GFDL - Geophysical Fluid Dynamics Laboratory

GFDL Accomplishments (January – June 2012)

Since the last Intergovernmental Panel on Climate Change report in 2007, climate models at GFDL have evolved towards greater comprehensiveness, as well as finer resolution. Preliminary studies with a new coupled climate model, CM2.5, with an atmospheric grid of 50 km and an ocean grid of 10-27 km, have been very encouraging.

Earth system modeling (ESM) activities at GFDL are focused on expanding beyond the physical climate to represent the marine and terrestrial biosphere and atmospheric chemistry. These models enable us to investigate the exchange of carbon from fossil fuel burning and other sources between the atmosphere, ocean and land. Now that the primary development phase of our ESMs is complete, we are shifting our focus to assess the utility of these comprehensive models to improve understanding of climate impacts on ecosystems and human activities.

Over the next few years, the improved realism and finer spatial resolution of our models will allow us to capture regional climate characteristics.

Endangered Marine Turtles Threatened by Climate Change Heat Waves over North America: Projections for the 21st Century Transport of Asian ozone pollution into surface air over the western United States in spring 21st Century Projections of North Atlantic Tropical Storms

Assessing the potential impacts of climate change on individual species is essential for the stewardship of ecosystems and biodiversity. Marine turtles must lay eggs on sandy beaches, so climate change can affect both their marine and terrestrial habitat. GFDL scientists and colleagues studied a population of critically endangered eastern Pacific leatherback turtles nesting on the coast of Costa Rica, in terms of its sensitivity to contemporary climate variability in the nesting beach and ocean.

This study combined an earth system model, climate projections, and a population dynamics model to estimate a 7% per decade decline in the nesting population at Playa Grande, Costa Rica over the 21rst century, primarily due to the negative impacts of increased air temperature on hatchling recruitment from the nesting beach. This suggests that climate change could drive eastern Pacific leatherbacks in Costa Rica to extirpation, even in the absence of fisheries mortality. The importance of the beach phase climate response suggests that anthropogenic climate-mitigation of leatherback nests in Costa Rica may sustain present-day hatching success, emergence rate, and sex ratio and therefore maintain a sustainable nesting population.
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Heat waves in North America precipitate a substantial number of human casualties and huge economic costs. Understanding the processes that contribute to heat waves and projecting changes in them in the 21st century, are an integral part of NOAA’s mission. Researchers at GFDL evaluated the fidelity of GFDL climate models in reproducing the characteristics of summertime heat waves in different parts of North America, and produced model-projected changes of these characteristics in the 21st century. Published in the Journal of Climate, these model projections indicate considerable lengthening of heat wave duration, as well as notable increases in the frequency of heat wave episodes during the 21st century, compared to the 20th century. The upward trends in heat wave duration and frequency are projected to be discernible in the early decades of the 21st century. Read more…

As Asian countries develop, they are emitting more ozone precursors that pollute surface level air. Many studies have documented this pollution being carried by air currents to the western U.S. To determine the extent to which this pollution is affecting air quality, researchers including GFDL scientists analyzed balloon soundings, aircraft, surface and satellite measurements using GFDL’s new global high-resolution chemistry-climate model. Their findings indicate that Asian pollution contributes as much as 20 percent of total ozone during springtime pollution episodes in western U.S. surface air.

Current guidelines from the Environmental Protection Agency dictate that surface level air should have no more than 75 parts per billion (8 hour average) by volume of ozone. Although local pollution plays a large role when that standard is not met in Southern California, the authors estimate that 53% of the instances where that limit was exceeded would not have occurred without the contribution from Asian air pollution. This research also showed that an index based on satellite observations of Asian pollution plumes could serve as an early warning indicator, with a lead time of 1 to 3 days, of Asian pollution influence on western US air quality. Read more…

In collaboration with Princeton University’s Civil and Environmental Engineering Department, GFDL developed a novel statistical tropical storm frequency model for this study. The results suggest that efforts to understand the likely future course of North Atlantic hurricane activity should focus on improving the ability of global climate models to represent the processes that control patterns of sea surface temperature change, by improving the representation of fundamental process (e.g., cloud physics, atmospheric convection and oceanic processes), the response to diverse forcing (e.g., aerosols) and enhancing model fidelity through spatial resolution.

Over the first half of the 21st century, radiative forcing changes increase North Atlantic tropical storm frequency, though the increase is not driven by greenhouse gas increases. Projected decreases in Atlantic aerosols are key to the projected increase. The largest uncertainties in tropical storm projections are driven by the chaotic nature of the climate system and by the climate response to radiative forcing. This research was published in Nature Climate Change. Read more…