Nearly half of the global reinsurance market has now divested some or all of its assets from coal, after Hannover Re revealed it had adopted a new exclusion policy today.
The German reinsurance giant will divest from companies that depend on coal for more than a quarter of their revenues, saying it would like to see a global "shift towards alternative energy".
The firm joins Swiss Re, Munich Re, SCOR, Lloyd's, Generali and the Markel Corporation in divesting from coal, which together controlled 45% of the £196bn in global reinsurance premiums in 2016.
Unfriend Coal campaign coordinator, Peter Bosshard, said: "The world's ultimate underwriters of risk clearly see no future for a fuel which is the biggest single source of carbon emissions.
"This sends a strong message to the governments, investors and financiers that decide on the future of the global energy sector."
Hannover Re was the world's largest reinsurer in 2016, with a 6.7% share of all premiums, and currently has approximately £48bn in assets under management.
However, despite adopting a stricter divestment policy than its peers, the reinsurer said it would continue to reinsure coal plants and other "fossil energy resources".
The firm argued that, as a private company, it was not their place to "act contrary to the decisions of sovereign nations" that wish to continue with such projects.
German environmental NGO Urgewald criticised the move after insurance firms Allianz, AXA, SCOR and Zurich had all committed to limit or stop underwriting coal projects.
The organisation's finance campaigner, Regine Richter, said: "Hannover Re's divestment from coal is a welcome first step.
"It is, however, disappointing that Hannover Re is still hiding behind others when it comes to insuring coal projects, rather than taking responsibility for the climate impacts of its own underwriting decisions."
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