This is what Earth's hottest summer on record looks like

Graphs show the dire reality of spiking temperatures around the world, in what is quickly shaping up to be Earth's hottest year since records began.

Antarctic sea ice was at record low levels in June, July, and August due to alarmingly high land and ocean temperatures. Credit: Ted Mead/Getty Images

Key Points

• New data shows that the northern hemisphere's 2023 summer was the warmest on record globally by a large margin.
• Such anomalous temperatures put 2023 overall just 0.01 degrees below 2016 for the warmest year on record.
• The impacts have led to global heatwaves, fires, and floods, with expects worried the trend could accelerate.

Earth just had its hottest three months on record.

The European Union-funded Copernicus Climate Change Service (C3S), which routinely reports on changes observed in global surface air temperature and sea ice cover, this week published a batch of research data on the 2023 northern hemisphere summer. Its findings were alarming.

“Global temperature records continue to tumble in 2023," said Samantha Burgess, deputy director of C3S. “The scientific evidence is overwhelming – we will continue to see more climate records and more intense and frequent extreme weather events impacting society and ecosystems, until we stop emitting greenhouse gases.”

Earth recorded its hottest European summer on record in 2023

Using billions of measurements from satellites, ships, aircraft, and weather stations around the world, C3S concluded that the months of June, July, and August in 2023 were, by a large margin, the warmest on record globally.

The global average temperature was 16.77C – 0.66 degrees above average – while the European-average temperature was 19.63C – 0.83 degrees above average.

Such anomalous temperatures put 2023 just 0.01 degrees below 2016 for the warmest year on record.

What do these high temperatures mean?

Extreme heat during the northern hemisphere summer has fuelled a spate of natural disasters, not only across Europe but around the world. Fires, floods, and heatwaves have devastated communities in North and South America, India, Japan, and China, to name just a few. If record temperatures keep rising on this trajectory, such impacts are likely to continue and increase.

“Climate breakdown has begun,” UN secretary-general António Guterres said on Thursday.

“Scientists have long warned what our fossil fuel addiction will unleash. Our climate is imploding faster than we can cope with, with extreme weather events hitting every corner of the planet.”

The world’s hottest day was on 7 July, with a global average of 17.23C, and the month overall was warmer than any other July in Earth’s recorded history.

August, meanwhile, is estimated to have been around 1.5C warmer than the preindustrial average for 1850 to 1900 - that is, the threshold below which the world’s nations are trying to keep global heating. If this temperature excess is sustained over months and years, then such climate ambitions will have failed.

What does this mean?

July saw record-breaking heatwaves in several locations around the world, notably in the United States, Mexico, and China, and around the Mediterranean. In addition to its impacts on crops and livestock, energy and transport infrastructure, and water supply, such extreme heat also poses serious dangers to human health.

A March 2023 study found that the early signs and symptoms of heatstroke can affect the nervous, digestive, and cardiovascular systems, and noted that extreme heat could lead to multiple organ dysfunction and failure, and death. Experts in the US have warned that 2023’s heatwaves could result in a record number of heat-related deaths this year.

Antarctic sea ice extent, which refers to the amount of frozen ocean around Antarctica and is extremely variable from season to season and year to year, remained at a record low for the June-July-August period.

The deficit, which measured 12 per cent below the monthly average, was by far the largest negative anomaly for August since satellite observations began.

What do low levels of Antarctic sea ice mean?

While Antarctic sea ice has usually been able to recover during its winter in June-July-August, it has not returned to expected levels this year. Sea ice is important for a number of reasons, but partly because it helps regulate Earth's temperature by reflecting the Sun's heat back into space, thus preventing it from being absorbed at the ocean’s surface and fuelling further warming.

Experts are worried that if the sea ice continues to deteriorate faster than it recovers, it may reach a point of no return and accelerate the warming of the planet even more.

Global average sea surface temperatures have been unusually high since April 2023, and continued to rise in August, reaching the highest level on record across all months at 20.98 degrees Celsius.

Every day from 31 July to 31 August global average sea surface temperatures were above the previous record from March 2016, and almost every day since 5 August the North Atlantic sea surface temperature has been above the previous record.

What do higher ocean temperatures mean?

Ocean temperatures influence other climate-related impacts, including both land temperatures and sea ice melt. Not only does the ocean soak up heat, which can contribute to ice melting and cause sea levels to rise, it also drives weather patterns such as heavy rainfall and heatwaves. Experts have suggested that rising ocean temperatures may have played a role in the northern hemisphere summer’s extreme heat and wildfires.

“I think we are definitely going to see a lot of extremes in the upcoming years simply because the system is more powerful,” CSIRO honorary fellow Dr Wenju Cai, who specialises in global climate variability and change, told the ABC last month. “There is a great deal of energy in that ocean warming, and it could power so much more extreme events.”