Is Desert Ever a Good Thing for the World's Climate?

[phinds]

I think this is actually an interesting question on its own. I first thought, of course its a local property that cannot be taken globally, and therefore any influence on rain in local areas doesn't affect other regions. However, the solar energy absorbed by Earth as well as the heating by ourselves are basically constant on a short time scale. The latter would support the zero-sum-game view.

As would trade winds and, I believe, other factors.

 

[PAllen]

I think this is actually an interesting question on its own. I first thought, of course its a local property that cannot be taken globally, and therefore any influence on rain in local areas doesn't affect other regions. However, the solar energy absorbed by Earth as well as the heating by ourselves are basically constant on a short time scale. The latter would support the zero-sum-game view.

But amount of rainfall, planet wide, is a cycle rate. The fraction of total solar energy driving the water cycle is hardly 100%. Thus I see no reason why this fraction can't vary up to some maximum. Granted, the total available energy is zero sum, but it requires a lot more analysis to go from there to total rainfall being zero sum. Further, to first order, the water cycle conserves energy, so it may not take much of an increase in solar fraction to kick up to a substantially higher cycle rate. Note, this is not a field I've ever studied, I'm just thinking in terms of basic physics and chemistry, and not seeing any obvious reason total rainfall can't change.

 

[Bystander]

rainfall, planet wide, is a cycle rate.

? Say "what?"

 

[PAllen]

? Say "what?"

The rate at which water passes through the water cycle per year is the total rain fall per year. Run the cycle faster, there is more rainfall per year. To run the cycle faster you need (for starters) to increase evaporation rate. I see no fundamental obstacle to doing so if temperature can change.

 

[Bystander]

I see no fundamental obstacle to doing so if temperature can change.

 

[PAllen]

So, temperature can easily change with fixed available total energy. That is simply a matter of the fraction used to heat oceans and air, which, again, is hardly 100%. Without getting into the PF forbidden territory of human driven climate change, there are any number of processes by which the atmosphere and oceans can be made to absorb a larger fraction of solar energy (e.g. a silly example: mix in dark dust - into the ocean and atmosphere; increase albedo of land masses).

[edit: also, since as I mentioned before, the water cycle is largely energy conserving, running it faster need not take extra energy to sustain. Higher temperature is hardly the only conceivable way to drive it faster. By analogy with any number of chemical manufacturing processes, there might be a 'pollutant' that can act as a catalyst to the cycle.]

 

[zoobyshoe]

Probably most have heard of the Salton Sea, the biggest lake in California, which was created by accident in 1905:

The most recent inflow of water from the now heavily controlled Colorado River was accidentally created by the engineers of the California Development Company in 1905. In an effort to increase water flow into the area for farming, irrigation canals were dug from the Colorado River into the valley. Due to fears of silt buildup, a cut was made in the bank of the Colorado River to further increase the water flow. The resulting outflow overwhelmed the engineered canal, and the river flowed into the Salton Basin for two years, filling the historic dry lake bed and creating the modern sea, before repairs were completed.[2] While it varies in dimensions and area with fluctuations in agricultural runoff and rainfall, the Salton Sea is about 15 miles (24 km) by 35 miles (56 km). With an estimated surface area of 343 square miles (890 km2) or 350 square miles (910 km2), the Salton Sea is the largest lake in California.[3][4] The average annual inflow is less than 1,200,000 acre feet (1.5 km3), which is enough to maintain a maximum depth of 44 feet (13 m) and a total volume of about 6,000,000 acre feet (7.4 km3).

I've always had that at the back of my mind when thinking about transforming a desert.To get a forest started you basically have to pump tons of water into the dry area. There aren't rivers to divert into most deserts so you'd have to get creative. So, you build desalinization plants on the sea coast of the Sahara and pump the water through a pipe into the interior and let it flow out. You might have to do that for years until you create a wet spot suitable for starting a forest, I don't know, but I wasn't thinking in terms of waiting for the rain patterns to change or of ever being completely dependent on them.

I can't think of anyone with the money to do something like that who has any incentive to even try, but it seems it would be possible if there were such an entity.

 

[Bystander]

(e.g. a silly example: mix in dark dust - into the ocean and atmosphere; increase albedo of land masses).

https://en.wikipedia.org/wiki/Year_Without_a_Summer
Like this?

 

[Bystander]

Cutting down rain forest causes desert, and this is viewed as an upset to the world's climate.

Does it? This is a "blanket" assertion that cannot be true, can it?

 

[Psinter]

Not bad for those who evolved to live there :)

You could say that again. You couldn't be any more right.

I have not found studies on the matter in the kind of desert you probably speak about (hot deserts), except for the Arctic (which is not a hot desert). At least not on the impact on Earth directly, however, it does impact societies. And if a human society is impacted, they are going to react maybe damaging other areas for the sake of their own survival.

https://www.amazon.com/dp/0195371127/?tag=pfamazon01-20[/URL]
The spring and fall migrations of the Sheikhanzai and their herds allow them to escape the extremes of heat in the summer and cold in the winter and to utilize pastures throughout the year that can be replenished in subsequent seasons and years as grazing sites.

A sedentary existence would have been harmful to the quality of pastureland and the health of livestock, not to mention disintegrating the social ties that exist between multiple camp groups and villages in sparsely populated and agriculturally marginal areas.

-Indigenous Cultures: Bahram Tavakolian

If you remove hot deserts from them, they are going to react in winter, either by becoming part of modern society (a sedentary existence) through force or finding ways to survive in new areas that they previously only passed by temporarily. But since they will be spending more time in one place, said place's landscape will probably change. With time, the quality of the water will change too and so on. Many modern societies are sedentary and there is more than enough evidence out there of what they do to to the landscape.

Spoiler: About the book

Note that this book is about essays of experts in the field. It does not have articles from professional journals. Usually a course in Environmental Sociology also includes other readings from professional journals and studies. Not this book alone.

Antarctica and the Arctic on the other hand are also deserts. While the conversation here is concentrated on hot deserts, destroying the Arctic at least, will certainly affect environments across the world and there are studies for that:

https://www.nasa.gov/content/goddard/nasa-study-shows-global-sea-ice-diminishing-despite-antarctic-gains]“One[/URL] of the reasons people care about sea ice decreases is that sea ice is highly reflective whereas the liquid ocean is very absorptive,” Parkinson said. “So when the area of sea ice coverage is reduced, there is a smaller sea ice area reflecting the sun’s radiation back to space. This means more retention of the sun’s radiation within the Earth system and further heating.”

Deserts also allow wind to flow with little resistance across long distances to eventually meet places which are not deserts. Destroying a desert could affect wind fronts, eventually affecting for good or bad other areas.

 

[PAllen]

https://en.wikipedia.org/wiki/Year_Without_a_Summer
Like this?

Ok,so that's not a good example. My main point remains: there is no reason of principle causing global total annual rainfall to be constant just because total energy budget is constant. You must add further assumptions about other factors being constant.

 

[zoobyshoe]

Does it? This is a "blanket" assertion that cannot be true, can it?

It's not a blanket assertion. It's "nutshell" language that refers to the occasions when it's true.

 

[zoobyshoe]

I have not found studies on the matter in the kind of desert you probably speak about (hot deserts), except for the Arctic (which is not a hot desert). At least not on the impact on Earth directly, however, it does impact societies. And if a human society is impacted, they are going to react maybe damaging other areas for the sake of their own survival.

If you remove hot deserts from them, they are going to react in winter, either by becoming part of modern society (a sedentary existence) through force or finding ways to survive in new areas that they previously only passed by temporarily. But since they will be spending more time in one place, said place's landscape will probably change. With time, the quality of the water will change too and so on. Many modern societies are sedentary and there is more than enough evidence out there of what they do to to the landscape.

There are lots of peoples who live and lived right inside great forests without having hardly any impact on those forests. I know of: Pygmies in Africa, and most South American tribal people off the top of my head. I believe a lot of North Eastern Native American tribes were also forest dwellers.

While you can devastate a forest nearly overnight, it would take many years to get a new one started again, so the transition for any people who have a current use for desert would be slower. And, I'm primarily talking about desert that has no current benefit to people, the kind where it's not possible to make any settlements, pasture, and which people avoid even traveling through. The reforestation I'm thinking of would, in fact, create vast new habitat for people who can adapt to forest life.

Let me approach my question a bit differently: are there any scientists who propose that some minimum amount of desert is required for a life sustaining Earth climate?

 

[Planobilly]

Deserts provide dust to the atmosphere. That dust disrupts the formation of hurricanes. Living in Florida that effect has value to me! So in that case, a desert "is a good thing".

Over long periods of time land now exist where seas use to exist and deserts have come and gone. Those changes don't appear to have had much effect on humans over the long term. Deserts provide environments for certain life forms to live which can not live elsewhere. If that is a "good" thing or not is pretty subjective. Some would be very opposed to any life form being destroyed or going extinct. I don't always agree with that position. I have enough trouble driving in Miami without having to deal with a Tyrannosaurus on the interstate...lol

It is obvious that deserts effect weather. When and if that effect is considered good or bad depends on the circumstances of the effect.

Cheers,

Billy

 

[zoobyshoe]

Over long periods of time land now exist where seas use to exist and deserts have come and gone. Those changes don't appear to have had much effect on humans over the long term. Deserts provide environments for certain life forms to live which can not live elsewhere. If that is a "good" thing or not is pretty subjective. Some would be very opposed to any life form being destroyed or going extinct. I don't always agree with that position. I have enough trouble driving in Miami without having to deal with a Tyrannosaurus on the interstate...lol

It is obvious that deserts effect weather. When and if that effect is considered good or bad depends on the circumstances of the effect.

Right. Reforesting a desert is obviously a sacrifice of whatever flora and fauna have 'figured out' how to live there, but that's in favor of the vastly greater number of species who will then have a place to flourish. In addition a much greater volume of carbon will be locked up in the plant life instead of floating around in gaseous states. A lot of "green" people think that latter would be a good thing.

Speaking of T-rex, back in the day when there was only one continent, it seems to have been primarily a tropical, swamp and forest one, and the rise of deserts, both hot and cold, did not happen till after it broke apart. Since my question is frankly anthropocentric, I have to wonder if more tropical area is good for people or not, despite the fact it seems extremely bio-friendly in general.

 

[Bystander]

"There are two types of global Earth climates: icehouse and greenhouse. Icehouse is characterized by frequent continental glaciations and severe desert environments. Greenhouse is characterized by warm climates. Both reflect the supercontinent cycle. We are now in a little greenhouse phase of an icehouse world."
From
https://en.wikipedia.org/wiki/Supercontinent_cycle
Speculative, but "state of the art" for immediate purposes.

 

[EnumaElish]

Perhaps, Prospero thought, the minerals on the sea floor and the sodium, potassium and calcium in the air above the water were coming from the same source: tiny grains of dust. That dust might ride the winds for thousands of kilometers before finally settling down onto the ocean. If true, it would mean that 30 to 80 percent of the mud on the sea floor actually came from distant lands!

https://www.sciencenewsforstudents.org/article/dust-creates-deserts-sky

 

[zoobyshoe]

https://www.sciencenewsforstudents.org/article/dust-creates-deserts-sky

So, that's it: dust from the Sahara makes the Amazon rain forest possible:
http://www.nasa.gov/content/goddard...s-how-much-saharan-dust-feeds-amazon-s-plants
When there is more rain in that part of the Sahara, there is less dust that travels to the Amazon.

 

[JonDE]

Probably most have heard of the Salton Sea, the biggest lake in California, which was created by accident in 1905:I've always had that at the back of my mind when thinking about transforming a desert.To get a forest started you basically have to pump tons of water into the dry area. There aren't rivers to divert into most deserts so you'd have to get creative. So, you build desalinization plants on the sea coast of the Sahara and pump the water through a pipe into the interior and let it flow out. You might have to do that for years until you create a wet spot suitable for starting a forest, I don't know, but I wasn't thinking in terms of waiting for the rain patterns to change or of ever being completely dependent on them.

I can't think of anyone with the money to do something like that who has any incentive to even try, but it seems it would be possible if there were such an entity.

Wasn't there someone that tried to transform the Sahara desert already? I have this nagging story in my mind that I can't remember the details of. Either he was rich or a prominent scientists, or both, in which he actually had working farms in the Sahara. I remember his efforts being cut short by one of the world wars, when I think his materials were all repurposed.

 

[zoobyshoe]

Wasn't there someone that tried to transform the Sahara desert already? I have this nagging story in my mind that I can't remember the details of. Either he was rich or a prominent scientists, or both, in which he actually had working farms in the Sahara. I remember his efforts being cut short by one of the world wars, when I think his materials were all repurposed.

I haven't heard of this and wasn't able to find anything by googling, but I don't doubt it. It's not an uncommon idea, and there are probably always people at work trying to reclaim the edges of desert for farming.

Just ran across this from 2009:

http://www.wired.co.uk/article/irrigation-system-can-grow-crops-with-salt-water

I am guessing this must not have worked somehow in practice because there's no other news about it. If it is viable it would be the perfect way to irrigate a desert because you could pump sea water inland without the great expense of de-salting it first. Still, you have to clean whatever has been filtered out of the water out of the pipes, and then what do you do with it?