Though the Limits folks do NOT, contrary to sloppy reading of the book, attempt to predict specific outcomes on specific timeframes, they DO look at the long-term implications of various policies.

For example, they take the assumption “if you use a non-renewable resource faster than it gets replaced, you will eventually run out” and build a model around it. Surprise–you eventually run out of your resource. You can tweak the parameters and assumptions about how much you have to start with, but all that changes is the amount of time before the resource tanks.

The 30-year update takes an oddly optimistic tone, even while examining 12 different combinations of policies in an attempt to find combinations that don’t lead to global collapse of one form or another. Almost all scenarios lead to one form of collapse or another. The only difference is what triggers the collapse (pollution, resource shortage, lack of farmable land, etc.) and how long we can go before it happens.

The only sustainable scenarios require shifts in many sectors at once. We need more renewable energy usage, achieve better resource distribution [poor people have more children, as that's the only form of old age security they have], etc.

If you haven’t read the book, I highly recommend it. While they don’t make specific recommendations, they clearly show combinations of policies that do and don’t lead to global collapse.

- Stever