Even if human populations were to cease all greenhouse gas emissions immediately, dramatic climate changes now appear inevitable over the coming millennium, a new study says. (CBC)

A study predicts there will be havoc akin to a big-budget Hollywood disaster movie in the next 1,000 years — even if people stop emitting all carbon dioxide into the atmosphere now.

Researchers from the University of Calgary and Environment Canada's climate centre at the University of Victoria say coastal areas will flood and the Earth's land mass will shrink as global sea levels rise by at least four metres over the next millennium.

They also believe parts of North Africa will dry out by up to 30 per cent and ocean warming is likely to trigger widespread collapse of the West Antarctic ice sheet, a region the size of the Canadian Prairies.

"It's probably slower playing than some of the disaster movies," said Shawn Marshall, a geography professor at the University of Calgary who holds the Canada Research Chair in Climate Change.

"We were kind of surprised by the result, actually. Even if we change behaviour and totally change society, we're still in store for a lot of bad scenarios. I feel a bit defeatist from it."

'There's a lot of legacy in the choices we make this century … just realize that these changes we're making to the atmosphere do have a long-term effect.'—University of Calgary geography professor Shawn Marshall

The team used computer modelling to speculate how the world would change by the year 3000 in a "zero emissions" scenario. The results are published in Sunday's advanced online publication of the journal Nature Geoscience.

The Northern Hemisphere fares better than the southern in the model, with patterns of climate change eventually reversing within the 1,000-year time frame in places such as Canada.

"Canada and Russia would fare the best," Marshall said. "I don't think you'll find many people really complaining about a five-degree warming. Canada is in a good position globally — there's no question about that."

The continued heat in Africa will create food shortages, however.

"In Africa, it just gets worse, but then other countries like Russia and Canada could get better. It's just a matter of whether we can reach some kind of model of global co-operation."

'Business as usual' dooms Arctic sea ice: forecast

Since zero emissions is not going to happen in the foreseeable future, the researchers also plotted out what will happen if the world keeps a "business as usual" approach."If we drop dead with emissions right now, the Arctic sea ice gets worse for another 10 or 20 years but then it comes back — so by 2100 it's back to what we're used to.

"If we keep business as usual, the sea ice in the Arctic is mostly gone."

Marshall said the most realistic scenario probably falls somewhere in the middle.

He hopes people will take away from the study that serious efforts to cut greenhouse gases need to be made now to mitigate the damage.

"There's a lot of legacy in the choices we make this century. We're seeing a lot of the early signs of climate change. If you're looking at a risk analysis, just realize that these changes we're making to the atmosphere do have a long-term effect."