[radford-neal]

"Almost everyone on HN recognizes that climate change is an existential threat to (most) life on earth."

No. There are no even remotely plausible scenarios in which most life (say, all mammals, to pick something specific) go extinct due to climate change caused by human CO2 emissions. If you think that, you have been lied to - and have not been smart enough to recognize the lies.

[cbHXBY1D]

Did you read the recent IPBES Global Assessment? An article on it from the NYT: https://www.nytimes.com/2019/05/06/climate/biodiversity-exti...

"Unless nations step up their efforts to protect what natural habitats are left, they could witness the disappearance of 40 percent of amphibian species, one-third of marine mammals and one-third of reef-forming corals. More than 500,000 land species, the report said, do not have enough natural habitat left to ensure their long-term survival."

A summary can be found here: https://www.ipbes.net/sites/default/files/downloads/spm_uned...

[radford-neal]

Talk of "efforts to protect what natural habitats are left" does not seem to relate to warming from CO2 emissions. Except, that is, that if you're concerned about protecting habitats, you should be concerned about some of the boondoggles destroying them that are justified by "global warming" alarmism - such as replacing natural forests with monocultures of trees that are converted to pellets and shipped long distances to be burned in place of coal. See https://www.draxbiomass.com

Also, "one-third" is not "most".

[cbHXBY1D]

These percentages represent the percent of species currently threatened with extinction. The report makes it clear that the conditions which created our current ecological collapse are accelerating:

"Human actions threaten more species with global extinction now than ever before. An average of around 25 per cent of species in assessed animal and plant groups are threatened(figure SPM.3), suggesting that around 1 million species already face extinction, many within decades, unless action is taken to reduce the intensity of drivers of biodiversity loss. Without such action there will be a further acceleration in the global rate of species extinction, which is already at least tens to hundreds of times higher than it has averaged over the past 10 million years."

The report doesn't factor in insect decline and how that will effect the rest of the foodchain (they are the words biggest pollinators). It does bring up the staggering loss of insect biomass:

"Population declines often give warning that a species’ risk of extinction is increasing. The Living Planet Index, which synthesises trends in vertebrate populations, has declined rapidly since 1970, falling by 40% for terrestrial species, 84% for freshwater species and 35% for marine species (established but incomplete){2.2.5.2.4}. Local declines of insect populations such as wild bees and butterflies have often been reported, and insect abundance has declined very rapidly in some places even without large-scale land-use change, but the global extent of such declines is not known (established but incomplete){2.2.5.2.4}. On land, wild species that are endemic (narrowly distributed) have typically seen larger-than-average changes to their habitats and shown faster-than-average declines (established but incomplete)."

Edit: also, in the future, let's refrain from the "not smart enough to understand" style arguments on HN.

[mirimir]

> Talk of "efforts to protect what natural habitats are left" does not seem to relate to warming from CO2 emissions.

They're connected. I mean, everything is.

Even if we didn't emit so much CO2, we destroy habitat for other species through agriculture and forest harvesting. And if we hadn't destroyed so much habitat, there'd be lots more slack for CO2 emissions.

And as you say, destroying habitat through biomass energy production -- whether it's fast-growing trees for pellets, or palm oil for biodiesel -- just makes it worse.

[mirimir]

Very belated edit:

I was in a hurry, and didn't say how habitat loss increases extinction rates from global warming. The issue is habitat fragmentation. We degrade/destroy habitat for other species through agriculture, forest modification and harvesting, urbanization, road building, etc. But that not only decreases the amount of high-quality habitats. It also fragments habitats.

Without global warming, habitat fragmentation hurts other species in various ways. At some point, fragments become too small to support viable populations for many species. Especially larger animals, for example. But overall, it's not a huge issue, relative to the amount of habitat loss itself.

However, with global warming, habitat fragmentation becomes a huge issue. As the planet warms, species tend to shift toward the poles, more or less, to stay in habitats that they're adapted to. But when habitats are fragmented, that can't happen. And so you end up with isolated populations on mountains, for example. Given that "up" ~ "away from the equator". And with further warming, there's no more up, so they die off. One mitigation is creating habitat corridors. Through cities and farmland. Across roads, using bridges or tunnels. You can see habitat bridges in I-78 in eastern New Jersey.

Another factor is the speed of anthropogenic global climate change. It's too fast now for evolutionary adaptation.

[arcticbull]

Cutting off your thumb and half your forefinger is one-third of your hand, and I'm ok calling that 'most of' in context, especially if I hope to ever grasp things again :P

[madaxe_again]

Almost every one of your posts here is to refute climate change.

Someone could be forgiven for thinking you have an interest in fossil fuels.

Edit: I see from your CV that you have a history of working with the fossil fuel industry - specifically, Exxon in Calgary in the early 80’s. I think it’s safe to disregard anything you have to say on the topic.

[sctb]

> Please don't make insinuations about astroturfing. It degrades discussion and is usually mistaken. If you're worried, email us and we'll look at the data.

Besides this, it's rude to address other community members this way. Just email us at [e-mail] if you have such concerns, we take them seriously and we have better options for addressing them.

https://news.ycombinator.com/newsguidelines.html

[radford-neal]

You appear to be unable to count. I've posted occasionally on climate change, but these are nowhere close to "almost every one" of my posts.

I have never worked for Exxon. I've no idea how you came up with that idea. I once worked briefly, 39 years ago, for a company that did production accounting for oil wells. I once worked, 30 years ago, for a SCADA company that may have had oil industry customers, though my recollection is that they had more to do with municipal water systems. The tendency of global warming alarmists to claim, on no evidence whatsoever, that any critic is funded by the fossil fuel industry is one of their most despicable characteristics (up their with trying to equate their critics with Holocaust deniers).

[boulos]

Fwiw, I was expecting your quote to include a number >50%. Not that this wouldn’t be catastrophic, but most does mean more than 50% :).

Edit: though now I’m curious by percentage of animals (presumably 40% of species may be, or even is likely, more than 40% of animals, because of power-law-style distributions).

[rexpop]

The initial disappearance of even this minority is significant enough to impact the rest. Ecosystems are fragile, symbiotic systems.

[astazangasta]

Eh? There absolutely are plausible scenarios. For example, the Permian-Triassic extinction event was probably the result of runaway warming, perhaps as a result of the "clathrate gun": https://en.m.wikipedia.org/wiki/Clathrate_gun_hypothesis

This event resulted in 96% of marine species dying and 70% of land animals dying. I don't think anyone thinks such an event is certain or likely, but it is surely a "remote possibility".

[lisper]

Can we agree that it's an existential threat to technological civilization? And isn't that enough to conclude that urgent action is needed?

[akvadrako]

Of course we can’t agree it’s an existential threat. If you consider the people who study existential threats in general, climate change doesn’t even make the list.

I think we can agree there is a some risk of higher costs if climate change is ignored.

Most likely it’ll be beneficial though.

[travisoneill1]

The truth is that both sides ignore the science, just in opposite directions.