Global ocean temperatures hit record level for April and May
Long-term warming of the oceans from climate change has coupled with short-term natural variation to create a record-breaking year.
Global sea surface temperatures in April and May were the highest on record for those months, the Met Office has said.
Climate change caused by human emissions, combined with natural phenomena like El Nino, have pushed up ocean temperatures during the spring to a level never before seen since records began in 1850.
Scientists are expecting more records to be broken as the summer advances.
The North Atlantic temperature in May was around 1.25C above the 1961-1990 average – the highest anomaly for any month on record.
Antarctic sea ice is also “exceptionally low, the lowest on record for this date by a wide margin”, the Met Office said.
El Nino, and its counterpart La Nina, cycle every few years in the tropical eastern Pacific and produce a warming and a cooling effect respectively on the world’s oceans and atmosphere.
US meteorologists said last week that El Nino has now begun, characterised by a 0.5C rise above the long-term average temperature in the tropical eastern Pacific.
Professor Albert Klein Tank, head of the Met Office Hadley Centre, said: “Typically, airborne dust from the Sahara helps to cool this region by blocking and reflecting some of the sun’s energy.
“But weaker-than-average winds have reduced the extent of dust in the region’s atmosphere potentially leading to higher temperatures. Additionally, lighter-than-usual trade winds could be playing a role.
“All of these elements are part of natural variation within the climate system which are coming together to elevate sea-surface temperatures to higher levels.
“It is not believed that these factors represent a climate change-induced tipping point that produces runaway temperatures. However, they will add to climate and weather impacts this year.”
Meteorologists are also investigating the influence of the warm phase of the Atlantic Multi-decadal Oscillation since 2020, reduced emissions from shipping and persistent easterly winds from land warming the sea surface.
The Met Office predicts there will be an above average number of hurricanes this season because of the warming North Atlantic, despite that number usually falling during El Nino periods because wind shear blows them apart before they can properly form.
Julian Heming, a tropical cyclone expert with the Met Office, said: “We are getting indications from models of an Atlantic tropical storm development east of the Caribbean by the middle of next week.
“This would be highly unusual in this area so early in the season. June storms normally form further west in the Caribbean or Gulf of Mexico.
“The high sea-surface temperatures in the tropical Atlantic would likely be one of the main factors if this development did happen next week.”
El Nino could also be contributing to the Antarctic sea ice record lows this year, along with the Southern Annular Mode – which affects winds in the southern hemisphere – and human-driven climate change.
Dr Ed Blockley, lead of the Polar Climate Group at the Met Office, said: “Antarctic sea ice has been at very low levels since November 2016.
“This year we have seen Antarctic sea ice shrink to a record low-point for the time of year, following a second successive annual record minimum sea ice extent in February.”
