The confirmation came last week: this summer, Earth experienced its hottest three-month period on record – and by quite a margin.

From June through to August, the global temperature was more than half a degree above average, at 16.7C.

The impacts of this hot spell have been hard to ignore: wildfires in Greece, Canada and Hawaii, which are estimated to have killed hundreds, endless drought in East Africa, warming of the oceans, and so much more.

There have been other extreme weather events, too, which have unleashed similar levels of death and destruction over the past three months – from flooding across Pakistan, Spain and China, to fearsome typhoons in the Pacific.

“Climate breakdown has begun,”António Guterres, secretary-general of the United Nations, said in a statement last week.

Assuming global temperatures continue to rise, the lives of millions – if not billions – of people will be drastically transformed in the years and decades to come. Here are five impacts to consider.

Uninhabitable heat

Britain’s summer may have been a washout, but for the vast majority of countries, it was anything but.

France, Greece, Italy, Spain, Algeria and Tunisia all reported new heat records, comfortably above 40C, and temperatures even topped 50C in Iran, China, Turkey and Morocco.

At such extremes, humans are pushed to breaking point. The chance of heat stroke is heightened, while the struggle to sweat and cool the body can cause dehydration and overwork the kidneys. In time, this increases the risk of kidney disease.

The heart works harder, too, labouring to pump more blood to the skin. For those exposed to high temperatures over a prolonged period of time, the heart rate will skyrocket. Blood flow to the brain, however, will be reduced, instead directed to other parts of the body. 

For the elderly, these impacts are intensified.

“As people age, their bodies become less efficient at regulating temperature and adapting to heat stress,” says Dr Raquel Nunes, Assistant Professor in Environmental Change and Public Health, at Warwick Medical School.

Research published in July estimates that more than 61,000 people died in Europe from the record-breaking 2022 heatwaves, with the highest loss of life recorded among the over-80s. 

Unless the cities, towns and homes we inhabit are adapted to cope with rising temperatures, living in these conditions will become unbearable. 

Water and food shortages

Finding safe and reliable water supplies for drought-stricken communities is already becoming increasingly difficult as a result of soaring temperatures. But as the world heats up, experts fear such an experience will become commonplace.

Currently, some 1.1 billion people worldwide lack access to water. Yet by 2050, more than three-quarters of the global population could be affected by drought, according to the UN. 

For an example of what could unfold across the globe, look no further than the Horn of Africa. 

The severe agricultural drought that has gripped swaths of east Africa since 2021, the worst in four decades, has led to widespread crop failures, animal deaths and left more than four million people in need of humanitarian assistance and 20 million at risk of food insecurity.

Scientists have concluded that this disaster “would not have occurred without climate change”, which has made the exceptional dryness of the Horn of Africa about 100 times more likely.

In any region facing drought, agriculture is always decimated. It accounts for about 70 per cent of freshwater consumption globally, although in some regions it can be much higher, so as water supplies dwindle, so too will production. 

Pollutants also lower the nutritional value of crops as carbon dioxide levels increase, driven by the burning of fossil fuels. Crop yields will subsequently suffer, further lowering food supplies and driving up prices. 

Morgan Stanley estimated in a report last year that at least 44 per cent of wheat, 43 per cent of rice, 32 per cent of maize and 17 per cent of soybean production globally comes from at-risk areas.

It’s a vicious cycle, with many contributing factors, and one that will be different to break once it starts to turn.

Extreme weather events

Climate change is causing extreme weather events to be more frequent and intense than ever before, driving unprecedented heat waves, droughts, forest fires and floods.

China broke its highest temperature record when it recorded 52.2C in July, and Chile experienced a “winter heat wave” the same month, with temperatures soaring as high as 20C above average. 

Raul Cordero, a climatologist at the University of Santiago, said that “having temperatures of 37C in the middle of southern winter is extraordinary”. 

“It is a temperature anomaly of almost 15C above typical values ​​and unfortunately it is not a local problem, it is a global problem,” he said.

As the hot weather draws moisture out of the ground and vegetation, tinder dry conditions are providing the perfect fuel for wildfires. 

“We’re seeing a string of heatwaves, certainly in Asia. The cascading and compounding effects associated with that – drought and all the heat – it just sets the places up to burn well,” said Dr John Nairn, a senior extreme heat advisor at the WMO.

In Maui, an entire city was wiped out as fire raged this summer, leaving at least 115 people dead and hundreds missing. 

Millions of people in North America were warned about the health risks of poor air quality as toxic smoke from Canada, which is having its worst year on record for forest fires, drifted across the continent.

India, China and Japan have also experienced another climate fallout: flooding and landslides.

In one week in July, Beijing experienced its largest rainfall in 140 years, while in India, as many as 2,038 people have lost their lives to floods, lightning and landslides this year. 

According to a report from the UN, there has been a “staggering rise” in the number of extreme weather events over the past 20 years, driven largely by rising global temperatures and other climatic changes.

From 2000 to 2019, there were 7,348 major natural disasters globally, killing 1.23 million people and resulting in $2.97 trillion in global economic losses. The previous 20-year period recorded 4,212 disasters, claiming 1.19 million lives and causing $1.63 trillion in losses.

Infectious diseases

Many infectious diseases are climate sensitive and global warming is giving them the opportunity to expand their reach, threatening the lives of millions. 

With flooding, population displacement and overcrowding caused by storms and extreme flooding, waterborne infections – such as cholera, typhoid and hepatitis – are on the rise. 

Milder winters, warmer summers, and fewer days of frost are also making it easier for disease-carrying mosquitoes to roam beyond their habitats, bringing infections like malaria, Zika and dengue fever closer to countries previously out of their reach. 

Climate change is also bringing humans into closer contact with disease-carrying animals, such as bats, which are increasingly able to migrate and thrive in areas of the globe they were previously unable to survive.

This increases the risk of ‘spillover events’, in which a pathogen common to a species of animals jumps into the human population and starts spreading – as seen with Covid-19, Sars, Mers, and several other major outbreaks in history.

A warming globe could drive changes in fungi, too. Ordinarily, humans are protected from fungi because of our high body temperature, but as the world warms, fungi are beginning to adapt to higher temperatures, making transmission easier. 

Cases of Candida auris, a fungus that was not found in humans anywhere until 2009, nearly doubled in Europe between 2020 and 2021.

In the US, there were 2,377 confirmed clinical cases diagnosed last year – an increase of over 1,200 per cent since 2017.

More generally, hospitalisations involving fungal infections increased 8.5 per cent each year in America from 2019 to 2021.

Migration

Climate change refugees are already on the move: since 2008, more than 20 million people have been displaced by extreme weather-related events. 

But by 2050 this could soar to 1.2 billion, according to the Institute for Economics and Peace think-tank.

Climate migration occurs when people flee their homes in the face of extreme weather, including heat waves, flooding, drought and wildfires. Slower moving challenges – like rising sea levels and intensifying water stress – also play a part. 

The impact is predictable in countries like Bangladesh, where one-third of the population lives along a sinking, low-lying coast. 

By 2050, more than 13 million Bangladeshis – nearly 10 per cent of the population – will likely have fled the country due to rising sea levels, according to the World Bank.

It would be easy to assume the risk mainly lies in economically vulnerable countries, but it exists in Britain and the US too. 

Locals in Fairbourne, Wales, have been told that their homes should be abandoned to the invading sea, with the entire village set to be “decommissioned” in 2045. Cardiff is projected to be two-thirds underwater by 2050. 

In the US, half a million homes will be on land that floods at least one a year by 2050. 

These northern nations won’t only have to contend with the demands of their own climate crisis, but also likely have to accommodate millions fleeing from the equator.