[esarbe]

It's very likely an existential threat.

We're currently on-track for a +5°C increase in temperature by 2050. Besides wreaking havoc to all existing ecosystems, it's also very likely that this will kill off most of the phytoplankton in the oceans. That's the stuff that makes most of the O2 for us.

There's no way we (humans) are going to survive this scenario.

[sleepysysadmin]

>It's very likely an existential threat.

Al Gore is of the opinion that it's not. You can take that with a grain of salt because Al Gore's predictions have been quite incorrect. He claimed the Icecaps would be completely gone 6+ years ago. He claimed Florida and India would be under water today.

>We're currently on-track for a +5°C increase in temperature by 2050.

I'm happy to tell you that it's not. The source of this is the IPCC report from 2014. The claim comes from RCP8.5 https://en.wikipedia.org/wiki/Representative_Concentration_P...

RCP8.5 was never an expected prediction, it was a theoretical worst case of some unknown huge increase in carbon emissions. When in reality, humanity has done some amount of decrease. The RCP8.5 claim is basically considered wrong now. In fact we are on track for RCP4.5 despite not doing what IPCC says we need to do to reach this. This is great news.

We also know fossil fuels mostly run out in around 2050-2060. A simple reality that even if we don't do anything, we simply run out and must adapt to life without fossil fuels.

So we are going to peak about 1.4celcius warmer. We are around 1celcius already. Therefore, we don't have much more to go.

>There's no way we (humans) are going to survive this scenario.

The reality is that climate change is impossible to stop; in fact it's probably a disaster to try to stop climate change. In the past 50 million years the earth has dropped 14 celcius. Between 20,000 years and 10,000 years ago we have increased 7 celcius.

Just 125,000 years ago the Earth was 2-4 celcius warmer than today: https://en.wikipedia.org/wiki/Eemian#Global_temperatures

Humans didn't affect any of these events. The climate changes, we shouldn't try to prevent it.

[esarbe]

> We also know fossil fuels mostly run out in around 2050-2060.

We don't know that, it will just get more expensive to extract it. And given that beneath the ice shelves of the arctic are untapped vast reserves of oil, we cannot even expect that to remain true anymore. Norway and Russia are already preparing exploitation of these reservoirs.

> So we are going to peak about 1.4celcius warmer.

At about 1.5 to 2°C we're going to see the methane in the East Siberian Arctic Shelf starting to be released. We were expecting this to start in the 2040ies, but guess what; it already started and we've seen the increase in CH4 ppm from 2018 through 2020. And while CH4 quickly degrades in the atmosphere, the release will very likely trigger a feedback loop that at about 3.0 to 3.5°C will start melting the suboceanic frozen CH4. This will then kick us easily up to 5°C (or above).

The IPCC models don't include any trigger points or feedback loops because our models are just not sophisticated enough.

> The climate changes, we shouldn't try to prevent it.

The climate change we're currently experiencing is human-made. It's orders-of-magnitudes faster than anything we see in the records. To say that this is just the same as the natural fluctuations of climatic behavior over tens of thousands of years is false equivalence. We definitely must do something about it or face extinction as a civilization (and possibly even as a species).

[sleepysysadmin]

>We don't know that, it will just get more expensive to extract it. And given that beneath the ice shelves of the arctic are untapped vast reserves of oil, we cannot even expect that to remain true anymore. Norway and Russia are already preparing exploitation of these reservoirs.

The cost - benefit scenario and amortization reality. IPCC's position seems to be saying CO2 peaks around 2040 and then declines. Though I believe I was adding slightly to those figures saying 2050-2060. I'm not sure it's that plausible to predict that far in advance anyway. There's a very long history of bad predictions that harm the climate change movement.

>At about 1.5 to 2°C we're going to see the methane in the East Siberian Arctic Shelf starting to be released. We were expecting this to start in the 2040ies, but guess what; it already started and we've seen the increase in CH4 ppm from 2018 through 2020.

Right, just like what we saw during the Eemian period. https://en.wikipedia.org/wiki/Eemian

The Eemian was 2-4celcius warmer; but there was no extinction despite it coming on very rapidly. There was migration. Florida people might prefer Michigan for example. Michigan might like Manitoba but overall life will very much flourish greatly; just like it did during the Eemian.

>And while CH4 quickly degrades in the atmosphere, the release will very likely trigger a feedback loop that at about 3.0 to 3.5°C will start melting the suboceanic frozen CH4. This will then kick us easily up to 5°C (or above).

Admitedly I'm not sure I followed. Like the link I provided. IPCC is predicting only 1.4c increase. Could you point to where the IPCC got that wrong?

>The IPCC models don't include any trigger points because our models are just not sophisticated enough.

I feel like this is a bad argument because if the IPCC models are bad, then I question the beginning assertions that climate change is even happening.

>The climate change we're currently experiencing is human-made. It's orders-of-magnitudes faster than anything we see in the records. To say that this is just the same as the natural fluctuations of climatic behavior over tens of thousands of years is false equivalence. We definitely must do something about it or face extinction as a civilization (and possibly even as a species).

https://en.wikipedia.org/wiki/Geologic_temperature_record#/m...

50 million years ago during the Eocene, the world was 14 celcius warmer. Life thrived. Yes, humans would not survive during this period. However, nobody is saying that we will reach that much warmer via our industrial endeavours.

You can also see like the Eemian, every 125,000 years temperature spikes on Earth and then slowly cools until the last glacial maximum and then spikes again. We should expect a similar spike.

Yet even with human caused warming, the predicted rise isn't as high as the Eemian.

In fact, we will never really know but between 20,000 and 10,000 years ago the world warmed 6 celcius. Then over the last 10,000 years it has fluctuated +- 1 celcius like the IPCC is predicting.

I don't think we understand the interglacial periods. https://en.wikipedia.org/wiki/Interglacial#/media/File:Ice_A...

We haven't quite gotten to previous maximums before; but predicting that we are facing extinction because of these interglacial periods seems far fetched.

[esarbe]

> Admitedly I'm not sure I followed. Like the link I provided. IPCC is predicting only 1.4c increase. Could you point to where the IPCC got that wrong?

From the report: "This report uses mainly RCP2.6 and RCP8.5 in its assessment, reflecting the available literature. RCP2.6 represents a low greenhouse gas emissions, high mitigation future, that in CMIP5simulations gives a two in three chance of limiting global warming to below 2ºC by 2100. By contrast, RCP8.5 is a high greenhouse gas emissions scenario in the absence of policies to combat climate change, leading to continued and sustained growth in atmospheric greenhouse gas concentrations."

In my estimation, you too easily dismiss RPC8.5 and take the RPC2.6, the high mitigation, low emission scenario, as the default one. We're not currently on path for RPC2.6 and given that no industrial nation responsible for any significant proportion of our CO2 output is anywhere near meeting the necessary reductions, I dare say we're rather nearer somewhere a high-emission, low mitigation scenario.

> I feel like this is a bad argument because if the IPCC models are bad, then I question the beginning assertions that climate change is even happening.

No need for that. We've seen in the past that the climate models tend to be very 'conservative' in the changes they predict. But there are many known path-dependent variables, feedback loops and tripping points that are missing from most of the models. So, if anything, incorporating these into the climate models would result in much more dramatic changes. (see https://e360.yale.edu/features/as-climate-changes-worsens-a-..., https://www.weforum.org/agenda/2019/12/climate-change-tippin...)

> The Eemian was 2-4celcius warmer; but there was no extinction despite it coming on very rapidly. There was migration. Florida people might prefer Michigan for example.

A change in 2° C will already result in migrations that will put a never-before pressure on our political systems. We've seen the effects of a 'small' migration wave during the more active phase of the Syrian civil war, where we had some 6 million refugees. The refugees from the changing climate will number in the hundred of millions. We can expect some quite volatile situations to arise from this.

[esarbe]

Sorry, I didn't really get into this claim in my previous reply. I meant to, but then forgot. :/

> In fact we are on track for RCP4.5 despite not doing what IPCC says we need to do to reach this. This is great news.

From my current understanding, that's not the case, is it?

https://www.sciencedaily.com/releases/2020/08/200831112101.h...

https://www.sciencemag.org/news/2020/07/after-40-years-resea...

https://www.pnas.org/content/117/33/19656