An 8C rise would occur if we kept burning fossil fuels, which would change the face of the planet, a climate scientist says.

Q: What would happen to the atmosphere if we burned all our fossil fuels?

A: Professor James Renwick, school of geography, environment and earth sciences, Victoria University says:

If we were to use up all of our planet's fossil-fuel resources, we'd increase the global average temperature by about 8 degrees Celsius globally by 2300, Canadian scientists report in Nature Climate Change.

The estimate is realistic, given the physical processes included in the models analysed.

The results are consistent with results shown in the last Intergovernmental Panel on Climate Change report, where the extended scenario: RCP8.5 – the one where we just keep burning the fossil fuels – showed warming of 8C or 9C by 2300.

The estimates in this paper are realistic – and very worrying.

An average warming of around 8C would take the climate into a vastly different state.

The Arctic has a more extreme temperature increase - this is a symptom of what's called polar amplification, where the poles warm much faster that the global average.

In the Arctic, a little warming leads to some melt of snow and loss of sea ice over the ocean.

Since snow and ice are white and very reflective, while the land or ocean underneath is much darker, the result is increased absorption of sunlight where the snow and ice has melted.

This heats the Arctic land and ocean surface, leading to more melt, and so on.

Eventually, this will also happen over the Antarctic and southern oceans, but because there's so much very thick ice on the continent of Antarctica, the accelerated warming takes a lot longer to get going.

The paper estimates climate change as far ahead as 2300 rather than 2100, because the greenhouse-gas emissions scenario assumed it would take that long to burn all the coal and oil.

We are unlikely to emit that much carbon dioxide by 2100, but it could be done within 250 or 300 years.

The paper is consistent with our understanding of how the climate responds to large injections of greenhouse gases and gives a stark warning of what the future could hold if we let fossil-fuel burning continue unabated.

The amount of warming and climate change shown by these results would throw global society into chaos and would likely result in billions of deaths, from hunger and conflict over resources.

Source: Science Media Centre