Gulf Stream, jet steam, and paving over California’s artificial streams

What we think of as the Gulf Stream is just one part of a larger system known as the Atlantic Meridional Overturning Circulation. Warm water travels north near the surface, riding over cooler water, but as it reached the Arctic, it cools and sinks flowing east, then back to the south, where it warms up again and the whole journey repeats. The net effect is that heat is much more spread out across the northern hemisphere than it would be if the hot water simply stayed put in the south, and the cold water was undisturbed in the north. By redistributing heat, the AMOC has a moderating influence over climate on both sides of the ocean, and really, around the world. 

For all its importance, it’s only been since 2004 that there have been stations taking direct measurements of temperature and salinity at regular intervals throughout the AMOC (That’s the same year as The Day After Tomorrow premiered. Coincidence? Naw, it’s probably because … aliens.) That system wasn’t complete until 2014, so the installation is still too recent to show long term trends, so the mostly Irish team behind the study turned to a number of “proxies”—such as changes in the size of sediment deposited by the current—to determine how the system was changing.

Despite using a number of independent measures, the results were all largely the same: Before the 1800s, fluctuations in the AMOC were minor, but as that century wore on, the strength of the current began to decline. Going into the 20th century, that decline accelerated and starting around 1960 it became particularly steep. There was a strange “bump” in the data, showing the current actually strengthening for a short period in the 1990s … but then it was right back on that downward track. 

What does this mean? Well, The New York Times has a graphics-laden piece which, if your browser is not overwhelmed by efforts to decorate the screen while doling out text a sentence at a time, eventually gets around to explaining some of the possible effects. In general: Europe gets colder. So do parts of the United States, particularly the upper East Coast. And on both sides of the Atlantic, the possibility of powerful storms increases. In short, a collapse of the Gulf Stream, or even a continued weakening from this point, will shift the northern hemisphere into a whole new climate regime, altering not just temperature but weather and rainfall patterns in ways that models suggest would be devastating to cities, coastlines, and agriculture. 

Contrails are not chemtrails, but they’re still bad

If you know someone who believes that the visible contrails left by high flying jets are actually the sign that the government is saturating the planet with mind-controlling substances, they’re wrong. Or at least, that’s what the government tells me to say.

However, those white lines in the sky turn out to be considerably more important, in a bad way, for reasons that go beyond just screwing up your picture of a beautiful sunset. The original studies on the issue go back to at least 2011, but two years ago, Science broadcast the surprising fact that the fluffy white paths passenger jets carve across the sky are actually worse, in terms of global warming, than all the CO2 produced by the plane’s engine. 

In large part, that’s because planes are flying extremely high, at a level far above most forms of clouds. They do this not just because the view is better and the air is calmer, but because the thin air of the upper atmosphere allows them to reach an optimal trade off between speed and fuel consumption. However, because they are so high, jet contrails are actually little lines of ice crystals and “unlike low-level clouds that have a net cooling effect, these contrail-formed clouds warm the climate.”

The next time you’re running one of those little calculators that shows how many trees you’d have to plant to offset your latest vacation, you should take that number and more than double it. But this week in New Scientist, there’s an article that offers hope in the form of simply getting rid of the contrails, and the answer lies with … government spies.

Specifically, it lies with lessons learned in creating planes like that Cold War favorite, the U-2 spy plane. The U.S. government, and others designing such planes, understood that when you’re trying to make a stealthy pass over an opponent’s territory, leaving behind a big white line that pointed like an arrow to your camera in the sky, wasn’t a great idea. Research was done at the time on how wing shape, engine ducting, and other steps could greatly reduce the presence of contrails so that when you look up to see a U-2 passing by, you … don’t.

Those lessons are now being incorporated into the designs of commercial jets, though retrofitting the thousands of existing planes may be challenging. However, there’s another step that can be taken: Reduce the amount of time that aircraft are flying at those altitudes where contrails are most readily generated. That doesn’t always mean flying lower; it means working with flight controllers, airlines, and pilots to put planes into conditions where contrails are less likely. Which could mean that planes gradually adjust their altitude several times over the course of a flight, seeking out layers where the ice-clouds don’t form. Studies have shown that these maneuvers would have a very small effect (well below 1%) when it comes to fuel consumption, but may be able to all but eliminate most contrails.

Jet contrails are one of those things that have become so ubiquitous; one of the strangest things about the days immediately following 9/11 was looking up into the September sky and not seeing it crisscrossed with white lines. But that’s certainly one sight we could get used to, especially if it also happens to help reduce a significant factor on climate change.

Covering canals with solar panels

People in California and water in California don’t tend to be conveniently co-located. It’s been that way for a long time, Isn’t that right, J.J.?

One of the ways this problem is corrected is by an aqueduct system that includes nearly 4,000 miles of largely uncovered water channels that largely carry the precious fluid around California’s agriculture-heavy Central Valley. The demand for this water is so high that it constantly triggers fights between the need for large amounts of water for crops and the need to allow some portion to actually sustain all those things that are not crops. None of that stressed has been helped by multiple severe droughts in the last decade.

For most of that 4,000 miles, water in the system flows through open canals. So naturally, considering that near-constant sunshine and a lack of rain are huge reasons why the canals are needed in the first place, it follows that a significant amount of water evaporates, and it does not conveniently rain back down in the same area.

So how to deal with a system that takes up a huge amount of space in a very sunny area, and also happens to be filled with water? A new paper in Nature Sustainability suggest that one good solution is to cover the canals in solar panels. The result is a system that, annually, could keep more than 60 billion gallons of waterfrom evaporating before it got to the places where it’s needed. And, as a not-insubstantial side benefit, the canals would also help the solar panels work better.

That’s because one of the factors in keeping solar panels efficient is keeping them cool. Chill panels can be difficult to maintain, seeing that they are not only exposed to sunlight but usually very dark. As the panels get hot, their rate of converting sunlight into electricity can plummet significantly; that’s where the water can help. Because the panels could be cooled by the passing water, electricity generation could be improved and increased. And even though the water would be warmed as a result, the panels would still help to reduce overall evaporation. 

Setting up the proposed over-canal systems would have a bigger upfront cost, but that cost should be rapidly paid back by the improved power generation, even without considering the savings in water. As the paper notes, “The net present value of over-canal solar exceeds conventional overground solar by 20–50%, challenging the convention of leaving canals uncovered and calling into question our understanding of the most economic locations for solar power.”

The most iconic version of a photovoltaic solar plant at the moment involves a large flat area covered in panels. Not only do these panels get hot; in locations that aren’t already barren, clearing the area for panels can mean cutting into areas that might have otherwise supported trees and other vegetation. Snaking solar panels along California’s waterways could result in solar power that’s more effective, cooler, and just … cooler.

Editorial Staff
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