We have seen how quickly and decisively a few months war at sea completely changed winter conditions in Northern Europe.Mild winters were suddenly replaced by the harsh conditions of the Little Ice Age, conditions the Europeans had not experienced for more than 100 years. This happened not only once, but three times in a row, namely during the first war winter (1939/40), the second war winter (1940/41) and the third war winter (1941/42).

From a climatic point of view,World War I ended with a severe “bang” during late 1918. At Spitsbergen, the winter temperatures jumped up by 8ºC in a few years. The Northern Hemisphere became suddenly and significantly warmer. The terms “Greening of Greenland” and “Warming of Europe” became common expressions.

Several important factors need to be mentioned first. The land war started in 1914, while the naval war commenced at its fullest only in the autumn of 1916.

The most significant climatic change which took place during the World War One occurred at Spitsbergen, a remote archipelagos situated between the North Cape of Norway and the North Pole. During the winter 1918/19, temperatures suddenly exploded, phenomenon described by the eminent Norwegian scientist B.J. Birkeland as probably the greatest temperature deviation on earth22.

When WWI started, in August 1914, the German Navy had 28 U-boats. Their capacity was limited. From August 1914 until December 1916, the Uboats sank 2,200,000 tons of enemy ships. This means a total number of 1,500 Allies’ vessels, or an average of about three vessels per day. On the other hand, the loss of U-boats increased mainly due to a newly developed depth charge with 300 pounds TNT or amatol, in 1915, which had become available and fully operable since 1916.

The situation became dramatic for Britain in early 1917. U-boats sank more ships than shipyards could deliver. In April 1917 only, the annual rate of the previous years was reached in only one month (860,000 tons). In 1917, U-boats alone sank 6,200,000 tons, the equivalent of more than 3,000 ships.

The onslaught of U-boats culminated with the sinking of almost one million tons per month (like, for instance, in April 1917). Although the British Navy was able to prevent hundreds of real or suspected attacks, the result was not at all encouraging. Only 11 U-boats could be sunk in a four-months period. New protection measures became a major necessity: convoying, patrols, a new promising weapon, depth charges, etc.

The main minefields from the North Sea were on the Britain’s East Coast including the Strait of Dover, Helgoland Bight and Northern Barrage. A rough figure for each of these areas is 50,000 mines. The total number of mines in the North Sea was of 190,000 and the total number during the whole WWI, of 235,000 sea mines.

Many intense encounters in the Barents Sea could have played a major role in the icing of the high North, in February 1915 and the harsh winter in the North-West of Europe (1916/17). Since early 1915, more than 450,000 tons of coal and 90,000 tons of weaponry had been shipped to the Russian port Archangel. Russian and German navies had laid thousands of sea mines. Dozen of minesweepers were permanently in service. U-boats sank 25 ships in late 1916 and 21 vessels between April and November 1917.

Let’s face the facts: WWI was the most destructive event the North-East of the North Atlantic had ever faced. Much of the North Atlantic water going North, and the whole North Sea was part of the naval battleground for four war years before moving northwards, towards Spitsbergen. Since 1918, the Arctic Ocean warmed twice: in 1938 and in 1980. Between slightly above the Arctic Circle and the pole, the warmest years on record in the Arctic Ocean were 1937 and 1938. War winter 1939/40 put an abrupt end to the Warming of Europe. The most convincing conclusion is that WWI has played a significant role in the warming of the climate since 1918, but how? We started the chapter on Spitsbergen warming in 1918 by pointing out that two decades of sustained warming could only come from the Norwegian Sea, and/or from the northern arm of the Atlantic Gulf current.

After having gone through three cold war winters (1939-1942 world), Europe was forced to go through an even much bigger climate change experiment. With Japan’s ambush at Pearl Harbour with dozen of ships and hundreds of bomber air planes, on the 7th of December 1941, a new chapter of anthropogenic climate change began to be written. For the following four decades, climate switched to a colder status. There is nothing pleasant about global cooling. Yet, for all those who are overwhelmed by the scientists affirmations that carbon dioxide is warming up our earth, the large area experiment initiated by the naval warfare can come as a blessing. Global statistics have never shown such a pronounced temperature downturn trend before war winter 1939/40, phenomenon which lasted until 1980th and which only went back to the level of 1939 in 1980. Carbon dioxide (CO2) can be excluded from the list of possible reasons for the global cooling. In the 70s, a serious debate on the danger of a new ice age broke out. The New York Times reported that scientists observed many signs according to which Earth may be heading for another ice age. The Science magazine published articles about the possible extended glaciations of the Northern Hemisphere, and regarded a return of the Ice Age as a very possible event. TIME magazine claimed that, climatologically speaking; cassandras are becoming increasingly worried about their cooling trend findings, which may be considered as the signal of another ice age.

The overview of the naval warfare in the wide oceanic spaces will always remain incomplete. The exterior aspect of the seas remains unchanged before and after a sea battle. All signs left on the water surface by ship movement, sea mine explosions, or shipwrecks disappear quickly. Only oil and cargoes may disturb the picture of unadulterated nature for a short while. Any scenery of action is back to normal very soon, as far as an external viewer is concerned.

Naval war and supply across the seas became part of ocean physics for a long time. Allies sailed with 300.000 vessels across the North Atlantic. If every ship turned the sea about on a width of 20 meters, we can sum all up to 6 Million meters or 6,000 km. This means that the sea surface of the North Atlantic Ocean was ploughed through three times. Naval Escort Vessels and freely operating war ships certainly doubled the space of ‘turnover’. Many thousands of torpedoes, many hundred thousand depth charges and bombs, and multi-millions of shells certainly doubled again the already ‘doubled space’ of turnover. Presumably not less than a dozen times the surface layer of the middle North Atlantic Ocean was completely ‘churned and turned’ in just over six years. Any ‘turning’ effect could reach down to a few meters, five to ten meters (vessel draught), 200-300 meters (depth charge), thousands of meters (sinking ships, cargo, ammunition, etc). As mid-latitude, seasonal climatology heavily depends on the upper sea surface layer of about 30-60 meters, global naval war is a force to reckon.

The climatic change during WWII has two distinct periods, namely the period before Pearl Harbour and the period thereafter. From September 1939 until early 1942, naval warfare was largely confined to European waters. Great climatic relevance of the war at sea in the North Europe became dramatically clear during the extremely cold winters of 1939/40, 1940/41, and 1941/42. Outside European waters, naval activities during 1940 and 1941 were largely confined to Eastern North Atlantic. The most affected areas were the transportation routes from Britain to North America and from Britain to Gibraltar and Dakar.

A number of German U-boats were already in the Atlantic when the war broke out, in September 1939. Britain came up rapidly with the convoy system. A convoy consisted of up to sixty, either slow or fast vessels, accompanied by up to ten naval escort ships. The first convoy set off in September. Also in September 1939, groups of three to five naval vessels were formed to control large areas in the North Atlantic Ocean. These groups criss-crossed the seas day and night searching for U-boats and dropping depth charges when a U-boat was detected, or assumed to be around. German surface naval vessels, such as the battleships Deutschland, Scharnhorst and Gneisenau, sailed in the Atlantic escorted by a number of escort vessels. Until the end of December 1939, the Allies and Neutrals had lost 55 vessels with a total tonnage of 300,000. Five U-boats were also sunk.

Effective supply was essential in order to obtain a war victory. Thousands of accounts talk about dramatic events at sea. On September 21/22, 1940, the Convoy HX72 was caught in a twelve-hour battle, in which eleven ships were sunk and other two damaged, with a total loss of 100,000 tons of supplies and around 45,000 tons of fuel. At the beginning of the war, the convoy escort was small in number and not always sailing with the group for the full distance of the voyage. In 1941, the average size of a convoy was of about forty ships, accompanied by six naval vessels as escort. Later on, certain escorts became quite massive. For example, in 1942, the Convoy ON202, made up of 38 merchant ships, had an escort of 3 destroyers and 3 corvettes; while the escort for the Convoy ONS18 comprised 6 destroyers, 8 corvettes, and one trawler.

On December 8th 1941, The New York Times reported: Yesterday morning Japan attacked the United States at several points in the Pacific, with a major attack on Pearl Harbour. President Roosevelt ordered United States forces into action and a declaration of war was expected soon. Seven hostile actions from a naval ship off the coasts of San Francisco to Malaysia were reported (NYT, 08 December 1941). This was going to continue for four years. Allied forces, namely USA, Britain and the Netherlands, had a total strength of about 220 big naval vessels, including 70 submarines. Japanese had 230 naval vessels and 64 submarines in December 1941. Several aircraft carriers were available on both sides, able to deploy many thousands of airplanes.

The use of planes during the Atlantic war progressed tremendously as the USA entered the war after the attack of Pearl Harbour, in December 1941. The US production was estimated at 127,000 planes in 1942, which exceeded the total number of German aircraft production during the whole war period. It meant that more aircrafts of a much better quality and power were available for surveillance, bombing and combat missions in the Atlantic Ocean. Even in August 1942, eighteen American B-24 aircraft, called ‘Liberator’, were ready to escort Atlantic convoys. These planes had a range of 2,400 miles, fuel tanks of 2,500 gallons and reached altitudes of 30,000 feet. After the winter 1942/43, anti-submarine missions were assigned to the long-range aircrafts in the Atlantic, which sank 33 submarines between April 1943 and September 1944. 209 long-range bomber aircrafts were available in the US navy in July 1942 and the number increased progressively to 2,200 aircrafts which searched and chased U-boats between June 1943 and May 1944.

There was a short period, from January until June 1942, when U-boats operated successfully along the American East coast. Within half a year, they sank about 400 vessels. In only two weeks a few U-boats could sink 25 ships with a total tonnage of 200,000, out of which 70% were tankers. The summer of 1942 meant the end of the U-boat operation called ‘Paukenschlag’ (Drumbeat). The US Navy had become effective. The Gulf Current flows from Florida to Cape Hatteras, before turning around at Cape Hatteras and flowing into the Atlantic and eastwards, to Europe. The warm current together with the colder Atlantic water off Cape Hatteras built a highly sensitive water body having a significant impact on the daily weather, seasons and climatic conditions in the Northern Hemisphere. The war in these sea waters is to be held responsible for considerable changes of the seawater sphere.

In August 1942, the German U-boat fleet had reached the number of 340, with almost 300 boats more than three years earlier. During the whole war period, the U-boat force was of about 1,100 boats, out of which 850 participated in at least one combat mission and 630 were destroyed during enemy attacks.

As already mentioned above, the Allies completed over 300,000 Atlantic voyages during this war period. The heroic story of merchantmen has been written and rewritten in an uncountable number of books and essays. Here is only one case. In March 1943, two convoys (SC122 and HX229) suffered forty-four hour attack of the U-boats on their route. During the three-day battle that ensued, twenty-three merchantmen of the two convoys were killed. At the same time, the convoy HX229A, which included thirteen tankers, eight refrigerator and four cargo liners (39 ships), was directed northeast, towards Greenland. There they came upon Arctic conditions. The three convoys, with a total of 131 ships, carried about 1,000,000 tons of cargo – petroleum fuel, frozen meat, food, tobacco, grain, timber, minerals, steel, gunpowder, detonators, bombs, shells, lorries, locomotives, invasion barges, aircraft and tanks.

The destiny of many tankers proved to be extremely disastrous for their crew and for the ocean waters in the same time. The Allied and Neutral countries had about 1,000 tankers permanently in service since 1942. The total loss of tankers with a size of over 1,600 tons was of 4,221 ships between December 1941 and May 1944.

One of the most effective means of penetrating deep below the sea surface is the depth charge. Depth charges, which could explode at a depth of 500 feet, were in use since 1942. The ‘Hedgehog bomb’, a highly powered explosive fired by a multi-barrelled mortar and filled with Torpex, was also in use. Its range was of 250 yards ahead of the escort vessel. When attacking ships, they could fire twenty-six depth charges in pairs, set to explode at 500 feet and 740 feet alternately, every ten seconds.

After the WWI experience, transport ships were equipped with guns for protection against U-boats and surface raiders. During 12 months of war, 3,000 vessels were armed with a 4.7-inch gun manned usually by six trained gunners.

Russians received about 4,000,000 tons of cargo, including 7,000 aircrafts and 5,000 tanks via the most difficult and dangerous route going from Britain to Murmansk. Climatically, this was the most sensitive sea route and probably many times more effective in climate changes terms then the naval activities at one thousand miles further south. Out of the total shipped cargo, 7% was lost in the sea. Danger came not only from the arctic climate, but from the attacks of the German Navy and Luftwaffe from their North Norway bases. The Luftwaffe had 264 aircrafts in that area, while the British Fleet Air Arm and the Royal Air Force flew 17 combat missions to North Norway between January 1942 and November 1944, which involved around 600 airplanes. Convoys started to sail in August 1941; the 35th convoy sailed in May 1945; convoys guarded a total of 715 ships. 100 merchant ships, with a total of 600,000 tons, were lost. The German side lost five surface naval ships including a battle ship and a battle cruiser and 32 submarines. British Navy lost 20 surface vessels and one submarine.

Between 1940 and 1943, an 110,000 mines barrage was placed by Britain between Orkney and Iceland. The ‘Mk XX’ mines were supposed to prevent U-boats from reaching shipping routs in the Atlantic. Whether the barrage was a serious threat to U-boats or not is not a certain fact. It seems that it was not. But it would have been a tremendous threat to the sea if the mines had exploded prematurely.

Even if information can’t be very extensive in such a brief presentation of the naval warfare between 1942 and 1945, it is enough to give a general idea of the climatic phenomenon and to raise the awareness that oceans had been ‘stirred and shaken’ in a way that could have caused their unusual cooling which lasted four decades.