Shipping is highly efficient per product. I can't imagine this would have much of an effect.
In other words, it's not marginal numbers that matter, it's absolute numbers, and something absolutely has to be done about those numbers.
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[0]: https://www.weforum.org/agenda/2020/10/shipping-industry-car...
In a world that has climate change under control, there's for sure going to be a reduction in pollution produced by global shipping, but in the world we live in there's much better places to start than by limiting global shipping.
That said a carbon tax certainly does limit shipping, as some of it will no longer be profitable. Fortunately when doing it with a carbon tax, it just so happens to be the shipping that we shouldn't have been doing in the first place!