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Comment by JoshTko | Hacker News Reader

Given that the energy needed to change ocean temp is massive and the current momentum, no tech solution will be able to prevent ocean ecosystem collapse of 90% ocean lifeform death. We're probably past the point of no return already.

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Why do so many people believe this notion that current trends of warming imply looming mass extinction? What is the argument or evidence for this?

As others have explained, there is the unprecedented loss of diversity of species and change in climate. I’d add that there’s also no evidence this will slow or stop (at least that I’m aware of), but there is mounting evidence that it will continue and even accelerate (which we are possibly even witnessing today).

The loss[1] of diversity is primarily due to the way we abuse the ocean - bottom dredging of shellfish beds destroying whole slow-growing ecosystems, dumping sediments, toxins and excessive nutrients (which amount to toxins) in the ocean via runoff from land, indiscriminately catching whole populations of free-swimming fish, and so on.

Climate change is just the cherry on top, really, compared to our other efforts to reduce biodiversity.

1. I don't know why we use the word "loss", which implies an accidental outcome, when we're systematically setting out to plunder and strip-mine ecosystems.

Do you know if diversity collapses in the ocean is more severe than on land? I know vast deforestation and destruction of the water cycle (either by reduction or degrading via pollution) has a virtually incalculable impact on this, but perhaps in the ocean it’s even worse.

Warm water can’t solve as much oxygen, plus there are plenty of self-reinforcing effects that might have already started happening.

Life won’t die, we had plenty of mass extinction, but most of current species do like their oxygen. Also, their shells.

But there's also plenty of negative feedback processes. Why assume there'll be extreme runaway apocalypse from the warming.

There's negative and positive feedback processes. On balance the positive feedback processes outweigh the negative ones. e.g.

* Melting ice caps mean more heat absorption

* melting permafrost releases methane

* Warming oceans freeze frozen methane

I'm forgetting a bunch, doing this from memory. What negative feedbacks do you believe outweigh these?

What’s runaway is our rate of change in releasing co2, compounding annually at something like 1-2%

Why assume there won't be? Seems like the risk there is greater.

The mass extinction isn't looming. We're in the middle of it right now.

The current mass extinction doesn’t have much to do with the climate crisis though, it’s caused by good old fashioned massive exploration of the environment for human gain. (This is, of course, not a good thing. It’s an already massively fucked with ecosystem that climate change is causing increasing strain in)

> Habitat destruction is the leading cause of biodiversity loss.

https://en.m.wikipedia.org/wiki/Habitat_destruction

> Why do so many people believe this notion that current trends of warming imply looming mass extinction? What is the argument or evidence for this?

A truck filled with ecological research

The velocity of change is historically unprecedented and we have a good amount of empirical evidence of what it takes to collapse ocean ecosystems.

We’ve been collapsing ocean ecosystems simply through fishing.

200 million tonnes of seafood per year is an unprecedented and unsustainable change. Global warming will of course make things worse but it’s not like the oceans are currently healthy.

historically unprecedented

Unprecedented in the last 100 years, million years, or 500 million years? That's a lot of precedent with some major and rapid climate changes.

Pre-history usually refers to a time period approximately up to the invention of writing, so some several thousand years. If your time scale is the past 500 million years, there have been some real big mass extinctions to go along with those rapid climate changes. Not sure that's an encouraging precedent.

The climate has rapidly changed throughout Earth's history. Our current period of warming over the past couple of centuries began at the end of a mini ice age, so its not surprising temperatures rise when exiting the ice age. Just like its not surprising that temperatures rise after winter into spring & summer. CO2 is more likely a side effect of warming, coming from the warming ocean, than it is the driver of the warming.

This is just badly wrong and ignorant. Ask anyone who's actually studied the interglatial periods - in other words, the scientists who've provided the temperature information you're referring to - and they'll tell you why you're wrong.

Unprecedented in the era of human farming is sufficient enough for my worry. Yes, life as a whole probably survives whatever happens in one form or another. But those rapid climate changes tend towards seriously limiting the resources available to species living through them. Modern civilization relies on keeping things in a situation where it’s possible to grow enough food to feed 7+ billion people, and I’d rather we not create our own mass environmental change that has a serious possibility to disrupt said food making process.

Are you aware of the climate and antmosphere ever changing so abruptly according to ice core records?

Ice core records don’t go back that far. But some past mass extinction events were believed to be caused by more rapid climate swings resulting from asteroid impacts etc.

The thing about our situation is that no asteroid strikes or major geological events have occurred. So we know it’s possible to have major swings, but it’s less clear that they should occur without some obvious trigger.

What resolution does ice core records have? Do they really show year-over-year change or are the core records being smoothed through natural processes?

I read a book about this once, forget the title. Greenland’s cores have clear annual layers for several thousands of years (validated by extra ash layers from known volcanic eruptions), and they can measure carbon and temperature from the isotopes trapped inside (temp is measured due to some effect of oxygen isotopes following a reliable temperature gradient or something like that, they had a couple independent measurement methods that matched up). At some point the compacted layers start to merge but they can still reliably estimate because the overall cyclic trends (on multi thousand year scales, due to mathematically regular wobbling of earth’s rotation and other factors) follow the same trends from the clearly annual layers. This goes back several hundred thousand years, with temp increases always following carbon increases.

Edit: the book was The White Planet by Jean Jouzel, Claude Lorius, and Dominique Raynard

Great questions, and I don’t have the answers. I’ll definitely look into it though.

These ocean-surface temperatures concern the top few millimeters of the ocean. The thermal mass in question is far far lower than the ocean itself.

> only the top few millimeters

This is not how we measure ocean surface temperatures. The researching cube is sink entirely. Two m deep is still surface.

Apparently the meaning of 'surface' depends on the article. From wikipedia " The exact meaning of surface varies according to the measurement method used, but it is between 1 millimetre (0.04 in) and 20 metres (70 ft) below the sea surface." https://en.wikipedia.org/wiki/Sea_surface_temperature

My understanding of this came from an article Karina Von Schuckmann, for which I can't find the PDF right now, which said they were measuring the top few millimeters.

One thing is the definition of the surface layer of water (0 to -20m correct) and other how to measure its temperature.

If you use a floating thermometer the sun-rays are probably warming it or the winds are cooling it, so you are including an error in your sample. The results are higher or lower water temperatures than the real ones.

It is assumed that the water layer mix uniformly in the first meters by wave forces and wind so we can measure surface at 10m perfectly

Ad absurdum, dust in the higher parts of the atmosphere can cause to literally freeze over the whole planet.

I am no optimist, but not due to technological limitations, but economic ones — the only hope is “unknown unknowns”. We might invent some new technology that could wipe clear our existing estimates for the better.

In the last few million years there were massive swings in Earth (and sea) temperature.

A couple hundred million years ago there was a warm era, there were no ice anywhere on Earth.

I can see how climate change might be highly destructive to human habitat, but "90% ocean lifeform death" is the best excuse for not taking climate activists seriously.

It all depends on the rate at which things change. Greenhouse gasses we emitted already changed temperatures faster than ever before (1ish °C in less than 2 centuries). Nature doesn't have time to adapt to such a repentine change and so another "great dying" is a concrete possibility.

https://xkcd.com/1732/

Also, oxygen and CO2 solubility changes heavily with temperature.

Did it also fluctuate as quickly in the past?

I bet it did when meteor struck Earth.

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