Hottest July on record hits 1.5 degrees above pre-industrial age, new data shows

Record ocean heat means extreme weather in Ireland becoming ‘more unpredictable’

July was the hottest month ever recorded on Earth, new data shows, leading scientists to call for more urgent action to reduce greenhouse gas emissions as global average temperatures for the month hit a new peak of about 1.5 degrees above pre-industrial levels.

The new data is from the European Union’s Copernicus Climate Change Service, which collates billions of measurements from satellites, ships, aircraft, and weather stations around the world.

“We just witnessed global air temperatures and global ocean surface temperatures set new all-time records in July,” Samantha Burgess, deputy director of the Copernicus Climate Change Service, said in a statement.

“These records have dire consequences for both people and the planet exposed to ever more frequent and intense extreme events.”


The average global temperature in July was 1.5 degrees above the pre-industrial average for the month, according to Copernicus measurements, hitting the level that global leaders agreed should be the limit to global warming in the Paris Agreement of 2015 so as to avoid the most dangerous consequences of climate change.

The new record reflects a sharp upward trend in global temperatures, though it does not mean that the world has warmed by 1.5 degrees permanently given the variability of the climate from year to year.

“Even if this is only temporary, it shows the urgency for ambitious efforts to reduce global greenhouse gas emissions, which are the main driver behind these records,” Dr Burgess said.

The new measurements confirmed that the global average temperature for July 2023 was the highest on record for any month, after the previous month was the hottest June ever recorded.

Global sea surface temperature also reached a record high in July, hitting 0.51 degrees above the average from 1991-2020, following a long period of unusually high sea surface temperatures that began in April.

Temperatures were particularly high in the North Atlantic, hitting 1.05 degrees above average in July. There were marine heat waves south of Greenland, in the Labrador Sea, in the Caribbean basin and across the Mediterranean Sea.

High ocean temperatures drive extreme weather because they put extra heat and moisture into the atmosphere and can alter air flows, according to Professor Robert Marsh of the University of Southampton’s National Oceanography Centre. This can cause severe wet weather in places like Ireland.

“The extra warmth and moisture provides for potentially extreme wet weather, wherever Atlantic low-pressure systems reach Europe,” Prof Marsh told The Irish Times.

Furthermore, warmer oceans add to unpredictability, because if they alter the jet stream – an airflow high in the atmosphere – it can cause more intense heat and drought in Europe by diverting storms away.

“Because of our latitude and location far to the northwest of Europe, Ireland and the UK are sensitive to small changes in the jet stream, hence summer 2022 was hot and dry while summer 2023 is cool and wet,” Prof Marsh said.

“In short, our weather – and extremes thereof – are apparently becoming more unpredictable.”

While there was drought in the Mediterranean and dry conditions in parts of Asia, the United States, and Latin America, July was wetter than average in most of northern Europe including Ireland.

The month was also wetter than average across large parts of the world, including the northeast of North America, Afghanistan, Pakistan, northeastern China, northern and eastern Australia and Chile.

Overall, the month was 0.72 degrees warmer than average temperatures for July between 1991 and 2020 and about 1.5 degrees above the pre-industrial average.

While July saw heat waves around the world, including in the Mediterranean, temperatures in Antarctica and several South American countries were well above average.

The level of Antarctic sea ice was by far the lowest seen in July since satellite observations began, at 15 per cent below average.

Naomi O’Leary

Naomi O’Leary

Naomi O’Leary is Europe Correspondent of The Irish Times