Oceanic Warming

As the earth is warmed by its increasing atmospheric greenhouse gas content, the vast majority (91%) of this excess heat is taken up by the oceans (Lindsey and Dahlman, 2023). As the sea surface is quick to reflect these temperature changes, Sea Surface Temperature (SST) is a useful metric for tracking overall ocean warming. 
71% of the world's coastlines warmed over the period of 1982–2010 (Ruela et al 2020). Fig. 1 demonstrates this trend - since 1994, global SSTs have consistently measured above the 1955-2006 average, with most years reaching above average since 1987 (Lindsey and Dahlman, 2023)

SST is projected to increase most significantly in the Northern Atlantic, as is demonstrated in fig. 2 from Ruela et al (2020). Figure 2.a is based on the intermediate emissions outcome (RCP 4.5), while figure 2.b is based on the extreme worst-case scenario (RCP 8.5) in which emission continue to increase. Regardless of scenario, it seems the Northern Atlantic will experience the most intense warming globally. 

Scottish waters are already reflecting this Northern Atlantic warming. Hughes et al (2018) estimate for the 1893–2016 period, an average of between 0.05-0.07oC warming occurred every decade in Scottish waters. Fig. 3 from Tinker and Howes (2020) shows the distribution of this warming. Warming is seen around entire Scottish coastline, with the Northeast experiencing the highest warming in the country (equivalent to the Southeast English coast) at between 0.2 - 0.24oC per decade (Tinker and Howes, 2020). Looking to the future, Tinker and Howes (2020) collate various studies to conclude a predicted continued warming trend for the North Sea of between 2.6 and 3oC for the period of 1960 – 2099.

Impacts
Oceanic warming brings a multitude of negative impacts, both to biodiversity and to humanity. Rising ocean temperatures change the range in which marine species can comfortably live. Invasive species previously thought unsuited to cold Scottish waters are now increasingly observed surviving in the country, such as Pacific Oysters and Slipper Limpets (please see linked sheets). Invasive organisms compete with native, economically important species, negatively affecting the industries depending on them. 
In addition to gradual changes, worsening marine heatwave events bring short-lived, extreme heat that can wipe out marine life within their concentrated areas (Frölicher et al, 2018). Furthermore, oceanic warming is known to increase the risk of extreme weather events (Venegas et al, 2023) – patterns that have already been observed in Scotland. 2023 was found to be the wettest year on record in the country, despite also being the 13th sunniest, suggesting multiple extreme storm events were responsible for the extreme volumes of rain (James Hutton Institute, 2023).