Genuine question here. What would be the expected change over the same period? The abstract says 53% of lakes saw declines...does that mean 47% saw no change or gains? If so, that seems pretty close to net stable to me globally. Or frankly what we would expect to see (some gains, some losses)
Also, this is stated later in the doc:
"Between 1984 and 2015, a loss of 90,000 km2 of permanent water area was observed by satellites—an area equivalent to the surface of Lake Superior, whereas 184,000 km2 of new water bodies, primarily reservoirs, were formed elsewhere (14)"
My first impression was that this means there has been a growth in total permanent water area from 1984-2015. Am I just reading this wrong?
The article also states “climate change and human activities increasingly threaten lakes that store 87% of Earth’s liquid surface fresh water”, but neglects to mention that only 0.3% of freshwater is liquid surface water in the first place. All in all a giant nothing burger, as with so many climate change alarmist “science” nowadays.
> but neglects to mention that only 0.3% of freshwater is liquid surface water in the first place.
But what percentage of the water we can actually use? The Arctic and Antarctic are far away from most of us, and groundwater is limited and probably spread out quite a bit. Water vapour is hard to extract from the air.
You are trivializing it by saying it is just a tiny percentage of freshwater, but it is actually where most of our used water currently comes from.
> But what percentage of the water we can actually use?
What percentage of lake water could we use prior to literal millennia of engineering effort was put into moving it where we need?
> most of our used water currently comes from
This is technically true today, but barely. Nationwide roughly twice as much water comes from surface as the ground, but it varies dramatically by region. If you live in NY, 90% of your water already comes from the ground. It’s certainly not the case that we’re “locked in” to lakes, rather we are very capable of adapting to local conditions.
> What percentage of lake water could we use prior to literal millennia of engineering effort was put into moving it where we need
All of it, people built settlements on lakes and rivers for this very reason
> It’s certainly not the case that we’re “locked in” to lakes, rather we are very capable of adapting to local conditions.
No, we are locked in to rivers and lakes because thats the only big source of renewable fresh water. The underground aquifiers under midwest and under much of middle east will be gone in 50 years and will never return
You should not incorrect people here without basic facts at your disposal
And yet they built aqueducts and wells too. Local surface water has been insufficient for civilization for at least 2000 years.
> The underground aquifiers under midwest and under much of middle east will be gone in 50 years and will never return
> You should not incorrect people here without basic facts at your disposal
Nothing quite as HN as someone making bold alarmist unsupported assertions about the future of climate for all of time, then following it up with a sentence demanding an appreciation for “basic facts”.
Are you at odds with basic addition or something? We are pumping out the aquifers faster than they recharge. Basic math lets you calculate that they will run out in a few decades.
The aquifers are left over from the ice age. Once depleted, the aquifer will take over 6,000 years to replenish naturally through rainfall.
So we now agree the aquifers have the capacity to refill on human timescales, especially given climate change is suspected to have a tendency to cause more rainfall. And by your omission I’ll take that we agree civilization cannot exist without significant engineering efforts to bring water to it, surface or otherwise. I don’t really know what’s left to say, besides hurling personal attacks back and forth as you seem want to steer this.
You would think that on a planetary scale, climate change result in more water, not less. Increased oceanic surface temperatures would cause more storms and thus more rain.
Is not only a matter of how much as where it rains.
Raining could increase exponentially over open sea and not much would change for the lakes. We had also a lot of monster wildfires in the last decade. Feels like a competition about who is able to sink the ship faster.
The link you point to claims 1.2% of fresh water is surface water, fyi. According to the link, the bulk is in glaciers and icebergs (~69% - nice). 30% is ground water, which is cool and all, but replenishes slowly from what I know.
Not to lecture but write out my thoughts, I feel like the discussion on climate change consistently revolves around who supports or opposes the idea and who/what is to blame. To me, looking around, it’s a conversation about responsibility. I don’t see how, say, having a bunch of casinos in Las Vegas is responsible behavior for a society. Same goes with eating a ton of calories and sitting around all day.
And you can say it’s not, no biggie, people do crazy shit all the time. But like a body, it can only take so much before (to extend the latter example) diabetes sets in. At some point it seems like a wise decision to be responsible with our planet and our bodies, collectively. But I don’t really see people willingly assuming responsibility for their actions, let alone their impact on the collective. Oof, especially in the US where the interest in “independence” has a large following.
Yes 1.2% is on the surface, but most of that is frozen. Only 0.3% is liquid surface water, as I said.
As for the rest, so much of the discussion seems to rest on a sort of cognitive dissonance people hold that on one hand humans are terrible for the planet and our horrible actions must be stopped, but on the other we must do everything possible to keep humanity going on forever. To me this doesn’t jive - if humanity is so awful, let us die and let this astronomically mind-bogglingly fertile rock bring about new life that might perhaps learn from our mistakes. If not, stop all the damn doomsaying. It doesn’t make for interesting reading, it’s without fail entirely speculative, and there’s evidence to suggest many of the youth have become severely depressed by it - far beyond what the “science” could possibly support. A dear cousin of mine recently killed himself before the age of 18; it’s impossible to know all the reasons, but based on his writings climate change terror was a significant part of it.
What do you think the “obvious” correlation coefficient is between the two? Or even its sign? I suppose it’d be far too much to ask for the R value too.
Science is supposed to answer these questions, instead this article carefully withholds information to make molehills into mountains.
I didn't read the parent's comment as you did. To me it looked like someone just trying to get a handle on the relative amounts and variability. They provided some relevant data and appeared open-minded.
Your response to that added little to the discussion. You might have selected the parts of the article that answered those questions, but instead opted to shut down further discussion on a valid question. Which, may or may not be addressed in the sources.
So we should have 100% faith in what we're being told in the article? If the author was trying to deceive then they wouldn't cite data that provided contradiction. Seems more like a religious approach than a logical one. There are papers, that were well cited, claiming there would be no sea ice by 2010, which never occurred.
> So we should have 100% faith in what we're being told in the article?
If you're asking questions that are answered in the article then that means you're discussing things without any context or insight or understanding, and have no intention to gather that context or insight or understanding. You aren't asking questions in good faith if you purposely avoid the answers.
That sounds reasonable. The water would have to go somewhere, but that alone could be catastrophic regionally. Cities are built around water sources, so having them move on timescales of human lifespans is worth worrying about.
It would require a lot of expansion for the required volume.
A barrel of oil has about 159 litres in it. The Keystone Pipeline would have transported 1.1 million barrels if it were fully expanded. 174,900,000 million litres per day. The City of Phoenix by itself uses about 1 billion litres per day.
I was going to say "but that probably double-counts recycled water" and then I looked it up and recycled water is only 8% of Phoenix's water usage, and it's 10% nationally in the US.
Here in the Netherlands they decided to increase the water level of our lakes by 5cm to handle the drought season this year. Since the amount of snowfall in the Alps was lower than normal.
If they wouldn't, the Netherlands would literally not exist. Not only are large parts of the country below sea level, there is also the constant threat of flooding via Maas (Meuse) and Rhine. Raising levees is not enough, water management in the Netherlands must always look at the whole country.
I live in a country with one of the richest water tables in the world. Due to (a forecasted!) drought and lack of planning we're literally running out of water to drink. It's like Saudi Arabia running out of oil, absolutely shameful.
The Netherlands been claiming land from the sea for centuries and some areas are already well below sea level - I don't think they'll neglect their dykes any time soon.
The Afsluitdijk just got heightened and reinforced. As someone who's biked across it, I'm psyched because now you can bike on the North Sea side - previously, there was only 1 bike path on the Zuiderzee side.
With all due respect, the Netherlands is perhaps the furthest a place can be from long-term sustainability. The place is a mix of monoculture + concrete.
History may not repeat but it does rhyme. Harappan civ thought to have declined due to less water. Petra once thrived due to a system of dams, cisterns, and water conduits, but never-repaired damage after an earthquake and increasing aridity meant it less and less supported urbanism and so declined. The Soviets overexploited the Aral Sea which has yet to (and will likely never) recover. It is now spoiling the surrounding region with dust storms carrying with them pollutants from industry that settled in the drying lakebed. Owens Lake in California once fed LA, but when it dried up it too caused polluting dust storms.
Gov't has not learned from this history. The western US's water rights are outdated to the point of creating utterly backwards incentives. For example, Utah has use-it-or-lose-it water rights and the lion's share of water in the Great Salt Lake's watershed gets used to grow alfalfa. Alfalfa itself isn't necessarily a bad choice if you're going to grow stuff in an arid region, the issue is more how much of it is grown and in a wasteful way (little to no drip irrigation and no incentive to start using it, instead farmers are incentivized to flood areas during times of heavy rainfall or risk losing water rights). However even city and residential water use (a much smaller %) is still per capita wasteful compared to nearby Vegas which has done a much better job of becoming efficient in its water use. Utah got lucky this year in its snowpack, potentially buying some time to change, but is that gonna happen? No, they're praying for moisture and thinking their prayers got answered. Any guesses how long it'll be before the Great Salt Lake becomes the US/capitalism's Aral Sea? 5 years, 10, 15? Any techies wanting to move out here might think twice, homes without water and with seasonal arsenic-laden dust clouds probably won't have much resale value.
The vital role of vegetation is often overlooked - we've significantly reduced forest cover over the past centuries.
Global forest cover loss between 1990 and 2020 was estimated to be around 178 million hectares, representing a reduction of approximately 10% in the total global forest area.
To restore water resources we should prioritize aforestation.
- Evapotranspiration: Vegetation influences the water cycle by releasing moisture into the atmosphere through transpiration, affecting cloud formation and regional rainfall patterns.
- Surface runoff and infiltration: Vegetation intercepts rainfall, slowing down surface runoff and promoting better water infiltration into the soil, which helps mitigate drought conditions.
- Shade and temperature regulation: Vegetation provides shade, lowers surface temperatures, and reduces evaporation rates, potentially alleviating drought intensity.
- Feedback loops: Healthy vegetation enhances soil moisture levels, maintains humidity, and supports water resources, while stressed or absent vegetation can worsen drought conditions.
- Forests and rainfall patterns: Forests contribute to local and regional rainfall by releasing moisture through transpiration, and their removal or degradation can disrupt precipitation, potentially contributing to drought.
This is very high on my list. It seems most hydrologists interested in climate change are talking a lot about afforestation for all of those reasons. It isn’t something I hear about often at all, though.
For a while I pointed people to a study showing that geohydrological model of the Amazon rain forest indicates that it is well past a breaking point in which the hydrology there will never be recovered, and the landscape will likely transform dramatically. It’s very poorly received though. Not because it’s a bad study but I guess no one thinks what’s happening in the Amazon happens anywhere else. As though it’s fear-mongering to point to this phenomenon despite that deforestation occurs the entire world over.
My understanding is that there’s no known feasible way to improve future hydrology as inexpensively or low-tech, too. Here in British Columbia, Canada we have a fairly aggressive forestry practice which generates a shockingly small portion of our GDP. I seriously wonder if our GDP could be maintained or increased overall by converting forestry efforts to afforestation efforts.
Were we to succeed in recreating healthy forests here, the impact on other sectors through improved hydrology (healthier rivers and lakes, better water retention in forests, better forest fire outcomes, eventually strengthened tourism, etc) actually seems like it could be a net positive. This would be an extremely long term project though, and virtually impossible to enact given jobs would be lost on the short term.
This is also important for us because so much of our energy is generated from rivers. We need stable, consistent flows to power almost every home in the province. We should be hyper focused on efforts to improve hydrology, and forestry works directly against that.
It’s such a big part of our history and so broadly evident and present in our lives here. Most people assume it’s a major part of our economy and that we could never function without it. I sincerely wonder if it’s a net drain on the province though. Not only does it visibly and measurably harm the environment here (even with our “green” forestry practices), but a lot of our forestry products are immediately exported for absurdly low prices. I think I would support a ban on exports and reducing our forestry to supporting domestic needs, based on what I know of the situation.
It’s scary stuff, anyway. And it seems like not many people are aware or listening.
- atmospheric rivers (rainforest deforestation influencing rainfall even on other continents)
- biotic pump theory (or something like it) - without continuous/significant forest we lose rain inland and get droughts
- forestry practices - those sorry ass patches of trees (33% of land) surrounded by fields and pastures (50%) in europe should not be called forests, they don't force wind to go over them, because they're not multilevel canopies, so wind goes through and dries them up and they're dying more quickly and don't function as well as they could if they were larger and properly structured (like primaeval forests). Our foresters make them look like monoculture parks, even removing dead branches and stumps ... no wonder that they're almost biodeserts.
- cca 50% of felled roundwood (paper, celulose, furniture) could be replaced with cca 5% of animal agriculture lands and hemp
> It’s scary stuff, anyway. And it seems like not many people are aware or listening.
All great points, too. These are all well documented in research spanning decades but yeah, not enough people are concerned about it.
Forests are as much our lifeline as the seas in my opinion. They’re a major factor in stabilizing climate — they quite literally make it rain, in more ways than one.
I’ve heard the biotic pump theory referred to as “rain hopping” quite often, recently. Is it still a theory, or very evidently real now? I know some hydrologists refer to it very plainly, but maybe it isn’t officially in the books as a known phenomenon. I seem to recall it was considered as a factor in the irreversible changes in the Amazon, but I’d need to review it. I might be assuming that.
I don't understand that telephone pole picture, the ground did not move around the telephone pole surely. I don't understand the graphics either. 1ft/year generally, but slower than that in the most extreme?
When you remove the water from the ground, the drained soil compacts. The topmost sign on the pole pole shows where the ground level was 50 years earlier, caused by excessive taking of groundwater.
It's about sweet water. If it "goes away" it typically ends up in the ocean.
Previously it was in lakes, groundwater it glaciers. Glaciers which ultimately kept rivers flowing all year around even when not much snow falls in a given winter. Once all the glaciers are melted, the rivers can dry up completely. The glacier water has already made it to the ocean and doesn't need to travel there anymore via river. With groundwater depleted, we cannot use that anymore to substitute and some sources of creeks will dry up.
Are there any studies on waterflow to/from underground oceans? It's difficult to understand how comprehensive a claim is without knowing the entire system.
> The subducting slabs also carry deep-sea sediments piggyback into the Earth’s interior. These sediments can hold large quantities of water and CO2. But until now it was unclear just how much enters the transition zone in the form of more stable, hydrous minerals and carbonates – and it was therefore also unclear whether large quantities of water really are stored there.
> The answer has now been provided by an international study. The research team analyzed a diamond from Botswana, Africa. It originated at a depth of 660 kilometers, directly at the interface between the transition zone and the lower mantle, where the dominant mineral is ringwoodite. Diamonds from this location are very rare, even among the extremely rare diamonds of super-deep origin, which account for just 1% of all diamonds. The studies found that the stone had a high water content due to the presence of many ringwoodite inclusions. The study team was also able to establish the chemical composition of the stone.
We're changing the weather with greenhouse gases and whatnot, and we regularly pump it out to go to our homes, or even use it to make electricity with dams.
Yes, more total rain. A steady steam from the mountains is a much better source of water though to keep lakes, rivers and our water supply going. The rain isn't evenly distributed through both space and time. We might get a drought for years and then torrential rainfalls. We are already seeing this. It's happened in California and Germany. Both places I'm most tide to. So maybe it's sampling bias. At my parent's in Germany, most fir trees are dead from the multi-year drought and then in June 2021 half the village was destroyed by a flood.
So you point to a change in your local normal climate as showing there isn't... climate change? Just trying to clarify what you are trying to say here?
Climate has always changed…it’s a feature of the earth, not a bug…you being born is part of the climate change. When you decompose, that will also be part of the climate change. The magnitude of your so called calculations is minuscule compared to the life of earth and merely speculation just like stocks on Wall Street. Don’t try to control something you did not invent. You’re welcome!
Of course climate has always changed. It's just that in the past it changed over the course of thousands or millions of years rather than within the span of a human lifetime like we're now experiencing.
IIRC These can have thier own host of problems because the 'brine' byproduct doesn't mix well back into the ocean and can settle/pool and create marine dead zones. Although suppose that will be less of a priority if people are thirsty.
The ocean is way too big for removing some drinking water (which is going to end up back in the ocean anyway) to have a material effect on the salt concentration.
The problem is strictly local: if the brine produced by the plant is dumped in an area with low flow, it can hang around and affect sea life.
If you use a big discharge pipe and put it a decent distance offshore in a current where it can mix effectively, there’s very little effect.
This is not a reason to shoot down desalination plants as a concept, it’s a design constraint to take into account when building them.
There are commercial salt harvesting operations which use such brine. No need to flush it back in the ocean.
If you have ever flown into SFO you have seen the reddish pools. (By the way the red color comes from Brine Shrimp, which presumably there is also use for)
And it’s not just salt. Other chemicals can be harvested from that brine before you need to dispose of the leftovers, e.g. magnesium carbonate. I know because I run a climbing company that sells chalk (MgCO3) from that production pathway.
Which is good, but may not potentially scale up - if we were desalinating 5X, 10X as much seawater, it seems unlikely we could make use of that much salt, and would have to bury it or dispose of it some other way.
When you have a practically free resource which is waste from a large scale industrial process, cottage industries to make use of the free waste sometimes pop up. It's a solvable problem.
We pump brine inland to a large flat expendabe plain and flood it to allow the water to evaporate off and the salt to sette. 20-50 years later, pod racing on the salt flat.
How does that work for e.g. small scale salt farming in many European countries that flood areas with sea water, then harvest the salt after the water has evaporated [0]?
Instead of pumping the brine into a pool, pump it into a ship. As the ship sails, it slowly releases the brine at a rate much more tolerable. When the tanks are 50% empty, turn around and come home. lather rinse repeat.
We had the same problem with power plants dumping hot untreated water back in the environment. This is why cooling towers are synonymous with nuclear power plants. This is an easy solution to fix, but like all engineering it costs extra. For power plants it was fixed through legislation. You literally have an entire oceans worth of water to reconstitute the brine. This was more problematic of older system using distillation.
People are coming up with some wacky solutions, but am I missing something or can you just pull in more seawater and dilute the brine closer to the ocean's natural salinity before you send it back into the ocean?
That always looked like a no-problem to me. Can't the brine be put in a pool and let evaporate instead? You get drinking water from the desalination plant and salt.
Or (at least in the US), we will simply stop doing things like growing alfalfa in the desert to feed cows being raised in Texas. Sure beef will be a little more expensive but…
You’re actually right. We’ll probably burn garbage and radio hosts will call people against burning garbage effeminate names.
If handling waste and burying it costs X carbon, and burning it creates Y carbon, and Y is less than X, then burning is better than burying.
You'd have to do the math, it's not manifestly obvious that it's not the case (especially once you consider all the transportation involved in sending waste around the country and across the ocean).
On first principles, there's no reason that the cost of transporting trash to the incinerator is any less carbon intensive than transporting trash to a landfill.
Maybe people prefer incinerators in their community over landfills in their community (unclear), but if that's the case, that's a policy decision and not one that seeks to minimize carbon emissions.
Problem is that everything needs X powered by clean energy, which means we need both a lot more clean energy and, if we want to slow/stop climate change, to massively reduce our use of fossil fuels... which requires a lot more clean energy.
We also, so far, globally have not shown any evidence of replacing fossil fuels with green energy, only supplementing them.
Direct carbon capture, electric vehicles, electric building heat, electric industrial process heat, and desalination are all massive new sectors that need to be powered that are barely on the radar of the existing electric grid.
And we need more power to let emerging economies rise out of poverty, where having electric pumps and washing are truely life-changing from a quality of life perspective.
So we need about 5x more total energy while also shifting from 80% fossil to 0% fossil.
This is why I advocate for nuclear while most people advocate for wind and solar. We need advocates for all clean energy. Nuclear can actually use its own direct low-carbon heat to help with buildings (district heat) and industry, and that heat can also help in desal in some cases, though RO is the preference these days and doesn't really need that much heat input.
Tidal power is a thing. Tidal power for ocean desalination eliminates the need for transmission infrastructure. Desalination has so many obvious upsides that I'm increasingly suspicious of the people insisting it's too difficult to contemplate, none of whom contribute anything of value to the discussion.
> where you think the water will go, if not to other places on earth
I afraid that a lot of fresh water is going to become an ocean water. Flooding theory creates the impression of transferring fresh water from one place to another where it will remain just as fresh. It is incredibly hard to create a fresh water from salty one.
Indeed, and it's interesting to note that this natural desalination process also incorporates long-term storage mechanisms. Historically, vast quantities of freshwater have been stored in the form of snow packs and glaciers. However, in our changing climate, this storage is not occurring at the same scale as it used to. This could potentially exacerbate future water scarcity issues, making man-made desalination techniques even more crucial. As challenging as creating freshwater from saltwater may be, it's a puzzle we need to solve with urgency.
on the other hand, global warming will pump much more water in the atmosphere, and we will have more precipitation. In fact, global warming would not be a problem at all if what I said above was not true. CO2 alone could only raise the temperature by 1C no matter how much we would put in the air (by year 2100). The water vapor creates a positive feedback loop that warms it far beyond what CO2 can do alone.
But that's not actually helpful. Occasional massive rains don't refill aquifers very well. There needs to be a buffer to allow water to slowly make it's way into the system in a manageable way. Currently that is mountain snow melting over the warm season.
I mean, sure, but never in enough volumes to be actually usable by us. It’s not like we can capture every single evaporated water droplet before it cools to form fresh water.
So while technically it happens all the time, practically it’s as if it isn’t happening at all when it comes to the concerns talked about here, specifically the quantity of available fresh water declining.
I think you are quite wrong about that. The evaporated ocean water becomes rain. Evaporated ocean water is the source of over 80% of all rain on earth.
About 80% of that rain happens back over the ocean, and then about 25% of the rain that happens over land actually gets captured as ground water. Even that isn’t the main point though, the issue is we’re currently using water faster than rain replenishes it in many places. At worst as I understand it, in some places they’ve collapsed their aquifers by over-pulling from them, and that means less of the rainfall in those areas will be recoverable in the future. At some point we have to enter a mode where we only pull water in a way that is sustainable or we’ll suddenly find that we do indeed need desalinization to keep up with our use.
And most of that rain is going to go into the ocean again. Or be distributed in a large area. Neither of which can really be captured in any sort of predictable and scalable manner.
You know, unless we build a massive “roof” of devices to capture all that rain. Literally covering the entire planet. At that point yeah it would dev a reasonable thing to bring up in the context of fresh water reserves falling.
So I very much stand by the point that while, sure, it happens all the time, that does nothing to actually help with the topic at hand.
The ocean covers the majority of the Earth's surface. The ocean is full of salt.
Water which rains out over the oceans is unusable as drinking or irrigation water without expensive processing (desalination).
If historic rainfall patterns change, there is absolutely no requirement that the rain land anywhere useful for our existing infrastructure or human habitation.
Yes, the water won't disappear, but if the effect is rainfall hits the ocean, or say, flood-prone regions even harder then it normally does, it's still going to be coming down somewhere not useful to us.
The problem is not that we can't solve these problems, it's that is is staggeringly expensive to do so.
Something like 600 million people live below the poverty line, which with current inflation is at $2.15 per day; so for them a 38 cent per day rate means diverting almost 20% of their income just on water. For comparison, that's a much larger share than what USA residents spend on food (~13% of their income).
Kind of leaving out the main point there. People don't use a lot of water. Industry and Farming do. We depend on both of those for...pretty much our entire society.
Water-intensive industrial processes can move to where the water is. Farming is more of a challenge but some crops need more water than others; there's a lot of scope for substitution.
I think many of us working in software can be overconfident about how easy it is to scale things, probably because of the peculiar progress in the improvement of integrated circuits and the commensurate increased availability of raw compute for not that much more energy. But many processes (including desalinization, as far as I understand it) are energy bound. It is really hard to make exponential progress when a process is bound by how much energy you can muster up to put into it. That is why rockets haven't had an exponential increase in the amount of weight they can get into orbit in the last 100 years. With gravity you must pay the piper.
I doubt scaling desalinization is as hard as hurling stuff into space, but it may not be easy to scale either. There are plenty of places on earth which are very dry, adjacent to salt water, and extremely rich and yet no great desalinization technologies have come from them.
I think many of us working in software can be overconfident about how easy it is to scale things, probably because of the peculiar progress in the improvement of integrated circuits and the commensurate increased availability of raw compute for not that much more energy.
You may have neatly (and politely) pinned down why we computer folks are so arrogant about how easy problems outside our direct field would be to solve, if only we were the ones “allowed” to solve them.
There are more than a few places where desalination is necessary, and we still haven’t come up with a way to make it cheap.
The current issue is that there is just no way that we know of to reliably desalinate that isn’t super energy intensive, so it comes down to trading energy for water. That’s why desalination is expensive.
It's easy to overlook the effects of transpiration, which is a result of photosynthesis, which is impacted by biodiversity loss. It short circuits water's path back to the ocean and puts it back into the air above land where it can precipitate into lakes a second time.
Without it, snowmelt-fed rivers dry out earlier.
As more ice melts there might be more liquid water available, but the ecosystems that would process that water into vapor are struggling. So you end up with a situation where the only source of water vapor in the air is the oceans.
As temperatures increase that'll again be a net increase in ocean-driven evaporation, but it'll be less evenly distributed than evaporation+transpiration was.
So the concern is that the only available water will be too salty to drink, or too destructive to capture.
Higher global average temperatures means higher global average specific humidity. As the air warms it can hold more water vapour, which means less condensation. I don’t know how much difference this makes, but I expect it’s not insignificant.
True, but oceans only evaporate from the surface while the air retains moisture by volume. There is considerably more low, warm air than there is ocean surface.
The earth as a whole is roughly a closed system, but "usable water" is not.
Most resource problems are not about the quantity of some thing changing as a percentage of earth's matter. Most resources are about density and composition.
If all of the (non-ice) freshwater on earth was suddenly dumped into the ocean, we'd have the same amount of overall water - but little to no drinkable water.
Likewise, we're not really creating new carbon by burning fossil fuels. We're moving and re-distributing it. Compared to being deep underground, the form we create by burning captures much more heat, causing many problems.
It fascinates me how things have obvious consequences but human race just ignore them till literally everything is burning. As it is with water shortages, climate change or Hitler.
A sizable majority (including in the US) recognize the danger of global warming, but are politically blocked from taking action by the actions of a small group of extremely wealthy individuals and corporations working to maintain the status quo to their benefit.
... then they start talking about km^2 of lost surface area. Which if you read the paper they cite, it says "Between 1984 and 2015 permanent surface water has disappeared from an area of almost 90,000 square kilometres, roughly equivalent to that of Lake Superior, though new permanent bodies of surface water covering 184,000 square kilometres have formed elsewhere." On top of that, shallow lakes fluctuate wildly in surface area. The great Salt Lake for example. VS Lake Tahoe which can drop 10 ft and the surface area loss is tiny.
Yes of course the relationship between volume and area depends on the lake depth, are you suggesting the paper implied anything else? The Great Salt Lake has dropped rather dramatically in the last ten years, so much so that it has already changed pretty much all recreation and commercial activity on the lake - the primary boat dock closed because the marina was completely dry and by last year the shores had moved inward, by kilometers in some cases. Unusual precipitation this year has brought levels up a little, but this might only be a blip in the downward trend. The known reasons include drought conditions, unusually high temperatures, and greater upstream use. The Great Salt Lake’s recent history very much backs up the claims of this paper, no?
This, and why 1992-2020? How many of these large lakes are distributed in say, Midwest America/Canada. What were the precipitation levels in that region just a few years prior? Why did they need to involve climate models when we have observable data?
Given the significant use of satellite data, I imagine the start point was chosen based on when some classes of data became available from recently launched satellites. An earlier time may not have sufficiently comparable data.
They used a technique for water segmentation described in an earlier paper [1]. The validation dataset for that method goes back to 1992...
"All applied images have 30-m spatial resolution and were acquired during October 1, 1992 to October 31, 2018. The period was set with regard to the availability of the validation dataset"
[1] Yao, J. Wang, C. Wang, J.-F. Crétaux, Constructing long-term high-frequency time series of global lake and reservoir areas using Landsat imagery. Remote Sens. Environ.232, 111210 (2019).
I think this might be just because their comment is borderline useless - it is so condensed that one can hardly make any sense of it.
So what did they want to say? Is it "Science, it works?" like in XKCD comic #54? Or are the quotes around science the actually important thing, casting doubt on it? It's hard to tell because they did not bother to spend a few seconds to actually write it out.
Beside that there is more to papers than just their abstract. If you are curious, you can check section "Global LWS trends and drivers" for the answers to your questions.
The intention was to get people to read the main thesis critically. That quote is sort of a tell about the quality of this paper, and the more I dig into this paper the more it confirms this is isn't good science.
Also, this is stated later in the doc:
"Between 1984 and 2015, a loss of 90,000 km2 of permanent water area was observed by satellites—an area equivalent to the surface of Lake Superior, whereas 184,000 km2 of new water bodies, primarily reservoirs, were formed elsewhere (14)"
My first impression was that this means there has been a growth in total permanent water area from 1984-2015. Am I just reading this wrong?