Visitor publish by Jim Steele,
Revealed within the Pacifica Tribune December 31, 2019
When Warming is Cooling!
The media has been awash with doomsday headlines, trumpeting a human-caused “local weather disaster” just because the estimated common international temperature has risen about 1.7°F because the finish of the chilly Little Ice Age 150 years in the past. Nevertheless, the Arctic has been the best local weather outlier and its a lot hotter temperatures, averaging three.6°F increased than the 1951–1990 common, has shifted the worldwide warming common upwards.
Moreover, elevated air flow of saved ocean warmth has contributed to a lot of the Arctic’s latest excessive temperatures. Ventilating warmth warms the air however cools the ocean, and local weather historical past reveals ventilating warmth has triggered a number of bouts of maximum warming. Over the previous 100 thousand years Greenland’s ice cores recorded 24 excessive warming episodes when air temperatures immediately rose 14°F – 28°F in a number of a long time or much less. Extra not too long ago over 4000 years within the Canadian Arctic, a long time of fast ice loss accompanied air temperatures three°F -10°F hotter than at the moment, shortly adopted by centuries of extra sea ice and colder temperatures. Though the physics of these dramatic warming occasions are nonetheless in play at the moment, the excellent news is: warming climates reduce such dramatic heat occasions.
Essentially the most excessive Arctic warming episodes had been named “Dansgaard-Oeschger occasions” in honor of two scientists who found them. Though Greenland skilled the best warming, Dansgaard-Oeschger occasions affected climates globally. Ventilating heat modified international atmospheric circulation, shifting European forests and altering California’s ocean currents. Counter-intuitively, every Dansgaard-Oeschger excessive warming occasion occurred over the last Ice Age when the northern hemisphere was coated with nice ice sheets and international temperatures had been 5°F-14°F colder than pre-industrial occasions.
The local weather dynamics answerable for these dramatic heat occasions is definitely demonstrated, and a easy experiment would possibly ease the troubled minds of scholars plagued with “local weather disaster” anxiousness. Warmth a big coated pot of water. Measure the air temperature above the pot’s lid. In the event you don’t have a thermometer, merely maintain your hand above the lid. Then take away the lid and really feel the escaping warmth. In a similar way, Arctic sea ice (and a floor layer of brisker water) act just like the pot’s lid. Take away the ice and the air dramatically warms. Conversely, in depth ice-cover will cool the air however heat the underlying ocean.
Ocean currents continuously transport tropical warmth in the direction of the poles, making Arctic climates far hotter than doable if solely the solar and greenhouse gases managed the Arctic’s local weather. Heat dense “Atlantic water” continuously enters the Arctic Ocean. Some warmth ventilates however some is saved at intermediate depths. At present there’s sufficient saved warmth to soften sea ice many occasions over. The in depth sea ice of the final Ice Age insulated the Arctic Ocean inflicting warmth to more and more accumulate. Ultimately that nice retailer of warmth melted sea ice from under, permitting warmth to vent and enormously heat the environment.
The identical dynamics triggering previous Dansgaard-Oeschger occasions present perception into at the moment’s Arctic warming. Through the 1970s and 80s, measurements over an ice coated Arctic recorded cooling air temperatures prompting researchers to publish, “Absence of Proof For Greenhouse Warming Over the Arctic Ocean Within the Previous 40 Years.” These cooling air temperatures didn’t cut back trendy Arctic sea ice. However different components did.
Arctic winds can entice ice within the Arctic inflicting ice to thicken. Nevertheless when the winds shift, thick sea ice will probably be blown out and soften in hotter Atlantic waters. The ensuing open water and thinner ice permits extra Arctic subsurface warmth to ventilate. Along with wind-driven ice loss, satellites reveal the best space of open Arctic waters corresponds to the pathway the place heat dense tropical waters, by way of a department from the Gulf Stream, enter the Arctic and soften sea ice from under. It’s now broadly believed excessive inflows of heat Atlantic water helped to soften sea ice and set off the Dansgaard-Oeschger heat occasions, simply as oscillating heat inflows now soften Arctic sea ice at the moment.
A brand new monitoring system established off the coast of southern Florida in 2002, reviews heat water more and more flowed in the direction of the Arctic till 2008, however since then heat inflows have been reducing. So, we are going to now witness a pure experiment that checks competing local weather hypotheses. If the growing inflows of heat water triggered many of the Arctic’s latest sea ice loss, then lowered flows ought to permit sea ice to get well inside one other decade. In distinction, the competing speculation is warming from growing CO2 concentrations will trigger an ice-free Arctic Ocean. Early predictions of an ice-free Arctic have already failed. However many nonetheless predict an ice-free Arctic by 2030 or 2050. Of better curiosity, if sea ice does get well, will the discount of Arctic warmth ventilating to the environment, additionally cut back international temperatures and avert the ballyhooed “local weather disaster”?
Jim Steele is director emeritus of the Sierra Nevada Discipline Campus, SFSU and authored Landscapes and Cycles: An Environmentalist’s Journey to Local weather Skepticism.