Ancients stood on shore and watched the tall masts of ships appear and disappear over the horizon. They observed the shape of the moon. They, also, observed lunar and solar eclipses. The educated people who were astute knew that the Earth was curved, hence round. This, combined with other observations, enabled them to then calculate the size of the Earth. The average common man could have understood that the planet was round if it'd been explained properly, though he'd not have necessarily understood the geometry used to determine its size. The simple minded person would not have been able to comprehend these inferences.
Today, we see ancient
glaciers and Greenland melting away, ocean levels rising, world
temperatures slowly and steadily increasing as weather patterns shift.
We observe increasing CO2 levels in the atmosphere and
the acidification of the oceans. We find that methane hydrate is
gassing out from ever deeper depths of the ocean as well as from the
melting tundra. The inference that increasing levels of greenhouse gases
being released can only amplify the temperatures now and in the future
is hard to ignore.
Evangelicals should note that though God
promised us that he would not destroy mankind again, He did not indicate
that He would stop us from destroying ourselves.