The author has some freedom to choose how to define death in this case, yes. But then he should include the definition he used. Otherwise it's just fear mongering.
I can understand that you might think other people would be misled by the rhetorical structure... but I encourage you to not get upset at imagined misunderstandings on behalf of others. (Not that it's wrong, it's just makes your life a little less happy)
The problem is, global warming is largely an issue _because_ of the "misunderstandings on behalf of others", so in this case, it is a real issue.