In the past, the Intergovernmental Panel on Climate Change, founded in 1988 by the United Nations, has focused on the slow inexorable rise of temperatures and oceans as part of global warming. This report by the panel is the first to look at the less common but far more noticeable extreme weather changes, which lately have been costing on average about $80 billion a year in damage.
"We mostly experience weather and climate through the extreme," said one of the report's top editors, Chris Field, an ecologist with the Carnegie Institution of Washington. "That's where we have the losses. That's where we have the insurance payments. That's where things have the potential to fall apart.
"There are lots of places that are already marginal for one reason or another," Field said. But it's not just poor areas: "There is disaster risk almost everywhere."
The report specifically points to New Orleans during 2005's Hurricane Katrina, noting that "developed countries also suffer severe disasters because of social vulnerability and inadequate disaster protection."
In coastal areas of the United States, property damage from hurricanes and rising seas could increase by 20 percent by 2030, the report said. And in parts of Texas, the area vulnerable to storm surge could more than double by 2080.
Already U.S. insured losses from weather disasters have soared from an average of about $3 billion a year in the 1980s to about $20 billion a year in the last decade, even after adjusting for inflation, said Mark Way, director of sustainability at insurance giant Swiss Re. Last year that total rose to $35 billion, but much of that was from tornadoes, which scientists are unable to connect with global warming. U.S. insured losses are just a fraction of the overall damage from weather disasters each year.
Globally, the scientists say that some places, particularly parts of Mumbai in India, could become uninhabitable from floods, storms and rising seas. In 2005, over 24 hours nearly 3 feet of rain fell on the city, killing more than 1,000 people and causing massive damage. Roughly 2.7 million people live in areas at risk of flooding.
Other cities at lesser risk include Miami, Shanghai, Bangkok, China's Guangzhou, Vietnam's Ho Chi Minh City, Myanmar's Yangon (formerly known as Rangoon) and India's Kolkata (formerly known as Calcutta). The people of small island nations, such as the Maldives, may also need to abandon their homes because of rising seas and fierce storms.
"The decision about whether or not to move is achingly difficult and I think it's one that the world community will have to face with increasing frequency in the future," Field said in a telephone news conference Wednesday.
This report the summary of which was issued in November is unique because it emphasizes managing risks and how taking precautions can work, Field said. In fact, the panel's report uses the word "risk" 4,387 times.
Field pointed to storm-and-flood-prone Bangladesh, an impoverished country that has learned from its past disasters. In 1970, a Category 3 tropical cyclone named Bhola killed more than 300,000 people. In 2007, the stronger cyclone Sidr killed only 4,200 people. Despite the loss of life, Bangladesh is considered a success story because it was better prepared and invested in warning and disaster prevention, Field said.
A country that was not as prepared, Myanmar, was hit with a similar sized storm in 2008, which killed 138,000 people.
The study forecasts that some tropical cyclones which include hurricanes in the United States will be stronger because of global warming. But the number of storms is not predicted to increase and may drop slightly.
Some other specific changes in severe weather that the scientists said they had the most confidence in predicting include more heat waves and record hot temperatures worldwide and increased downpours in Alaska, Canada, northern and central Europe, East Africa and north Asia,
IPCC Chairman Rajendra Pachauri told The Associated Press that while all countries are hurt by increased climate extremes, the overwhelming majority of deaths occur in poorer, less developed places. Yet, it is wealthy nations that produce more greenhouse gases from burning fossil fuels, raising the issue of fairness.
Some weather extremes aren't deadly, however. Sometimes, they are just strange.
Report co-author David Easterling of the National Climatic Data Center says this month's U.S. heat wave, while not deadly, fits the pattern of worsening extremes. The U.S. has set nearly 6,800 high temperature records in March. Last year, the United States set a record for billion-dollar weather disasters, though many were tornadoes.
"When you start putting all these events together, the insurance claims, it's just amazing," Easterling said. "It's pretty hard to deny the fact that there's got to be some climate signal."
Northeastern University engineering and environment professor Auroop Ganguly, who didn't take part in writing the IPCC report, praised it and said the extreme weather it highlights "is one of the major and important types of what we would call 'global weirding.'" It's a phrase that some experts have been starting to use more to describe climate extremes.
Field doesn't consider the term inaccurate, but he doesn't use it.
"It feels to me like it might give the impression we are talking about amusing little stuff when we are, in fact, talking about events and trends with the potential to have serious impacts on large numbers of people."
The Intergovernmental Panel on Climate Change: http://www.ipcc.ch