Indications of Positive Feedback in Climate Change Due to a Reduction in Northern Hemisphere Biomass Uptake of Atmospheric Carbon Dioxide

by Alexander Brown

It is commonly understood that ecosystems have been taking up more carbon dioxide (CO2) as the concentration of atmospheric CO2 increases and the climate changes. The progressive increase in CO2 uptake by terrestrial ecosystems is generally thought to continue until 2030, when the trend is expected to reverse due to ecosystem damage. However, Dr. James C. Curran and Dr. Samuel A. Curran (2016) have found evidence that the trend may have already begun to reverse. They base this on analysis of the atmospheric CO2 measurements taken between 1958 and 2015 from the Mauna Loa observatory in Hawaii, known as the Keeling Curve. These data show a continual rise in atmospheric CO2 levels within a pattern of intra-annual fluctuation. The intra-annual fluctuation consists of decreased atmospheric CO2 levels throughout the summer months (Northern Hemisphere), and increased atmospheric CO2 throughout the rest of the year. Continue reading

Global Climate Change Inequity: Who’s Carrying Whom?

by Coco Coyle

Because the Earth’s atmosphere intermixes globally, all areas of the globe are equally exposed to greenhouse gas emissions (GHGs). However, some countries are more vulnerable to the effects of these emissions, while some countries release more GHGs into the atmosphere than others. Althor et al. (2016) compare each country’s vulnerability to climate change to its creation of GHGs for the years 2010 and 2030. They found that the countries least vulnerable to climate change were higher GHG emitters, and the most vulnerable countries were least responsible for GHG emissions. By 2030 the inequity will have worsened. The authors call for climate change policies that place more responsibility for mitigating climate change on the high-emitters. Continue reading

Modeling CO2 and CH4 Fluxes in the Arctic using Satellite data

by Rebecca Herrera

The peatlands and tundras of the Arctic perform vital ecosystem services to the earth through their ability to sequester carbon (CO2) and methane (CH4) and function as a carbon sink. The ability of the permafrost in the peatlands and tundra ecosystems of the Arctic to continue to function as a natural reservoir for carbon and methane may be disrupted by rising global temperatures that increase the rate of soil decomposition. Watts et al. (2014) integrate a terrestrial carbon flux (TCF) model to include a newly developed CH4 emissions algorithm. The new TCF model simultaneously assesses CO2 and CH4 fluctuations and the corresponding net ecosystem carbon balance (NECB), which is contingent upon gross primary productivity (GPP) subtracted from ecosystem respiration. The integrated TCF model uses data gathered through satellite remote sensors to assess fluxes in CO2 and CH4. Continue reading

Global Warming Reduction by Switching to Healthy Diets

by Shelby Long

The consumption of food and beverages accounts for 22–31% of total private consumption greenhouse gas (GHG) emissions in the EU (Tukker et al. 2009). More specifically, the production of meat and dairy products tend to produce greater GHG emissions (Audsley et al. 2009). Saxe et al. (2012) examine how different diets, which are composed of different foods, are associated with varying potential GHG emissions. They use consequential Life Cycle Assessment to compare the emissions, or global warming potential (GWP), from food production for an Average Danish Diet (ADD), the Nordic Nutritional Recommendations (NNR), and a New Nordic Diet (NND), which was developed by the OPUS Project. They determined that the GHG emissions association with NNR and NND were lower than those associated with ADD, by 8% and 7%, respectively. When taking into account the transport of food, NND emissions are 12% less than ADD emissions. With regard to organic versus conventional food production, GHG emissions are 6% less for NND than for the ADD. Saxe et al. adjusted NND to include less beef and more organic produce, and they substituted meat with legumes, dairy products, and eggs, which made the diet more climate-friendly. As a result of this adjustment, the GHG emissions associated with NDD was 27% less than emissions for ADD. Continue reading

What Has Worked to Slow Global Warming

by Emil Morhardt

Last week, in anticipation of the United Nations climate conference in New York, The Economist concluded that the single most important action to slow global warming so far has been enactment of the Montreal protocol. Say what? This isn’t on most environmentalists’ radar as an important factor. The Montreal protocol is the 1987 international agreement to save the ozone layer by phasing out Freon and other chlorofluorocarbons used in refrigeration. But these substances are powerful greenhouse gases as well as destroyers of stratospheric ozone, and the protocol caused millions of tonnes of them not to be released into the atmosphere. The article concludes that this avoided release of the greenhouse gas equivalent of 5.6 billion tonnes (bt) of CO2. This is about twice as much avoided CO2 as the next two most effective actions, global use of nuclear power (2.8 bt) and hydroelectricity (2.2 bt), and four times that of the fourth most effective action, China’s one-child policy (1.3 bt). I’m guessing that most of the 300,000 demonstrators in New York last week are not proposing an expansion of these latter three items, but their past effectiveness does make one think. The most effective actions taken specifically to reduce energy usage and CO2 emissions have been worldwide adoption of renewables (0.6 bt), US vehicle emissions standards (0.5 bt), and Brazil forest preservation (0.4 bt). The remaining 11 items on The Economist’s list are small potatoes, totaling less than 1 bt collectively. Continue reading

Very Large Wildland Fires Predicted to Increase in Rocky Mountains and Pacific Northwest

by Emil Morhardt

In the middle of one of the worst fire seasons on record for Northern California comes a new modeling paper by scientists at CalTech’s Jet Propulsion Laboratory, the University of Idaho, and the US Forest Service Pacific Wildland Fire Sciences Laboratory predicting no effect of climate change on Northern California Very Large Wildfires (VLWFs), but potentially large increases in them in the Pacific Northwest and Rocky Mountains under future greenhouse gas (GHG) emissions scenarios. It may well be that the size of the Northern California fires won’t reach the threshold of 50,000 acres used in this study (the top 2% of wildland fires), but if these not-so-large fires are disturbing, then the prospect of even larger ones more frequently in much of the western US is even more so. Continue reading

Cutting Climate Costs of Nitrogen Fertilizer Production

by Emil Morhardt

Nitrogen fertilizer, crucial for growing commercial crops, is based on ammonia made in factories using the energy- and CO2-intensive Haber-Bosch process; hydrogen is stripped off natural gas using steam, then reacted with nitrogen in the air. The process uses repeated cycling at high temperature and pressure, and consumes 2% of the world’s energy production. Stuart Licht and colleagues at George Washington University noticed, however, that a recently developed fuel cell using ammonia as a fuel and producing electricity as an output might be run in reverse: electricity in, ammonia out, with a whole lot less temperature and pressure (and energy) required. Even better, it wouldn’t need natural gas as a hydrogen source—with its attendant CO2 production—being able to get it from air and steam at a temperature lower than a household oven baking bread and at ambient pressure. Furthermore only simple materials would be required; molten sodium and potassium hydroxide (inexpensive commodity chemicals), nickel electrodes, and an iron oxide catalyst, all in a single pot.

After considerable experimentation with different temperatures, voltages, forms of iron oxide, Continue reading

The Other Ocean Acidification Problem: CO2 as a Resource

by Dawn Barlow

This study addresses the effects of enhanced CO2 levels in the ocean by looking at how increased acidity might indirectly cause phase shifts in community structure of coral reef and kelp forest ecosystems in temperate and tropical waters. Under elevated acidity and temperature conditions, productivity of certain photosynthetic organisms such as mat-forming algae (low-profile ground-covering macroalgal and turf communities) can increase, making CO2 not only a direct stressor but also an indirect stressor by being a resource for certain competitive organisms, creating enormous potential for shifts in species dominance. Additionally, ocean acidification acts together with other environmental stressors and primary consumers, and these factors also influence community response to acidic conditions. Connell et al. (2013) investigate the prevalence of mat-forming algae in three different scenarios where CO2 levels were either ambient or elevated: in the laboratory, in mesocosms in the field, and at naturally occurring CO2 vents that locally alter the seawater chemistry. They find that in all the scenarios, the algae mats respond positively to the elevated conditions, increasing growth rate and cover to so that the algae became a majority space holder regardless of any herbivory. This is likely because the new environmental conditions favor species with fast growth and colonization rates and short generation times, and these are the species that are capable of completely… Continue reading

Way More Methane than EPA Thinks, Maybe

by Emil Morhardt

The amount of the powerful greenhouse gas, methane (natural gas) released into the atmosphere by farmers and gas and oil companies is substantially underestimated by the USEPA according to a team led by Scott Miller, a Harvard Ph.D. student, published late last year in the Proceedings of the National Academy of Sciences. The previously unaccounted sources are ruminants, manure, and fossil fuel extraction and processing in the South-Central US, traced back to their sources from fixed towers and aircraft-based methane sensors using the Stochastic Time-Inverted Lagrangian Transport model (STILT). On the other hand, Hristov et al.(2014), in response to the Miller et al. paper, calculated cattle methane releases from the ground up  based on the number of cattle in the US and thought that the EPA had it right in the first place. So we have a calculation based on numbers of cattle competing with empirical data from the methane sensors processed through an interesting atmospheric model. This type of atmospheric modeling–tracing airborne chemicals back to their source–is what NASA is about to use with the data from its newly launched (July 2, 2014) Orbiting Carbon Observatory, OCO-2, except that the observatory will detect CO2 rather than methane. No public data from it are available as yet, but since methane oxidizes to CO2 in the atmosphere, it is possible that the satellite will soon confirm the sources of the methane. You can find out about the OCO-2 instrument here.

Miller, S.M., Wofsy, S.C., Michalak, A.M., Kort, E.A., Andrews, A.E., Biraud, S.C., Dlugokencky, E.J., Eluszkiewicz, J., Fischer, M.L., Janssens-Maenhout, G., 2013. Anthropogenic emissions of methane in the United States. Proceedings of the National Academy of Sciences 110, 20018-20022.

Hristov, A.N., Johnson, K.A., Kebreab, E., 2014. Livestock methane emissions in the United States. Proceedings of the National Academy of Sciences 111, E1320-E1320.

Please let me know if you are aware of new papers that should be written about by the Climate Vulture


Challenges and Opportunities for Mitigating Nitrous Oxide Emissions from Fertilized Cropping Systems

Nitrous oxides are a potent greenhouse gas emitted from a multitude of sources.  Agricultural processes constitute a significant portion of these emissions, and attempts have been made at reducing nitrous oxide.  This paper intends to be a thorough review of the potential strategies and future research needs specific to nitrous oxide emissions by focusing on the management of individual fertilized cropping systems.   Venterea et al. (2012) investigate methods in reducing nitrous oxide emissions, and goes into detail about what has and hasn’t worked, as well as why.  What follows is a summary of this investigation as well as recommendations that the authors have in reducing nitrous oxide emissions. — Anthony Li
Venterea, R. T., Halvorson, A. D., Kitchen, N., Liebig, M. A., Cavigelli, M. A., Del Grosso, S. J., Motavalli, P. P., Nelson, K. A., Spokas, K. A., Singh, B. P., Stewart, C. E., Ranaivoson, A., Strock, J., Collins, H. 2012. Challenges and opportunities for mitigating nitrous oxide emissions from fertilized cropping systems.  Frontiers in Ecology and the Environment 10. 10: 562-570

Nitrous oxide emissions are the product of several processes occurring in the soil, which include nitrification, nitrifier-denitrification, chemo-denitrification, and denitrification.  All these processes are exacerbated in crop systems, as the addition of nitrogen fertilizers provide the necessary ingredients.  Because these processes can occur under a range of soil conditions, optimizing soil conditions to reduce nitrous oxides production can be difficult and may not be feasible.  Nitrous oxide is of particular concern, as it is 300 times more potent as a greenhouse gas than carbon dioxide, and is expected to increase by 2% per year through 2015.  Experts agree that the main challenge in reducing agroecosystem nitrogen losses and nitrous oxide emissions is to maximize the amount of nitrogen fertilizer that is actually used by the crops, or the optimization of nitrogen use efficiency (NUE).  The authors investigate current methods of optimizing NUE, and how they can be improved upon.
The synchronization of the application of nitrogen fertilizers with the demand for nitrogen in plants holds a lot of potential in improving NUE.  Currently, large amounts of nitrogen fertilizers are applied before the growing season, resulting in lower than 40-50% recovery in crops while contributing to unnecessary nitrous oxide production.  The nitrogen that is not recovered by plants is often moved to downwind/stream ecosystems where it is still converted into nitrous oxides.  However, the timing of fertilizer use not only has to be in sync with crop demands, but also during appropriate climatic conditions.  In past cases, applying nitrogen fertilizers during the growing seasons in warmer or wetter conditions has led to an increased amount of nitrous oxides emitted.  With this in mind, synchronizing fertilizer application will require the need for accurate systems that can predict nutrient demand in crops while accounting for climatic conditions.  It’s also common for large amounts of nitrous oxides to be emitted in response to management practices and climatic events.  We can address these emissions by investigating these practices and events individually and seeing how they affect nitrous oxides production.  On a broader scale, we can reduce nitrous oxide emissions from soils overall by using smaller and more frequent nitrogen applications, which would lessen fertilizer-induced pulses of nitrous oxides emissions, and by using carbon rich residues for short-term nitrogen immobilization, which can reduce pulses of nitrous oxides emissions during the decomposition of nitrogen rich residues.
Another solution for the nitrous oxides is reducing the nitrogen rate, or the amount of nitrogen applied per area of field during a growing season.  This cuts straight to the source of the emissions, while also solving problems such as nutrient runoff and a dwindling nitrogen supply.  However, “because crop yields, and therefore farmers’ profits, are also highly sensitive to nitrogen rate, the feasibility of nitrogen rate reduction as a strategy for mitigating nitrous oxide must consider economic impacts and other policy ramifications.”  Solutions that result in economic damage are unattractive and will unlikely be implemented.  It should also be noted that reducing nitrogen rate in one area might increase the nitrogen rate, and its associated nitrous oxide emissions, in another area via leakage effect.
In dealing with this nitrous oxides issue, the authors have a number of suggestions they believe to be most effective.  They recommend frequent additions of nitrogen fertilizer that are applied to coincide with crop demand and avoid wet conditions.  This would maximize amount of nitrogen absorbed by crops, while avoiding conditions that can result in elevated nitrous oxides production.  The authors also recommend using nitrogen rates that are adjusted spatially to match in-field variations in crop nitrogen demand and soil nitrogen supply, as the demand and supply of nitrogen in a field varies spatially and would benefit from maximum nitrogen use efficiency.  The authors finally recommend developing a system that can deliver nitrogen close to the root system in a chemical form that is stabilized to minimize losses of all other reactive nitrogen species.  This solution would reduce nitrogen runoff, which would in turn reduce eutrophication and the likelihood of nitrous oxides being produced downstream.  It should be noted that all these solutions are in common in that they focus on improving the efficiency of nitrogen use.  Increasing nitrogen use to compensate for low nitrogen recovery rate in crops would only produce more nitrous oxides, while decreasing nitrogen will result in a leakage effect that would offset any amount of nitrous oxide saved.  The lesson we should take away from this is that improving efficiency should be our goal in addressing any environmental issue.  The consequences of increasing/decreasing the inputs for a greenhouse gas are reviewed here and should be considered when addressing other greenhouse gases.