Climate Crisis, Biosphere & Societal Collapse

Good news, we're on track to blast right by that!

This study is indeed disturbing, drawing on multiple lines of evidence suggesting melting may happen faster than previously assumed, I'll study more.

However, there never was any magic safe (global-average-surface-) temperature level, to save polar ice sheets. Melting, and the penetration of heat, is cumulative, so to a first approximation it is the integral of the warming that counts (maybe we could talk about a heating budget, similar to the concept of carbon-budget to avoid a specific temperature).

Although diplomats may stress that the concept of safe level is baked into Article 2 of the Climate convention, that orginally applied to "concentrations" not temperature. Back in the day (early 2000s) I among others pushed (this wasn't easy) to adopt temperature as a goal closer to real impacts, pointing out that required peak+decline concentration pathways.
Nevertheless we always knew that a stable (higher) temperature does not bring a stable sea-level (on a multi-century timescale) . While for some other types of impacts - e.g. ecosystem adaptation, it may be the rate (derivative) rather than the integral that matters more. The 'level' concept was a compromise to coalesce policy (within which - round numbers like 2.0 or 1.5 C also arbitrary).

Maybe it could help motivate the global debate, to specifically (dis)agree goals of sea-level rise we try to avoid ? That's a more tangible level ( at least until we get into regional sea-level-rise variations...) , but due to the double integral, it's harder to implement.

While globe has warmed significantly since 2010, the Arctic has not significantly. Though starting in 2010, 3-5C warmer than 1995 with most of the warming from late August to April. Simply, as the Arctic loses ice, warmer oceans boost air temperatures that feed into warmer oceans, and slower refreezing in winter, with less maximum ice extent.

Arctic ice volume will decrease even if peak summer temperatures in Arctic don't change from post 2010 levels, which is about 1C higher than 1995 levels. About the same as global summer temperatures differentials in last 2 years. Even as 2023 and 2024 global temperatures made a large step up, Arctic temperatures are still clustered in post 2010 era.

Antactic sea ice has finally decreased starting in 2022. Similar feedbacks can occur, and much of the coast gets exposed in peak summer now.

Sea rise is about the land in polar areas. For Arctic, Baffin sea, Canadian Islands, and Hudson Bay temperatures and clearing are most impactful to Greenland. Antarctic, any clear ocean will impact it, but specific glacier shelves are more vulnerable to clear ocean impacts.