Large insured losses from catastrophes last year and this year plus the recent release of a revised windstorm model will prompt reinsurers to push for higher rates worldwide, Towers Watson & Co. said in an analysis released Tuesday.

However, the push by reinsurers to increase rates will not be as severe as after Hurricane Katrina in 2005, the consultant said in a statement.

Despite the devastation from the March earthquake and tsunami in Japan, insured losses will not greatly affect the capital of Japanese insurers or the global reinsurance industry, New York-based Towers Watson said. But overall insured losses from catastrophes in 2010 and 2011 plus Risk Management Solutions Inc.'s release of its latest windstorm model will result in a push to boost reinsurance rates, it said.

Property catastrophe rates will harden but also will vary on a geographic basis.

“Absent another event, we do not foresee the same level of price increases that we saw at the beginning of 2006,” William Eyre, managing director of Tower's Watson's reinsurance brokerage business, said in the statement.

“The 2010-2011 losses are widely believed to be more of a significant ‘earnings' event rather than an impairment to capital,” he said. “Additionally, though rating agencies may adjust their views of risk because of the international catastrophe experience, we do not expect the same type of downgrades seen in 2005 and 2006.”

Towers Watson estimated insured losses in the Japan disaster would range from $20 billion and $45 billion—including likely losses from residential and commercial property, business interruption, marine, auto and life insurance coverage—with $12 billion to $15 billion reinsured internationally.

Towers Watson added that potential nuclear liabilities “are not significantly insured by the private market and remain the responsibility of the Japanese government.”

François Morin, Tower's Watson's global product leader for property and casualty claims reserving, said a greater portion of the total Hurricane Katrina losses were insured and reinsured than in Japan.

After Hurricane Katrina, catastrophe rates increased by as much as 50% to 100% for peak-zone U.S. exposures, Towers Watson noted.

“Unlike Katrina, the vast majority of this loss will not be borne by the world reinsurance market, and for some reinsurers, their loss from the two recent New Zealand earthquakes may surpass their loss from Japan,” said Mr. Eyre.

At reinsurance renewals this month, Towers Watson forecast that rates for Japanese programs likely would increase 20% to 50%. Rate increases also are likely for business in Australia and New Zealand, much of which renews July 1.

Industry observers expect there will be some upwards pressure on U.S. hurricane-exposed business that renews in June and July, Towers Watson noted.