A sweeping new report has highlighted the enormous impact climate change is already having on our health and wellbeing.

The report, just published in major medical journal The Lancet, found crop yields had declined in 30 countries due to global warming, raising concerns about malnutrition in some regions.

Risks of dengue fever, vibrio and malaria had also markedly increased around the planet.

And the increases in extreme weather events, which in 2017 numbered 712 events resulting in US $326 billion in economic losses, were bringing with them injuries and deaths, displacement, post-traumatic stress, and other short and long-term impacts to health.

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Climate change was further driving migration in some regions, with significant geopolitical impacts.

Another section of the report, authored by New Zealand-based environmental and occupational health expert Professor Tord Kjellstrom, found hotter temperatures cost workers 153 billion productive hours in 2017, in turn impacting family incomes and agricultural output to compound the risks to health.

The worst-hit regions were India, southeast Asia, and sub-Saharan Africa, and South America, but Kjellstrom added impacts on New Zealand's labour force would also become more pronounced as heat levels climbed.

The authors of the report called on world leaders, about to meet in Poland for the next UN summit on climate change, to make urgent commitments to reduce greenhouse gas emissions between now and 2020 that would limit global warming to 1.5C.

Although New Zealand and 196 other parties signed the Paris Agreement that emerged from the UN climate negotiations in 2015, many were not yet meeting their initial commitments to reduce greenhouse gas emissions - and those initial commitments fell far short of what was needed to limit global warming to below 1.5C to 2C, as agreed to in Paris.

Delaying action not only put people's health at risk from climate change, the authors said, but also missed the major opportunities for near-term improvements to health that climate action offered.

Seven million people per year die prematurely from air pollution, and The Lancet found that air quality worsened in 70 per cent of the world's cities last year.

It was estimated that the health benefits of mitigating climate change to achieve the targets set in Paris could more than pay for the cost of that mitigation, from reductions in air pollution alone.

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"The potential benefits are staggering, and we know what actions are needed," said Dr Rhys Jones, Co-convenor of OraTaiao: The NZ Climate and Health Council.

"Rapidly phasing out coal, oil and gas; switching from car trips to more walking, cycling and public transport; healthier diets lower in red meat and dairy; and energy efficient, warm homes will all cut emissions while also reducing many of the major diseases that kill New Zealanders."

"Politicians meeting next week must act now and make strong and bold commitments to secure a healthy future for all.

"The nature and scale of the response to climate change will be the determining factor in shaping health for current and future generations."

Meanwhile, another report has set out what New Zealand needed to learn to better adapt to drought conditions likely under future climate change.

Although New Zealand has historically been "water-rich", the report, produced by the Deep South Challenge: Changing with our Climate, suggested the country wasn't well-prepared to cope with a future involving more drought in some areas.

It found this may well have the single most significant future impact on the country's economy.

Its authors say we need to know more about New Zealand's level of risk in relation to drinking water availability, both in urban and rural areas, as well as the impact on vulnerable communities through shifts in labour patterns and house prices.

They suggest we need more research into how changing drought patterns might affect energy production and consumption.

"As climate changes into the future, water supply systems will have to be adapted accordingly, which may include new sources, new technologies, increased storage capacity and better management of water usage," said Tonkin + Taylor's Wageed Kamish, who is leading a new project focused on the issue.

"In parallel, we need to carefully manage the quality of existing and potential sources now, so as not to jeopardise them for future use.

"Adaptation may take several years, so in many cases the planning process needs to start right now."