All organisms naturally release carbon dioxide as a product of respiration. Why was global climate change not an issue in the past as it is today ?

Because of humans

Explanation:

We have polluted the Earth so much. There are tons of plastic in the ocean and ice caps are melting faster and faster. Smoke from factories and vehicles are destroying the ozone layer making it even hotter.

i believe the answer is a or 1

"1. it should be, it has been for about 20 years, and it's really not much different in the end than breeding animals to have particular traits. there are always concerns about genetically engineered animals/plants affecting the environment in unexpected negative ways, but i can't think of an example where the fears didn't turn out to be baseless.  

first, as you point out, it would be a great advance in pharmacology, to be able to tailor drugs and their doses to me. the pros involve better medical treatment. the cons involve privacy issues like insurance companies denying coverage to people with genetic risk factors. looking at dna markers wouldn't affect the frequency of genetic diseases, but it would allow detection of them earlier. and ok, actually i suppose that if people used this information to avoid having children with genetic diseases, some might decrease in frequency."