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Comment by matthewdgreen | Hacker News Reader

I don't see a path to global decarbonization that doesn't include major reductions in fossil fuel production, and I don't see a path to major reductions in fossil fuel production that doesn't produce major price variability in (fossil) fertilizer production inputs. It's good that we aim to reduce our datacenter energy usage, but that may not prevent the avoidable starvation of millions of people.

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Reducing car size and mileage would be a good start - I don‘t have numbers at hand for the US, but in Germany, the individual mobility via cars produces about 20% of the entire CO2. Even a speed limit would already cut that by a few percent. Immediately, as in „the day after the law is in force“.

In 2021, cars (trucks not included) used 60 billion tons of fuel in Germany alone and rising https://www.umweltbundesamt.de/sites/default/files/medien/38... Shutting down the BASF steamcrackers would be equivalent to a reduction of that fuel consumption by 0.5% or so. So, a speed limit would be more effective and faster to implement.

But that’s a holy cow no one touches, neither here, nor in the US.

Note that just because that would cut CO2 does not mean its worth doing. E.g. that speed limit could easily cost more QALYs (e.g. via longer commutes meaning more tired people and less quality time with kids and more spousal arguments) than are saved with it. Particularly if, for example, geoengineering via sunshades or somesuch proves viable this century.

Like civilization died in all the surrounding European states? It’s a bleak wasteland of people trecking for days to reach their workplace, ravaged by wars kicked off because a spouse got tired of waiting for their husband.

I’m sorry for the ridicule, but that’s frankly the worst argument I’ve ever heard rejecting speed limits.

I'm stating that it may not be worth doing. You'd have to actually do the maths to confirm either way.

Disclaimer: as a public transport user I have no dog on this fight.

I can try a back of the envelope I guess...

If I assume a time in a car is around 0.9x as good as average time (which feels about right to me and indeed seems to match actual usage with risk level tolerance from 40 years ago), assume moderately large speed limit reduction enough to increase travel time by 20% and use a figure of 10kg of CO2 per hour (seems about right looking at estimates of modern car gas consumption) and the NICE QALY value of £30k we get around £100 worth of QALY loss per ton of CO2. This is a bit over the largest estimates for a CO2 tax that would cover CO2 emission externalities ($100 per ton) (using the latest estimates for the costs of climate change over the next 100 years).

Given the large error bars in the rough work above, it looks quite plausible that the real calculation could go either way, with a speed limit possibly being net good or net bad.

Can I have something of what you are taking too make such nonsense more bearable? Just imagine what our grandgrandchildren will say when they rediscover such a comment, lol. I mean those having those sunshades then up in the sky...

The Netherlands has such a speed limit on its highways and it's quite effective.

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