The main purpose of this ongoing blog will be to track planetary extreme, or record temperatures related to climate change. Any reports I see of ETs will be listed below the main topic of the day. I’ll refer to extreme or record temperatures as ETs (not extraterrestrials).😉
Main Topic: The Mediterranean Sea is Experiencing a Record-Smashing Heat Wave
Dear Diary. We’ve highlighted heatwaves on land this season, but what is going on in the oceans and seas? Last year the Atlantic basin had a record warm year. Thankfully there is a bit of a reprieve there this year but not in an adjacent body of water. The Mediterranean Sea is having a record warm season during 2025.
Here are more details from the Washington Post:
https://www.washingtonpost.com/weather/2025/07/04/record-marine-heat-wave-mediterranean-sea
The Mediterranean Sea is experiencing a record-smashing heat wave
Water temperatures have surged above 85 degrees in the Mediterranean Sea, where records have been broken every day for weeks.
July 4, 2025
People paddleboard on the Mediterranean in Barcelona on Wednesday. (Nacho Doce/Reuters)
By Ben Noll and Chico Harlan
The most extreme heat event on the planet right now is happening not on land but at sea.
A prolonged, record-smashing marine heat wave is scorching the Mediterranean, where water temperatures have hit levels unprecedented for the early summer. The Mediterranean’s average temperature is currently 26 degrees Celsius (78.8 degrees Fahrenheit), compared with a long-term average of 23 degrees Celsius (73.4 degrees Fahrenheit) at this time of year.
On a gradient map showing ocean temperature anomalies, the Mediterranean is a deep, blazing red.
In certain parts of the sea, particularly the western basin around Spain, France and Italy, temperatures are more than 7 degrees Celsius (12.6 degrees Fahrenheit) above the average.
“For large water bodies that’s ludicrous,” Jeff Berardelli, a U.S. meteorologist, said on social media.
Sea temperatures in the Mediterranean Sea have been record-breaking on more than 50 days so far in 2025. (Ben Noll/Data source: ECMWF/ERA5)
For most people, the event might not seem as obvious as the brutal heat wave hitting the region on land. Europe this week baked under an intense heat dome that led the Eiffel Tower to close its summit. But elevated marine temperatures can have extensive and dangerous consequences.
They can raise temperatures and humidity in coastal communities. They can provide extra moisture to the atmosphere, fueling stronger storms. And they can upend ecosystems, bleaching coral and triggering mass mortality events of certain species — such as sea grasses and sponges — that cannot escape to cooler waters.
“This particular event is a very concerning one,” said Karina von Schuckmann, a senior adviser on ocean science for policy at Mercator Ocean International. She described the ocean as the “sentinel” for planetary warming because it absorbs most of the excess energy generated linked to greenhouse gas emissions.
The Mediterranean as a hotspot
Marine heat waves are marked by long-lasting, expansive areas of well-above-average ocean temperatures, and are increasing in frequency and intensity amid a warming climate.
A yellow stony coral undergoes bleaching due to rising sea surface temperatures off the coast of Lebanon on June 27. (Ibrahim Chalhoub/AFP/Getty Images)
The Mediterranean — semi-enclosed and in one of the world’s fastest-warming regions — has become particularly prone to heat waves. The U.N. Intergovernmental Panel on Climate Change (IPCC) has described the Mediterranean as a “hotspot” for global climate risks. A 2023 study said that Mediterranean marine heat waves have grown in intensity, duration and frequency, “especially in the last decade.”
The Mediterranean typically hits its warmest point deep in the summer, around Aug. 18, topping out on average at 26.1 Celsius (79 Fahrenheit). Its all-time warmest temperature came last year, on Aug. 13, hitting 28.5 (83 Fahrenheit). But last year, in early July, the Mediterranean was 24 Celsius (75.2 Fahrenheit) — 2 degrees Celsius (3.6 Fahrenheit) cooler than it is now.
A buoy near the island of Mallorca, Spain, reported a water temperature of 31 degrees Celsius (87.8 degrees Fahrenheit) this week, while water offshore of Venice and Sanremo, Italy, was around 30 degrees Celsius (86 degrees Fahrenheit), according to satellite estimates.
Sea temperatures in the Mediterranean Sea are more than 7 degrees Celsius (12.6 degrees Fahrenheit) above-average in some places, with the highest actual temperatures near 30 degrees Celsius (86 degrees Fahrenheit). (Ben Noll/Data source: Copernicus Marine Service)
A severe (Level 3 out of 5) marine heat wave is affecting ocean areas between Spain and Sardegna, currently qualifying as one of the most intense on the planet. In recent days, the heat wave intensified to extreme (Level 4 out of 5) levels in the Alboran Sea, south of Spain, as well as in the Gulf of Lion, south of France.
What drives heat in the oceans
For a marine heat wave to form and intensify, several atmospheric and oceanic drivers need to converge.
During June, a powerful high-pressure system, spanning the lower and middle atmosphere, has been anchored over southern Europe and the Mediterranean Sea.
High-pressure systems cause air to sink, compress and warm. This particular dome of high pressure drew unusually warm air from North Africa into Europe, further increasing the level of heat it could produce.
Underneath the system, winds were light, and sunshine was plentiful — preventing cooler, subsurface seawater from churning to the surface.
Long-term warming of planet and its oceans, including a record-breaking year globally in 2024, is raising the bar on the potential intensity and duration of marine heat waves.
The convergence of natural and human-influenced factors is probably intensifying the heat wave in the Mediterranean, a region that saw consecutive years of record-breaking ocean warmth in 2023 and 2024.
A significant change in weather patterns, such as stronger winds and cooler air temperatures, is needed for this marine heat wave to ease. With another serious heat wave possible in mid-July, the Mediterranean heat is likely to last at least a few more weeks.
Here are more “ET’s” recorded from around the planet the last couple of days, their consequences, and some extreme temperature outlooks, as well as any extreme precipitation reports:
Here is More Climate News from Tuesday:
(As usual, this will be a fluid post in which more information gets added during the day as it crosses my radar, crediting all who have put it on-line. Items will be archived on this site for posterity. In most instances click on the pictures of each tweet to see each article. The most noteworthy items will be listed first.)