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Comment by dane-pgp | Hacker News Reader

> In many ways, this scenario is even gloomier than BAU, and many say that it predicts the dire outcome of allowing climate change to go unchecked.

But if they are using the same World3 model, created in 1972, with a single variable representing "pollution", then surely it's just a coincidence if the effects of climate change end up modelled correctly.

The climate is a non-linear system, and there certainly weren't good models for its influence on / from the economy back in 1972. If the model (even just the updated one) has managed to include some universal physical law that can predict the aggregate of the interactions between the global climate and economy, then that deserves much more attention than the clickbait "societal collapse" prediction.

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I thought that "pollution" chart showing it dropping off sharply in all scenarios (due either to clean technology or societal collapse) were unlikely. If you are counting CO2 as pollution (and you should) then it's very hard to get it back out of the air, especially in a short timeframe. So in all cases the pollution line ends up in a steady state at roughly wherever society either weaned itself from fossil fuels or collapsed.

"If you are counting CO2 as pollution (and you should)"

There is a caveat. They only consider CO2 from specific sources to be pollution, so we can't just blanket call it pollution. For example, the CO2 I exhale would not be considered pollution, but if it's coming from fossil fuels or even burning trees, then it is. I'm not sure how they handle the natural burning of tree, like wildfires though.

I am absolutely not a climate scientist but my understanding is c02 from the likes of us isn't a problem as we are naturally part of a cyclical process. Same goes for forest fires which is burning trees that had been absorbing carbon.

However we are releasing an excess amount that had been trapped and removed from that cyclical process, adding more energy into the system than its natural equilibrium usually takes.

"Same goes for forest fires which is burning trees that had been absorbing carbon."

This actually isn't true. They say they burning of trees requires such a long cycle time that the release of CO2 does contribute to global warming.

My main point was that this distinction isn't something that people commonly think about. Usually think mercury, sulfur, etc, which are not things we naturally emit.

Rather than burn coal to smelt steel beams, we could start opting for more timber frame construction and growing more trees, capturing carbon out of the air and turning it into housing.

A very rough ballpark estimate is that you'd need to use at least as much timber as we've mined coal. Probably a lot more since coal has a higher carbon content than timber and we've also burned plenty of oil and gas. That's a mind boggling amount of timber.

They are saying to stop using steel in construction.

Even a sin(x) function can be approximated as a line for small values of x. Potentially the predictions will start to diverge as feedback loops come into effect?

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