approximately 80% simulated rise tropopause over 1979-1999. Their primary contributions through cooling (caused ozone) warming troposphere gases). A model-predicted fingerprint is statistically...
The potential role of solar variations in modulating recent climate has been debated for many decades and papers suggest that forcing may be less than previously believed. Because variability before the satellite period must scaled from proxy data, large uncertainty exists about phase magnitude forcing. We used a coupled system model to determine whether proxy-based irradiance series are capable inducing climatic resemble found reconstructions, if part estimated range past changes could...
A new monthly volcanic forcing dataset is included in a coupled GCM for more physically consistent treatment of the stratospheric sulfate aerosol history from explosive volcanism. The different previous versions that there an individual evolution each event. Thus seasonal and latitudinal dependence can affect global climate realistic way prior to satellite period, compared earlier datasets. Negative radiative activity greatest early 20th century 1915 late after 1960. combination solar...
Abstract. We update the forcings for PMIP3 experiments Last Millennium to include new assessments of historical land use changes and discuss suggestions calibrating solar activity proxies total irradiance.
Widely distributed proxy records indicate that the Medieval Climate Anomaly (MCA; ~900–1350 AD) was characterized by coherent shifts in large-scale Northern Hemisphere atmospheric circulation patterns. Although cooler sea surface temperatures central and eastern equatorial Pacific can explain some aspects of medieval changes, they are not sufficient to account for other notable features, including widespread aridity through Eurasian sub-tropics, stronger winter westerlies across North...
Ensemble simulations are run with a global coupled climate model employing five forcing agents that influence the time evolution of globally averaged surface air temperature during twentieth century. Two natural (volcanoes and solar) others anthropogenic [e.g., greenhouse gases (GHGs), ozone (stratospheric tropospheric), direct effect sulfate aerosols]. In addition to individual experiments, an additional eight sets performed forcings in various combinations. The late-twentieth-century...
Explosive volcanism is known to be a leading natural cause of climate change. The second half the 13th century was likely most volcanically perturbed half‐century last 2000 years, although none major eruptions have been clearly attributed specific volcanoes. This period in general time transition from relatively warm Medieval colder Little Ice Age, but available proxy records are insufficient on their own assess whether this associated with volcanism. context motivates our investigation...
It has been suggested that the Toba volcanic eruption, approximately 74 ka B.P., was responsible for extended cooling period and ice sheet advance immediately following it, but previous climate model simulations, using 100 times amount of aerosols produced by 1991 Mount Pinatubo have unable to produce such a prolonged response. Here we conduct six additional simulations with two different models, National Center Atmospheric Research Community Climate System Model 3.0 (CCSM3.0) Aeronautics...
We present results from continued investigations into the fidelity of covariance‐based climate field reconstruction (CFR) approaches used in proxy‐based reconstruction. Our experiments employ synthetic “pseudoproxy” data derived simulations forced changes over past millennium. Using networks these pseudoproxy data, we investigate sensitivity CFR performance to signal‐to‐noise ratios, noise spectrum, spatial sampling locations, statistical representation predictors used, and diagnostic...
Abstract Two widely used statistical approaches to reconstructing past climate histories from “proxy” data such as tree rings, corals, and ice cores are investigated using synthetic “pseudoproxy” derived a simulation of forced changes over the 1200 yr. These experiments suggest that both should yield reliable reconstructions true history within estimated uncertainties, given estimates signal noise attributes actual proxy networks.
Several state‐of‐the‐art general circulation models (GCMs) predict that large volcanic eruptions should result in anomalous dry conditions throughout much of monsoon Asia. Here, we use long and well‐validated proxy reconstructions Asian droughts pluvials to detect the influence radiative forcing on hydroclimate region since late Medieval period. Superposed epoch analysis reveals significantly wetter over mainland southeast Asia year an eruption, with drier central Our model comparison...
Abstract. Understanding natural climate variability and its driving factors is crucial to assessing future change. Therefore, comparing proxy-based reconstructions with forcing as well these paleoclimate model simulations key gaining insights into the relative roles of internal versus forced variability. A review state modelling last millennium prior CMIP5–PMIP3 (Coupled Model Intercomparison Project Phase 5–Paleoclimate Modelling 3) coordinated effort presented compared available...
Understanding the dynamics of climate change in its full richness requires knowledge long temperature time series. Although long-term, widely distributed observations are not available, there other forms data, known as proxies, that can have a statistical relationship with temperatures and been used to infer past before direct measurements. We propose Bayesian hierarchical model reconstruct integrates information from different sources, such proxies temporal resolution forcings acting...
Suppose you are a city planner, regional water manager, or wildlife conservation specialist who is asked to include the potential impacts of climate variability and change in your risk management planning efforts. What information would use? The choice often local projections downscaled from global models (GCMs; also known as general circulation models) detail at spatial temporal scales that align with those decision problem. A few years ago this was hard come by. Now there Web‐based access...