by Staff Writers
Livermore, CA (SPX) Jun 18, 2012
The oceans have warmed in the past 50 years, but not by natural events alone. New research by a team of Lawrence Livermore National Laboratory scientists and international collaborators shows that the observed ocean warming over the last 50 years is consistent with climate models only if the models include the impacts of observed increases in greenhouse gas during the 20th century.
Though the new research is not the first study to identify a human influence on observed ocean warming, it is the first to provide an in-depth examination of how observational and modeling uncertainties impact the conclusion that humans are primarily responsible.
"We have taken a closer look at factors that influence these results," said Peter Gleckler, an LLNL climate scientist and lead author of the new study that appears in the June 10 edition of the journal, Nature Climate Change.
"The bottom line is that this study substantially strengthens the conclusion that most of the observed global ocean warming over the past 50 years is attributable to human activities."
The group looked at the average temperature (or heat content) in the upper layers of the ocean. The observed global average ocean warming (from the surface to 700 meters) is approximately 0.025 degrees Celsius per decade, or slightly more than 1/10th of a degree Celsius over 50 years.
The sub-surface ocean warming is noticeably less than the observed Earth surface warming, primarily because of the relatively slow transfer of ocean surface warming to lower depths. Nevertheless, because of the ocean's enormous heat capacity, the oceans likely account for more than 90 percent of the heat accumulated over the past 50 years as the Earth has warmed.
In this study the team, including observational experts from the United States, Japan and Australia, examined the causes of ocean warming using improved observational estimates.
They also used results from a large multi-model archive of control simulations (that don't include the effects of humans, but do include natural variability), which were compared to simulations that included the effects of the observed increase in greenhouse gases over the 20th century.
"By using a "multi-model ensemble," we were better able to characterize decadal-scale natural climate variability, which is a critical aspect of the detection and attribution of a human-caused climate change signal. What we are trying to do is determine if the observed warming pattern can be explained by natural variability alone", Gleckler said.
"Although we performed a series of tests to account for the impact of various uncertainties, we found no evidence that simultaneous warming of the upper layers of all seven seas can be explained by natural climate variability alone. Humans have played a dominant role."
Livermore co-authors include Benjamin Santer, Karl Taylor and Peter Caldwell, whose work was funded by the U.S. Department of Energy (contract DE-AC52-07NA27344). International collaboration from Australia was funded through the Antarctic and Climate Ecosystems Cooperative Research Centre and the Australian Climate Change Science Program, a joint initiative of the Department of Climate Change and Energy Efficiency, the Bureau of Meteorology and CSIRO, with additional support provided from CSIRO's Wealth from Oceans Flagship. Collaborators from the U.S. are funded by Scripps Institution of Oceanography and the National Oceanic and Atmospheric Administration. Collaborators from India are funded by the Indian Institute of Technology Delhi, and collaborators from Japan are funded by the Frontier Research Center for Global Change.
DOE/Lawrence Livermore National Laboratory
Water News - Science, Technology and Politics
Comment on this article via your Facebook, Yahoo, AOL, Hotmail login.
Microbial communities shifted dramatically after Deepwater Horizon spill
Durham NH (SPX) Jun 15, 2012
Communities of microbial organisms - species such as nematodes, protists and fungi - on beaches along the Gulf of Mexico changed significantly following the Deepwater Horizon oil spill in April 2010, research from the University of New Hampshire's Hubbard Center for Genome Studies (HCGS) and partners found. The findings, which analyzed marine sediments from five Gulf Coast sites prior to and sev ... read more
|The content herein, unless otherwise known to be public domain, are Copyright 1995-2012 - Space Media Network. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA Portal Reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. Advertising does not imply endorsement,agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. Privacy Statement|