Paul Homewood considers the claim from MIT's John Marshall that global warming is temporarily cooling Antarctica.
Nature World News report:
Massachusetts Institute of Technology researchers explain why global warming has led to Arctic losing sea ice, but the same has not been observed in Antarctica.
Over the past few years, Arctic has shown considerable reduction in sea ice levels due to global warming. However, Antarctica has cooled and has even gained some ice recently. A new study suggests that ocean circulation can explain why the polar regions have different reactions towards rise in earth’s temperature.
John Marshall, the Cecil and Ida Green Professor of Oceanography at MIT and colleagues used computer models to see how ocean dynamics is changing the effects of global warming.
MIT scientists found that Southern Ocean and North Atlantic Ocean absorbs excess heat from greenhouse gas emissions. But the heat doesn’t stay there; instead, oceanic circulation redistributes the heat around the equator.
In the Southern Ocean, strong, northward-flowing currents send the heat to the equator, while northward-flowing current system in the Northern Atlantic takes the heat towards the Arctic. The study shows that oceanic currents redistribute the heat in such a way that Arctic experiences accelerated warming, while Antarctica warms up mildly.
The study even found that the ozone hole over the Antarctica has briefly paused sea ice loss in the region. Scientists said that when they accounted for the ozone hole in their model, they found that winds over the Southern Ocean grew faster and shifted southwards. These winds initially cool the area. But, the process eventually begins to warm the Antarctic and shrinks the ice cover.
"Around Antarctica, the ozone hole may have delayed warming due to greenhouse gases by several decades," Marshall said in a news release. "I’m tempted to speculate that this is the period through which we are now passing. However, by 2050, ozone hole-effects may instead add to the warming around Antarctica, an effect that will diminish as the ozone hole heals."
"The researchers present a useful and timely reminder that the ocean is not a passive bath tub when it comes to climate change, but play an active role in shaping the spatial structure of climate change," said Richard Seagar, the Palisades Geophysical Institute/Lamont Research Professor at the Lamont-Doherty Earth Observatory, who was not involved in the study.
The study is published in the journal Philosophical Transactions of the Royal Society.
There are a number of points here:-
1) They are now admitting that Antarctica is actually cooling. This rather puts the kybosh on the “Melting glaciers” theory.
2) There a number of references to models, so it appears we can take the whole study with a hefty shovelful of salt. I particularly had to laugh at:
Scientists said that when they accounted for the ozone hole in their model
3) They talk of excess heat from greenhouse gas emissions. But what evidence do they have that it is “excessive”. What they are actually describing are perfectly natural ocean currents and cycles. He presents no evidence that these natural processes are doing anything different than what they have done for centuries.
4) What we are left with is that ocean currents have contributed to a warming Arctic and cooling Antarctic.
This graphic and description illustrates nicely how ocean currents naturally redistribute water around the world.
Decades of research on ocean currents have revealed that there is a large scale oceanic circulation system. The Gulfstream that moves into the North Atlantic finally sinks as it cools and returns south across the Atlantic seafloor, flows as a bottom current into the South Atlantic, and then rises to the surface again in the Indian Ocean and the Eastern Pacific, only to warm up (absorbing heat from overlying air masses) and turn west to feed back into the Gulfstream. Actually, the sinking of the Gulf Stream is not so much a consequence of cooling and density increase, but one of salinity. Equatorial surface waters are more saline (high evaporation), and the waters of the North Atlantic are less saline (because they mix with meltwater [low salinity] from icebergs and from the Greenland ice cap). Thus, once the Gulfstream cools sufficiently it is heavier that the lower salinity North Atlantic seawater and sinks. A complete run through this current system is estimated to take about 1000 years.
www.indiana.edu/~geol105/1425chap4.htmNote that the complete run takes 1000 years. The idea that such a system, associated as it is with the enormous heat capacity of the ocean, could be hijacked in the space of a few years is frankly junk science.
Finally, a real scientist does not say “I’m tempted to speculate”, and expect to be treated seriously.
The real story can be seen in the sea temperatures in the Southern Ocean. Below are the SST Anomalies, from NOAA, of the ocean between 60S and 70S, the area where sea ice is expanding. ( The anomalies are set on a baseline of 1971-2000).
nomad1.ncep.noaa.gov/cgi-bin/pdisp_sst.sh?ctlfile=monoiv2.ctl&ptype=ts&var=ssta&level=1&op1=none&op2=none&month=nov&year=1981&fmonth=jul&fyear=2014&lat0=-70&lat1=-60&lon0=-180&lon1=180&plotsize=800×600&title=SST+Anomalies+60S+to+70S&dir=There’s not much sign of any excess heat there.
Link:
notalotofpeopleknowthat.wordpress.com/2014/08/26/global-warming-causes-cooling-in-antarctica-or-maybe-its-just-natural-2/