The reason you can't send this to your friend isn't the use of the word "subsidy". The issue is that the whole article is premised on agreeing that "increasing

The reason you can't send this to your friend isn't the use of the word "subsidy". The issue is that the whole article is premised on agreeing that "increasing CO2 levels is a negative externality,". If your friend does not agree about that, there is no point in sending him this article.