* CalSTRS among backers of Climate Action 100+ group

* 40+ asset owners say group effective at addressing risk

* Follows exit of some U.S. members after political backlash

LONDON, May 29 (Reuters) - Asset owners overseeing $4.6 trillion have signed a statement throwing their support behind the Climate Action 100+ investor group after several high-profile Wall Street investors left the global initiative.

Signatories included the California State Teachers' Retirement System (CalSTRS) and California Public Employees Retirement System pension managers, as well as more than 40 others from countries including Britain, Canada and Sweden.

In the statement on CalSTRS' website, the groups, many of which employ asset managers to invest in markets on their behalf, said they were "deeply concerned" about the investment risks posed by climate change.

Encouraging companies to plan for those risks aligned with their economic interests and CA100+ was an "effective and efficient way" to address the issue, "which is why we remain fully committed to participating in this valuable initiative", the pension managers said in the statement.

The decision to offer public support to CA100+, which encourages the world's heaviest corporate emitters to cut climate-damaging emissions, follows the high-profile exit this year of investors including Pimco.

Others to leave included the fund arms of JPMorgan, State Street and Invesco while the world's biggest investor BlackRock reduced its involvement with the group.

The exits came after the coalition asked signatories to take stronger action over corporate laggards and amid a backdrop of rising political pressure from some U.S. politicians who said the membership of such groups could break antitrust laws.

The investor statement said further action to address systemic risk was "essential", addressing climate risk was a "fiduciary imperative" and collaborative engagement was "a vital tool".

While the groups recognised the "complexities and nuance" around the issue, these "cannot preclude those committed to addressing climate-related investment risk from taking the action needed to protect the investments that provide security for our beneficiaries". (Reporting by Simon Jessop; Editing by Rod Nickel)