By Simon Jessop LONDON (Reuters) – Thirty-four investors managing more than $7 trillion in assets have warned 17 of Europe’s largest companies, including BP and Volkswagen, that they could challenge board directors over their accounting of climate risks. The move is the latest push by investors to pressure companies and their auditors, charging them with not moving fast enough to adapt to the world’s transition to a low-carbon economy or being clear enough about the potential impacts. In letters sent between December and February and seen by Reuters, the investors told the companies their acco…