The world's sea surface is also at its highest ever recorded average temperature - yet another sign of the widespread nature of climate records. As the chart below shows, it's particularly notable given that ocean temperatures don't normally peak for another month or so.
Science groups differ slightly on precisely how much temperatures have increased, but all agree that the world is in by far its warmest period since modern records began - and likely for much longer.
Limiting long-term warming to 1.5C above pre-industrial levels - before humans started burning large amounts of fossil fuels - has become a key symbol of international efforts to tackle climate change.
A landmark UN report in 2018 said that the risks from climate change - such as intense heatwaves, rising sea-levels and loss of wildlife - were much higher at 2C of warming than at 1.5C.
Why has 1.5C been broken over the past year?
The long-term warming trend isunquestionably being driven by human activities- mainly from burning fossil fuels, which releases planet-warming gases like carbon dioxide. This is also responsible for the vast majority of the warmth over the past year.
In recent months, a natural climate-warming phenomenon known as El Niño has also given air temperatures an extra boost, although it would typically only do so by about 0.2C.
Global average air temperatures began exceeding 1.5C of warmingon an almost daily basisin the second half of 2023, when El Niño began kicking in, and this has continued into 2024. This is shown where the red line is above the dashed line in the graph below.
An end to El Niño conditions is expected in a few months, which could allow global temperatures to temporarily stabilise, and then fall slightly, probably back below the 1.5C threshold.
But while human activities keep adding to the levels of warming gases in the atmosphere, temperatures will ultimately continue rising in the decades ahead.
An extra half a degree - the difference between 1.5C and 2C of global warming - also greatly increases the risks of passing so-called tipping points.
These are thresholds within the climate system which, if crossed, could lead to rapid and potentially irreversible changes.
For example, if the Greenland and West Antarctic Ice Sheets passed a tipping point, their potentially runaway collapse could cause catastrophic rises to global sea-levels over the centuries that followed.
But researchers are keen to emphasise that humans can still make a difference to the world's warming trajectory.
This has meant some of the very worst case scenarios of 4C warming or more this century - thought possible a decade ago - are now considered much less likely,based on current policies and pledges.
And perhaps most encouragingly of all, it's still thought that the world will more or less stop warming oncenet zero carbon emissionsare reached. Effectively halving emissions this decade is seen as particularly crucial.
"That means we can ultimately control how much warming the world experiences, based on our choices as a society, and as a planet," says Zeke Hausfather, a climate scientist at US group Berkeley Earth.
"Doom is not inevitable."
Cover photo: Chile has seen forest fires in several regions in February, including La Araucanía (pictured)