[Lore]

Who cares about the Venus hypothesis? We will already be moving out of civilization's comfort zone within the next few decades. All of our economies, food security, land and water resources is built around and depends on the climate we've had for the last several thousand years.

[dohboi]

Thanks for that perspective, dis. My impression is that atmospheric dynamics cannot be boiled down to one equation. But I don't think T intended for this to be about extreme possibilities (or impossibilities), but just what is most likely to be within the range of probable outcomes. So we should probably drop it or start a new thread, if we want to discuss Venusian issues further.

[dissident]

Who cares about the Venus hypothesis? We will already be moving out of civilization's comfort zone within the next few decades. All of our economies, food security, land and water resources is built around and depends on the climate we've had for the last several thousand years.

Points I have been making for several years on this forum. But people prefer doomer porn and thus shoot themselves in the foot by making themselves look like cranks.

[dohboi]

It sounds like many here will like this video, then:

https://www.skepticalscience.com/the-co ... times.html

[Newfie]

Who cares about the Venus hypothesis? We will already be moving out of civilization's comfort zone within the next few decades. All of our economies, food security, land and water resources is built around and depends on the climate we've had for the last several thousand years.

Points I have been making for several years on this forum. But people prefer doomer porn and thus shoot themselves in the foot by making themselves look like cranks.

Dis,
I'm not a dummy, but with all that is going on between work, prepping, and family I don't have time to educate myself so that I can absorb and appropriately understand and evaluate all the material out there.

I take it you have some background the science?

But that is the value of these forums, we plebs have access to folks with greater understanding, such as yourself.

One of the reasons I wish we had tighter moderation would be to rid ourselves of the shills so the clear voices of reason are less drowned out.

Thanks for your post.

[dohboi]

"I take it you have some background the science?"

He does indeed, but so does Hansen--and quite a bit more of it for quite a bit longer and in these exact fields. That said, dis's position (though perhaps less belligerently stated) does seem to reflect something more like the general attitude toward this issue among most scientists in the field, as far as I have read.

[Subjectivist]

Indeed, I like Dr. hansen and have loosely followed him since I discovered him in 1988. That was the year of the great midwestern drought and he was testifying about global warming as we passed the 350 ppm CO2 level. I think he is very worried about the world his descendents will inherit from us so he has become increasingly inclined to emphasize the low probability but more grim predictions.

I take a more middle of the road approach, the word is warming, we have proof of the physics of green house gasses and proof that humankind is dumping them into the atmosphere faster that natural processes remove them. Logically this thread makes sense, we examine the past climate when the world had this kind of atmosphere and ask, what will our world look like in comparison?

We are at Mid to late Miocene levels now, and the Northern Hemisphere looked very different in that time frame. Warmer everywhere, wetter in some places and drier in others. The problem is the mountains are different now in Tibet, Switzerland and western North America so that changes air flow, and as Dissidant pointed out in several places the Panama isthmus and Indonesian straits have narrowed or closed so ocean currents are changed too. Heck humans dug the Suez canal that has changed the water flows into the Eastern end of the Mediterranean Sea so we have even changed flows ourselves.

On top of all that our civilization is dumping greenhouse chemicals at an ever growing rate which islikely to accellerate as oil runs short and we burn more cheap coal to compensate. I think it was dohboi who pointed out CO2 is four ppm higher than a year ago on this date, that is half the yearly cycle of eight ppm up in the winter and down in the summer. Think about that for a second, humans are not putting ou as much CO2 as all of the organic material decay for half a year! Decay bacteria make up about 70% of all life on the planet and we are emitting half as much CO2 as half of them, or 35% of all life on our planet. What hubris it is for us to so overwhelm the natural system and expect no consequences as a result?

[Tanada]

Tanda,
First, I really hope you are right, that we do not face a Venus like future.

I would feel more comfortable if CO2 levels were posted on that graph also so I could get a sense of what temp equated to which CO2 level.

But I have two points I ponder.

My understanding is that the Venus hypothotsis rests on the assumption that moving to a warm world state would release vast amounts of methane in unprecedented quantities, moving the CO2 levels above what has been experienced previously. To make an anology, it is as if Earth has built up cumulative quantities of a toxin, and we are about to release it all at once.

Secondly, I think it's pretty clear that such an event is, in human terms, pretty far off. Several generations at least. On a shorter scale however we have the greater possibility of some significant die off due, in part to climate change. I don't fear sea level rise, an annoyance at best. I do fear that the cumulative stresses of sea level rise, drought, floods, and greater environmental variability on food supplies will conspire with peak oil, and general resource depletion to destabilize our global financial and govermental system so that we experience some degree of societal/cultural contraction/collapse.

There are several types of extinction. We all face personal extinction for we all die. Species extinction occurs when our genetic line dies. But succeess in keeping alive some small number of breeding pairs seems cold comfort. Not that I'm happy with our curren overshoot state, but I don't relish the curative either.

Diss pretty well demolished the Clathrate Gun as Venus hypothesis a little further down the thread. The two basic stable temperatures for the Earth throughout its long geological record demonstrate that natural forces damp out any changes that would exceed these upper and lower bounds. For example, the closer you get to the upper temperature boundary the more water vapor that accumulates in the atmosphere and the easier it is for highly reflective cloud layers to form increasing the Albedo of the Earth and reflecting more sunlight away before it has a chance to heat anything up. At the other end of the scale as more and more of the surface is covered with ice less CO2 is able to be captured into mineral sources or into water so more of it accumulates in the atmosphere until it warms the planet enough to prevent further ice formation. During the two or three snowball earth episodes it got cold enough that the whole surface near enough froze over, but volcanoes continued to emit CO2 until the level was high enough to cause a meltdown.

I read as much Climate information as I can stand and try and synthesize all the data together into something that makes sense to me. Based on many sources read over several decades the world is likely to change in the near (less than 1,000 years) future into something resembling the Miocene. The more CO2 we emit the further back our climate will resemble. If we make it all the way back to early Eocene there won't be any ice left on the whole planet and Antarctica will be tropical on the coast and warm temperate at the pole.

[dohboi]

"highly reflective cloud layers to form"

Indeed, but as we know, clouds do not all have the same reflective value. If so, there would be no global warming danger, since clouds would block the sun to the extent that the atmosphere heated enough to evaporate water. This theory, iirc, was called the Iris Effect, but it was pretty thoroughly disproven over a decade ago.

But, again iirc, the Venus Syndrome does count on clouds forming only at just the exact right altitude to not reflect too much incoming sun but to effectively hold in heat. This seems unlikely to most, but Hansen claims that it can't be ruled out completely.

In any case, I agree that it is much more worth while trying to figure out the much more likely and much more immediate consequences of our new Miocene world than to go on much more about highly unlikely, at best, distant future possibilities. As I said above, if you go out far enough into the future, the oceans will indeed boil, but that is at least hundreds of millions of years away when the sun itself becomes much bigger/hotter.

Tanada, you mentioned both atmospheric heat and slr in your opening to this thread. Which do you expect to be the most imminent threat to humans?

[dissident]

A strong limiter on any Venus-like regime is the direct thermal pumping by convection. I have already pointed out that too much carbon has been sequestered in rocks to return to conditions at the early stage of this planet. But suppose deus ex machina we have some super warming. Do not forget we started in a Venus-like regime and somehow the climate evolved to colder temperatures and condensed oceans. If we have significant evapouration of the oceans we will have a deeper troposphere and convective towers penetrating to a new tropopause at a higher altitude. This is a valve acting to bleed thermal energy directly into space. This valve is acting today as well and we need continuous solar heating otherwise the atmosphere would freeze out in about a month (with a long tail from the slower cooling of the oceans).

This convective valve explains why we went out of the Venus-like regime in the first place. We had moist convection billions of years ago when the surface was too hot for liquid water to pool. Over millions of years this pump overcame the runway greenhouse in the lower atmosphere. (The convection was not between the surface and 15 km, it was much deeper and topping out probably somewhere around 70 km since the atmosphere was thicker and much hotter). It is water vapour that is key to the efficiency of this convective heat pump. Venus for some reason has lost most of its original water to space. This likely reflects multiple factors: closer proximity to the Sun, solar output intensification, likely different initial water amounts compared to the Earth and other variables. We simply cannot stress the climate system of the Earth with the available reserves of carbon to put it in the Venus regime.

The runaway effect we need to worry about is the transition to a new climate regime that will be significantly different from today. Not Venus different, but different in the distribution of agricultural zones and mammal habitability zones. We do not need epic Venus warming to do this. The planet will remain habitable but with massively rearranged ecosystems. The huge population of humans on this planet that is maintained by the current agricultural regime is not going to survive with current numbers. Humans will not go extinct.

[AgentR11]

I would feel more comfortable if CO2 levels were posted on that graph also so I could get a sense of what temp equated to which CO2 level.

I missed this question.

I have a chart referencing a paper by R.A. Berner, 2001; but don't know where to hunt a linkable image. Brief summary is before 350mya CO2 is in the 3000 ppm and above zone; capture occurs through the carboniferous, and then gets back up into the 2000ppm range at the Permian/Triassic boundary; staying solidly over 1000-2000 through the Jurassic, and then steadily falling till the advent of industrial humans. An interesting point of reference though, is that the chart in question appears to show no situation in which the Earth had 500ppm CO2 and was not (going)into that hot phase. Going back that far, I don't think you have the resolution to say at 400 this and 200 that; but it gives a clear enough view that we can put enough CO2 into the atmosphere to force that shift.

I think its:
Science 4 May 2001:
Vol. 292 no. 5518 pp. 870-872
DOI: 10.1126/science.1061664

Of course this is all based on proxy markers in various things, so critics can certainly complain, but I don't really see anything unreasonable about either chart.

The venus thing though seems silly, just the underlying reality that the hotter a black body gets, the more heat it radiates will hit balance with solar input long before the oceans boil. Unless of course we're having another large body impact that will liquify the planet; then of course, we can turn all that water into steam again... However, worrying about Climate Change at that point seems kinda pointless.

[Serial_Worrier]

I think a lot of people on this forum subscribe to the Clathrate Gun hypothesis. Honestly I have faith that science will figure out a way for us to provide for all the energy needs of humanity before we reach too high of CO2 level in the atmosphere. Nuclear energy might be that.

[Newfie]

I do worry about the Clathrate Gun, but the above explanations seem plausible and it does provide a fair measure of hope. Of course Jo one here will be around to know for sure, still it's nice to know there is good reason for hope.

There are enough challenges to face in our lifetime. I have been trying to concentrate on them.

[dohboi]

Dis wrote: "The runaway effect we need to worry about is the transition to a new climate regime that will be significantly different from today."

This, at least, is something we can agree on.

Thanks for bringing up the convection piece. Where is that working most strongly as a 'valve' right now?

"Humans will not go extinct."

None of us, of course, can know this for sure. And, like everything else, given enough time, it will inevitably happen. But I doubt it will in the very short time frame some have proposed.

[Subjectivist]

Personally I think we are all talking about too far into the future, after we ourselves have long passed away.

What about the next 50 years while many of us will still be alive? Is the near term future too unpredicatable, or just not grim enough to pay attention too?

Will the climate of 2064 be appreciably different than the climate of today, and if so in what ways?

[dohboi]

"we are all talking about too far into the future"

I agree.

"Will the climate of 2064 be appreciably different than the climate of today"

Yes.

"and if so in what ways?"

You don't want to know.

[Tanada]

Personally I think we are all talking about too far into the future, after we ourselves have long passed away.

What about the next 50 years while many of us will still be alive? Is the near term future too unpredicatable, or just not grim enough to pay attention too?

Will the climate of 2064 be appreciably different than the climate of today, and if so in what ways?

If you have Netflix watch National Geographic: Six Degrees Could Change the World, and stop the show when you get to the three degree scenario. Right now we are at the 2 degree by 2064 mark, assuming we get our senses and don't keep making things worse before then.

[dohboi]

Those certain that the past is a good predictor of future climate could do worse than consider this recent post at SkS, which concludes:

...the scenarios for future fossil fuel use stand out as being even more extreme, and the business as usual scenario (RCP8.5) would amount to a climate forcing by CO2 that is largely unprecedented in the geological record (as far as we can tell).

...winding the clock back to EECO CO2 levels in the coming century will not result in a simple return to the Eocene climate...

https://www.skepticalscience.com/Past-a ... e-CO2.html

[Subjectivist]

Those certain that the past is a good predictor of future climate could do worse than consider this recent post at SkS, which concludes:

...the scenarios for future fossil fuel use stand out as being even more extreme, and the business as usual scenario (RCP8.5) would amount to a climate forcing by CO2 that is largely unprecedented in the geological record (as far as we can tell).

...winding the clock back to EECO CO2 levels in the coming century will not result in a simple return to the Eocene climate...

https://www.skepticalscience.com/Past-a ... e-CO2.html

Interesting graph, that shows we have not been at 400 ppm for 18 million years more or less, until now that is. That would put us back around the middle of the Miocene.

[Subjectivist]

http://youtu.be/s9OW8vaRVdQ

Fascinating lecture on tipping point mathematics with many examples, but a focus on climate for the second half. 45 minutes long but well worth investing your brain time.