This is just too cool:

Bikerafting Alaska’s Lost Coast: Yakutat to Glacier Bay. from lacemine29 on Vimeo.

Welcome to Climate Central’s climate science roundup. This roundup summarizes noteworthy climate science studies published in the previous two weeks, with a special emphasis on articles that might not have been covered by major media outlets. Cross posted from Climate Central

This week in climate science:

• Climate change may dramatically increase wildfires in Yellowstone.
• Questionable claims from satellite data.
• Reservoirs are a real but small source of greenhouse gases.
• Sea level rise threatens shorebirds.
• Nitrogen fertilizer both heats and cools the planet.
• "Fracking" produces almost the same amount of greenhouse gases as conventional natural gas exploration.

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Paper Title: Continued warming could transform Greater Yellowstone fire regimes by mid-21st century
Journal: PNAS
Authors: Anthony L. Westerling, Monica G. Turner, Erica A. H. Smithwick, William H. Rommed, and Michael G. Ryane

Summary: This study models how climate change may affect wildfires in and around Yellowstone National Park in Wyoming, finding a dramatic increase in the number of large fires by 2050.

Significance: Large wildfires account for the majority of land burned in the Yellowstone region — fewer than five percent of forest fires account for over 95 percent of the burned land. For example, in 1988, fueled by warm temperatures, dry weather, and strong winds, more than a third of Yellowstone National Park was engulfed in flames.
Conditions that promote big fires will dramatically increase the area that is burned. According to this study, at some point after 2050, due largely to warmer temperatures, almost every year will have similar climatic conditions to 1988.
Normally, a plot of land in Yellowstone sees a fire about once every 100 to 300 years, which gives forests time to recover in between burns. If this study is correct, fires may return in less than 30 year intervals, meaning that ecosystems would be completely altered, since forests can’t regrow in just three decades. The authors conclude: “There is a real likelihood of Yellowstone’s forests being converted to nonforest vegetation during the mid-21st century because reduced fire intervals would likely preclude postfire tree regeneration.”

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Paper Title: On the Misdiagnosis of Surface Temperature Feedbacks from Variations in Earth’s Radiant Energy Balance 
Journal: Remote Sensing
Authors: Roy W. Spencer and William D. Braswell

Summary: The authors argue that satellite measurements show that energy lost to space is greater than climate models predict. That would imply that the Earth is cooling itself off, counteracting climate change.

Significance: This paper’s analysis has been strongly criticized. The blog realclimate questioned the study’s statistical analysis, and Climate Central’s Mike Lemonick explained how the central idea of the paper — that changes in cloudiness drive climate change, instead of responding to climate change — has been discredited.

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Paper Title: Carbon emission from hydroelectric reservoirs linked to reservoir age and latitude
Journal: Nature Geoscience
Authors: Nathan Barros, Jonathan J. Cole, Lars J. Tranvik, Yves T. Prairie, David Bastviken, Vera L. M. Huszar, Paul del Giorgio, and Fábio Roland

Summary: When reservoirs are built and water floods the landscape, the submerged organic matter decomposes, producing methane and carbon dioxide (CO2), both of which are greenhouse gases. These gases then diffuse into the atmosphere. The authors of this paper surveyed studies of reservoir emissions and found that younger dams produce more greenhouse gases, as do dams near the equator. They find that global emissions from dams is about 300 million tons of CO2-equivalent per year.

Significance: The estimated emissions from reservoirs amounts to a little less than one percent of all emissions from human activities. In other words, dams are a real but relatively small source of greenhouse gases.
Young dams in the tropics, though, produce disproportionately large amounts of methane and CO2. In fact, for a few hydroelectric reservoirs in the Amazon Basin, the ratio of greenhouse gases emitted to electricity produced is higher than it is for coal power plants.

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Paper Title: The impact of sea-level rise on Snowy Plovers in Florida: integrating geomorphological, habitat, and metapopulation models
Journal: Global Change Biology
Authors: Matthew E. Aiello-Lammens, Librada Chu-Agor, Matteo Convertino, Richard A. Fischer, Igor Linkov, and H. Resit Akcakaya

Summary: This study estimates the chance that the snowy plover, a small shorebird that breeds on sand and gravel coastlines, will become extinct in Florida due to sea level rise. The authors model how sea level rise will reshape the coastal ecosystems, and how populations of the bird will respond to such changes.

Significance: The risk of snowy plovers becoming extinct in Florida would increase by only two percent if sea level rises by three feet, and four percent if sea level rises by six feet. That isn’t very significant. However, the study does find that if sea levels rise six feet, the habitat of these birds could be reduced by about 25 percent.
This paper highlights the fact that rising oceans could reduce the size of coastal ecosystems that provide a home to unique species. When sea levels rise, coastal ecosystems might not be able to migrate inland for two reasons: sea levels might rise too quickly for ecosystems to respond, and human structures and settlements might block inland migration.

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Paper Title: Carbon benefits of anthropogenic reactive nitrogen offset by nitrous oxide emissions
Journal: Nature Geoscience
Authors: Sönke Zaehle, Philippe Ciais, Andrew D. Friend, and Vincent Prieur

Summary: Nitrogen fertilizer stimulates plant growth, thus removing extra CO2 from the atmosphere. However, nitrogen fertilizer also causes emissions of nitrous oxide, a strong greenhouse gas. This study compares these two effects, finding that globally, the warming effects of nitrous oxide slightly outweigh the cooling caused by plant growth.

Significance: Nitrous oxide emissions are an important but relatively small source of greenhouse gases — about seven percent of annual greenhouse gas emissions are nitrous oxide, most of which is due to fertilizer use. This paper shows that most, but not all, of these emissions are offset by increased plant growth, and it estimates that about one fifth of the carbon sequestered in ecosystems between 1996 and 2005 was due to extra nitrogen fertilization.

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Paper Title: Life cycle greenhouse gas emissions of Marcellus shale gas
Journal: Environmental Research Letters
Authors: Mohan Jiang, W Michael Griffin, Chris Hendrickson, Paulina Jaramillo, Jeanne VanBriesen, and Aranya Venkatesh

Summary: The authors analyze the total greenhouse gas emissions associated with extracting shale gas through hydraulic fracturing, often referred to as “fracking.” They find that the energy required to build the wells, as well as the methane leaks from the wells, cause slightly more emissions than conventional methods of extracting natural gas.

Significance: Hydrologic fracturing, or “fracking,” to extract shale gas has become increasingly common, as enormous resources of shale gas have been reported to exist in the United States and internationally. Some recent reports explain how plentiful, cheap natural gas, largely from fracking, could provide an increasing amount of energy to our economy. It is thus important to know if fracking increases greenhouse gas emissions.

A previous study, which was highly publicized, suggested that fracking dramatically increased greenhouse gas emissions, largely because of methane that escaped to the atmosphere from wells. That study, however, was widely criticized for how it accounted for greenhouse gas emissions.
This newer paper estimates that fracking produces relatively few greenhouse gas emissions, and that the emissions due to extracting the gas are small in comparison to the emissions from burning it. They find that gas produced from fracking yields only three percent more greenhouse gas emissions than conventionally mined gas.

Welcome to Climate Central’s climate science roundup. This roundup summarizes noteworthy climate science studies published in the previous two weeks, with a special emphasis on articles that might not have been covered by major media outlets. Cross posted from Climate Central.

The Gist: In the Amazon basin, reservoirs may emit more greenhouse gases than coal-fired power plants.

Summary: Although hydropower uses almost no fossil fuels to generate electricity, it can still produce greenhouse gases. Reservoirs flood previously productive ecosystems, replacing them with bodies of water where organic matter decomposes into the greenhouse gases carbon dioxide and methane. This problem is worst in warm, shallow dams, such as those found in the Amazon basin.

These researchers studied the Balbina reservoir, which, because it's extremely large (900 square miles), shallow (less than 100 feet deep at its deepest point), and located in the hot Brazilian Amazon, produces large amounts of CO2 and methane. In fact, after analyzing gasses released from the surface of the reservoir and the river just beyond the dam’s turbines, the authors found the dam is responsible for about three million tons of CO2-equivalent per year.

That is a lot of greenhouse gases. If a comparable coal-fired power plant were built instead of the reservoir (producing about 115 megawatts of power on average), it would produce one-tenth as much CO2, the study found.

Because of its size, shallowness, and location, the Balbina reservoir produces many times more greenhouse gases than most dams. Nonetheless, it shows that dams are not necessarily greenhouse gas-free sources of electricity.

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Paper Title: Atmospheric Carbon Injection Linked to End-Triassic Mass Extinction
Journal: Science
Authors: Micha Ruhl, Nina R. Bonis, Gert-Jan Reichart, Jaap S. Sinninghe Damste, Wolfram M. Kurschner.
The Gist: The mass extinction event that occurred about 200 million years ago, between the Triassic and Jurassic periods, may have been caused by a massive release of methane from the ocean floor — an event some scientists fear could happen today.

Summary: By studying carbon isotopes in fossilized plant material, these scientists determined that (most likely), a large volcanic eruption injected enormous amounts of CO2 into the atmosphere about 200 million years ago. This CO2 warmed the planet, which made methane hydrates — a frozen form of methane gas trapped on the ocean floor — become unstable and be released into the atmosphere. Because methane is a potent greenhouse gas, this further warmed the planet. 

Many scientists fear that a similar situation could occur today. If the oceans warm sufficiently through global warming, the methane on the ocean floor may become unstable, instigating a potentially catastrophic positive feedback to global warming (between the Triassic and Jurassic periods, about half of all life on earth went extinct, probably due to this drastic and sudden climate change).

This analysis shows that this worst-case scenario may have happened in the past. Of course, it isn’t clear how likely this event is to happen today. On the one hand, the amount of CO2 released via the Triassic volcanic eruptions was more than 10 times what humanity is expected to put into the atmosphere. On the other, it was probably released over a few thousand years instead of a few hundred, as is the case with humanity’s current experiment.

Overall, most scientists still rate the likelihood of methane hydrates being released anytime soon as low.

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Paper Title: The role of ocean thermal expansion in Last Interglacial sea level rise
Journal: Geophysical Research Letters
Authors: Nicholas P. McKay, Jonathan T. Overpeck, and Bette L. Otto‐Bliesner.

The Gist: Both the Antarctic and Greenland Ice Sheets may be more sensitive to temperature variability than previously thought.

Summary: During the last interglacial warm period, a little more than 100,000 years ago, global average surface temperatures were about 1°C warmer than today, and sea levels were about fifteen feet higher. The seas were higher due to a combination of the partially melted Greenland and Antarctic ice sheets, and the fact that water expands when it warms.

This study used geological data and computer models to estimate that the vast majority of past sea level rise was due to melting ice and not expanding water. What that means is that a slight warming in the earth’s climate may have melted the ice sheets more than many scientists previously believed.

 

Check out this animated graphic of the Sierra Nevada snowpack. Usually, by this time of year, the snow would be mostly gone. It is still here. To play the animation, you have to hit “stop” and then hit “play” again.

 
Here is the same graphic for 2006-2007 winter, which had almost no snow on June 1st:

 

I have recently become enthralled by a new social network called iNaturalist. It is a part crowd-sourced science and part wikipedia field guide. Here are my observations: