Today's health is being harmed by climate change through effects from deadly upper waves in Europe to dengue fever in tropical regions, according to the report.
Many hours of farm work were lost at high temperatures and global warming damaged the ability to grow crops.
Lancet countdown to health and climate change was produced by 150 experts from 27 universities and institutions, including the World Health Organization and the World Bank.
"The result is clear and the rates can not be higher," said Tedros Adhan Ghebreyesus, WHO CEO. "We can not postpone climate change measures, and we can not sleep well."
The report outlines the implications of global warming for health clearly. "The rapidly changing climate has harsh consequences for all aspects of human life, exposing vulnerable populations to extreme climatic conditions, changing patterns of infectious diseases and threatening food safety, safe drinking water and clean air," he said.
Nick Watt, Managing Director of Lancet Countdown, said, "It's not going to happen in 2050, but it's the things we see today, we think of it as a canary, ironically, a coal mine."
On Tuesday, the United Nations said carbon emission reduction measures had to be tripled to avoid catastrophic warming. International negotiations on climate change were to continue on Monday in Poland.
The Lancet report states that the lack of progress "threatens human lives and the viability of the national health systems on which it depends, with the potential to overcome health services."
A survey in leaders of almost 500 global cities has revealed that half of them expect their public health infrastructure to be seriously threatened by climate change, which means systemic failure such as shutting down hospitals.
In summer in Europe, heat wave was associated with hundreds of premature deaths in the UK. MEPs said in July that the United Kingdom was "woefully unprepared" for mountain waves.
The Lancet report states that populations in Europe and the eastern Mediterranean are at greater risk than Africans and Southeast Asian countries due to the high proportion of vulnerable and elderly people living in cities.
With temperatures rising around the world, the report says that in 2017, 157 million more vulnerable people were exposed in 2017 than in 2000. Warm conditions directly damage health due to heat but dehydration and worsening of conditions such as cardiac diseases are also very dangerous. Heat also aggravates air pollution and mental health problems.
Professor Kristie Ebi of Washington University says: "Increased mortality in extreme temperature waves is happening now [but] there is a lot of evidence that communities are not ready to continue increasing the frequency, intensity and duration of waves. "
The Lancet report states that in 2017 153 billion hours of work were lost due to extreme heat, of which 80% was in agriculture. Almost half of the losses were in India, equivalent to 7% of the total working population, while China lost 1.4% of its workers. "This has led to huge losses for national economies and household budgets," said prof. Joacim Rocklöv from Umeå University in Sweden.
Relatively small changes in temperature and precipitation could cause major changes in the transmission of infectious diseases spreading with water and mosquitoes. Dengue fever transmission capacity – its "vector capacity" – reached record values in 2016, according to a report of 10% above the base figure of the 1950s. Dangers from the risk of cholera are also rising in areas such as the Baltic states where the sea is rapidly warming.
Doctors who were not mentioned in the report said they provided convincing evidence. "It is clear that climate change has a direct impact on our health," said Howard Frumkin, Head of Wellcome Trust, our planet, our health program. "All sectors must prioritize climate action if we want to significantly reduce the potentially devastating impact on our planet and our health and influence future generations."
Professor Paul Ekins, of University College London, said the benefits to addressing climate change in the health sector have long been underestimated, with only 5% of the means to adapt to global warming being spent on health.
"These benefits are enormous, short-lived and immediately affect our health," Ekins said. "If you influence these benefits, you will reduce emissions [keep the temperature rise below] 1.5C will be a cash benefit for humanity. "
The Lancet report has seen promising trends such as the phasing out of coal production and the growth of electric cars.
Prof. Hilary Graham of the University of York and part of the Lancet Countdown team said that linking health and climate change could help support further steps. "Health is what people feel, creating a direct connection with their lives and the lives of people who care, like their children and grandchildren."