Lori Sentman

ABSTRACT NOAA-GFDL developed two new Earth System Models (ESMs) for the CMIP5 / IPCC AR5 project. Both ESMs were built from the atmospheric and sea ice components of GFDL-CM2.1 and contain a fully interactive carbon cycle, new land and ocean components , and a coupled ocean biogeochemistry model. The two ESMs differ only in their ocean component - ESM2M uses a fixed-depth vertical coordinate while ESM2G uses an isopycnal coordinate. NOAA-GFDL will contribute ``concentration-driven'' and ``emission-driven'' experiments with both models to the CMIP5 project. An overview of the initialization of the pre-industrial control experiments along with an update on the status of the ESM CMIP5 experiments will be given. Early results for both the physical climate and biological components will be presented based on the historical experiments (1861-2005) and the idealized climate projection experiments (e.g. 1% per year increases in CO2 and abrupt 4xCO2 scenarios). Comparisons of both ESMs will also be made to the GFDL-CM2.1 model and to observations of the historical period.

of the dissertation .......................................................................................... ii Acknowledgements .................................................................................................... vi Dedication ................................................................................................................... x Table of

<p>Near-term climate forcers (NTCFs), including aerosols and chemically reactive gases such as tropospheric ozone and methane, offer a potential way to mitigate climate change and improve air quality--so called "win-win" mitigation policies.   Prior studies support improved air quality under NTCF mitigation, but with conflicting climate impacts that range from a significant reduction in the rate of global warming to only a modest impact.  Here, we use state-of-the-art chemistry-climate model simulations conducted as part of the Aerosol and Chemistry Model Intercomparison Project (AerChemMIP) to quantify the 21st-century impact of NTCF reductions, using a realistic future emission scenario with a consistent air quality policy.  Non-methane NTCF (NMNTCF; aerosols and ozone precursors) mitigation improves air quality, but leads to significant increases in global mean precipitation of 1.3% by mid-century and 1.4% by end-of-the-century, and corresponding surface warming of 0.23 and 0.21 K.  NTCF (all-NTCF; including methane) mitigation further improves air quality, with larger reductions of up to 45% for ozone pollution, while offsetting half of the wetting by mid-century (0.7% increase) and all the wetting by end-of-the-century (non-significant 0.1% increase) and leading to surface cooling of -0.15 K by mid-century and -0.50 K by end-of-the-century.  This suggests that methane mitigation offsets warming induced from reductions in NMNTCFs, while also leading to net improvements in air quality.</p>

Oceanic heat uptake (OHU) is a significant source of uncertainty in both the transient and equilibrium responses to increasing the planetary radiative forcing. OHU differs among climate models and is related in part to their representation of vertical and lateral mixing. This study examines the role of ocean model formulation—specifically the choice of the vertical coordinate and the strength of the background diapycnal diffusivity K d—in the millennial-scale near-equilibrium climate response to a quadrupling of atmospheric CO2. Using two fully coupled Earth system models (ESMs) with nearly identical atmosphere, land, sea ice, and biogeochemical components, it is possible to independently configure their ocean model components with different formulations and produce similar near-equilibrium climate responses. The SST responses are similar between the two models ( r2 = 0.75, global average ~4.3°C) despite their initial preindustrial climate mean states differing by 0.4°C globally. Th...

NOAA’s Geophysical Fluid Dynamics Laboratory (GFDL) has developed two new Earth System Models (ESMs) to better understand the interactions and feedbacks between biogeochemical cycles and the climate system. ESM2M and ESM2G, recent contributors to the Coupled Model Intercomparison Project Phase 5 (CMIP5) database, are based on GFDL’s coupled Climate Model version 2.1 (CM2.1) and successfully simulate the global climate and carbon cycle. The land component, LM3, has been designed to simulate the effects of land use on terrestrial carbon pools, including secondary vegetation regrowth following land use disturbances which has been shown to be an important terrestrial carbon sink. Because of the long time scales associated with the carbon adjustment of imposing land use when simulating secondary vegetation regrowth, special consideration is required when initializing the GFDL ESMs for historical CMIP5 simulations. We explore the uncertainty in the terrestrial carbon stores and fluxes ass...

The dynamic vegetation and carbon cycling component, LM3V, of the Geophysical Fluid Dynamics Laboratory (GFDL) prototype Earth system model (ESM2.1), has been designed to simulate the effects of land use on terrestrial carbon pools, including secondary vegetation regrowth. Because of the long time scales associated with the carbon adjustment, special consideration is required when initializing the ESM when historical simulations are conducted. Starting from an equilibrated, preindustrial climate and potential vegetation state in an offline land-only model (LM3V), estimates of historical land use are instantaneously applied in five experiments beginning in the following calendar years: 1500, 1600, 1700, 1750, and 1800. This application results in the land carbon pools experiencing an abrupt change—a carbon shock—and the secondary vegetation needs time to regrow into consistency with the harvesting history. The authors find that it takes approximately 100 years for the vegetation to r...

ABSTRACT This study examines the behavior of coupled terrestrial and atmospheric system in a series of experiments with the GFDL atmospheric model AM2 coupled with the dynamic land model, LM3V. The simulations were driven by the HadISST historic record of sea surface temperature and historic greenhouse gas forcings. In all experiments, the vegetation was fully interactive with the atmosphere; the difference between experiments is the assumptions about the land use applied in the model. We examine the change in terrestrial carbon storage in various pools and the associated carbon fluxes between land and the atmosphere. The results are compared against the run without the land use, that is the potential vegetation experiment. The results indicate that the assumptions about the human land use practices, in particular about the secondary vegetation harvesting and shifting cultivation, are important for the reconstruction of the historic terrestrial carbon fluxes.

ABSTRACT NOAA-GFDL developed two new Earth System Models (ESMs) for the CMIP5 / IPCC AR5 project. Both ESMs were built from the atmospheric and sea ice components of GFDL-CM2.1 and contain a fully interactive carbon cycle, new land and ocean components , and a coupled ocean biogeochemistry model. The two ESMs differ only in their ocean component - ESM2M uses a fixed-depth vertical coordinate while ESM2G uses an isopycnal coordinate. NOAA-GFDL will contribute ``concentration-driven'' and ``emission-driven'' experiments with both models to the CMIP5 project. An overview of the initialization of the pre-industrial control experiments along with an update on the status of the ESM CMIP5 experiments will be given. Early results for both the physical climate and biological components will be presented based on the historical experiments (1861-2005) and the idealized climate projection experiments (e.g. 1% per year increases in CO2 and abrupt 4xCO2 scenarios). Comparisons of both ESMs will also be made to the GFDL-CM2.1 model and to observations of the historical period.