What would happen to the earth if all the water on earth changed to chocolate milk instantly?
How long would it take before everything died, and what would happen if all the ice turned to chocolate ice?
Clouds will stay Clouds. Humans will stay humans. Only the water in rivers, oceans and ice would change into chocolate milk.
The temperature isn't going to change.
We'll die.
All oceans will suddenly turn to chocolate milk. I don't know if it was ever tested, but I think the majority of the sea flora and fauna can't survive for long when immersed into milk. Not only fishes wouldn't be able to breathe but algae would also die by lack of sunlight.
Plus, milk is denser than water ( milk: 1031.6 kg/m3, water: 999.97kg/m3) and have different physical properties. So replacing all water clouds by chocolate milk would certainly make them start to "crash" onto the ground in a matter of minutes. This alone would cause major damages to land life. Plus, most humans live in non-arid climate, so this cataclysm would destroy a lot of cities and farm lands, and kill a bunch of humans.
See here what would happen in a somewhat similar scenario : massive rain drop
(there the water of one cloud is concentrated into a spherical drop, so we have to speculate on what would happen if instead the water mass had a flatter and thinner shape)
The air humidity would precipitate and cover everything in a sticky layer, killing a lot of insects. (I don't have a source to confirm it right now, but I think the death of most ants and bees would hit our ecosystems pretty hard)
To these damages you can add the massive floods and landslides caused by the melting of ice caps and glaciers, which in addition of being now brown and absorbing more of the sun light, have also a lower freezing point (milk: -0.250°c, water : 0°C).
I also assume that the increase of around 3% of the oceans mass would cause an increase of seismic activity all around the world. (I can't find anything to estimate the effects of this for now, sorry).
Plants would be covered with a layer of sugar, cocoa and fat, which would decrease their "sun intake". In addition of that, the flow of the earth "water" would be altered, leading to droughts. Animals wouldn't be able to survive for long by drinking only rotten milk, most of them would die from thirst and diseases.
Humans wouldn't be able to water their crops and cattle, and our food sources would quickly disappear.
In the remaining cities, most infrastructure will stop functioning overnight. Electric plants would stop working, nuclear plants would experience "incidents". Without cooling fluid, most motor vehicles would heat up and break down. Our medicine stocks would be unusable.
Extracting drinking water from increasingly rotten milk would be a challenge too. Amidst this chaos, I doubt the survivors would organize themselves fast enough to provide for everyone.
As for our atmosphere, I don't know if it will stay breathable after the death of the majority of plants (remember that ALL algae dies instantly) and the massive release of gases produced by milk decomposition.
With devastated lands and dead oceans, not only most of the human population would die during the first days of the "chocolate milk apocalypse", but the damages to our ecosystem, lack of food and water and development of diseases caused by the rotting milk covering everything would cause the death of the remaining population in the course of a few years.
Note : I've used milk weight and freezing point in my answer because calculating those of chocolate milk is a bit more complicated.
It's worth noting that milk is, in itself, over 80% water.I'm going to guestimate 85% as an average of the various types of milk. Assuming that this milk-forming operation isn't recursive, and only affects free-flowing water or liquids containing water, we can instead rewrite the question as:
What would happen if 15% of the world's water turned into biological solids?
By biological solids I mostly mean fats, though the milk from various species contain varying amounts of other materials, and we have to account for the sugar and cocoa solids to make the milk chocolate. Needless to say, this would be a bad thing.
For starters: You've just reduced the amount of water available to evaporate into the atmosphere by 15%. The volume of water in the oceans and rivers makes the volume of water in the atmosphere seem like a drop in the bucket (pun intended), so humidity worldwide drops like a stone, causing climate havoc. Oh, and the phrase 'chocolate rain' becomes literal and thoroughly unpleasant for the first few months until the normal water cycle reasserts itself.
Secondly: You've effectively altered the density of water worldwide, leading to current currents changing in a wildly unpredictable manner. Again: Climate havoc.
Thirdly: Any number of marine species aren't going to be able to cope with the immediate change in salinity, viscosity, composition, oxygen content or acidity of their habitat, and will die, choking to death as they try to breath fat, sugar and cocoa instead of clear water. This is bad, and would turn the seas into a singularly unpleasant chowder.
Fourthly (is that a word?): The coastlines/riverbanks everywhere would become huge banks of fatty, fishy deposits as the water in the chocolate milk evaporated and left the solids behind. This rotting mass of sour solids would not be good for any creatures relying on that particular water source, though creatures near fresh water springs or relying on rainwater would avoid this issue. Evaporated water from the milk still forms fresh rain, and aquifers are often pumped up through layers of porous material that would filter the milk back to water, if they didn't clog up.
Despite all of the above: I think humanity would survive. Coastal countries or cities would have the worst of it, with alpine or icebound nations being able to last best (thanks to the ready supply of frozen, nutritious milk in the glaciers/snowbanks) Edit: After seeing Spacelizard's numbers on the melting point of chocolate milk, I'm going to have to revise this a little. Alpine countries would not last well (Nobody likes chocolate flash floods). Countries in the far, far north or at extreme elevations would probably be OK. Siberia would be a good bet as it's high, dry and cold.
After a few months of weather hell the normal water cycle would start to reassert itself, leading to desertification, and leaving behind roughly 800,000,000 metric tonnes of fat, sugar and cocoa solids (humanity weighs roughly 290,000,000 tonnes). This would provide fresh water for the remaining humans/land species/sea species that can survive milk (Looking at the snails , worms and bacteria mostly), along with a vast nutrient bank for any remaining vegetation.
Scroll forward a few hundred years and a lot of the milk would have been recycled by the biosphere, leading to a very dry but also nutrient rich world. The few areas that aren't desert would be lush oases, where the new mankind would never, ever look at milkshakes the same way.
