I agree totally that if there are any other Earth-like planets out there we should keep the hell away from them, or at least limit our contact to carefully sterilised probes. We should respect any and all life we find out there, if we ever do.
But Earth-like planets are almost certainly a very small fraction of the available real estate in the galaxy. The overwhelming majority are small, lifeless rocks that we can use to house space habitats of various kinds. I would even recommend we evacuate the Earth and allow its various ecologies to recover from the Anthropocene extinction.
But in the meantime the era that follows the Anthropocene (call it the Cosmocene) could see a radiative event, thanks to deliberate genetic engineering and adaptation to new environments off the Earth. Far from being the end of life’s diversity, we could be on the threshold of an evolutionary radiation far greater and more important than the Cambrian radiation.
Yes, the AGW would continue (for a while) if humans suddenly disappeared. Keep in mind that CO2 naturally fluctuates between 190 and 280 but humans have pushed it up to 400. So let’s consider some scenarios…
[a] CO2 keeps going up, 410, 420, 430, and by the end of this century it reaches 600.
** CO2 flattens out around 420 and stays there.
[c] CO2 stops right at 400 and then gradually starts going back down again.
[d] CO2 magically returns to 280 overnight.
Of those four scenarios, the only one where AGW stops in its tracks is the impossible [d]. If humans were to suddenly disappear, that would be scenario [c]. But none of that changes the fact that there’s a significant difference between the outcomes of scenarios [a] and **. That’s what’s a stake when we talk about trying to reduce our CO2 output. It’s not a question of “can we stop the warming?”; the answer to that question is a firm No. The real question is “would you rather have a little bit of warming or lots of warming?”; that’s the choice we are facing now.
Getting back to the topic at hand, with CO2 currently at 400 it would take decades after all the humans disappeared before the CO2 would fall naturally back down to 280. And during those decades, yes the warming would continue. And if the Sahara has gotten bigger during those decades, it would take decades more for it to shrink again.
Thing about trees is that something on the order of 99%+ of a mature tree is not doing anything. The only active parts of a tree are the leaves and the cambium (a very thin layer under the bark). The other plants that are not trees most likely sequester a lot more carbon per kilogram of vegetation (and liter of water) than do trees. Trees are awesome, but as a mitigation, I suspect they are a tad overrated.
One of the primary reasons that the disappearance of humans will not result in huge immediate CO[sub]2[/sub] declines and arrested warming is that humans are not going to disappear. Seven billion human corpses rotting away will be outgassing methane as they decay, which of course is a major greenhouse gas.
Let’s consider Day Zero as the day humans are no longer on the planet. On Day One, even if car drivers were raptured, there would be no CO[sub]2[/sub] emitted by automobiles at all. By 90 days or so, there would be no more CO[sub]2[/sub] from power plants or home/office heating units, depending on the fuel storage maintained by them.
So after 6 months to 1 year, all major human-generated sources from fuel burning of CO[sub]2[/sub] would stop. I would say that’s pretty dern sudden. Maybe AGW wouldn’t stop “in its tracks,” but it would have a serious setback. Tell me how it could continue for 40 more years under these circumstances?
Now that’s one CO[sub]2[/sub] source I hadn’t considered, but I doubt if it would last long.
You’re missing the point that, even if we suddenly stop pouring more CO2 into the atmosphere, that doesn’t magically get rid of the CO2 that we already put up there. AGW is driven by the total CO2 level that’s in the atmosphere, not the amount that gets emitted each year.
Imagine you have a credit card which you use occasionally and you always pay it off at the end of the month. Some months it’s $100 and some months it’s $200 but you always have enough money to pay it off. And then one day you get a new romantic relationship and you let your partner use the card. Your SO starts racking up huge bills, $900 per month, $1200 per month, $1600 per month… You don’t have the money to pay it off so you just make as much of a payment as you can, which is $200. But your SO keeps spending money, another $1500 last month, and another $1700 this month. Finally the total passes $9,000 and you say “I’ve had enough”. You take back the credit card and cut it in half. The $9,000 doesn’t just go away. It will take you YEARS to pay it off at just $200 per month. In this analogy, the money being charged each month is how much CO2 we’re emitting, the credit card balance is the total CO2 level in the atmosphere, and the $200 payment you make is the rate that the earth can reabsorb the CO2.
It’s a nice idea and one I hadn’t thought of. Because if you think that will happen — we’d limit ourselves to lifeless rocks — you’ve got far more faith in humanity as a whole than I do.
Sure one group might decide that. But another group will just move on into any Earth-like planet we get near — especially if said planet doesn’t have an intelligent species with the technology to repel us.
I’m really, really hoping that we never find a way to travel between the stars.
Until we discovered water moons, I might have been okay with us going out into the solar system as there didn’t appear to be much we could mess up. But now I’m voting for Homo sapiens living and dying here on Earth.
[QUOTE=lalaith]
I wrote years ago, “The single best event for Earth’s biological diversity since we evolved will be our extinction.”
from The Notebooks of Maggie A - Part Six
[/QUOTE]
For a couple hundred million more years, perhaps. Then it’s all collectively fucked. Only chance any life on this rock has, long term, is us at this point.
Also, I think that oxygen is the ‘single best event for Earth’s biological diversity’, since after it killed off more stuff than we have it opened things up for the biological explosions for everything interesting that’s come since.
I thought this was one of the lazier articles ‘Cecil’ (who has kind of become more of a left leaning eco Rah! Rah! type in the last few years, at least that’s how it seems) has written. Humans basically span the globe and are in every sort of environment there is. Trying to extrapolate what will be able to be seen by alien archaeologists (who, presumably would have satellites and ground penetrating radar at least as good as ours) from what New York seems a bit shallow, to me at least. We’ve had more interesting discussions about this subject on this board that ‘Cecil’ could have used to make a more entertaining article on the subject than what was used. shrug
There are areas that were once lava fields and basically all plant and animal life as well as the soil is wiped away to be replaced by a layer of lava.
What is interesting is to walk along these lava beds and watch how life returns. In only 5 years or so the lava begins to erode and algae appears. Then little bits of grass. Then bugs start to get in there. Then you see small vines and trees growing. Soon you are walking in a new tropical rainforest that just 50 years earlier was a lava bed.
I disagree with Cecil on his idea that elephants and rhinos would re-establish throughout Europe and Asia.
Unless they start with a viable population, just how would they get to Europe? Elephants do live in Asia and India but could they adapt and move into other areas like China or the middle east?
Rhinos live only in Africa. Unless they can swim how could they move across the Mediterranean or go around via the middle east?
But even then, barring a major change what are the odds they would expand all the way thru deserts and colder zones to live in Europe?
I dont know it just seems like the elephants and rhinos of the past were a breed that could live anywhere whereas nowadays the animals have evolved into their ecological niche.
Don’t know how well Asian elephants and rhinos would be able to migrate. They seem to be more adapted to tropical conditions than the African varieties. Even with a land bridge restored if the Sahara expands as predicted somewhere above it will be desert that keeps them from migrating out of Africa. But with humans gone and everything else we’ve done to the environment the climate may change to reduce the Sahara.
The topic-within-a-topic here is “Will the pyramids be recognizable in 10,000 years?”.
Remember that the original column asked what Earth would look like in 10,000 years. Cecil said streets, skyscrapers, and suspension bridges would be gone but stone walls might last thousands of years and Mount Rushmore should still be recognizable for millions of years.
Then, in this thread, TriPolar, said “The pyramids in Egypt and other such structures around the world may outlast all of our modern artifices.”
… to which Exapno Mapcase replied “But will the pyramids be visible? I’d expect that sands would cover them in not too many hundred years, given an expansion of the Sahara from warming.”
… to which Musicat replied “So you expect warming to continue with no human activities to fuel it? If that’s the case, why are we so worried about anthropogenic warming now?”
… to which I replied “with CO2 currently at 400 it would take decades after all the humans disappeared before the CO2 would fall naturally back down to 280. And during those decades, yes the warming would continue. And if the Sahara has gotten bigger during those decades, it would take decades more for it to shrink again.”
The relevance of CO2 levels remaining high for “decades” is that, if AGW is large enough to cause the Sahara to continue expanding to the point that sand dunes cover the pyramids in a century or two, they might not be recognizable 10,000 years from now. But if the Sahara doesn’t expand too much, they pyramids (which are already 6,000 years old) might still be recognizable when they are 16,000 years old.
I’m a pro-human optimist. While humanity definitely has done a lot of damage to the environment, and has the capacity to do a lot more, we also have the capacity to be the greatest environmental savior the Earth has ever seen. I mean this literally – nothing humans could do could come close to being as bad for the environment as a large asteroid or comet impact, and humans might have the capability to redirect an asteroid/comet on a collision course, thus preventing enormous mass extinctions.
So ultimately, humans could be the best thing for the environment in Earth’s history, in addition to the possibility of spreading Earth life to other planets.
Most people don’t recognize how artificial the modern Egyptian landscape is. This pictureof the Giza pyramids gives an idea of how much irrigation has gone into creating a country in a desert.
Without humans, that green area will disappear quickly. The clear areas around the pyramids won’t last long either. The pyramids that were discovered under sand were not farther west. Some of those still waiting to be uncovered are just as close to the green areas.
[QUOTE=sbunny8]
… to which I replied “with CO2 currently at 400 it would take decades after all the humans disappeared before the CO2 would fall naturally back down to 280. And during those decades, yes the warming would continue. And if the Sahara has gotten bigger during those decades, it would take decades more for it to shrink again.”
[/QUOTE]
Why is 280 (presumably PPM) ‘natural’? It’s varied to quite large degrees in the past.
I’m unsure of your larger point as well. Why would a large expansion of the Sahara make the pyramids go away? I’d think just the opposite. They would be covered in sand which would do more to preserve them for the long term.
Why in both cases? I don’t see an expansion or contraction of the Sahara having either impact.
Being covered doesn’t make them go away, however. In fact, the way we are finding new sites in Egypt are by simply looking at satellite images and using ground penetrating radar. At a guess, space aliens from another star system will have the same sorts of tech available…and they would be able to see more than just stone buildings. Even in the case of New York, while the structures themselves might have rotted away long ago the outline of the cities would still be there 10k years from now. Certainly our large mega cities in arid regions would still be visible, since many of them would also be covered in sand. Considering that we still find things like rope and parchment from several thousand years ago (not to mention bodies), I’m skeptical that a world spanning civilization such as ours would leave nothing behind that would be visible 10k years from now except those things in sand. I think with luck you could find something from human civilization millions of years from now, preserved by the same processes that have preserved some dinosaur tissue and bone, or dinosaur foot prints or myriad other things you’d think would be long gone but are still here to find.
I enjoyed Life Without Humans as well as Population Zero, but they were only slightly better than other shows on the same channel (such as Ancient Aliens :p) and were more for entertainment value than any deep look at the subject.
