Aon Re Global and Impact Forecasting LLC Release 2004 Annual Global Climate and Catastrophe Report

CHICAGO � March 10, 2005 — Unusually violent weather throughout the U.S. and
the Pacific Rim made 2004 one of the most active years for natural phenomena in
recent memory, according to a recently-released Aon report.

Aon�s 2004 Global Climate and Catastrophe Report, produced by Aon Re Global and
Impact Forecasting, LLC, subsidiaries of Aon Corporation (NYSE: AOC), depicts a
year of freakish weather patterns, ending with the worst natural disaster in
modern times: the December 26th tsunami. The earthquake-driven massive sea
wave killed more than 159,000 people across Sri Lanka, Indonesia, and India and
obliterated villages and seaside resorts in ten countries across southern Asia
and eastern Africa. By contrast, the worst natural disaster in 2003 was the
Bam, Iran earthquake in which 26,271 people perished.

The 2004 hurricane season in the U.S. was among the most active on record. The
western Atlantic produced 15 named storms and 9 hurricanes, which is above the
norm of 10 tropical systems and 6 hurricanes. The United States and Caribbean
Islands experienced a rough August and September, with 6 major hurricanes
making landfall in 2004, well above the average normal landfall of 1-2 storms.
By contrast, 2003 saw only two of seven hurricanes making landfall. It had
been half a century since Florida sustained hits by three destructive
hurricanes in rapid succession. In 1950, hurricanes Baker and Easy made
landfall in or near Florida within a six-day period.

The United States tornado season was also especially busy in 2004. The
tropical storms that battered the southern part of the country were partially
responsible for the higher incidence of tornadoes last year. The
higher-than-usual number of hurricanes helped to spawn some of the 1,722
tornadoes in the United States in 2004, according to the Storm Prediction
Center in Norman, Oklahoma. That�s up from the previous year�s total of
1,376. A normal tornado season yields an average of 1,200 tornadoes.

Of the 1,722 storms in 2004, 20 were so-called �killer� tornadoes, resulting in
36 deaths. That�s down from 2003�s 23 �killer� storms and 54 fatalities. Both
years were below the normal count of 25 �killer� storms resulting in an average
of 54 deaths nationwide.

Aon�s report indicates at least one category showed some improvement. There
were fewer typhoons than normal in the western Pacific Ocean. That region
generated 21 typhoons in the 2004 tropical season, lower than the average 27.
In 2003 there were 17 typhoons. Japan was struck by seven tropical systems,
four of which were typhoons. This represents the most typhoon landfalls in
Japan since 1982.

Aon Re Global and Impact Forecasting’s annual report, issued during the first
month of every year, analyzes the current state of the world’s climate and
summarizes the past year’s natural catastrophes. According to the report,
2004’s climate across the globe was warmer and wetter than normal, which is a
change from previous years, where warmer but drier than normal conditions
existed. Precipitation amounts were also higher than normal for the first time
in four years. Though many areas still experienced drought conditions, some
locations received an overabundance of rain, leading to severe flooding that
killed thousands of people this last year, primarily across Southeast Asia and
through the Caribbean Sea.

Aon Re Global and Impact Forecasting’s annual report also summarizes 2004’s
record-breaking natural disasters, many of which broke long-standing records.
Haiti and the Dominican Republic were hit with two massive flooding events in
2004, killing over 5,000 people in May and September combined. Monsoon
flooding across Bangladesh, India, and China claimed more than 1,900 lives from
late June through early August. Landslides and flooding from successive
tropical systems killed thousands of people in late November in the

Impact Forecasting, LLC is a wholly owned subsidiary of Aon Corporation.
Impact Forecasting’s staff of science, finance and insurance professionals
model and analyze the financial implications of natural catastrophes to help
clients make risk management decisions.

Aon Re Global provides traditional, alternative risk transfer and capital
markets based reinsurance advisory and execution services to insurers and
reinsurers. Aon Re Global’s client advisory services include dynamic financial
analysis, rating agency capital modeling assistance, capital allocation and
optimization services, catastrophe modeling services, regulatory assistance,
tax planning and capital markets structuring and placement services.

About Aon

Aon Corporation ( is a leading provider of risk management
services, insurance and reinsurance brokerage, human capital and management
consulting, and specialty insurance underwriting. The company employs
approximately 48,000 professionals in its 500 offices in more than 120
countries. Backed by broad resources, industry knowledge and technical
expertise, Aon professionals help a wide range of clients develop effective
risk management and workforce productivity solutions.

This press release contains certain statements relating to future results,
which are forward-looking statements as that term is defined in the Private
Securities Litigation Reform Act of 1995. These forward-looking statements are
subject to certain risks and uncertainties that could cause actual results to
differ materially from either historical or anticipated results, depending on a
variety of factors. Potential factors that could impact results include the
general economic conditions in different countries around the world,
fluctuations in global equity and fixed income markets, exchange rates, rating
agency actions, resolution of pending regulatory investigations and related
issues, including those related to compensation arrangements with underwriters,
pension funding, ultimate paid claims may be different from actuarial estimates
and actuarial estimates may change over time, changes in commercial property
and casualty markets and commercial premium rates, the competitive environment,
the actual costs of resolution of contingent liabilities and other loss
contingencies, and the heightened level of potential errors and omissions
liability arising from placements of complex policies and sophisticated
reinsurance arrangements in an insurance market in which insurer reserves are
under pressure. Further information concerning the Company and its business,
including factors that potentially could materially affect the Company�s
financial results, is contained in the Company�s filings with the Securities
and Exchange Commission.