When sea surface temperatures get warmer the mount of evaporation increases. No one has any doubts about this. But what about the rate of evaporation? Does it also change? I have not seen any relevant data, or other kind of evidence, but have a gut feeling that it probably does.increase a bit, per square meter of surface area, with each degree of warming. If this is true, and vapor growth is actually exponential relative to surface warming, we have a cause for concern, because it can lead to unwanted consequences more quickly than expected. That’s because the warmer the water is the warmer the air above the water will be, providing the energy needed to lift more quantities of vapor higher and higher into the atmosphere. When the water reaches 25C or more we start to see some quantities being lofted all the way up to where the jetstreams and a whole new wind system are found.
Vapor that does not reach that high level can still spread out, extending the effect of its greenhouse energy trapping powers. It can also start condensing into clouds, which have their own greenhouse powers, separate but roughly equal to that of the vapors they replace. All of this material will add its energy effect to the surface below, regardless of altitude.The material that reaches the jetstream wind level will mainly differ by having a greater prospect of being transported over great distances, adding energy to a greater variety of surfaces below. Some of these would normally receive much less greenhouse energy, especially those situated in the higher latitudes. No matter where they are located, all surfaces on the receiving end, near and far, are likely to become warmer than otherwise.
We need to pay close attention to all surface waters that are growing warmer, especially those that are getting warmer at a faster than usual rate, and even more especially those that have the highest temperatures to begin with. Once a surface has passed 25C its evaporation effects will be maximized in all of these ways, generating ever-greater amounts of additional energy over a widespread area. Let’s look at some particularly interesting data where all of these considerations have come into play in just the past three to four decades, which takes us to the whole set of inland waters in the Mediterranean region:
You should be able to see plentiful signs of averages increasing more than 3C, and up to as high as 5C in places. Thankfully, they are all seasonal, and the effects are only temporary, but these numbers are astounding. Next, we’ll see how these increases translate into actual temperatures at this time, reaching levels above 25C in one place after another. Recent letters have described the effects, causing air temperature increases way out of proportion to most of those found elsewhere. Imagine what the increases will be like if similar rates of warming of these sea surfaces continue for another 30 to 40 years. Could we possibly end up with more of them resembling today’s Persian Gulf?
I also want to take a quick look at the other side of the world, where the Gulf of Mexico is perfectly positioned as a source of extraordinary quantities of precipitable water over much of North America. To date, its surface has not warmed as rapidly as it might have, considering its tropical location, perhaps because of the “gulf stream” (or AMOC) ocean currents that have traditionally entered into and circulated around a good part of its area. The AMOC is thought to be slowing down and changing course in several ways. If it completed stopped, what would be the effect on the Gulf of Mexico? Here is how its anomaly looks today:
And here is the Gulf’s current surface temperature, which ranks among the very warmest for any large tropical body of water. For now at least, streams of PW arising from the Gulf are best-known for torrential rains produced over the southeastern US and Atlantic seaboard, more so than for heating the continental air.
Carl