Ocasio-Cortez was touting her "Green New Deal" program at a NAACP forum Wednesday when she addressed critics who have called her plans "not realistic."
"What is not realistic is not responding to the crisis -- not responding with a solution on the scale of the crisis," she said. "Because what's not realistic is Miami not existing in a few years. That's not realistic. So, we need to be realistic about the problem."
In a video last month, Ocasio-Cortez said the alternative to large-scale solutions was large amounts of people dying from climate change's impacts.
"We need to start getting comfortable with how extreme the problem is," she said, "because only until we accept ... how bad climate change is and how bad it can be for our children's lives, are we going to be comfortable pursuing really big solutions."
Conservatives previously mocked Ocasio-Cortez when she suggested that the world only had 12 years to support life because of climate change.
Ocasio-Cortez, in turn, derided Republicans for failing to recognize what she described as "sarcasm."
The freshman congresswoman has also called for a ban on single-use plastic and predicted that melting glaciers could release ancient diseases with unknown effects on humans.