ESSL LAR

CGD's Climate Change Research Section

The Climate Change Research Section (CCR) is part of the Climate and Global Dynamics (CGD) Division at the National Center for Atmospheric Research (NCAR).

The CCR section makes extensive use of state-of-the-art coupled climate system models to study the sensitivity and stability of the Earth system to a variety of forcings, including changes of greenhouse gases, aerosols, solar irradiance, volcanic forcing, land characteristics, and land use change. CCR is a focal point for NCAR and university paleoclimate research and serves as a resource to the paleoclimatic and climate change research community in the use of the Community Climate System Model (CCSM). CCR scientists collaborate closely with major U.S. Department of Energy (DOE) laboratories in developing and using high-performance coupled climate models to address national climate research and climate change policy questions.

Present and Future Climate Change Research

CCR's Climate Change and Prediction (CCP) research focuses on the sensitivity and stability of the Earth system to a variety of forcings, including changes of greenhouse gases, aerosols, solar irradiance, volcanic forcing, land characteristics, as well as land use change. In addition, CCP continues to conduct centuries long simulations and ensembles of simulations.

The Climate Change and Prediction group primary focus is on the second of the five key global change issues outlined by the Climate Change Science Program (CCSP) and U.S. Global Change Research Program (USGCRP) documents:

    (1) seasonal to interannual climate variability
    (2) climate change over decades to centuries
    (3) changes in ozone, ultraviolet radiation, and atmospheric chemistry
    (4) changes in land cover and in terrestrial and aquatic ecosystems and
    (5) the role of aerosols

In addition, we continue to conduct centuries long simulations and ensembles that address all five key global change issues.

Release of the Breakthrough IPCC Fourth Assessment Report

The 2007 Intergovernmental Panel on Climate Change (IPCC) AR4 report presents a clear picture of a planet undergoing a rapid climate transition with significant societal and environmental impacts. The strength and clarity of the IPCC AR4 report can be attributed, in part, to DOE/NSF supercomputing centers making it possible to deploy climate models of unprecedented realism and detail. With the question of anthropogenic climate change settled, our next challenge is applying the new class of Earth System Models that include the detailed physical, chemical, and biological processes, interactions and feedbacks in the atmosphere, oceans, and land surface, to carry out policy-relevant adaptation/mitigation scenarios.

The Intergovernmental Panel on Climate Change (IPCC) released its Fourth Assessment Report (AR4) in 2007. Capping a six-year effort, 23 different models from 16 different modeling centers around the globe participated in a coordinated experiment that included intense scrutiny of current climate change science, and compared observational data with climate model simulations of past, present, and future climate states. With more than 10,000 model years simulated at a higher resolution than has ever been attempted before, the DOE collaboration with NSF/NCAR and Japan's Central Research Institute of the Electric Power Industry (CRIEPI) resulted in the largest data contribution to the IPCC AR4 project of any center in the world.

The AR4 findings are stronger and clearer than any previous IPCC assessment report. IPCC Working Group 1, charged with looking at the physical basis of climate change, concluded that warming is unequivocal and that it is very likely that the warming observed in the 20th century is due to human emissions. Working Group 2, focusing on climate change impacts, adaptation and vulnerability, predicted large-scale changes in food and water availability, dramatic changes in ecosystems, and increases in flood hazards and extreme weather. Working Group 3, examining mitigation of climate change, concluded that some of the devastating effects of climate change can be avoided through quick action, and that existing technologies can balance climate risks with economic competitiveness.

Figure 1.

High resolution figure Unprecedented coordinated climate change experiments from 16 groups (11 countries) and 23 models collected at PCMDI (over 31 terabytes of model data), openly available, accessed by over 1200 scientists; over 200 papers. Committed warming averages 0.1°C per decade for the first two decades of the 21st century; across all scenarios, the average warming is 0.2°C per decade for that time period (recent observed trend 0.2°C per decade).

The strength and clarity of the AR4 message is directly attributable to the IPCC authors' increased confidence in the soundness of both the model output and observational data. Access to DOE and NSF high-performance computing and data services at ORNL, NERSC and NCAR significantly improved model simulations over. These computers made it possible to run more realistic physical processes, at higher resolutions, with more ensemble members, and longer historical validation simulations. Similarly, there was much greater credibility in the observational data with satellite and ground observations showing a consistent picture of warming worldwide. Additionally, there has been definitive resolution of some of the inconsistencies that have appeared previously in the observational record.

Finally, there is much better agreement between climate model results and the observations. For example, glaciers, nature's independent climate integrators, are showing increased edge melting and buildup in the centers, consistent with the model predictions that we will be moving to a warmer/wetter world. Unlike previous IPCC assessment reports, there has been broad acceptance of the IPCC AR4 conclusions from government, industry, and the public that has fundamentally changed the dialog on climate change in this country and around the world.

Recent publication information can be found at:

Paleoclimate

CCR's paleoclimate group studies climates of the prehistoric past. The largest climate changes that have occurred on Earth, such as the Ice Ages, are those recorded in the geologic record. Understanding the causes of such past climate changes is an essential part of developing and validating models of future climate change.

Paleoclimates offer a unique perspective to understand both the Earth's climate sensitivity and stability. NCAR climate models have been used to study past natural variability of the Earth system since the 1970's. The development of a coupled climate model, the Climate System Model (CSM), in the 1990's included a lower resolution (but otherwise equal) version of the model, PaleoCSM, which was particularly useful for the long simulations required to study past climates. PaleoCSM was successfully used to study mechanisms responsible for changes in the coupled climate system and to determine associated magnitudes of changes for various climatic variables. Simulations covered a large range of applications, including the last millennium, Holocene ENSO, the Last Glacial Maximum, Paleocene Eocene Thermal Maximum, and Late Permian. The simulations with the newer CCSM3 highlight the importance of considering feedbacks among the atmosphere, ocean, land surface, and sea ice in establishing the magnitudes of past climate change to changes in past forcings. These simulations not only acted as a benchmark for CCSM but allowed testing of various hypotheses of mechanisms to explain proxy records of past climate change.

Recent publication information can be found at: