To be fair, he did not say countries would flood by 2000, he said if not reversed by 2000 countries would flood. We are seeing more flooding among the most susceptible cities (Venice most recently). The data he used predicted a 1-7° rise in temperature over the next 30 years and the reality (1°) fits that window.
I agree that alarmists consistently overstate their cases, but alarmists are the only ones who get the headlines.
A couple years ago I looked closely at the actual historic climate data - skeptically - and calculated the probability of last century's sharp increase in temperature happening randomly at no more than 20%** (NASA, even under the current administration, says there is a 95% chance humans are contributing to climate change). Yes, there is still a chance the temperature fluctuation is part of the noise of natural cycles, but the odds are at least as against it as going all in preflop with pocket kings against pocket aces: it is not a bet you want to make...
** As a skeptic, the main potential flaw in the prediction is the reliance on proxies for temperature. But while any individual temperature proxy (like tree ring or coral growth) can have significant error, combining hundreds of corroborating proxies greatly reduces this risk.