He will be paid a base salary of £675,000 a year.
Mr Carne, aged 54, was formerly executive vice president for the Middle East and North Africa for Royal Dutch Shell and is credited with helping Shell achieve a strong position in countries such as Iraq.
Earlier in his career he helped to lead the company's response to the 1988 Piper Alpha disaster.
Mr Carne studied engineering at Exeter University and is a Fellow of the Institute of Mechanical Engineers.
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