The assessment is the most comprehensive probe yet by the 194-nation Intergovernmental Panel on Climate Change (IPCC) into the impact of climate change on extreme weather events.
A 20-page draft "summary for policymakers" obtained by AFP says in essence that global warming will create weather on steroids.
It also notes that these amped-up events -- cyclones, heat waves, diluvian rains, drought -- will hit the world unevenly.
Subject to modification, the draft summary will be examined by governments at a six-day IPCC meeting starting on Monday in the Ugandan capital of Kampala.
In the worst scenario, human settlement in some areas could be wiped out, the report warns.
"If disasters occur more frequently and/or with greater magnitude, some local areas will become increasingly marginal as places to live or in which to maintain livelihoods," it says.
"In such cases migration becomes permanent and could introduce new pressures in areas of relocation. For locations such as atolls, in some cases it is possible that many residents will have to relocate."
Three years in the making, the underlying 800-page report synthesises thousands of recent, peer-reviewed scientific studies.
The authors expresses high confidence in some findings but stresses uncertainty in others, mainly due to lack of data.
They also emphasise that the vulnerability of human settlements depends as much or more on exposure, preparedness and the capacity to respond as it does on the raw power of Nature`s violent outburts.
Average global temperatures have risen by nearly 1.0 degree Celsius (1.8 degrees Fahrenheit) since pre-industrial times, with forecasts for future warming ranging between an additional 1.0 C to 5.0 C (1.8-9.0 F) by 2100.
But these worldwide figures mask strong regional differences.
Among the findings:
-- Western Europe is at risk from more frequent heat waves, in particular along the Mediterranean rim.
Record-busting temperatures in 2003 responsible for some 70,000 excess deaths across Europe may become closer to average summer peaks by as early as mid-century, the report suggests.
-- The eastern and southern United States and the Caribbean will probably face hurricanes amplified by heavier rainfall and increased wind speeds.
Greater population density in exposed areas, rising property values and inadequate infrastructure will boost vulnerability, the draft warns. Hurricane Katrina, which hit New Orleans in 2005, is seen by some scientists as an example of just such an confluence.
-- For small island states, the top threat is incursion from rising seas, which not only erodes shorelines but poisons aquifers and destroys farmland as well.
Already measurable, these impacts are "very likely" -- a 90-percent or greater probability -- to become worse over time, even intolerable, the report concludes.
"In some cases, there may be a need to consider permanent evacuation," it says.
-- Climate models hold out the prospect of more droughts for West Africa, raising the spectre of famine in regions where daily life is already a hand-to-mouth experience for millions.
Factor in the biggest population boom of any continent over the next half-century and the danger of food "insecurity" in Africa becomes even greater, it cautions.
-- In South Asia and Southeast Asia, computer models see a doubling in the frequency of devastating rainstorms. In East Asia, exceptional heatwaves will become hotter, and less exceptional.
By mid-century, temperature peaks in East Asia will be around 2.0 C (3.6 F) more than today, and by 2100 some 4.0 C (7.2 F), even under scenarios that see some efforts to reduce greenhouse-gas emissions.
The IPCC co-won the 2007 Nobel Peace Prize after publishing a landmark "assessment report" that sparked worldwide awareness about climate change and its impacts. That document made only a brief reference to extreme weather events, leaving a gap that the panel hopes to fill with the new report.
The draft summary for policymakers will be reviewed, line-by-line, during a joint meeting of the IPCC`s Working Group I, which focuses on physical science, and Working Group II, which examines impacts. It is set to be released on Friday.
(U.H-RN)
Editor: Priyambodo RH
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