The document suggests that the industry should switch some of the $100bn(£63bn)- plus of investment it has worldwide in fossil-fuel industries into generators of alternative energy.
The report, which has been obtained by the Independent on Sunday, is the latest sign of growing alarm that man-made climate change is posing a threat to the viability of the insurance industry, after an unprecedented series of natural catastrophes.
Compiled as the result of a visit by a high-level delegation from Lloyd's of London to an international climate conference in Berlin last month, the report says that "global warming is probably taking place already" bringing an "increased likelihood of extreme climatic events". It adds: "It is imperative for insurers to make every effort to mitigate their exposure."
In the last seven and a half years, 15 natural catastrophes have each cost the world insurance industry more than a billion dollars: no previous "billion dollar cat" had ever occurred.
Giant floods devastated the United States in 1993 and the Netherlands earlier this year. Nine American insurance companies collapsed after two hurricanes - Andrew and Iniki - hit Florida and Hawaii within seven weeks in the autumn of 1992. And by the beginning of the next year, 24 reinsurers had pulled out of the Caribbean after a similar battering by storms.
Yet the industry got off lightly: had Hurricane Andrew - which caused $16.5bn of damage - strayed just 20 miles further north, to take it through downtown Miami, the insurance bill would have been $75bn. If it had maintained strength and hit New Orleans, this would have risen to $100bn - more than half the entire capital and surplus of all the property and casualty insurance companies in the US.
Insurers are now increasingly making common cause with scientists and environmentalists, who are warning of the dangers of global warming. Scientists expect that the weather will get more stormy as the climate heats up, mainly as the result of pollution from carbon dioxide, arising overwhelmingly from the burning of coal, oil and gas. The changing climate would also cause the seas to get warmer and expand, flooding coastal areas.
Last month, a three-man delegation - Richard Keeling, theformer Lloyd's deputy chairman, David Mann, a leading underwriter, and James Anderson from Gibbs Hartley Copper - attended the first meeting of the parties to an international treaty to combat climate change, which was signed at the Earth Summit in Rio three years ago.
The confidential internal report of their visit, written by Mr Anderson, says: "The scientists and all the delegates for the various countries were unanimous in their belief that global warming was occurring and that an increased frequency of extreme climatic events was probable."
The report - which has been sent to the leaders of Lloyd's, the Association of British Insurers and the Institute of London Underwriters - says that the fossil-fuel industries are lobbying against steps to tackle global warming and "are likely to effectively emasculate any measures that might be taken". The report adds: "It is thus probable that the insurance industry is going to have to take some initiatives, either by itself or along with the banking industry."
American Re, the third largest US reinsurer, has already set up its own company to help develop environmentally friendly technologies, and is inviting solar power companies to offer themselves for investment.