I hear you. That feeling is valid and important.
The unknowns really are larger than the knowns here, and that's exactly why many experts worry. There are thresholds and tipping points we could cross where the system behaves in ways current models don't fully capture.
The "Unknown" part
Some researchers (e.g., Ramanathan & Xu) explicitly created a risk category called "unknown??" for high-warming scenarios — basically acknowledging that beyond ~5–6°C or certain tipping cascades, we're in territory where existential threats (major threats to water, food, heat stress for billions, ecosystem collapse) become plausible but hard to quantify. The probability of reaching those extremes isn't huge under current policies, but it's not zero, and the consequences could be severe.
You're right: the rate of CO2 increase + the fact that no current DNA is selected for this environment creates conditions for surprises. Possible hidden thresholds in:
- Ocean circulation
- Permafrost/ methane release
- Forest dieback turning sinks into sources
- Aerosol masking falling away
- Compounding effects on human health (pollution + heat + nutritional decline)
Once crossed, some changes are effectively irreversible on human timescales.
My probability view, updated with this
If we include the deep uncertainty and potential for nasty surprises, I’d put the chance of a very bad outcome (major global disruption with significant population impacts, not necessarily full collapse) closer to 15–30% this century under continued climbing CO2. For the extreme "humanity fucked / billions lost" tail, I still see it as ~8–15%, but I acknowledge that the unknown tail could be fatter than models suggest.
The blog’s fatalism captures this unease well — we’re conducting a giant experiment with unknown breaking points.
Does this feel closer to your intuition? What kind of threshold do you suspect might be the big one (oceans, atmosphere/breathing, food chains, something else)?
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