Earth’s 12 months of record warmth
Today, Copernicus – Europe’s Earth observation programme – announced that May was the warmest on record globally. Yet another month of record-breaking global warmth makes it the 12th month in a row that has been Earth’s warmest on record.
The global average surface air temperature for the last 12 months (June 2023 – May 2024) has been 1.63C above the 1850-1900 pre-industrial average. This makes it higher, albeit temporarily, than the aspirational limit of 1.5C set out in the Paris climate agreement back in 2015.
It’s worth emphasising that the 1.5C limit will be considered crossed when human-induced global warming consistently exceeds this level. Nevertheless, the past year gives a flavour of what the future holds for climate and weather if we stay above this threshold.
Sea surface temperature has broken records too, with May being the 14th month in a row where it has been the warmest on record for the respective month of the year.
Why has it been so warm?
The primary cause of this long stretch of record-breaking global warmth is human-induced climate change, caused by the ongoing release of greenhouse gases into the atmosphere.
This enhances Earth’s natural greenhouse effect, causing the atmosphere and oceans to retain even more heat, and causes the climate to warm further.
Another small influence during the past year has been the naturally occurring El Nino climate phenomenon. This leads to a warming of the equatorial Pacific Ocean, which in turn causes Earth’s atmosphere to become warmer – by up to around 0.2C.
Why does it matter?
As our atmosphere and oceans warm, the amount of heat energy and moisture available for weather systems increases.
A warmer atmosphere increases the intensity and likelihood of heatwaves, which in turn can worsen droughts and create environments in which wildfires are more able to thrive.
Having more moisture in the atmosphere can lead to greater amounts of rain falling, and the rain that falls can be more intense, which heightens the risk of flooding and puts pressure on infrastructure.
Increases in global temperature are causing sea ice and glaciers to melt, which is leading to rising sea levels, threatening coastal communities.
Effectively, the warming climate is making our weather and its impacts more extreme, with far-reaching impacts on us and our environment.
How long will it continue?
El Nino is currently fading, with predictions that there will be a switch to its counterpart, La Nina, later this year. La Nina is a cooling of the equatorial Pacific Ocean, which tends to cool Earth’s atmosphere by up to around 0.2C.
Therefore, there is an expectation that the second half of this year will see an end to the streak of record-breaking global temperatures each month. Nevertheless, they are expected to remain massively above the pre-industrial average.
The UK’s 10 warmest years on record have occurred since the year 2000. After the warmest spring and May on record, all eyes are on whether 2024 will join this list.
