ScienceDaily (Oct. 25, 2009)
— The possibility that climate change might simply be a natural
variation like others that have occurred throughout geologic time is
dimming, according to evidence in a Proceedings of the National Academy of Sciences paper published October 19.The research reveals that sediments retrieved by University at
Buffalo geologists from a remote Arctic lake are unlike those seen
during previous warming episodes.
The UB researchers and their international colleagues were able to
pinpoint that dramatic changes began occurring in unprecedented ways
after the midpoint of the twentieth century.
"The sediments from the mid-20th century were not all that different
from previous warming intervals," said Jason P. Briner, PhD, assistant
professor of geology in the UB College of Arts and Sciences. "But after
that things really changed. And the change is unprecedented."
The sediments are considered unique because they contain rare
paleoclimate information about the past 200,000 years, providing a far
longer record than most other sediments in the glaciated portion of the
Arctic, which only reveals clues to the past 10,000 years.
"Since much of the Arctic was covered by big ice sheets during the
Ice Age, with the most recent glaciations ending around 10,000 years
ago, the lake sediment cores people get there only cover the past
10,000 years," said Briner.
"What is unique about these sediment cores is that even though
glaciers covered this lake, for various reasons they did not erode it,"
said Briner, who discovered the lake in the Canadian Arctic while
working on his doctoral dissertation. "The result is that we have a
really long sequence or archive of sediment that has survived arctic
glaciations, and the data it contains is exceptional."
Working with Briner and colleagues at UB who retrieved and analyzed
the sediments, the paper's co-authors at the University of Colorado and
Queens University, experts in analyzing fossils of bugs and algae, have
pooled their expertise to develop the most comprehensive picture to
date of how warming variations throughout the past 200,000 years have
altered the lake's ecology.
"There are periods of time reflected in this sediment core that
demonstrate that the climate was as warm as today," said Briner, "but
that was due to natural causes, having to do with well-understood
patterns of the Earth's orbit around the sun. The whole ecosystem has
now shifted and the ecosystem we see during just the last few decades
is different from those seen during any of the past warm intervals."
Yarrow Axford, a research associate at the University of Colorado,
and the paper's lead author, noted: "The 20th century is the only
period during the past 200 millennia in which aquatic indicators
reflect increased warming, despite the declining effect of slow changes
in the tilt of the Earth's axis which, under natural conditions, would
lead to climatic cooling."
Co-authors with Briner and Axford are Colin A. Cooke and Alexander
P. Wolfe of the University of Alberta; Donna R. Francis of the
University of Massachusetts; John P. Smol, Cheryl R. Wilson and Neal
Michelutti at Queens University; Gifford H. Miller of the University of
Colorado and Elizabeth K. Thomas, who did this work at UB for her
master's degree in geology.
Biofuel Displacing Food Crops May Have Bigger Carbon Impact Than Thought
ScienceDaily (Oct. 25, 2009) — A report examining the impact of a global biofuels program on greenhouse gas emissions during the 21st century has found that carbon loss stemming from the displacement of food crops and pastures for biofuels crops may be twice as much as the CO2 emissions from land dedicated to biofuels production. The study, led by Marine Biological Laboratory (MBL) senior scientist Jerry Melillo, also predicts that increased fertilizer use for biofuels production will cause nitrous oxide emissions (N2O) to become more important than carbon losses, in terms of warming potential, by the end of the century.
Using a global modeling system that links economic and biogeochemistry data, Melillo, MBL research associate David Kicklighter, and their colleagues examined the effects of direct and indirect land-use on greenhouse gas emissions as the production of biofuels increases over this century. They report their findings in the October 22 issue of Science Express.
Direct land-use emissions are generated from land committed solely to bioenergy production. Indirect land-use emissions occur when biofuels production on cropland or pasture displaces agricultural activity to another location, causing additional land-use changes and a net increase in carbon loss.
No major countries currently include carbon emissions from biofuel-related land-use changes in their carbon loss accounting and there is concern about the practicality of including such losses in a system designed to reduce fossil-fuel emissions. Moreover, methods to assess indirect land-use emissions are controversial. All quantitative analyses to date have either ignored indirect emissions altogether, considered those associated from crop displacement from a limited area, confused indirect emissions with direct or general land-use emissions, or developed estimates based on a static framework of today's economy.
Using a modeling system that integrates global land-use change driven by multiple demands for land and that includes dynamic greenhouse-gas accounting, Melillo and his colleagues factored in a full suite of variables, including the potential of net carbon uptake from enhanced land management, N2O emissions from the increased use of fertilizer, environmental effects on carbon storage, and the economics of land conversion.
"Our analysis, which we think is the most comprehensive to date, shows that direct and indirect land-use changes associated with an aggressive global biofuels program have the potential to release large quantities of greenhouse gases to the atmosphere," says Melillo.
Melillo and his colleagues simulated two global land-use scenarios in the study. In Case 1, natural areas are converted to meet increased demand for biofuels production land. In Case 2, there is less willingness to convert land and existing managed land is used more intensely. Both scenarios are linked to a global climate policy that would control greenhouse gas emissions from fossil fuel sources to stabilize CO2 concentrations at 550 parts per million, a target often talked about in climate policy discussions. Under such a climate policy, fossil fuel use would become more expensive and the introduction of biofuels would accelerate, ultimately increasing the size of the biofuels industry and causing additional effects on land use, land prices, and food and forestry production and prices.
The model predicts that, in both scenarios, land devoted to biofuels will become greater than the total area currently devoted to crops by the end of the 21st century. Case 1 will result in more carbon loss than Case 2, especially at mid-century. In addition, indirect land use will be responsible for substantially greater carbon losses (up to twice as much) than direct land use.
"Large greenhouse gas emissions from these indirect land-use changes are unintended consequences of a global biofuels program; consequences that add to the climate-change problem rather than helping to solve it," says Melillo "As our analysis shows, these unintended consequences are largest when the clearing of forests is involved."
In their model, Melillo and his colleagues also simulated N2O emissions from the additional fertilizer that will be required to grow biofuel crops in the future. They found that over the century, N2O emissions will surpass CO2 in terms of warming potential. By 2100, Melillo and his team estimate that in both study scenarios, biofuels production will account for more than half of the total N2O emissions from fertilizer. "Best practices for the use of nitrogen fertilizer, such as synchronizing fertilizer application with plant demand, can reduce N2O emissions associated with biofuels production," the scientists say.
