Climate Variation During Greenhouse Conditions
Researchers from the National Oceanography Centre in Southampton, England, have concluded that man-made global warming would probably not greatly change the influence had on the environment by inter-annual climate instances such as El Niño – Southern Oscillation (ENSO) or the Arctic Oscillation/ North Atlantic Oscillation (AO/ NAO).
“Even in the warm Cretaceous period, the patterns of these climatic oscillations changed over longer decadal timescales,” explained Professor Alan Kemp of the University of Southampton’s School of Ocean and Earth Science based at the National Oceanography Centre, Southampton. “It is therefore difficult to predict whether anthropogenically driven warming will lead to systematic changes such as persistently milder European winters (a positive AO/ NAO) as some have suggested.”
All indications suggest that the Arctic will be ice free in the next 15 to 50 years, but what that means for the environment as a whole seems to be anybody’s guess.
“A key question is how an Arctic without permanent ice cover will affect atmospheric circulation and climate variability, particularly over high and mid-latitudes,” said Kemp.
The researchers headed back in time, to the Late Cretaceous period, in an attempt to see what our own future could be like. This was the time when dinosaurs roamed the planet, and the Arctic Ocean was ice free almost all year round.
“Understanding Late Cretaceous climate should inform debate about future climate trends and variability under greenhouse conditions,” said Kemp, whose team’s new findings are published in Geophysical Research Letters.
The team’s analysis of sediment cores from a marine ridge in the Arctic Ocean revealed that the Arctic climate of the Late Cretaceous period varied, with some periods of time closely matching those currently observed in the Arctic. This suggests that the Arctic of the Late Cretaceous period was subject to some of the same climatic influences of current day Earth, including the El Niño – Southern Oscillation.
This research has been long needed, as there has been an ongoing debate over whether natural modes of climate variability like ENSO and AO/NAO would continue or be enhanced by anthropogenic global warming.
Within the scientific world, particular controversy has surrounded the suggestion that current warming would eventually cause a permanent El Niño state or milder European winters.
“Based on our findings, it seems unlikely that man-made global warming would cause a permanent El Niño state,” concluded Kemp.