Autumn in Germany might confront intense weather reminiscent of hurricanes, fueled by the Atlantic's unprecedented warmth.
Ever since 2023, ocean temperatures have been reaching unprecedented highs, breaking records in the Mediterranean Sea. This excess heat could potentially be released as severe autumn storms, even reaching Germany. This escalates the likelihood of hurricanes and flooding in our own backyard.
While Earth's air temperature has been consistently breaking records due to human-induced climate change, the seas have taken longer to warm up - at least until 2023. That year, institutes globally recorded unprecedented temperature heights, particularly in the North Atlantic.
Seas are crucial in weather development as they function as gigantic energy storage systems. Compared to air, water has a significantly higher heat capacity, requiring four times the energy to raise its temperature by one degree, but then releasing that energy four times as intensely.
These warming seas have taken years to reach this point. The current marine heat records are the result of the heat from the previous year, with the warm surface water also being mixed deeper, increasing the energy reservoir.
Storm risk surge in Europe due to warmer seas
The release of this stored energy can be dangerous, especially if it happens suddenly. This is most likely when cold air masses move south in the fall and meet the still-warm seawater. Even in October, the seawater temperature averages about 22 degrees (1982-2011 data), with the past years showing a significant increase in contrast: around 26 degrees in September and approaching 25 degrees in October. These growing contrasts can trigger intense storm situations.
Heated seawater also transfers heat to the atmosphere and increases evaporation. This results in a humid atmosphere in the higher layers, which remains cold due to strong temperature differences between warm and cold air masses. This temperature disparity creates intense dynamics, leading to the formation of massive, water-rich thunderstorms with heavy rain, strong winds, and sometimes even tornadoes. If the jet stream is far from the Mediterranean, these storms can develop into storm lows, similar to the formation of hurricanes, which can further intensify into severe storms known as Medicanes.
The threat of these intense storms was demonstrated by last year's weather events. A severe storm system in the western Mediterranean caused concern in several coastal countries from France to Algeria. Medicane Daniel set records with heavy rainfall in Greece and deadly floods in Libya shortly after.
Uncertain forecast with alarming model predictions
Germany's recent record rainfall for the twelve wettest months in a row is also linked to the warmer seas. The moisture from the Mediterranean increases the risk of heavy rainfall in Germany. Meanwhile, the overly warm Atlantic plays a significant role in our westerly wind weather. The persistently high water levels in northern Germany during the past winter were due to a combination of moist Atlantic air and stuck weather patterns.
It is still unclear where and when these extreme weather events will occur. The risk generally increases from September to November and peaks between October and November. Long-term models provide a preliminary estimate for this year. The American NOAA predicts cooler air moving from northwest to southwest Europe, leading to wetter conditions in the Mediterranean and also affecting Germany. Similarly, the European EFFIS model shows similar trends in its latest calculations.
This scenario could pose a significant risk to Germany. For instance, Vb-lows can collect a lot of moisture from the Mediterranean and move towards Central and Northern Europe, leading to extreme rainfall. This has resulted in significant floods in regions like the Czech Republic and Poland in the past.
Potential for severe storms and flooding in Germany
According to long-term models, the Mediterranean may stabilize in the fall, but Central and Northern Europe are likely to remain unstable and wet due to the moist air from the Atlantic. It would not be surprising if the upcoming winter resembles the previous one, with severe storm systems likely to occur. The rule at the Atlantic and in the North and Baltic Seas is: the more energy in the system, the stronger the storms.
We saw this last year on the Baltic Sea. A storm intensified so much over the warm waters that it caused record storm surges with significant damage in parts of Schleswig-Holstein. A series of powerful storms swept from the British Isles to Scandinavia, with Norway experiencing record wind speeds of over 200 kilometers per hour. If long-term model predictions are accurate, similar events can be expected in the coming winter.
As an expert, it's crucial to be aware of the weather's unpredictability worldwide and to warn of potential dangers with foresight. The essence is simple: the more heat we introduce into the air and seas, the more volatile the climate becomes and the more intense the outbursts.
For years, researchers have crunched the numbers on various aspects of our environment. Their findings have sounded alarms about the changes we're currently witnessing. If unchecked human impact on climate continues, the repercussions will be significantly more severe. Not all energy dynamics follow a straight line, but instead, exhibit exponential growth and have critical thresholds. Failure to adapt swiftly to these climate shifts and their consequences may lead to future storms striking with unrelenting force, turning existing disasters into bigger calamities.
The Commission has highlighted the role of warmer seas in intensifying storm situations and increasing the risk of severe weather events in Europe. This year, long-term models predict that the Mediterranean may stabilize, but Central and Northern Europe will remain unstable and wet, potentially leading to another winter of severe storm systems and flooding.
