Note the very long period from May 2010 to the present, some 21 months where Out going Long wave Radiation [ OLR ] has been continuously positive, ie as below, the earth is losing heat energy [ watts / sq metre ] in and around the equatorial regions that cover half the perimeter of the planet from 170 E to 170 W.
And this is the main planetary region where incoming solar radiation has the greatest impact on the all important ocean heat content and through that, on the global atmospheric temperatures.
This may not be the sole reason for the drop in global temperatures but it is likely to be another very important factor.
Bob Tisdale in fact claims that
La Nina's with their clear and relatively cloudless skies across the equatorial Pacific are actually the Ocean heat recharge side of the
ENSO but the positive OLR ie; outgoing Long wave Radiation somewhere near the infra red spectrum bands, in this region during a
La Nina is a puzzle to me.
From the BOM's
ENSO commentary;
http://www.bom.gov.au/climate/enso/Cloudiness near the dateline:Cloudiness near the dateline has remained suppressed over the past two weeks.
Cloudiness along the equator, near the dateline, is an important indicator of
ENSO conditions, as it typically increases (negative OLR anomalies) near and to the east of the Date Line during an El Niño event and decreases (positive OLR anomalies) during a La Niña event.
If you go to the
"South Pacific" infra red maps [ "Pacific" is found by mousing over "Basins"] you can see the remarkable lack of clouds across the central equatorial Pacific. Conversely to the NW of Australia where the Pacific Warm Pool seems to have temporarily migrated to there is very heavy could cover. If you google for OLR maps you will see negative OLR anomalies in that cloud covered Eastern Indian Ocean equatorial location to the NW of Australia and positive OLR anomalies in the near cloudless Arabian Sea and in the equatorial Pacific.
Now this is only a part of the explanations for the current rapid and probably temporary drop in global temperatures but I suspect that the long term
La Nina and the very long period of positive OLR's; ie more heat energy being radiated back into space than is being absorbed by the oceans, out of the main solar heat absorbing ocean regions of the planet around and on the equatorial Pacific is a significant reason for the drop in temps.
And don't forget that the maximum solar heat input to that equatorial ocean area only lasts about 8 hours before the heat energy input drops off with the low sun angles and then the radiation of accumulated ocean surface heat back into a clear sky really gets going through the night.
Think of those cold clear nights when it really gets cold due to the unimpeded radiation of the day's heat back into the night skies compared to the clouded nights when it stays reasonably warm and you will see the significance of a cloudless sky and the link with much higher OLR 's.
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