Ship logbooks help to understand climate variability

Trabajo presentado en el 2nd International Workshop on Maritime Flows and Networks, celebrado en París (Francia), del 25 al 27 de abril de 2016Since the early times of sail navigation, weather and climate conditioned shipping routes and dates. Thus, the transatlantic ships tried to avoid the Azores High Pressure Center to prevent getting stack in the middle of the dead calms and suffering starvation and scurvy. The hurricanes seasonality (with peak activity between June and November) dictated the traveling dates to and from the Caribbean. For the travel back to Europe, navigation profited from the Atlantic westerlies regularity. In the Indian Ocean, the English and Dutch trade with India and Indonesia was adapted to the Asian monsoon seasonal cycle. These few examples illustrate how ships depended on weather and climate. Lives and properties onboard relied on the ability of captains, officers and crew to scrutinize and interpret weather and sea. Consequently, weather observation was one of the most important topics in the training of seamen. Due to this relevance, the content of the ship logbooks (a legal document recording the main facts occurred on board) included thorough daily or even hourly records on weather and sea conditions, including wind force and direction, cloud cover, precipitation, sea estate and currents. Fortunately, dozens of thousands of these logbooks have been preserved in different archives, mostly in Europe (Wheeler and García-Herrera 2008). Although meteorological instruments were systematically onboard only after the Brussels Conference in 1853, it has been shown that wind observations are reliable and comparable to the modern records since the 17th century (García-Herrera et al 2005). These observations are highly valuable because they cover a period of centuries when climate was only modulated by natural forcings and extend into the industrial era when human emissions of strong anthropogenic Greenhouse Gases emissions. Additionally, they are the only known source of meteorological observations over the world’s Oceans for the pre-instrumental era In this presentation we will show how these records can be used to build centennial long indices able to characterize the behavior of different climate phenomena. The records from the Manila Galleon (a commercial route connecting Manila and Acapulco for more than 250 years) will help to unveil secular trends in the behavior of the Pacific monsoon through (García et al 2001). Wind records from the English Channel will be used to construct the longest instrumental series of atmospheric circulation over the Atlantic, which allows to characterize climate variability over Europe since the end of the 17th century (Barriopedro et al, 2014), and the influence of wind circulation anomalies on the occurrence of European extreme precipitation and temperature events. Finally, we will show how the observations of the ships connecting Europe with their African and Asian colonies can be used to build the first objective records of the West African Monsoon strength and the Indian Summer Monsoon onset since the 19th century (Gallego et al 2015). These are just some examples of the climatic potential of ship logbooks records. Only a joint effort between historians, seamen, meteorologists and climatologists could fully exploit all the possibilities kept in the archives towards a better understanding of past climates and future changes.Peer reviewe