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Climate Hustle

2018 SkS Weekly Climate Change & Global Warming News Roundup #33

Posted on 18 August 2018 by John Hartz

A chronological listing of news articles posted on the Skeptical Science Facebook Page during the past week.

Editor's Pick

Research Highlight: Climate Model Predicts Faster Warming for the North Atlantic Ocean

As aerosol emissions decline, heat uptake in the North Atlantic could increase dramatically

Gulf Stream & AMOC 

The Gulf Stream, part of the larger Atlantic Meridional Overturning Circulation system. Photo: NASA

Researchers at Scripps Institution of Oceanography at UC San Diego have predicted faster rates of warming than previously predicted for the North Atlantic Ocean in a recent paper published in the Journal of Climate. This warming could disrupt major oceanic cycles and have worldwide impacts on climate systems.

The researchers modeled scenarios based on possible future greenhouse gas and aerosol emission rates. One likely scenario focuses on future decline in aerosols and continued increase of greenhouse gases in the atmosphere. Aerosols are minute particles suspended in the atmosphere. Some scatter sunlight, thereby actually acting as cooling agents.

The aerosol cooling effect is about 50 percent of the warming effect of anthropogenic carbon dioxide at present. Aerosols released from human activities are pollutants, however, and their health concerns have triggered worldwide efforts to curb emissions. An aerosol decline could spark an interesting catch-22: Because of their cooling effect, this decline would accelerate ocean warming that is already being caused by increasing carbon dioxide emissions–most notably initiating major warming in the North Atlantic.

Historically, the Southern Ocean has been the predominant heat absorber, accounting for roughly 72 percent of uptake of anthropogenic greenhouse heat in the oceans, due in part to the area’s low levels of cooling aerosols. The opposite is true of the North Atlantic: under strong aerosol cooling, the North Atlantic has not taken up much heat, meaning that most of the warming in the Northern Hemisphere is happening in the atmosphere and not in the ocean.

“The ocean heat uptake moderates atmospheric warming by storing much of the greenhouse heat below the surface,” said Shang-Ping Xie, a climate researcher at Scripps and co-author of the study. “We now show that the ocean uptake is not only uneven, but its distribution also evolves with time."

Research Highlight: Climate Model Predicts Faster Warming for the North Atlantic Ocean by Chase Martin, Scripps Institution of Oceanography, Aug 14, 2018


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Comments 1 to 4:

  1. With ocean warming there is going to be more evaporation and a higher specific humidity and this will increase snow melting. People might find it strange that the albedo of fresh snow is 0.90 or so (it reflects about 90% of solar radiation and only absorbs about 10%), yet the absorptivity of snow can be about 99% (absorbs 99% of the radiation falling on it). The albedo refers to absorptivity of sunlight (solar energy) and the absorptivity here refers to the absorptivity of the usual radiation (about 3 microns to 100 microns in wavelength) from objects on earth. So snow acts almost like a blackbody concerning normal temperature objects around it, absorbing practically all radiation received from surroundings, but is a good reflector of sunlight (reflecting about 95% of solar energy). The atmosphere radiates mostly radiation of wavelengths from about 5 to 8 microns in wavelength and from about above 14 microns. So practically all radiation from the atmosphere is absorbed by snow and most radiation from the sun is reflected by snow. Because atmospheric radiation is increasing I am saying we are going to see rapid melting of snow and ice. I have free Delphi code for night radiative cooling at www.facebook.com/DelphCode/. So solar absorptivity of snow could be about 0.1 and absorptivity for snow for the normal radiation from objects at the earth's surface could be about 0.99. The "downwelling sky radiation code" at the above site could help you determine whether snow will melt at night.

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  2. On the other hand, in the short term, there could be short periods of severe cooling of the Atlantic as the warmer conditions greatly accelerate the melting of Greenland and the more mobile ice exits the Arctic ocean in larger amounts.  The corollary is that tropical waters will warm up as the heat is not exported to the north with some very nasty stroms as a result.

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  3. Good comments Swayseeker, but wouldn't evaporation from warming oceans primarily cause more snow to form rather than to melt? 

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  4. Hi Nigelj

    It is an interesting balance.  If humid air rises from the ocean and blows accross to Greenland, indeed this could result in more snow.  On the other hand, The specific heat of the phase change from water vapor to water is about 5 times as great as the heat of the phase change from ice to water.  In other words, a liter of water condensing out of air which is warmer than the ice it comes in contact with gives out enough heat to melt 5kg of ice.  Moreover, if this contact occurs, let's say, at the top of Greenland, 3km above sea level, and the air is made more dense by the cooling effect of the ice, air density currents are created with the denser air pouring down the sloping ice.  From 3km up to sea level the compression of the air would heat up the air almost 30 degrees C.  Of course it wouldn't actually heat up.  This heat would be given up to the ice, melting more ice.  A fascinating problem in balancing temperature, pressure latent heat and wind direction.  My guess would be more snow initially but at some point hugely increased melting of Greenland.

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