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CGD Features

Highlighted Publications

  • Model-based evidence of deep-ocean heat uptake during surface-temperature hiatus periods.

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    Staff Authors: G. Meehl, J. Arblaster, J. Fasullo, A. Hu, and K. Trenberth

    There have been decades, such as 2000-2009, when the observed globally averaged surface-temperature time series shows little increase or even a slightly negative trend (a hiatus period)... [article]

  • Influence of initial conditions and climate forcing on predicting Arctic sea ice.

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    Staff Author: M. Holland

    The recent sharp decline in Arctic sea ice has triggered an increase in the interest of Arctic sea ice predictability, not least driven by the potential of significant human industrial activity in the region. In this study we quantify how long Arctic sea ice predictability is dominated by dependence on its initial conditions versus dependence on its secular decline in a state-of-the-art global circulation model (GCM) under a 'perfect model' assumption. [article]

  • The boundary layer response to recent Arctic sea ice loss and implications for high-latitude climate feedbacks.

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    Staff Authors: J. Kay and A. Gettelman

    This study documents and evaluates the boundary layer and energy budget response to record low 2007 sea ice extents in the Community Atmosphere Model version 4 (CAM4) using 1-day observationally constrained forecasts and 10-yr runs with a freely evolving atmosphere. [article]

  • An assessment and interpretation of the observed warming of West Antarctica in the austral spring.

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    Staff Authors: D. Schneider, C. Deser, and Y. Okumura

    We synthesize variability and trends in multiple analyses of Antarctic near-surface temperature representing several independent source datasets and spatially complete reconstructions, and place these into the broader context of the behavior of other components of the climate system during the past 30-50 years. [article]

  • The community climate system model version 4.

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    Staff Authors: P. Gent, G. Danabasoglu, M. Holland, D. Lawrence, R. Neale, M. Vertenstein

    The fourth version of the Community Climate System Model (CCSM4) was recently completed and released to the climate community. This paper describes developments to all CCSM components, and documents fully coupled pre-industrial control runs compared to the previous version, CCSM3. [article]

  • A flux-form version of the conservative semi-Lagrangian multi-tracer transport scheme (CSLAM) on the cubed sphere grid.

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    Staff Author: P. Lauritzen

    A conservative semi-Lagrangian cell-integrated transport scheme (CSLAM) was recently introduced, which ensures global mass conservation and allows long timesteps, multi-tracer efficiency, and shape preservation through the use of reconstruction filtering. This method is fully two-dimensional so that it may be easily implemented on non-cartesian grids such as the cubed-sphere grid. [article]

  • Historical (1850-2000) gridded anthropogenic and biomass burning emissions of reactive gases and aerosols: methodology and application.

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    Staff Author: J.-F. Lamarque

    The primary purpose of this inventory is to provide consistent gridded emissions of reactive gases and aerosols for use in chemistry model simulations needed by climate models for the Climate Model Intercomparison Program #5 (CMIP5) in support of the Intergovernmental Panel on Climate Change (IPCC) Fifth Assessment report (AR5). [article]

  • Drought under global warming: a review.

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    Staff Authors: A. Dai

    This article reviews recent literature on drought of the last millennium, followed by an update on global aridity changes from 1950 to 2008. Projected future aridity is presented based on recent studies and our analysis of model simulations. Dry periods lasting for years to decades have occurred many times during the last millennium over, for example, North America, West Africa, and East Asia. [article]

  • Jet Alignment in a Two-Layer Quasigeostrophic Channel Using One-Dimensional Grid Warping.

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    Staff Authors: J. Tribbia

    Because of position errors traditional methods of data assimilation can broaden and weaken jets or other flow structures leading to reduced forecast skill. Here a technique to assimilate properties of coherent structures is developed and tested. [article]

  • Quantifying carbon-nitrogen feedbacks in the Community Land Model (CLM4).

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    Staff Authors: G. Bonan and S. Levis

    Recent studies indicate that nitrogen biogeochemistry affects the carbon cycle feedback in climate simulations. We use the Community Land Model version 4 (CLM4) with carbon-only and carbon-nitrogen biogeochemistry to assess the influence of nitrogen on the land carbon budget for 1973-2004. [article]

  • Changes in Arctic clouds during intervals of rapid sea ice loss.

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    Staff Authors: M. Holland and D. Bailey

    We investigate the behavior of clouds during rapid sea ice loss events (RILEs) in the Arctic, as simulated by multiple ensemble projections of the 21st century in the Community Climate System Model (CCSM3). [article]

  • Twentieth century tropical sea surface temperature trends revisited.

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    Staff Authors: C. Deser and A. Phillips

    This study compares the global distribution of 20th century SST and marine air temperature trends from a wide variety of data sets including un-interpolated archives as well as globally-complete reconstructions. [article]

  • Parameterization Improvements and Functional and Structural Advances in Version 4 of the Community Land Model.

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    Staff Authors: D.M. Lawrence, K.W. Oleson, S.C. Swenson, P.J. Lawrence, S. Levis, G.B. Bonan

    The Community Land Model is the land component of the Community Climate System Model. Here, we describe a broad set of model improvements and additions that have been provided through the CLM development community to create CLM4. [article]

Research Highlights

Wet and dry together: New ways to measure hydrologic extremes. If 2011 could be dubbed the Year of Extreme U.S. Weather, its most tenacious element was the intense contrast between record drought in the Southern Plains and record-setting precipitation elsewhere. Both are noteworthy, and the combination is especially striking. But how best to quantify such a dual impact? Several indices help point the way. [highlight]

A world's worth of climate research The weather in Denver on 24-28 October echoed the theme of the first-ever Open Science Conference of the World Climate Research Program (WCRP). As the meeting unfolded, conditions outside swung from record-warm readings of 80°F (27°C) to a wet snowfall. [highlight]

The October snow blitz: What made "Snowtober" so unusual? Autumn in New England brings to mind crisp air, dappled sunshine, and explosions of scarlet foliage-not tree-breaking snowfall. Yet nature ignored the calendar this year and delivered the biggest October snowstorm ever recorded for many areas from the Mason-Dixon line to Maine. On mainstream and social media, it's been dubbed "Snowtober." [highlight]

Blocking the way. A world's worth of climate research. The concept of atmospheric blocking might not be familiar to the general public, but millions have come face to face with the results of spectacular blocks over the last couple of years. Every so often, a dome of upper-level high pressure sits in place for a few days, sometimes as long as several weeks. A major block can produce seemingly endless stretches of blazing heat or bitter cold. It also blocks the typical eastward flow of the polar jet stream (thus the label "blocking") and throws storm systems far from their usual tracks. Along those displaced paths, the storms can generate successive bouts of heavy rain or snow. By the time it dissipates, a major block may leave behind a whole stack of broken weather records and an array of disastrous consequences. [highlight]

Ice sheets and climate change during the late Pleistocene. New research that involves NCAR scientist Bette Otto-Bliesner questions conventional wisdom with regard to massive iceberg discharges in the North Atlantic Ocean during the last glacial period, pointing toward climate rather than ice sheet instability as a cause. [highlight]

Announcements

CGD Seminars
Speaker: Jian Lu, COLA/George Mason Univ.
Title: The oceanic role in the coupled climate response to greenhouse gas forcing.
Date & Time: 02/14/12, 3:30pm
Location: Mesa Lab Main Seminar Room
[2011-2012 schedule]

Speaker: Carsten Eden, University of Hamburg
Title: Breakthroughs in the understanding of mesoscale mixing.
Date & Time: 02/27/12, 3:30pm
Location: Mesa Lab Main Seminar Room
[2011-2012 schedule]

17th Annual CESM Workshop
The 17th Annual CESM Workshop will held at The Village at Breckenridge, Breckenridge, CO, 18 - 21 June 2012.

Community Earth System Modeling Tutorial
30 July - 03 August 2012, National Center for Atmospheric Research, Boulder, CO [announcement] [application]

Upcoming CESM WG Meetings
WAWG, 1 February, 2012
AMWG, 1-3 February, 2012
PCWG, LIWG, PaleoWG, 15-17 February, 2012
LMWG, BGCWG, ChemClimWG, SDWG, 27 February - 2 March, 2012


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