Process Modeling of Global Soil Nitrous Oxide Emissions

http://globalchange.mit.edu/research/publications/2213Nitrous oxide is an important greenhouse gas and is a major ozone-depleting substance. To understand and quantify soil nitrous oxide emissions, we expanded the Community Land Model with prognostic Carbon and Nitrogen (CLM-CN) by inserting a module to estimate annually- and seasonally-varying nitrous oxide emissions between 1978 and 2000. We evaluate our soil N2O emission estimates against existing emissions inventories, other process-based model estimates, and observations from two forest sites in the Amazon and one in the United States. The model reproduces soil temperature and soil moisture relatively well, and it reconfirms the important relationship between N2O emissions and these parameters. The model also reproduces observations of N2O emissions well in the Amazonian forests but not during the winter in the USA. Applying this model to estimate the past 23 years of global soil N2O emissions, we find that there is a significant decrease in soil N2O emissions associated with drought and El Ni˜no years. More study is necessary to quantify the high-latitude winter activity in the model in order to better understand the impact of future climate on N2O emissions and vice versa.NASA Upper Atmosphere Research Program grants NNX11AF17G and NNX07AE89

Greenhouse gas indices. Final report

The objective of this research has been to analyze the various components of a relative gas index, and to seek a procedure that is simple and transparent but still representative of the relationship among gases. To compare the relative effects on climate change of emissions of various kinds, including aerosol precursors, the approach pursued in this research has been to develop a computer algorithm encompassing the critically-linked elements which determine gas lifetimes and radiative influence, and the resulting climate effects. Elements to be considered in the course of work have included the following: regional economic growth and emissions, and the influence of mitigation measures; the latitudinal distribution of emissions; chemical auto-feedbacks; chemical-chemical feedback; multiple gases and aerosols, and their interactions; and the linking of gas effects to damage measures, to seek an economic definition of relative weights. As an outcome of this research, new capacity has been developed for analysis of these multi-gas issues as they relate to climate change. This report covers the accomplishments on this task. Publications and reports that have resulted in whole or in part from this research grant are listed in Section 3, and are included as attachments to this report

Prebiotic materials from on and off the early Earth

One of the greatest puzzles of all time is how did life arise? It has been universally presumed that life arose in a soup rich in carbon compounds, but from where did these organic molecules come? In this article, I will review proposed terrestrial sources of prebiotic organic molecules, such as Miller–Urey synthesis (including how they would depend on the oxidation state of the atmosphere) and hydrothermal vents and also input from space. While the former is perhaps better known and more commonly taught in school, we now know that comet and asteroid dust deliver tons of organics to the Earth every day, therefore this flux of reduced carbon from space probably also played a role in making the Earth habitable. We will compare and contrast the types and abundances of organics from on and off the Earth given standard assumptions. Perhaps each process provided specific compounds (amino acids, sugars, amphiphiles) that were directly related to the origin or early evolution of life. In any case, whether planetary, nebular or interstellar, we will consider how one might attempt to distinguish between abiotic organic molecules from actual signs of life as part of a robotic search for life in the Solar System

Data used to produce figures in the manuscript ‘Maximizing Ozone Signals Among Chemical, Meteorological, and Climatological Variability’ by Brown-Steiner et al. (2018)

Data used to produce figures in the manuscript ‘Maximizing Ozone Signals Among Chemical, Meteorological, and Climatological Variability’ by Brown-Steiner, B.; Selin, N. E.; Prinn, R. G.; Monier, E.; Tilmes, S.; Emmons, L.; Garcia-Menendez, F