Another study which looks at what conditions in our future might be like by comparing them to conditions in our planets history has shown that if global warming continues apace, we could set in a motion a change of events that could take tens of thousands of years to dissipate.
Hyperthermals, described as bursts of intense global warming, lasted tens of thousands of years, and have taken place numerous times throughout history.
The study which reveals the extent and timing of these hyperthermals appears in the March 17 issue of the journal Natureand was co-authored by Richard Norris, a professor of geology at Scripps Institution of Oceanography, UC San Diego, who noted that releases of carbon dioxide sequestered deep within the oceans interior were the cause for the hyperthermal events.
Research showed that the events raised the average global temperature by a 2° to 3° Celsius (3.6 to 5.4° F), amounts that roughly translate to estimates of how much our current temperatures might increase in the decades to come as a result of anthropogenic global warming.
“These hyperthermals seem not to have been rare events,” Norris said, “hence there are lots of ancient examples of global warming on a scale broadly like the expected future warming. We can use these events to examine the impact of global change on marine ecosystems, climate and ocean circulation.”
According to the research, the hyperthermals recorded in sediment cores collected off the South American coast took place every 400,000 years during a period of Earth’s history between 50 million and 40 million years ago, at which point the Earth entered a cooling phase: no hyperthermals have appeared in the geological record ever since.
The strongest of these hyperthermals coincided with the Paleocene-Eocene Thermal Maximum, the transition between the Paleocene and Eocene epochs 55.8 million years ago which saw global temperatures increase by 4° to 7° C (7.2° to 12.6° F) and needed 200,000 years before the climate returned to a historical norm.
Other theories have been presented to explain these hyperthermal events – such as large melt-offs of methane hydrates, terrestrial burning of peat and proposed cometary impacts – but according to Norris and Phil Sexton – a former student of Norris’ and now at the Open University in the UK – who led the study of the sediment cores the release of carbon from the deep oceans is a much more likely cause.