Publications by authors named "AS Denning"

The Amazon forest carbon sink is declining, mainly as a result of land-use and climate change. Here we investigate how changes in law enforcement of environmental protection policies may have affected the Amazonian carbon balance between 2010 and 2018 compared with 2019 and 2020, based on atmospheric CO vertical profiles, deforestation and fire data, as well as infraction notices related to illegal deforestation. We estimate that Amazonia carbon emissions increased from a mean of 0.

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Estimates of Amazon rainforest gross primary productivity (GPP) differ by a factor of 2 across a suite of three statistical and 18 process models. This wide spread contributes uncertainty to predictions of future climate. We compare the mean and variance of GPP from these models to that of GPP at six eddy covariance (EC) towers.

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Tropical South America plays a central role in global climate. Bowen ratio teleconnects to circulation and precipitation processes far afield, and the global CO growth rate is strongly influenced by carbon cycle processes in South America. However, quantification of basin-wide seasonality of flux partitioning between latent and sensible heat, the response to anomalies around climatic norms, and understanding of the processes and mechanisms that control the carbon cycle remains elusive.

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Agricultural emissions are the primary source of ammonia (NH) deposition in Rocky Mountain National Park (RMNP), a Class I area, that is granted special air quality protections under the Clean Air Act. Between 2014 and 2016, the pilot phase of the Colorado agricultural nitrogen early warning system (CANEWS) was developed for agricultural producers to voluntarily and temporarily minimize emissions of NH during periods of upslope winds. The CANEWS was created using trajectory analyses driven by outputs from an ensemble of numerical weather forecasts together with the climatological expertize of human forecasters.

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Article Synopsis
  • The North American Carbon Program (NACP) conducted a significant research initiative in 2007 to explore the carbon cycle in the productive agricultural regions of the Midwestern US, involving 45 projects and hundreds of researchers across five agencies.
  • The main goal was to assess how well atmospheric inversion techniques can estimate CO2 flux using calibrated mixing ratio data, by comparing these estimates with a detailed inventory of CO2 emissions from crops, mainly corn and soybeans.
  • The study found that different inversion systems produced slightly higher CO2 sink estimates than the inventory, but all estimates were statistically similar, demonstrating that accurate estimates of CO2 fluxes can be achieved at smaller scales when there is enough observational data and atmospheric transport details.
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Measurements of midday vertical atmospheric CO2 distributions reveal annual-mean vertical CO2 gradients that are inconsistent with atmospheric models that estimate a large transfer of terrestrial carbon from tropical to northern latitudes. The three models that most closely reproduce the observed annual-mean vertical CO2 gradients estimate weaker northern uptake of -1.5 petagrams of carbon per year (Pg C year(-1)) and weaker tropical emission of +0.

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The African continent has a large and growing role in the global carbon cycle, with potentially important climate change implications. However, the sparse observation network in and around the African continent means that Africa is one of the weakest links in our understanding of the global carbon cycle. Here, we combine data from regional and global inventories as well as forward and inverse model analyses to appraise what is known about Africa's continental-scale carbon dynamics.

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Methods: A questionnaire was administered to 958 women attending the antenatal clinic at Mercy Hospital for Women, Melbourne, to ascertain their choice of title during pregnancy Midwifery, nursing and medical staff (376 in total) were also invited to respond to a similar questionnaire.

Results: The response rate was 73.6% from the survey of all women who were overwhelmingly in favour of being called 'patient' as their first choice (34%), followed by 'other' (20%) and then 'mother' (19%).

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Information about regional carbon sources and sinks can be derived from variations in observed atmospheric CO2 concentrations via inverse modelling with atmospheric tracer transport models. A consensus has not yet been reached regarding the size and distribution of regional carbon fluxes obtained using this approach, partly owing to the use of several different atmospheric transport models. Here we report estimates of surface-atmosphere CO2 fluxes from an intercomparison of atmospheric CO2 inversion models (the TransCom 3 project), which includes 16 transport models and model variants.

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Knowledge of carbon exchange between the atmosphere, land and the oceans is important, given that the terrestrial and marine environments are currently absorbing about half of the carbon dioxide that is emitted by fossil-fuel combustion. This carbon uptake is therefore limiting the extent of atmospheric and climatic change, but its long-term nature remains uncertain. Here we provide an overview of the current state of knowledge of global and regional patterns of carbon exchange by terrestrial ecosystems.

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Atmospheric general circulation models used for climate simulation and weather forecasting require the fluxes of radiation, heat, water vapor, and momentum across the land-atmosphere interface to be specified. These fluxes are calculated by submodels called land surface parameterizations. Over the last 20 years, these parameterizations have evolved from simple, unrealistic schemes into credible representations of the global soil-vegetation-atmosphere transfer system as advances in plant physiological and hydrological research, advances in satellite data interpretation, and the results of large-scale field experiments have been exploited.

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