Every month since June 2023 has ranked as the warmest ever recorded on the planet, compared to the corresponding month in previous years, stated the Copernicus Climate Change Service (C3S) in a monthly bulletin.

Including April, the global average temperature was the highest ever recorded for a 12-month period, with 1.61 degrees Celsius above the pre-industrial period average from 1850-1900.

Some of the extremes recorded - including months where sea surface temperatures set records - have prompted scientists to investigate whether human activity has now triggered a turning point in the climate system.

"I think many scientists have been asking themselves whether there could be a change in the climate system", said Julien Nicolas, lead climate researcher at C3S.

Greenhouse gas emissions from fossil fuel burning are the main cause of climate change. In recent months, the natural phenomenon El Niño, which warms surface waters in the eastern Pacific Ocean, has also raised temperatures.

Scientists have already confirmed that climate change has caused some specific extreme weather phenomena in April, including a heatwave in the Sahel, linked to possibly thousands of deaths.

Hayley Fowler, a climate researcher at Newcastle University, said the data show that the world is dangerously close to breaking the 2015 Paris Agreement goal of limiting global warming to 1.5 degrees Celsius.

"At what point do we declare that we have lost the battle to keep temperatures under 1.5? My personal view is that we have already lost this battle and that we need to seriously consider keeping it under 2C and reducing emissions as rapidly as possible", she said.

Countries agreed to the 1.5C goal at a UN climate summit in 2015. This is the level scientists say would avoid the most disastrous consequences of warming, such as lethal heat, floods and irreversible ecosystem loss.

Technically, the 1.5C target has not yet been missed, as it refers to a global average temperature over decades. However, some scientists have said the goal can no longer be realistically met and have urged governments to reduce CO2 emissions more quickly to limit overshooting the target.

The C3S dataset dates back to 1940, which researchers cross-checked with other data to confirm that last month was the warmest April on record since the pre-industrial period.