LONDON (Reuters) - Investors managing around $20 trillion in assets on Tuesday called on the heaviest corporate emitters of greenhouse gases to set science-based targets on the way to net zero carbon emissions by mid-century. AXA Group and Nikko Asset Management Co are among 137 investors urging 1,800 companies responsible for a quarter of global emissions to act, coordinated by non-profit group CDP. While more companies are pledging their support for the 2015 Paris agreement on climate change, aiming to be carbon neutral by 2050, not all have been clear about how they will get there. To help limit global warming to no more than 1.5 degrees Celsius above pre-industrial norms by 2050, companies need to set out their pathway to net zero and ensure it is consistent with the science and independently verified, the investors said. “Climate change presents material risks to investments, and companies that are failing to set targets grounded in science risk losing out - and causing greater damage to the world economy,” said Emily Kreps, Global Director of Capital Markets at CDP. The companies targeted together annually contribute 13.5 gigatonnes of emissions directly and indirectly tied to their operations, equivalent to 25% of the world’s total, CDP said. Specifically, the investors said they wanted companies to set targets through the Science-Based Targets Initiative to help ensure the goals can be more easily compared and assessed. More than 1,000 companies have already set science-based targets, of which around 300 have targets in line with the 1.5 degrees goal. “Companies that do not set science-based targets risk being surprised by increased costs or lost business that could result from the increasing focus on climate change by society and regulators,” said Ted Maloney, Chief Investment Officer at MFS Investment Management.