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Comment by hn_throwaway_99 | Hacker News Reader

I actually think this is a fair question, because I feel like there are 2 issues that get conflated:

1. First, you are correct, the Earth was much hotter in the past, and I haven't seen anything convincing that global warming will lead to a fundamental "runaway greenhouse" effect a la Venus that makes life as we know it on Earth unsustainable.

2. That said, a huge climate change in a relatively short amount of time could easily lead the the deaths of billions of people, with a B. One third of the human population lives within 60 miles of the coast. Rising temperatures will lead to huge portions of the planet that are currently densely populated that will no longer support humans. The resulting migrations, "resource wars", and overall increase in extreme weather events (more hurricanes, more droughts, more floods) will lead to death and misery to a huge portion of humanity.

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but if this change happens on the order of 100 years, that seems enough time to respond

Yes, and we should start responding.

Sea level has to actually start rising enough that the rich folks who live waterfront are affected and then we will see some geoengineering efforts or at the very least some solid seawalls.

I'm waiting for someone to figure out how to use solar + hotter temperatures + seawater to give us desalinated water

You say that, but its effecting Florida now and they're still just denying AGW

But it doesn't and won't. E.g. the sea level may creep up slowly, and then all of a sudden you get a giant flood or hurricane that makes a huge portion of the coast unlivable.

And regardless, if you think moving a third of humanity to vastly different lands will be hunky dory smooth sailing, you should study history.

Not just that, but the places we currently grow our food have been primed to fertility over thousands of years of relatively stable climates. If many of those areas become substantially less useful for growing crops (because of storms, temperature changes, drought, whatever have you), it's foolish to assume that we will see just as many places that haven't had millennia of vegetation growing on them become fertile.

That depends. Migrations and wars are the responses we can expect if its not handled in an organized way.

We've known about it for over 50 years and have done basically nothing. Why would you expect another 100 to matter?

US CO2 per capita is down 1/3 from peak. Europe is way down. China is peaking out. It's a start.

Much of this decrease in CO2 per capita in 1st world countries is just because we have outsourced much of our CO2 production to 3rd world countries

This is the graph that counts, and there is no discernible improvement in the curve: https://de.wikipedia.org/wiki/Datei:Mauna_Loa_CO2_monthly_me...

Hundreds of years starting in 1800s gives us until about 2100. 80 years will be within our childrens lifetimes for us millennials.

You need to look at arable land distribution, most of them are far from seas.

NZ is the worlds largest dairy exporter. ALL of NZ is close to the sea. Many islands are the world's food basket for bananas, coffee, coconut, palm oil (which is MASSIVE) and those are just the ones I can think of off the top of my head.

> Rising temperatures will lead to huge portions of the planet that are currently densely populated that will no longer support humans.

This does not seem likely, the bar for a region being "unable to support humans" is very high. People already live in cities that need to support themselves with food from elsewhere, and worldwide calorie production per capita is increasing.

Land that is underwater would count as unable to support humans, I think.

A few areas of the world that are unusually low-lying and situated over permeable rock like limestone will be flooded. For the rest of the world, dikes are a well-understood technology, and quite cheap compared to sacrificing large land areas or moving cities. Even worst-case shortest-timeline estimates of sea level rise are not an existential crisis.

There are pacific islands losing land to water rise NOW. This is an existential crisis for them. What do you say to them? Sorry, we couldn't be bothered to fix the problem? (That we created and you are suffering the consequences of)

They should move. Perhaps it would soften the blow if they were also told platitudes about fault and blame, but realistically (a) the problem is not going to be solved in time, and (b) the plight of a small number of people is not going to move the needle in regards to the willingness of the world to address the issue. People who still think that the damage can be averted entirely are just as deluded as people who think that sea level rise is an existential threat to human civilization.

This statement is bizarre. Have you seen what a sea-level rise map of Bangladesh looks like? Unless Bangladeshis start evolving gills I'm pretty sure the area where many of them currently live will no longer support humans.

The Dutch have been living below sea level for centuries. It’s not the end of the world and ultimately dikes cost a lot less than losing significant land area and moving massive population centers. A few places like Florida that are awkwardly situated above porous rock like limestone and have little elevation above sea level even well inland are kinda screwed, but for the most part sea level rise is an expensive but entirely solvable problem.

It took a huge flood to mobilize the political will to spend a fuckton of money on flood prevention.*

I feel like the problem with climate change is that by the time the effects get so bad that everyone will be on board to actually put a significant amount of resources into prevention and mitigation, it will be too late to do anything, because there is a time lag between ceasing emissions and the climate stabilizing. Additionally, all the greenhouse gasses you have already emitted are still in the atmosphere so just stopping emissions will only stop the heating up (if we are lucky) and not automatically result in the climate returning to "normal".

*: https://en.wikipedia.org/wiki/North_Sea_flood_of_1953

Building flood barriers is a lot cheaper and a lot easier to throw money at than reducing emissions. Barriers can also be constructed on a local or regional level, whereas emission reduction requires achieving an intractable global consensus. It doesn’t follow that the same dysfunctions that have prevented emission reduction will prevent the construction of flood barriers.

Putting up barriers won't stop the water rising. And the vast majority of small island nations won't be able to afford to wall off their entire landmass

As mentioned above, places with porous geology that have low elevation even well inland are not salvageable. And the vast majority of small island nations don’t contain very many people. It seems like the goalposts are being moved here from “sea level rise is an existential threat to human civilization” to “sea level rise will disrupt the way of life of some people”.

I see this argument all the time and it feels like I must be missing something. There is no way people actually believe the whole world can go Dutch, right?

I hope this doesn't come across as overly-aggressive, but it seems to me like you don't really understand much about how the Dutch lived below sea levels for centuries.

Yes, over many centuries, they have built all sorts of contraptions in order to gain more land from the sea or lakes. But this is expensive, takes up a vast amount of skill and planning and is only feasible in certain terrain. The Netherlands is also a small and very rich country. To believe that the whole world can do this is complete insanity.

The whole world doesn’t need to. A sea level rise of 2m doesn’t matter for most of the world, or even for most coastal regions. And of the coastal regions that will be impacted most can be sacrificed with limited disruption. For the much more limited areas of the world that are coastal, have low elevation even well inland, and are densely populated or otherwise economically valuable, flood control is totally realistic (with the exception of some places like Florida that are screwed by the underlying geology).

A massive amount of humanity lives on or near the coast. In the US, 40% of the population is coastal. The cost of walling off the entire coast would be astronomical.

I think you didn’t read the comment you responded to.

It seems like you understand very little about systems collapse.

A huge portion of our farming is currently unsustainable. Yes, we are producing more right now, but this production is on a clock. Even without any change in climate we are screwed. Look at how many places in the world are currently undergoing water system collapse. California, a huge crop producing state, has areas that have sunk nearly 30 meters because of pumping too much water. Those same areas are highly dependant on bringing in water from long distances away. Now add unstable weather patterns the the propensity for longer droughts and tell me what you think will happen?

We are not dealing with a climate change problem. We are dealing with

A long term water supply problem

A soil salinization over vast areas problem

A soil decarbonization problem over vast areas

Increasing temperatures that are pushing our current high yield crops to their limit problem

A globalized transportation system that will quickly spread crop diseases problem

Humanity is playing russian roulette with these issues. We will get a perfect storm one of these years, for example across the midwest US being hit by a drought and crop rust and we could see a near complete failure of our corn harvest. We are talking about the potential loss of 750 million tons of calories that will rock the world to its foundations.

We really should learn more about the Bronze Age collapse... Interconnected empires with hundreds and thousands of years simply vanishing in one generation due to a combination of wars, famine and possibly climate change in the Mediterranean. Supply lines got dismantled, a lot of technology was lost, Mycenaeans even forgot how to write!

Sounds like a cautionary tale to our current situation.

When the combination of heat and humidity gets high enough (look up wet bulb temperature) then it means death for even fit young people, even when sitting in the shade with access to drinking water. We are thermodynamically incapable of surviving too high of web bulb temperatures.

Huge swaths of the globe will experience fatal web bulb temperatures multiple times a year by the end of the century. Very clearly this makes a region "unable to support humans".

A large fraction of the human population have been living in parts of the world where the external environment is lethal for months of the year for thousands of years. It’ll certainly be an interesting development when air conditioning becomes a matter of life and death the way heating in winter already is in much of the world, but air conditioning is also much less energy intensive than heating.

I don't think it is reasonable to compare other hostile environments to one where humans are literally incapable of being outside for extended periods of time. Even in harsh cold climates, it is possible to wear suitable clothing, or build a fire. That is simple, resilient, low tech and low carbon. Requiring a structure with AC and power is a much larger challenge.

Furthermore, a lot of the areas that will suffer from fatal wet bulb temperatures do not have the wealth to provide AC to everyone. This will drive mass migrations of people on a scale we have never seen before, destabilizing neighbouring countries (or more likely, leading to mass murder).

Finally, this is another positive feedback loop: more AC required -> more energy required -> more severe global warning.

Cooling and dehumidifying a residence to a non-lethal temperature and humidity doesn’t take all that much energy or particularly expensive or sophisticated technology. And emissions from the residential electricity generation required isn’t a particularly pressing concern. Intermittent power capacity like solar and wind is most available at the same time it’s most needed for driving residential air conditioning, and large countries like India, China, Brazil, Nigeria etc that are going to be facing this issue don’t have the same paranoia about nuclear power that’s so common in the West.

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