A new report from Lawrence Livermore National Laboratory has stated that the simultaneous warming of the upper layers of all seven seas over the past 50 years cannot be explained by natural climate variability alone. The scientists’ computer modelling study reveals that human alterations to the environment, such as the observed increases in greenhouse gas, are causing the warming of the world’s oceans, and as an result, affecting the natural climate cycles.
While this may not sound like a completely surprising revalation, the study is the first to provide an in-depth examination of how observational and modelling 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 in a statement “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 team’s research, which is published in the June 10 edition of the journal, Nature Climate Change details how the observed global average ocean warming (from the surface to 700 meters) was approximately 0.025 degrees Celsius per decade, or slightly more than 1/10th of a degree Celsius over 50 years.
The team also saw that the sub-surface ocean warming was noticeably less than the observed Earth surface warming, due to the relatively slow transfer of ocean surface warming to lower depths. As the ocean has an enormous heat capacity, the team believes that the world’s sea likely accounts for more than 90 percent of the heat accumulated over the past 50 years as the Earth has warmed.
Working with observational experts from the United States, Japan and Australia, the LLNL team examined the causes of ocean warming, using improved observational estimates.
“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.”
Via Discovery News
Image: Rising sun on the horizon, blue sea, ocean from Shutterstock