Which doesn't really matter because people don't put milk in their coffee to add x amounts of calories. So in almost all cases, they will use the same amount in volume/weight.
And a lot of other plant based milk alternatives have an even lower environmental impact, the difference between your average milk and milk alternative will be even bigger.
Meaning in terms of actual nutrition vs pollution, cow milk is over twice as effective.
Calculation= cal in alm milk/cal in alm milk : cal in cow milk / 2 × cal in alm milk. (2 in this equation stands for the rate of pollution multiplicity sourced from the title of this post, twice as much gasses).