Mapua's Dr Tord Kjellstrom says heat exposure and stress from climate change will be the greatest threat to human life in the next 100 years.

Mapua's Dr Tord Kjellstrom has researched the impact of climate change heat stress on manual labourers for 20 years. He says people are already dying but the loss of production, particularly in hot countries, could drive a major global economic decline. Helen Murdoch reports.

Imagine you are your grandchild living in a world which has not tamed climate change. You are cradling your newly born grandchild in your arms. What life would you wish for the infant?

It is a scenario Dr Tord Kjellstrom uses to illustrate the growing threat of climate change.

Kjellstrom is the co-ordinator of the eight-member Ruby Coast Research Centre (RCRC) which is based in Mapua gathers and and provides international research and data on the impact of the rising global temperature on human health to leading global organisations and decision makers.

"We have to act now to protect our future families and the environment. Mitigation is extremely important because adaption or protection are not going to help the poor people in tropical countries."

For nearly 20 years Kjellstrom, and more lately the RCRC team, have researched the impact of climate change heat-stress on working people and the lost production and resulting downward slide in national Gross Domestic Product (GDP).

Kjellstrom, is a softly spoken medical doctor and also holds a masters in mechanical engineering. He has 40 years experience of teaching and research in environmental and occupational health, and epidemiology. He has held professor positions in universities in Sweden, New Zealand, Australia, and United Kingdom.

He worked 12 years at the World Health Organization in Geneva and was the WHO's Office of Global and Integrated Environmental Health director ,with responsibility, for climate change and health from 1994 to 1997.

Kjellstrom said it is not storms or rising sea levels that will be climate change's greatest threat to human life in the next 100 years - but heat exposure. He says it is here already and people are dying.

"I think somehow that some of the experts want to keep the calculations around heat exposure and its effects low-key," Kjellstrom said. "I don't know why."

Researching and disseminating data and publications about the health impacts of rising heat levels is a focus of the RCRC.

The centre makes its research available through keynote speeches, academic journals, commissioned reports, book chapters, and a website climatechip.org which points to the groups, publications, power points, analysis tools and interactive pinpoint data on temperature trends at thousands of locations around the world.

The work highlights Kjellstom's primary concern - that rising heat and associated stresses and deaths will hit the globe's temperate, tropical and subtropical zones the hardest.

"We have 4000 million people already at risk."

The ideal core body temperature for humans is around 37 degrees C. Once it rises to 39C heat stress and strain sets in, organs can be damaged and at higher temperatures death may occur.

Kjellstrom said poor workers were already dying in parts of the world from kidney disease and heart failure in locations ranging from the sugar cane fields of El Salvador and Nicaragua to Qatar where 185 workers died in 2013 building stadiums and infrastructure for the 2022 FIFA World Cup in sweltering conditions.

Poor manual workers in hot countries faced major hurdles, he said. They had to work to survive, they could often not carry or source enough potable water to hydrate daily, they usually lived without cooling systems and they faced major migration barriers.

The overall results were health impacts, deaths and was lower production output.

"There are millions and millions of people who do all the work by hand. When it gets up to a certain heat level you can not keep up the pace of work," he said.

He acknowledged the issue of heat was not a big problem in New Zealand.

"But if you are in the south of India and the average temperature in the afternoon is 45 degrees and it goes on for maybe three or four months it's extremely difficult for people to keep up the work.

"So people as individuals will have health effects, lose income and be less productive.

"If that is among self-employed farmers, it is a family economy that is affected. But if you estimate, like we have done, what might be the impact on a country we are talking about several per cent loss of GDP.

"If you lose two per cent of your annual GDP over a 30 years period your average income in the country will be half as much as it could have been."

Even small changes in temperature impact on people.

"Even now construction workers in hot parts of the year can not work in the afternoons. This aspect of heat and how it affects people's lives has, until recently been more or less ignored or not given much emphasis.

"For the first time the IPCC report in 2014 mentioned these health impacts of heat. One could argue that is an achievement of this team in Ruby Bay because I was involved in putting material, together with my colleagues here, for the report. The further analysis we are currently doing will hopefully change the attitude towards this whole thing."

Members of the RCRC team also include Bruno Lemke, Matthias Otto, Olivia Hyatt, David Briggs, Chris Freyberg, Lloyd Hasson and Lauren Lines.

Bank of England governor Mark Carney recently also gave a stark warning that climate change poses a huge risk to global security.bbc.com/news/business-34396961