I tried searching, but the fluff to substance ratio is so high out there.
It's stable, as when you add up all the positive and negative feedback effects, the result is negative. The most important negative comes from the thermal radiation of the Earth into space, which increases with increasing temperature, resulting in more cooling. Methane in Siberian ice is a hypothesised positive feedback effect: higher temperature => more methane => more warming.
If all these effects ever add up to more than 0 (the "tipping point"), the system will no longer be stable, and will travel around until it finds another stable equilibrium. The actual consequences of this are nowhere stated because they are completely unknown. But we're not talking about measuring sea-levels, we're talking a completely different climate (e.g. Venus).
Could you point me to a few papers which expound on this view? I'd be interested to see the mathematical models behind this.
http://journals.ametsoc.org/doi/abs/10.1175/1520-0469(1963)0...
As a species, for long-term survival, we have two choices: ensure our survival on Earth, or go elsewhere. There is no certainty that our survival here is assured (and a considerable body of evidence to suggest it may be at risk), and there is no certainty that a mission to develop other planets or non-planetary habitats will succeed. Therefore failure to massively invest in both is to risk destruction of our entire species.
Now recognise that the development of any extraterrestrial environment capable of supporting an independent (i.e. large) human population will require a much deeper understanding of climates (and other ecosystem elements) than we have today.
Put simply: cutting climate research is a gamble with everyone's lives, and let's also go to Mars ASAP and start trying stuff.
If the worst comes to pass and the species needs to throw a hail mary, I have to think our chances of success would be improved (even if slightly) if we were to have these sorts of details ironed-out in advance.
Suppose we started to really use Fusion power not just at our current energy needs, but enough to directly warm the planet. There are hard limits on just how much heat per m^2 you can dump before you start to cook the planet.
Such a civilization may prefer low atmospheric pressure and a planet further from the sun simply for cooling.
In geologic time frames, we are likely to be entering a domain where glaciation entirely disappears, including in Antarctica. The world was last here ~34M years ago, and sea levels were 200ft (60m) higher. I'm sure anyone reading this understands that this will have huge impacts on our day to day, including the drowning of most of the today's population centers.
(If anyone is curious, research the Eocene, the era that likely has the best predictive power for what will be happening to our climate over the next few thousand years). Just imagine it running in reverse, at a greatly accelerated rate.
And if you're wondering how we might avoid this fate, from an engineering perspective we need to recreate something like this: https://en.wikipedia.org/wiki/Azolla_event
co2 material safety data sheet says 5000 ppm is max allowable for an 8 hour work day. [1]
co2 levels (appear to) have a direct impact on cognition [2], specifically strategy and information usage.
Ecoene had levels around 2000ppm. It'll be interesting to see if we overshoot or undershoot. Sensitive people start noticing effects at around 1k, perhaps as high as 2k for insensitive people. 2-5k "Headaches, sleepiness and stagnant, stale, stuffy air. Poor concentration, loss of attention, increased heart rate and slight nausea may also be present." [3]
I don't think there have been any studies of long term exposure to 2k+ ppm (with no recovery time). as far as i know, nobody has to deal with that level of exposure for months or years. It's likely not good. But, as you say, not Venus.
[1] https://www.airgas.com/msds/001013.pdf
[2] http://ehp.niehs.nih.gov/15-10037/
[3] https://www.kane.co.uk/knowledge-centre/what-are-safe-levels... (not a great source, but plausible)
Have we really reached the point where it's necessary to claim political correctness before embarking upon a discussion?
Do you think it's necessary in order to have your opinion taken seriously, or to avoid moral opprobrium?
Nobody knows when/if the methane problem will happen. The ice/ocean thing can be modeled.
Runaway global warming by melting methane clathrates is known as the Clathrate Gun Hypothesis: https://en.wikipedia.org/wiki/Clathrate_gun_hypothesis
In previous mass extinctions, such as the End of the Permian, 251 million years ago, 96% of species were lost - due to a similar event: " A cataclysmic eruption near Siberia blasted CO2 into the atmosphere. Methanogenic bacteria responded by belching out methane, a potent greenhouse gas. Global temperatures surged while oceans acidified and stagnated, belching poisonous hydrogen sulfide. "
https://cosmosmagazine.com/palaeontology/big-five-extinction...
This doesn't mean it's okay. Release of methane has always happened at the same time as major mass extinctions, possibly as the cause of it. It would create massive warming which would make large inhabited parts of the planet much less desirable, play havoc with the biosphere possibly making large areas of farmland unproductive, and in general being a massive economic drain and probably killing a lot of people.
We have a fairly good understanding of the onset of the current inter-glacial. We don't, because ice cores and other information gets progressively harder to read, the further you go back, know all that much about the onset of a glacial period, but it does appear to be fairly quick. (Not Day after Tomorrow quick, but definitely within a lifetime quick.)
We're coming to what would normally be the end of the current inter-glacial, we have record C02 levels, and the gulf stream has been slowing down for the last 20 years. Nobody really knows whats going to happen next - but the UK Met office was apparently sufficiently alarmed to issue a blog post saying absolutely nothing if you read it carefully.
Interesting times.
It's all well and good to say that if I personally generate less CO2 then I personally will have less impact on temperature rise, but collectively, the impact depends on lots of other people's decisions, on population growth, on animal populations particularly cows. And of course if we are already on a trajectory that will increasingly release methane from clathrates, then what if that dwarfs changes in human activity?
There does seem to be some evidence that things like carbon taxes are mainly a bureaucratic boondoggle to enrich some people and to hide CO2 production by shifting it to some place that people don't look at too closely. We must never forget that bureaucracy drives corruption no matter what the underlying political system is. So if people are truly serious about collective human action to slow CO2 production or reverse it, we must be even more serious about cleaning out corruption at all levels in all countries.
The problem with it as a theme is that we really don't have a good idea of how the climate system operates long term, and by long term I mean geologically long term, not human long term. Even if we had pre-recorded satellite views of the planet and detailed measurements for the last 2,000 years that would be 2.6% of the 75 ky Ice Age cycle, and less than 0.0004% of the 50 My extinction cycle, or .000005% of the planet lifecycle.
For reference, 2.6% of a solar year is 9 days.
Humans measure time in terms of lifetime, its a very natural thing to do and since they typically live 70+ years, if you were to come to someone 9 days after you have first shown up on the planet and said "Can't you see, the temperature is a full 5 degrees warmer than it was when I started taking measurements!" And that human would pat them on the head and say, "Yes, you will see much bigger changes than that as the year goes by, it will get so hot you will will die of heat exhaustion if you stand outside all day without protection, and then later it will get so cold that you would freeze to death." And they aren't afraid and they consider it normal, because they have seen it many times before, over their whole life. But when the same person comes to them and says "The temperature is full 5 degrees warmer than it has been in 2000 years!", the fact that 2,000 years represents 100 - 200 generations of people (depending on how you choose a 'generation') it fills them with fear because nobody they know has ever experienced anything like that, its different, its scary, and its unknown.
Back in the day (we're talking the 60's) climate scientists would say "Gee, all of these geological records show that the climate changes in cycles, from very warm to very cold. And they noticed we were coming up on a time when the cycles suggest the end of the inter-glacial period was nigh and we should be looking for the leading edge of the next ice age.
Anyway, the planet has been warmer than it is now, its been colder, and it has changed with people present and without them present. The tipping point models have the climate becoming irreversibly destabilized after we pass it, what they don't say is what that means. Does it mean the planet gets really hot? does it mean an ice age starts? Nobody knows and the models don't help.
If climate change was slow enough and withheld within the parameters of the chemical processes that biological systems work with, this would be a non-issue. But the rate of change is too high for civilization and for ecosystems to adapt and create the necessary buffers.
https://en.wikipedia.org/wiki/Shutdown_of_thermohaline_circu...
One way of visualizing the impact of warming is by thinking of it like a speaker system. If you turn up the volume (adding more energy), does the average position of the speaker cone itself change much? Or is it just the extremes that change? Part of the concern with climate change is similar to that - the baseline temperature is changing upwards in amounts that don't sound that scary (really, what's the big deal about a degree or two?), but what's really going to do the most immediately noticeable damage is going to be the increased dynamic range which may include temporary instances of extreme cold (e.g. Siberia right now) or extreme heat.
Another concern though it breaks the analogy a bit, is whether there's a point at which a peak is such that it causes a permanent change to the whole system. In a speaker analogy, that's a blown speaker (torn cone, coil separation, etc.). In climate change/global warming, that may be thawing methane clathrates undersea (methane locked in the crystalline lattice of ice) or other underground methane reservoirs (e.g. in permafrost) thawing and injecting a temporary massive amount of methane into the atmosphere similar to what happens with CO2 in exploding lakes (which accumulate CO2 as carbonic acid until some event triggers a mass release). That shock of methane will be temporary since methane breaks down relatively quickly, but it's also a very potent greenhouse gas and even a geologically-quick few years of ongoing release may trigger massive changes in a relatively short time - changes that won't go backwards even after the methane degrades, and changes that will trigger massive political instability while they're going on.
Another possible tipping point might be Greenland's ice sheets - melt on them has been accellerating in recent years, and while the sheet is generally more than a mile thick and would take a long time to melt, it doesn't have to all melt to be a problem. In fact, if it all melted, the average sea level change around the world would be somewhere around 20 feet.
(edit: By the way, my reference to a methane "shock" was deliberate - if that happens, the impact may be disturbingly similar to the effect of a chlorine "pool shock" that kills off things in the pool then reverts back to a normal chlorine level as the chlorine breaks down into harmless forms.)