- 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.
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.”
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.
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.
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.
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.
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.