In a concession to shareholders, ExxonMobil agreed to report on the potential impact of climate change policies on its business. Announced one day ahead of the two year anniversary of the Paris Agreement, ExxonMobil's decision marks the latest in a growing trend of corporate disclosures regarding climate change risks. Wood Mackenzie's recently completed multi-client study, Positioning for the future: Benchmarking upstream corporate carbon emissions and value at risk, suggests that a US$40/tonne CO2 cost imposed on ExxonMobil's direct emissions would potentially reduce the value of ExxonMobil's upstream portfolio between 3% and 11%, depending on tax treatment of those costs and country risking. ExxonMobil has already made good progress repositioning its portfolio to be sustainable in a lower oil price environment. However, further high grading may be required to position the portfolio for a low-carbon future, with a focus not just on costs but carbon intensity.