Environment Question

[FatherRob]

I am curious -

I have been doing some research, but I evidently must not be looking in the right place.

If we immediately stopped production of anything that would add CO2 to the atmosphere (beyond normal pre-industrial levels), how long would it take for our atmosphere to revert to a pre-industrial state?

Rob+

 

[Squiggy]

From what's I've seen and read from "Life After People" and similar stories on what would happen if the Human race vanished one day, the Earth would continue to warm for about a century after the last manufacturing ceased. At that point, it would plateau and the Earth wouldn't necessarily revert to a pre-Industrial Revolution state but maintain at a higher level until something changed it.

 

[Garrovick]

I am curious -

I have been doing some research, but I evidently must not be looking in the right place.

If we immediately stopped production of anything that would add CO2 to the atmosphere (beyond normal pre-industrial levels), how long would it take for our atmosphere to revert to a pre-industrial state?

Rob+

Never. The Earth's atmosphere may be "cleaner", but every thing Humans do and use will continue to modify the atmosphere. Just think about it, how many little C02 generators are there on the planet? Even without machines.

 

[Jadzia]

I did work this out once, estimating the CO2 which 6 billion human beings create from their bodies alone, and how that adds to the atmospheric levels of the gas. I can't remember the result now, but it was something like 150 years of human breathing would account for the current atmospheric concentration.

Of course, greenery removes the CO2, but since we have less greenery than we once had, the dynamics are not the same as they once were.

CO2 is a minor gas in percentile terms (0.038%), such that increasing the concentration of it might increase the rate at which plants utilize it. I don't know if that balances out with deforestation though.

 

[JustAFriend]

Not just 6 billion humans, but all the animals we raise for food.

(Mankind has done a LOT of good-old-fashoned-way genetic engineering over the last 50,000 years!)

Who said what co2 levels are 'normal'??? Remember that they were a LOT higher during the dinosaur eras!!!

 

[PlixTixiplik]

Respiration is carbon-neutral - that CO2 you breathe out came from the food you ate, and was removed from the atmosphere a few months to maybe a year earlier by the plants that provided that food. Carbon cycling through the biosphere has too short of a residence time to be able to cause long-term perturbations (more than a few years) to atmospheric concentrations.

Methane production by livestock does contribute to global warming because methane is a much stronger greenhouse gas. So swapping one CO2 for one methane is bad.

As for the lifespan of anthropogenic CO2, it will be removed by several mechanisms. The first (and one that has been buffering our emissions) is through the ocean - that will remove the bulk of our emissions over the next couple hundred years. But the ocean's buffering capacity is limited so it will take the increase in continental silicate weathering, a slow geological process that will take tens of thousands of years, to remove the last parts.

 

[Jadzia]

Respiration is carbon-neutral - that CO2 you breathe out came from the food you ate, and was removed from the atmosphere a few months to maybe a year earlier by the plants that provided that food.

Oh I know this, I wasn't intending to create a proper model of where all the carbon comes and goes. I just wanted to see what the human population's respiratory output was in proportion to the earth's total.

Indeed, living biomass and atmospheric CO2 are the two reservoirs of carbon. And carbon shifts between these two states. If one decreases, the other increases.

Burning fossil fuels add to the environmental carbon. It isn't carbon we can realistically put back. Once it's out it's out for good.

 

[Meredith]

Respiration is carbon-neutral - that CO2 you breathe out came from the food you ate, and was removed from the atmosphere a few months to maybe a year earlier by the plants that provided that food.

Oh I know this, I wasn't intending to create a proper model of where all the carbon comes and goes. I just wanted to see what the human population's respiratory output was in proportion to the earth's total.

Indeed, living biomass and atmospheric CO2 are the two reservoirs of carbon. And carbon shifts between these two states. If one decreases, the other increases.

Burning fossil fuels add to the environmental carbon. It isn't carbon we can realistically put back. Once it's out it's out for good.

Earth's Carbon Balance has been getting lower and lower until Humans arrived, the decrease of Volcanic Activity in the last 100 million years is what is causing the CO2 levels to be lower than the time of the Dinos, In a way we are bringing it back to spec, but then again the concentrations are not that much when compared to the rest of the other atmospheric gasses. And Water Vapor is a far more effective Greenhouse gas and coolant than CO2 could ever hope to be. Though with extra CO2 plants grow better (that is why some greenhouses use CO2 to boost the plants). Those extra plants in different places than normal could change the albedio of the arth and this would have more of an effect on Earth's Temprature than the direct CO2 green house effect.

 

[FatherRob]

To give some more background, I am working on a story in which a spacecraft does a spectroscopic exam of a planet. I was trying to strike a balance between a natural CO2 level and a industrial one that might give our explorers interest in an abnormally high level, but where there was no evidence (at least not readily visible) of civilization.

Rob+

 

[PlixTixiplik]

As others in this thread have hinted at, there isn't a single "natural" CO2 level that all planets share. Even Earth's atmospheric composition has fluctuated quite a large amount throughout geological history. For example, current CO2 concentrations (about 378 ppm) are similar to naturally occurring CO2 levels in the Pliocene (3-5 million years ago).

You could use other chemicals instead - perhaps chlorofluorocarbons? It looks like they have a lifetime (in Earth's atmosphere) of 100 years, give or take.

 

[Squiggy]

I am curious -

I have been doing some research, but I evidently must not be looking in the right place.

If we immediately stopped production of anything that would add CO2 to the atmosphere (beyond normal pre-industrial levels), how long would it take for our atmosphere to revert to a pre-industrial state?

Rob+

Never. The Earth's atmosphere may be "cleaner", but every thing Humans do and use will continue to modify the atmosphere. Just think about it, how many little C02 generators are there on the planet? Even without machines.

You need to stop watching Glenn Beck.

 

[PlixTixiplik]

Just thought of this this morning. I don't think that spectroscopy would be able to measure the concentration of CO2 anyway. For example, we can detect characteristic absorption lines of water vapor, carbon dioxide, and carbon monoxide in the atmosphere of some exoplanets but that just indicates that those compounds are present.

 

[Ariadne]

To give some more background, I am working on a story in which a spacecraft does a spectroscopic exam of a planet. I was trying to strike a balance between a natural CO2 level and a industrial one that might give our explorers interest in an abnormally high level, but where there was no evidence (at least not readily visible) of civilization.

Rob+

You're probably barking up the wrong tree - see dinosaurs and volcanic activity above. (Especially if it's an explorer who isn't familiar with historical CO2 concentrations on the planet).


Maybe the explorers could detect life (or the water/oxygen in the atmosphere that is a sign of life) and decide it's worth having a closer look? How common is life at all in the universe in which your story takes place?

 

[FatherRob]

Maybe the explorers could detect life (or the water/oxygen in the atmosphere that is a sign of life) and decide it's worth having a closer look? How common is life at all in the universe in which your story takes place?

I guess I can spill the premise here...

In my story, humanity has not discovered any planets with advanced intelligence. Only non-sentient animals, plants, etc. They have discovered some number of earth-type planets. On the 24 month mission the crew I am writing about are on, they will visit 5.

The idea is that I want to show a planet with some degree of oddity, one that shows some indication in the atmosphere of having been inhabited, but with no evidence on the ground at all. It leads to an exploration, and then to a small group finding a cavern with a potential pointer to intelligent life.

Rob+

 

[Jadzia]

what about detecting man made elements like plutonium in the atmosphere? Which might be indicative of nuclear technologies. I'm not sure if spectroscopy would show concentrations so rarified though.

 

[oponda2009]

It does seem so. In the past 10 months we have had the Indian Ocean tsunami, hurricanes Katrina and Stan in the US and central America, massive floods in India and China and now the Pakistan earthquake. Watch television a lot, and you would think that the world is lurching from one disaster to another.

 

[Ariadne]

Maybe the explorers could detect life (or the water/oxygen in the atmosphere that is a sign of life) and decide it's worth having a closer look? How common is life at all in the universe in which your story takes place?

I guess I can spill the premise here...

In my story, humanity has not discovered any planets with advanced intelligence. Only non-sentient animals, plants, etc. They have discovered some number of earth-type planets. On the 24 month mission the crew I am writing about are on, they will visit 5.

The idea is that I want to show a planet with some degree of oddity, one that shows some indication in the atmosphere of having been inhabited, but with no evidence on the ground at all. It leads to an exploration, and then to a small group finding a cavern with a potential pointer to intelligent life.

Rob+

Basic vegetation, then? (Or cockroaches?) It's a long way from phytoplankton to technological life, so if they saw some greenery, they'd probably think "well, it's worth a shot", not "we've found them!".

(If you want to be technological about it, the oxygen concentration on Earth increased dramatically about 2.5 billion years ago because of photosynthesis.)

 

[JustAFriend]

It does seem so. In the past 10 months we have had the Indian Ocean tsunami, hurricanes Katrina and Stan in the US and central America, massive floods in India and China and now the Pakistan earthquake. Watch television a lot, and you would think that the world is lurching from one disaster to another.

Are you trying to blame those on HUMANS???

You DO know that disasters were happening long before we were here????

(Talk to the dinosaurs about that comet...)

 

[chardman]

It does seem so. In the past 10 months we have had the Indian Ocean tsunami, hurricanes Katrina and Stan in the US and central America, massive floods in India and China and now the Pakistan earthquake. Watch television a lot, and you would think that the world is lurching from one disaster to another.

Umm... Dude, better reset your watch and/or update your calender, 'cause none of those things happened in the last 10 months.

Not even the most recent events you cited, the Indian and China Floods, happened within the last 10 months, but slightly over a year ago.

Your other examples aren't even close, all having happened several years ago.

The Indian Ocean Tsunami happened in December of 2004.
The Pakistan (Kashmir Quake) was on October 8, 2005.
Katrina was in August 23, 2005.
Stan was in October of 2005.

 

[Jadzia]

You're talking to a bot chardman.

http://www.guardian.co.uk/environment/2005/oct/11/g2.naturaldisasters