What different ideas did scientists in the twentieth century have about the effect of adding carbon dioxide to the atmosphere?

In the 19th century, scientists realized that gases in the atmosphere cause a "greenhouse effect" which affects the planet's temperature. These scientists were interested chiefly in the possibility that a lower level of carbon dioxide gas might explain the ice ages of the distant past.

Explanation:

what was the

the right ones are in bold.

daintly refers to the fact she was reaching for what she ate, not necessarily what she is like.

greatest charm as in she possessed (=had) the greatest charm.

pleasant (her demeanor)

speaking (of her sensibility)

dead refers to the hypothetical mouse.

bleeding refers to the hypothetical mouse.