Why there is CO2 in the air we breathe ?
Among other reasons, because our breathing creates it.
We need Oxygen while the air consist of other gases mainly nitrogen.
We need the other gases as well, among other reasons because if air were too rich on oxygen we would intoxicate or even combust.
And no, that isn't really evidence of design, but rather of natural selection. People who suffocate, intoxicate or combust on their own natural atmosphere do not breed succesfully very often.
God said that he created everything as to be in balance and he asked not to disturb it, the global warming is a result of it.
Trouble is, our existence is only possible by disturbing the balance to some degree or another. Sure, we must be aware of that and seek sustainability. But you make it look like a very simple decision, and it is not so.
Global warming is hardly the only ecological consideration we need to have. And I'm pretty sure it can only be found very allegorically and dependent on interpretation and artistic license, if at all, in either Quran or Hadith. Or for that matter, Christian scripture, Torah or Talmud.
And the earth -We have spread it out wide, and placed on it mountains firm, and caused [life] of every kind to grow on it in a balanced manner, 15:19
Surely you realize that, laudable as the verse is, it is not at all specific. It is not even clear that it means any ecological considerations.
So as we avoid CO2, we have to avoid snakes and lions and to keep them in the jungle where they supposed to be.
We do, in fact, need CO2. It is not breathable, but it is not exactly toxic either. And besides helping in keeping the rate of oxygen in our air within survivable levels, it is absolutely indispensable for plants' survival. And humans could hardly hope to survive without plants for food.