[rekabis]

Point of contention:

> It can no longer be denied: Climate change is progressing unabated and accelerating. In 2023 and 2024, global average temperatures were 1.5 degrees Celsius above pre-industrial levels for the first time. It is even possible that the 1.5-degree limit for global warming agreed upon in Paris may already have been permanently exceeded.

The value they are talking about is the political definition, and not the scientific definition. The political definition requires a +1.5℃ increase to be unbroken across a number of years - 20 years, as set by the IPCC - before it is “accepted”.

Not the first year in which warming never again drops beneath +1.5℃, but 20 unbroken years of said minimum.

Many scientists consider +1.5℃ to have been reliably and consistently breached at some point in the very early 2010s.

And by that same metric we might have already blown past +2℃, which may have happened by 2023.

The reason why this is so alarming is because +4℃ is the point at which megafauna - all animals over 45kg, like humans - can no longer survive on this planet. They go extinct.

There are adults alive today which will see this come to pass.

[Alpha3031]

> Many scientists consider +1.5℃ to have been reliably and consistently breached at some point in the very early 2010s.

Do you have a source for that? The 20 year average (not minimum) is considered reasonable to provide an estimate the GWL 10 years ago and is simple to calculate but obviously we'd only have the data going up to 2015 if using those.

I don't think there are any, even current-year GWL indicators that have us at close to +2℃ above the standard 1850-1900 reference. LOESS is probably the simplest one (the others are usually 10 years of observations + 10 years of projections) and that was ~1.31 [1.16 — 1.42] in 2023 according to https://climate.metoffice.cloud/current_warming.html and 1.44 ± 0.09 °C for 2025 according to https://berkeleyearth.org/global-temperature-report-for-2025...

[adrian_b]

While I do not know directly about what happens in distant places on Earth, where I live in Europe there are about 15 years since the last time when I used my winter clothes and my winter boots.

When I was young, where I live there was permanent snow cover from early December until late March.

All the historical sources from hundreds of years ago mention similarly heavy winters.

Now there is more than a decade since there was any snow that lasted more than a day before melting.

So I find it strange when there are people who are still skeptical about the reality of climate warming.

[Alpha3031]

+1.4 °C on average is pretty serious warming, I don't know how you got the impression I was "skeptical about the reality of climate warming". I'm even willing to believe that AR6 WGI is more conservative than it should be on GMST and underestimating current levels, seeing as they have previously underestimated things like sea level rise, but I don't think I am out of line for actually asking to see those alternate estimates which put us potentially above +2 °C from the preindustrial reference before accepting such a conclusion.

[hyperhello]

In what way does +4C kill all animals exactly?

[rekabis]

Desertification, wet bulb temperatures, heat stress, loss of food in the environment, ecosystem collapse due to climate change happening too fast for ecosystems to migrate, and the massively increased range required to find food causing them to not find mates.

[RetroTechie]

To add: ratio of surface area (skin, sweating/cooling), versus volume/weight (muscle activity, biochemical processes etc).

The bigger the animal, the harder it is to keep cool.

[rekabis]

Yes, I tried to encapsulate that within the term “heat stress”, but thank you for laying that all out for those not in the know.

[enraged_camel]

We are already living through a mass extinction event: https://www.worldwildlife.org/news/press-releases/catastroph...

+4C would be game over.

[rekabis]

And capitalism demands the “business as usual” path that is also the worst-outcome-possible path.

Wholesale civilizational collapse has already been modelled to occur between 2035 and 2045 to an extremely high degree of confidence, with a 50-80% collapse in human population to occur before the end of the century. You can’t maintain a post-iron-age civilization through that degree of collapse.

I would even posit that a post-bronze-age civilization would be difficult enough to maintain. Because you need a fair amount of tech to work iron on scales larger than a blacksmith’s shop.

And these models do not include major attributes of climate change, such as wet bulb temperatures forcing billions to migrate into first-world countries to survive, or how regional ecosystem collapses cause trophic cascades that ripple around the globe. They only looked at simple things like desertification, topsoil loss, chaotic weather (unreliable rainfall) and so forth.

[RetroTechie]

True, high-tech supply & manufacturing chains are hard to mantain if social structures break down (as is happening already).

But you'll probably see large-scale crop failure first. It's simply not possible to grow the world's food supply indoors.

Migrant flows, political chaos & wars can do the rest.

Imho it's too strong to say that will happen worldwide. But on local (country/regional) scales? Absolutely.