As New South Wales suffers through torrential rain and flooding, climate change skeptics are attacking the forecasts of one of Australia’s most high profile and respected global warming campaigners, Tim Flannery.

Overnight, residents in the coastal city of Manly were warned they might need to evacuate because the Manly dam was at risk of overflowing.

Scores took to Twitter to berate Flannery, with one asking if, “the fake global warming guru” will apologise for saying in 2007, “even the rain that falls isn’t actually going to fill our dams and our river systems”.

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Flannery has long been an outspoken campaigner against the human prevention of climate change.

The respected professor believes humans need to improve their environmental habits while also planning for extraordinary events like droughts, with desalination plants used as an “insurance policy”.

He tried to explain himself further on Q&A in 2010, when asked by a climate change skeptic why cities were still at risk when water storages had replenished in Perth and Brisbane suffered record floods.

“The point I was trying to make is we need to act … we can’t just assume everything will be as it was,” he said.

“If nothing is done, and the trends continue, these cities will run out of water”.

While the professor has research to back up his beliefs, some aren’t as convinced.

Twitter user @Misty__Bella said the Sydney Storms meant, “#TheirABC scaremonger (was) exposed” while @Shescribes said, “haven’t seen #TimFlannery ‘it wont every rain in Sydney ever again’ anywhere around this week”.

#timflannery needs to be called to account. #climatechange https://t.co/LwnDGJi7us

— Raf Stary (@rafstary) April 21, 2015

Hey Tim Flannery. Guess what? It’s raining. Hahaha. Fool

— Warren (@bozowasher) April 22, 2015

Conservative commentator and climate change skeptic Andrew Bolt has led the campaign against Flannery, for what he describes as his “spectacularly dud predictions”.

As recently as September 2014, Bolt used figures from Professor Ross McKitrick to claim that there had been a ’19 year pause’ in global warming. 

“This is ‘the science’,” Bolt wrote. “Why do warmists keep ignoring it?” 

SkyNews Australia and The Australian commentator Chris Kenny took up the criticism of Flannery on Twitter, likening him to the left’s “travelling showman”.

Kenny said in early 2014, figures from the UK Met Office showed global average temperatures had stayed “steady” for the past 15 years.

“..we’ve seen just drought, drought, drought, and particularly regions like Sydney…water has been in virtual freefall..” Tim Flannery 05 — Chris Kenny (@chriskkenny) April 21, 2015

And yet the Left still consider Flannery to be more than a travelling showman. — Chris Kenny (@chriskkenny) April 21, 2015

Kenny and Bolt have no shortage of support to criticise Flannery’s forecast.

JUST IN: A message for the @climatecouncil to be passed on to Tim Flannery. More soon. https://t.co/L7ask18Nne — THE Journalist (@THE_Journo01) April 21, 2015

Can someone let Tim Flannery know the Manly Dam is spilling? Thanks. — Catherine (@catherine___c) April 21, 2015

Flannery was contacted by The New Daily for comment.