HEAR that rain on the roof last week? That’s nature telling us our politicians have been idiots. I’m talking about the politicians who let themselves be fooled into thinking it never would rain like this again.

I’m talking about politicians who listened to the likes of Tim Flannery, the 2007 Australian of the Year and then head of the Climate Commission.

From 2005 to 2008, Flannery, the global warming guru, made a string of outlandish claims like these:

“So even the rain that falls isn’t actually going to fill our dams and our river systems ...

“In Adelaide, Sydney and Brisbane, water supplies are so low they need desalinated water urgently, possibly in as little as 18 months ...

“There is a fair chance Perth will be the 21st century’s first ghost metropolis.”

Flannery wasn’t alone, of course. Greens leader Bob Brown in 2006 warned of a “permanent drought”, thanks to global warming.

Melbourne Water mourned: “Unfortunately, we cannot rely on this kind of rainfall like we used to.”

The Bureau of Meteorology’s head of climate analysis agreed, warning in 2007 that “climate change here is now running so rampant that ... almost every one of our cities is on the verge of running out of water”.

And politicians believed them.

In Queensland, Premier Peter Beattie decided to build a $1.2 billion desalination plant, saying “it is only prudent to assume at this stage that lower-than-usual rainfalls could eventuate”.

Labor politicians in every other mainland state built expensive desalination plants, too, rather than cheap dams.

Big mistake. Hear that rain?

The dams in Brisbane, Sydney, Melbourne and Adelaide we were told would be drained by global warming are instead at least 80 per cent full.

And in all of those cities, the desalination plants are mothballed or, in the case of Adelaide’s $2.2 billion plant, about to be.

But you’ll still pay.

New figures published in The Australian on Saturday show Victorian water users have so far paid more than $1 billion in charges for a plant that hasn’t produced water since it opened in 2012.

Sydneysiders pay $200 million a year for a plant that hasn’t produced water for two years.

The only effective plant is in Perth, which lacks natural dam sites — and rain.

Such colossal waste. Every drop on your roof should remind you of it.