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"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

"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 7y ago
Did you read the recent IPBES Global Assessment? An article on it from the NYT: https://www.nytimes.com/2019/05/06/climate/biodiversity-extinction-united-nations.html 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_unedited_advance_for_posting_htn.pdf https://www.ipbes.net/sites/default/files/downloads/spm_uned...
- boulos 7y ago
  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 7y ago
    The initial disappearance of even this minority is significant enough to impact the rest. Ecosystems are fragile, symbiotic systems.
- radford-neal 7y ago
  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 https://www.draxbiomass.com Also, "one-third" is not "most".
  - cbHXBY1D 7y ago
    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.
  - arcticbull 7y ago
travisoneill1 7y ago
The truth is that both sides ignore the science, just in opposite directions.
astazangasta 7y ago
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 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 7y ago
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 7y ago
  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.

cbHXBY1D 7y ago

Did you read the recent IPBES Global Assessment? An article on it from the NYT: https://www.nytimes.com/2019/05/06/climate/biodiversity-extinction-united-nations.html 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_unedited_advance_for_posting_htn.pdf https://www.ipbes.net/sites/default/files/downloads/spm_uned...

boulos 7y ago
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 7y ago
  The initial disappearance of even this minority is significant enough to impact the rest. Ecosystems are fragile, symbiotic systems.
radford-neal 7y ago
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 https://www.draxbiomass.com Also, "one-third" is not "most".
- cbHXBY1D 7y ago
  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.
- arcticbull 7y ago

travisoneill1 7y ago

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

astazangasta 7y ago

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 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 7y ago

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 7y ago
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.