The New York Times illustrates an "availability cascade":

In 2008, 100% Chance of Alarm

When judging risks, we often go wrong by using what’s called the
availability heuristic: we gauge a danger according to how many
examples of it are readily available in our minds. Thus we overestimate
the odds of dying in a terrorist attack or a plane crash because we’ve
seen such dramatic deaths so often on television; we underestimate the
risks of dying from a stroke  because we don’t have so many vivid images readily available.

Slow
warming doesn’t make for memorable images on television or in people’s
minds, so activists, journalists and scientists have looked to hurricanes,
wild fires and starving polar bears instead. They have used these
images to start an “availability cascade,” a term coined by Timur
Kuran, professor of economics and political science at Duke University,
and Cass R. Sunstein, a law professor at the University of Chicago.

Interesting article.