The Met Office is inviting potential providers to come up with low-carbon options and since half of the processing work - the research devoted to climate change - the computer could be located in countries blessed with easy sources of clean energy. Iceland with its geothermal sources and Norway with its hydropower is a possibility.

In the new project, the billion plus cost will cover not just the hardware itself but all the running costs too over a ten year period.

Penny Endersby, chief executive of the Met Office said: "We'll be streets ahead of anybody else. Ultimately it'll make a difference to every individual, every government department, every industry as people see forecasts becoming steadily better."

It'll be the biggest investment in the 170-year history of the organisation and will dwarf the £97 million bill for the current supercomputer.

In the new project, the billion plus cost will cover not just the hardware itself but all the running costs too over a ten year period.

It'll run what the Met Office calls its "digital twin" of the Earth's atmosphere, a highly detailed "model" of everything from the winds to the temperatures to the pressures.

And the start date for the new machine will be sometime in late 2022.