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Comment by mysterydip | Hacker News Reader

Rising sea levels and deep drought seem at odds with each other, but I'm not a climate scientist. Maybe they go hand in hand?

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1. Drought refers to lack of fresh water in a particular region. Sea level rise has next to no bearing on whether or not rain is going to fall in <some particular region>. A higher sea level does not meaningfully affect evaporation and precipitation rates.

2. Most of the sea level rise expected from conservative[1] projections of climate change will be hitting us decades and centuries from now. Sea levels have only risen by ~8 inches since 1900, but even if we stopped emitting carbon tomorrow, we would have another 3 feet to look forward to by 2100, and 4.5 more feet by 2200.

3. Storm surges[1], caused by stronger storms, caused by climate change can make low-lying coastal areas uninhabitable, without actually drowning them due to sea level rise.

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[1] Less conservative projections are dismissed out-of-hand as alarmist, but seem to provide a better roadmap for reality than fairy tales, like the 2C warming that the Paris Accord promised us.

[2] The sea level may have only gone up a few inches, but if an average worst-storm-of-the-year storm surge has gained a foot, it may be the difference between your house being fine, and having six inches of seawater in your living room for one day of every year.

Would increasing global ocean and air temperatures lead to more water evaporating and a net increase in total rainfall of fresh water across the globe, even if it might also result in changes to where the rain falls?

It could, or it could lead to more water being held in the air and this less rainfall.

Temperature increases can indeed have that effect.

Sea level rise, in itself, would not.

Thanks!

Upvoting this because it seems like they're genuinely trying to understand what's happening. They don't deserve the down votes.

Edit: Even I learned this[1] from this comment chain, so it seems to me like this isn't necessarily common knowledge.

[1]https://news.ycombinator.com/item?id=38255008

That comment doesn’t really seem relevant to the question: it’s answering “why do you need freshwater for the canal when you have sea water”, but if I understood correctly, they asked “why is there less freshwater around when there’s more seawater?”

Yes, I'm genuinely asking, thanks.

The drought is probably just bad luck. They should have had a couple hurricanes go through there. Sometimes you just don't get the rain. AFAIK from news people freaking out every time there's a hurricane (good source, I know) climate change is causing more of them.

I'm trying to figure out why they would seem at odds to you. Can you elaborate please?

Don’t know about original commenter, but I vaguely remember from high school science that seawater evaporates into the clouds and becomes rain. So if you picture it all as water going through a cycle, you’d expect there to be more water in all stages if there is more water in one?

Perhaps there would be more water in total on land, but it doesn't mean it would be distributed evenly. Weather pattern changes caused by the rising sea level could mean that some areas get drought, even while standing right next to the ocean.

No, it makes perfect sense: more water in the oceans means less in circulation.

It's less in ice.

It's also probably more in circulation. Way more. But it almost certainly also means that water will circulate through different places, making sure you have both catastrophic floods and droughts.

Yes, that's true.

Unfortunately, one really needs to divide it as "freshwater" "saltwater" and "ice".

It's ice thats seeing the biggest declines. Freshwater is mostly just being redistributed.

Why do they seem at odds with each other?

Because at least intuitively the panama canal seems to rely on seawater, which would seem like it is unaffected by drought, and only positively effected by sea level rise.

> Canal locks at each end lift ships up to Gatun Lake, an artificial freshwater lake 26 meters (85 ft) above sea level, created by damming up the Chagres River and Lake Alajuela to reduce the amount of excavation work required for the canal, and then lower the ships at the other end. An average of 200,000,000 L (52,000,000 US gal) of fresh water are used in a single passing of a ship.

https://en.m.wikipedia.org/wiki/Panama_Canal

No the Panama canal passes through freshwater, and you cannot let seawater enter for ecological reasons.

Someone else linked this video and definitely helped me understand better

https://www.youtube.com/watch?v=jh79YSCC8mM

I know the video covered that it has been tried before, but it seems like the long term solution would be to actually excavate and connect the seas. We have much better excavation technology, and would allow for much, much higher throughput than this elaborate contraption subject to climate change.

If you look at the example of the Suez canal, where some 700 species from the Red Sea have now colonized the eastern Mediterranean, the idea of directly connecting the Pacific and the Caribbean sounds like an environmental disaster. Not to mention the difference in sea level - there would be a lot of water flowing west to east before that balanced out, and raising the sea level in the Caribbean does not seem likely to make anyone happy.

While I don't disagree with the environmental concerns, ships use HFO (a very dirty type of fuel that's essentially tar) and account for ~3% of all greenhouse gasses. It may be a net win overall if a proper canal can save many more ships thousands of miles of emissions per trip.

The Caribbean is facing seal level rise anyway if we don't find a way to reduce emissions. Again I'm not an expert on this subject, but it doesn't seem cut and dry that a canal would be an environmental disaster if it were possible to excavate.

The seas aren't at the same elevation. The Pacific is a couple dozen cm higher than the Atlantic Coast, and the amount varies. Cutting the peninsula would turn into a disaster pretty quickly, even with sci fi excavation technology.

I'm not so sure that it would make such a huge difference that it would be an immediate disaster, across that kind of distance there are plenty of examples of more elevation, what you would have is a river flowing one way instead of two rivers flowing towards the see. Not unlike any other island that the sea flows around.

Or is there something in particular that would make this connection into a disaster area if that flow got started?

The length of the canal is about 75 km, a few dozen cm across that distance would be on the order of 0.04 mm / meter, which is barely enough to make water flow in a particular direction.

It'd be highly susceptible to erosion, and the channel wouldn't be stable. It'd either expand gradually over time with all sorts of ecological ramifications, or deposition would clog the channel constantly. Who knows, might do both depending on seasonal factors? Imagine the damage a hurricane might do to those massive cliffs, for example.

That all sounds quite different from an immediate disaster. Those things apply to any river and those typically have a slope well in excess of that. Not that I would argue in favor of cutting a channel between the two but it doesn't sound as though this is an insurmountable problem, basically well within the elevation difference that even a single minor lock would be able to handle.

You might even have to add a pumping system to the lock to ensure that it would fill up fast enough.

Tides would take care of the filling. The Pacific tidal range is something like +-6.5m, the Atlantic side is <1m, plus whatever offset due to weather and phase error in the tidal times due to the earth being a sphere. A system of locks could handle it, that's exactly what the existing canal is after all. It's just more expensive and impractical to construct/maintain the deeper into the continent that canal cuts.

Ecologically, it's mainly about connecting the Atlantic and Pacific hydrologically. They're different temperatures, salinities, turbidities, etc.

Yes, but whatever the elevation difference if it were done at sea level (presumably the average between the two nominal levels on both sides) there would always be less water to be displaced in the resulting locks and that would in itself be a win, but the amount of material displaced to make the channel may well outweigh that by a considerable margin. I take it the engineers have run the numbers and decided that the current solution is the optimum or very close to it in terms of economics.

Interesting that the video only posed how labor intensive an excavation would be, but not the differences in sea level as a blocker. I suppose it would be related to how wide the canal is?

Of course I'm not a subject matter expert on this, just wondering what options exist today that didn't before.

Keep in mind that water flows downhill free but you have to pay for pumping to go uphill.

Climate change CAN impact availability of fresh water in the form of rain since warm air holds more moisture, but that's double edged - there's more evaporation from freshwater bodies as well, and the rain can be unpredictable and dangerous since some will be in the form of major storms dumping water nobody's equipped to store along with all the other storm damage.

It's mostly above sea level.

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