Sea surface temperatures in the Northern Hemisphere are almost certainly setting modern records this summer. Their anomaly over 3 1/2 decades is a full 1.0C, which seems exorbitant compared with any other major index you can find for such a short time period. Ocean water surfaces and the air just above always record practically the same temperature, and this combined temperature generally rises at only about half the rate of land air temperatures, globally, on a long-term basis. Suddenly it has moved out in front of everything, even the NH land average, and we have to wonder how long this will last. The SH is meanwhile lagging far behind in all categories because of so much energy being used up by the Antarctic meltdown. Something strange must be going on in the NH ocean waters. Here is a map with many of the highlights, showing significant warming distributed in multiple locations farthest to the north and also in those vast stretches of western Pacific and Indian Ocean regions that already are known for reporting the highest of all ocean temperatures. Their surfaces naturally yield the heaviest of all rates of evaporation, which most likely are now accelerating to new extremes in concert with the latest warming.
I have found little that can explain the cause of this much warming but certainly do take an interest in the effects. More specifically, how will all the added heat and evaporation influence land temperatures farther north via potentially increased movements of water vapor into and throughout the upper atmosphere, as described in yesterday’s letter? The first thing to look for is simply the general effect on cloud cover and precipitation, where today’s map shows how a large majority of the tropical warm surfaces are covered over by thick clouds and heavy rainfall:
I think this situation may have been going on for some time, with a mixture of temperature effects. When all those clouds and rain get shifted over adjacent land areas they sometimes bring mild warm anomalies along with them but just as often, if not more so, the result is a cooling, but that’s not the whole story. There will always be some areas where the sky above these warmest waters remains totally clear, allowing the emerging vapors to move freely into open space without obstruction. These are always good prospects for forming into the streams that journey on over the continents. Will more warming add to the number or volume of content of these streams or could it possibly result in a decrease? Having a good answer to this question would be helpful to those making climate forecasts, but I don’t see anything unusually informative in the current picture. A couple of good stream generators are visible on the image and are for the most part doing their job in a typical manner. The one that is most intriguing is the very large body of Pacific water lying directly off the east coast of Japan. It matches up well with a strong anomaly in the top map and also checks out on the surface temperature map with readings up to 30C, which puts it right up there with the leaders. Still, I have not been able to figure out how much it has actually generated in the way of an overhead vapor stream because there is no clear stream path to look at, but I think it is contributing and certainly worth watching in days to come. The Persian Gulf and north end of the Arabian Sea are definitely big players, as we saw yesterday. Otherwise the entire section of Asiatic ocean waters that we see is pretty much swamped with clouds and rain, leaving the future of all this very warm water engulfed in mystery just the same as what can be said about the cause.
Carl