Natural disasters are tending to kill fewer people but climate change may add to the toll by unleashing more extreme weather and causing after-effects such as disease and malnutrition, experts say.
Better warnings of cyclones or heat waves and an easing of poverty in developing nations in the past few decades have made many nations better prepared for weather extremes, helping to curb death tolls.
"In terms of actually saving lives we are doing well," said Diarmid Campbell-Lendrum, a senior expert at the United Nations' World Health Organization (WHO).
"But that's no guarantee for the future as we see the hazard increasing, particularly things like heat stress where we may not be very well prepared," he told Reuters.
Rising temperatures can aggravate the aftermath of disasters, as well as causing creeping changes from higher temperatures such as disruptions to food production.
"Climate change just adds another reason why we should be getting on with controlling malaria, diarrhoea and dealing with the problem of malnutrition," said Campbell-Lendrum. "Those are the big challenges."
UN studies project global warming will cause more droughts, wildfires, heat waves, floods, mudslides and rising sea levels - all threats for an increasing human population set to reach 9 billion by 2050 from 6.8 billion now.
And it is often the after-effects of natural disasters that are the worst, in terms of extra deaths.
Deaths from extreme weather this year such as in Pakistan's floods "are a warning that we need to renew efforts to bring climate change under control," said Andrew Haines, director of the London School of Hygiene and Tropical Medicine.
"There is an increased death rate from indirect causes - people become impoverished, so child death rates that are not normally counted rise," Haines said.
"There might be a substantial under-estimate in the deaths," he said. Climate change would add to the damaging after-effects of natural disasters.
Bigger risk from disease
More than 1,750 people have died in Pakistan's floods but millions more are at risk of disease. At least 54 people died from wildfires in Russia in July and August that drove up world grain prices - threatening malnutrition for the poor.
The WHO will issue a report next year updating an initial 2003 study that estimated an extra 150,000 people were dying every year from global warming - mainly from malnutrition, diarrhoea and malaria.
It projected that the toll was set to double by 2030. Campbell-Lendrum declined to predict the new numbers.
"The short-term response is disaster preparedness" to help save lives, said Achim Steiner, head of the UN Environment Programme, pointing to successes in Bangladesh and Cuba in limiting deaths from storms in recent decades.
In Bangladesh, for instance, advance warning and shelters have helped. Cyclone Bhola killed 300,000 people in 1970, while a 1991 cyclone killed 139,000, according to the EM-DAT disaster database. In 2007, Cyclone Sidr killed 3,500 people.
Alongside investments in flood defences in Pakistan, or better information about how to cope with heat waves, Steiner said, the long-term solution had to be cuts in greenhouse gases, mainly from burning fossil fuels. "Ultimately it is addressing the fundamental drivers of environmental change which will either lead the world to have increasingly to invest in disaster management or development," he told Reuters. "That is the choice of this generation."
Campbell-Lendrum said the WHO's 2003 study may have under-estimated the impact of inland flooding, such as in Pakistan, and of heat waves such as in Russia. Up to 70,000 people died in Europe in 2003 from a heat wave.
Bolster basic health services
He said climate change was an argument to bolster basic health services in poor nations, where 830 million people suffer malnutrition and are most at risk.
A changing climate also has both bad and good effects - more people are under threat from heat waves, for instance, but some elderly people also survive better with milder winters.
Other studies have linked warming to the spread of ticks, bearing encephalitis, in northern Europe. One hinted at a higher rate of suicides among Australian farmers during droughts, according to the UN panel of climate scientists.
The EM-DAT database shows deaths from natural disasters have fallen from about 500,000 a year a century ago to below 50,000 most recent years. The numbers include disasters unrelated to climate change such as tsunamis and volcanic eruptions. The worst recent year was 2004, with the Indian Ocean tsunami. - (Alister Doyle/Reuters Health, September 2010)