BP has warned it will write down up to $5bn (£3.7bn) from its green and low-carbon energy businesses as it refocuses on fossil fuels under its new chair, Albert Manifold. The company said the impairment mainly affects its gas and transition businesses but will not impact underlying profits when full-year results are published in February. BP has already cancelled hydrogen projects in the UK, Oman and Australia and is seeking to sell a stake in its solar…