Hacker News Reader

Comment by fooblitzky | Hacker News Reader

That Venus may once have had an Earth-like climate, until it hit a "runaway greenhouse gas state", is a scary thought considering our current challenges on Earth (and melting permafrost and methane bubbles). Sometimes people say "we might pollute enough to kill all humans, but nature will continue just fine without us." - Unless we do enough damage to trigger a runaway state and turn Earth into another Venus.

View on HN

I seem to remember the concentration of CO2 necessary for this to be 10-100 times higher than current. Also made worse on Venus by proximity to the Sun and collapse of the planetary magnetic field. Essentially, the greater solar wind / radiation flux and holes in magnetosphere disrupts atmospheric H2O and H2 is blown off planet, and O2 oxidizes C next (which then falls into a feedback loop with CO2 and H20 vapor driven greenhouse effect)

I'm extraordinarily concerned about global warming, but it's very likely humanity will kill itself well before it can create a runaway Venusian like greenhouse. I think the concentration of CO2 alone is fatal to human life well before that level.

edit: quick cites https://www.scientificamerican.com/article/fact-or-fiction-r... (30k ppm CO2, disputed), https://www.dhs.wisconsin.gov/chemical/carbondioxide.htm (5k ppm CO2 upper limit for workplace exposure)

I think a major concern is that a small rise in greenhouse gasses from human activity may result in a large release of greenhouse gasses stored in the earths crust. It is not expected that we would release all the gasses ourselves, but that our emissions would trigger a massive release.

I think the runaway greenhouse effect article accounts for the clathrate gun hypothesis. Not sure residency period of CH4 in the atmosphere would be consistent with the level of heat buildup to get the H20 vapor feedback loop going.

Climate change is a big potential ecological disaster - for us. Earth has had periods of much hotter temperatures than climate change is likely to induce. During the early Carboniferous period, the average global temperature was almost 10 degrees Celsius higher than today. It would take a long time to turn Earth into Venus, or even something similar to the Carboniferous

It’s also a disaster for thousands of non human species. Many species are going extinct because of human activity. Which in my opinion is a shame. Yes, in millions of years life may come back if we don’t trigger runaway greenhouse effects, but that’s still a lot of life destroyed.

It's not clear to me that we understand the conditions under which the earth was much hotter, or specifically what conditions resulted in cooler periods. There was a article a few days ago discussing the theory that one of the ice ages was caused by inter-planetary dust. This is an honest (and unpolitical) question: how much do we know about these past climate changes are what caused them?

Runaway states are an unrealistic scare mongering tactic that very rarely show up in nature. There are so many feedback loops, both positive and negative, but people always forget about the negative feedback loops and overemphasize the positive feedback loops. Sure, any positive feedback loops taken out of context can be scary but that’s because it’s an idealized state that doesn’t really exist.

Unfortunately, net positive feedback loops for climate are clearly evident in the geological record. A great presentation of the evidence is in Hansen's Storms of My Grandchildren.

He also says it's basically impossible for the Earth to reach a Venus-like state. But we could easily get runaway warming sufficient to add several extra degrees.

It's very unlikely that we can cause enough environmental damage to cause that: https://en.wikipedia.org/wiki/Tipping_points_in_the_climate_...

We're basically as significant to the Earth existing as a mold strain is to a mountainside. If we're idiotic enough to trigger a climate catastrophe that wipes us out, this ball will keep on spinnin'...

Spinning, yes. Habitable to some kind of life, probably. Habitable on the surface, to complex multi-cellular life, we could very well ruin that.

We could, and are, rather easily. The more complex the life-form/system, the more vulnerable it is to simple attack.

"There'll still be a lifeless ball of rock left" isn't the comforting point you seem to think it is.

My intent was to illustrate how incidental we are in the scheme of things, and thus should take extreme care if our goal is to continue to exist.

Venus probably had an Earth-like climate which evolved a wide variety of lifeforms, which culminated in the evolution of an intelligent species that built a global civilization. However, they powered this civilization with hydrocarbons pumped out of the ground, left over from decayed plant matter from eons before, so they could drive around in oversized SUVs, instead of living more densely and using trains to get around. Some of their species tried to warn them that disaster was imminent if they didn't change their ways, but the rest said this was just alarmism and that there was nothing wrong with cutting down their forests to have more grassland for raising large livestock for food. We can see now how this all worked out for the Venusians.

And as we can see from the downvotes here on a "tech site" (supposedly the most intelligent of people on this planet), Earth is obviously destined for the same fate.

This is most likely the explanation for the Drake Equation. We don't see other intelligent lifeforms, because they don't become intelligent enough fast enough, and they stupidly destroy their own environment, leading to their own extinction, before they can explore beyond their own star systems.

Reply on news.ycombinator.com