CGD Research: CCR Overview

CCR research consists of topical interests split between Paleoclimate Research and Present and Future Climate Change Research.

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Climate Change Research: Paleoclimate Research

Fingerprint of Solar Influence on Past Millennium Climate

Simulations with a fully coupled Climate System Model are used to show that a temporal fingerprint of solar influence on climate can be isolated. More...

Last Interglacial Arctic Warmth Confirms Polar Amplification

The warmest millennia of at least the past 250,000 years occurred during the Last Interglaciation, when global ice volumes were similar to or smaller than today and systematic variations in Earth’s orbital parameters aligned to produce a strong positive summer insolation anomaly throughout the Northern Hemisphere. More...

Kuwae Eruption Signal from Ice Core Records

We combined 33 ice core records, 13 from the Northern Hemisphere and 20 from the Southern Hemisphere, to determine the timing and magnitude of the great Kuwae eruption in the mid-15th century. More...

Last Glacial Maximum Temperatures Over the North Atlantic, Europe, and western Siberia

Evaluating the ability of models to simulate climates different from the modern one is important for climate prediction. Here we present a first comparison between results from simulations of the Last Glacial Maximum climate and continental and surface ocean reconstructions for the North Atlantic, Europe and western Siberia. More...

Climate Sensitivity of Community Climate System Model (CCSM)

The climate sensitivity of the Community Climate System model is described in terms of the equilibrium change in surface temperature due to a doubling of carbon dioxide in a slab ocean versions of the Community Atmosphere Model (CAM) and the transient climate response, which is the surface temperature change at the point of doubling of carbon dioxide in a 1% per year CO2 simulation with the fully coupled CCSM. More...

Robustness of Proxy-based Climate Reconstruction Methods

We present results from continued investigations into the fidelity of covariance-based Climate Field Reconstruction (CFR) approaches used in proxy-based climate reconstruction. Our experiments employ synthetic 'pseudoproxy' data derived from a simulation of forced climate changes over the past 1200 years. More...

Testing Fidelity of Methodologies used in "Proxy" Reconstructions of Past Climate

Two widely used statistical approaches to reconstructing past climate histories from climate “proxy” data such as tree rings, corals, and ice cores are investigated using synthetic “pseudoproxy” data derived from a simulation of forced climate changes over the past 1200 yr. More...

Robustness of the Mann, Bradley, and Hughes Reconstruction of N.H. Surface Temperatures

The Mann et al. (1998) Northern Hemisphere annual temperature reconstruction over 1400-1980 is examined in light of recent criticisms concerning the nature and processing of included climate proxy data. A systematic sequence of analyses is presented that examine issues concerning the proxy evidence, utilizing both indirect analyses via exclusion of proxies and processing steps subject to criticism, and direct analyses of principal component (PC) processing methods in question. More...

Comparison of low-latitude Cloud Properties and Response to Climate Change

Low-latitude cloud distributions and cloud responses to climate perturbations are compared in near-current versions of three leading U.S. AGCMs, the NCAR CAM 3.0, the GFDL AM2.12b, and the NASA GMAO NSIPP-2 model. More...

A Multi-Model Analysis of the Role of the Ocean on the African and Indian Monsoon during the mid-Holocene

We investigate the role of the ocean feedback on the climate in response to insolation forcing during the mid-Holocene (6,000 year BP) using results from seven coupled ocean–atmosphere general circulation models. More...

Statistical Methods for Analysis of Geophysical Extreme Events

Currently there is an increasing research activity in the area of climate extremes because they represent a key manifestation of non-linear systems and an enormous impact on economic and social human activities. More...

Past and Future Polar Amplification of Climate Change: Model and Ice-core Constraints

Climate model simulations available from the PMIP1, PMIP2 and CMIP (IPCC-AR4) intercomparison projects for past and future climate change simulations are examined in terms of polar temperature changes in comparison to global temperature changes and with respect to pre-industrial reference simulations. More...

Simulating Arctic Climate Warm and Ice field duing Last Interglaciation

In the future, Arctic warming and the melting of polar glaciers will be considerable, but the magnitude of both is uncertain. More...

Paleoclimatic Evidence for Future Ice Sheet Instability and Rapid Sea Level Rise

Sea-level rise from melting of polar ice sheets is one of the largest potential threats of future climate change. More...

Last Glacial Maximum and Holocene Climate in CCSM3

The climate sensitivity of the Community Climate System Model version 3 (CCSM3) is studied for two past climate forcings, the Last Glacial Maximum (LGM) and the mid-Holocene. More...

Climate Sensitivity of Moderate and Low Resolution version of CCSM3 to Preindustrial Forcings

Preindustrial (PI) simulations of the Community Climate System Model version 3 (CCSM3) at two resolutions, a moderate and a low resolution, are described and compared to the standard controls for present-day (PD) simulations. More...

Climate Change Research: Present and Future Climate Change Research

Studies of decade-century climate change: 20th Century and 21st Century

Studies have been performed with state-of-the-art global coupled climate models (AOGCMs) that address future climate change in the context of the natural variability of the ocean and coupled ocean-atmosphere-sea ice-land/vegetation-hydrological systems. More...

Analyis of IPCC AR4 Simulations: Committment and other Scenarios

Climate change scenario simulations with the CCSM3, a global coupled climate model, show that if we could have stabilized concentrations of all greenhouse gases (GHGs) at the year 2000, we were already committed to 0.4?C more warming by the end of the 21st century. More...

Multi-model Climate Change Committment Simulations

Climate change commitment in the 21st -century due to human activity in the 20th century is quantified using output from 16 global coupled general circulation models. More...

Abrupt Climate Change

We participated in the CMIP Coordinated Experiment on sudden climate change that addressed implications of a large amount of fresh water being input to the North Atlantic. More...

Southern Annular Mode

An observed trend in the Southern Annular Mode (SAM) during recent decades has involved an intensification of the polar vortex. More...

Ocean Warming

A warming signal has penetrated into the world's oceans over the past 40 years. The signal is complex, with a vertical structure that varies widely by ocean; it cannot be explained by natural internal climate variability or solar and volcanic forcing, but is well simulated by two anthropogenically forced climate models. More...

Permafrost Changes

The current distribution and future projections of permafrost are examined in a fully coupled global climate model, the Community Climate System Model, version 3 (CCSM3) with explicit treatment of frozen soil processes. More...

Global Land-Atmosphere Coupling Experiment

The twelve weather and climate models participating in the Global Land-Atmosphere Coupling Experiment (GLACE) show both a wide variation in the strength of land-atmosphere coupling and some intriguing commonalities. More...

Partitioning of Evaporation, Transpiration, Soil and Canopy Evaporation

Although the global partitioning of evapotranspiration (ET) into transpiration, soil evaporation, and canopy evaporation is not well-known, most current land-surface schemes and the few available observations indicate that transpiration is the dominant component on the global scale, followed by soil evaporation and canopy evaporation. More...

ENSO

Idealized forcing experiments with 1% per year CO2 increase to stabilized doubled and quadrupled CO2, 21st century transient scenario experiments (SRES scenarios A1B and B1), and stabilized 22nd century A1B and B1 experiments with two global coupled climate models (PCM and CCSM3) are analyzed for possible future changes of El Nin~o events. More...

Future Precipitation Changes

In a future climate warmed by increased greenhouse gases, increases of precipitation intensity do not have a uniform spatial distribution. More...

Bering Strait Throughflow and Thermohaline Circulation Changes

In this study, we employ a global coupled climate model to show that the Bering Strait is important to the variations of the thermohaline circulation. More...

Constraining Climate Sensitivity through use of Seasonal Cycle

The estimated range of climate sensitivity has remained unchanged for decades, resulting in large uncertainties in long-term projections of future climate under increased greenhouse gas concentrations. More...

Megadroughts and the Indian Monsoon

A 1360 year control run from a global coupled climate model (PCM) is analyzed. It simulates megadroughts in the southwest U.S. and Indian monsoon regions. More...

Monsoons Regimes in CCSM3

Simulations of regional monsoon regimes, including the Indian, Australian, West African, South American and North American monsoons, are described for the T85 version of the Community Climate System Model Version 3 (CCSM3), and compared to observations and Atmospheric Model Intercomparison Project (AMIP)-type SST-forced simulations with CAM3 at T42 and T85. More...

Impact of Volcanic Eruptions on Sea-Level and Ocean Heat Content

Ocean thermal expansion contributes significantly to sea-level variability and rise. However, observed decadal variability in ocean heat content and sea level has not been reproduced well in climate models. More...

Climate Sensitivity to Doubling of Carbon Dioxide Levels

Climate sensitivity, or the equilibrium warming resulting from a doubling of carbon dioxide levels, cannot be measured directly, since the real climate system will never be subjected to a carbon dioxide doubling and then allowed to come into equilibrium. More...

Solar Signal in Records and Simulations of Past Climates

Simulations with a fully coupled Climate System Model are used to show that a temporal fingerprint of solar influence on climate can be isolated. More...

Ocean Processes as Trigger and Amplifying Heinrich Events

Marine sediments recorded a series of Heinrich events during the last glacial period, massive ice surges which deposited prominent layers of ice-rafted debris in the North Atlantic. More...

Robust Bayesian Uncertainty Analysis of Climate System Properties

A Bayesian uncertainty analysis of 12 parameters of the Bern2.5D climate model is presented. This includes an extensive sensitivity study with respect to the major statistical assumptions. More...

Tempo-Spatial Structure and Mechanisms of the Tropospheric Biennial Oscillation in the Indo-Pacific Warm Ocean Regions

The observed structure and seasonal evolution characteristics of the tropospheric biennial oscillation (TBO) in the warm ocean areas of the Indo-Pacific region are explored using a seasonal-sequence EOF analysis approach. More...

Land-Cover Change in Simulating Future Climates

Adding the effects of changes in land cover to the A2 and B1 transient climate simulations described in the Special Report on Emissions Scenarios (SRES) by the Intergovernmental Panel on Climate Change leads to significantly different regional climates in 2100 as compared with climates resulting from atmospheric SRES forcings alone. More...

CGD Sectional Narratives

CAS | CCR | CDP | CMS | CSEG | OS | TSS |