I was meeting a client yesterday at their office, they offered me coffee and asked me if I wanted milk, then whether I'd like oat or regular. I said regular (usually drink oat but was somehow preoccupied) and the response was "yea, fortunately that's still available". To me that was a pretty striking example of how the realities of what climage change is going to push us towards are sinking in.
Probably someone somewhere out there already is and we’ll start seeing the headlines, blogs and podcasts about it in the near future. By building our societies around globalization, we have in some ways made our societies necessarily globalized. Everything we import/export has a fuel cost including ourselves when we’re the passengers, and that cost doesn’t stop at National borders, but incurs every time we move anything anywhere any distance.
So when you have a popular crop, coffee, almonds, tea, coconuts, whatever that can only be grown in certain parts of the world, it is going to have an outsized impact on the global fuel economy relative to crops that are grown and consumed locally. The more fuel we consume, the greater the amount of carbon emissions we output, and carbon dioxide only has a global warming potential of 1 (as the base unit). Methane has a GWP of 86 across a score of years and 34 across a century.
Now so far as I know, the GWP metric is only used for individual gases, but if you were to try to isolate it on a commodity by commodity basis, I’m betting Cow’s milk as transported to and sold in the supermarket today wouldn’t look great. I’ve worked in a cafe and I know approximately how much milk we went through in a week, often because I was the one buying it. Even a small mom and pop café can easily go through 40+ gallons a week, and that was hardly the only dairy product sold (cheeses of all sorts, whipped cream, ice cream, cheese cakes, chocolate cakes, pastries). I don’t even want to think about the amount of milk a single corporate chain like Starbucks or Peet’s goes through on a weekly basis.
Fortunately cow’s milk is still available. That is really an understatement on your client’s part. I think humanity will sooner die out or go back to a technological dark age from which it never fully recovers before we give up cow’s milk in its entirety in just the US, never mind the rest of the world.