The rising ocean temperature risk assesses the danger linked to the warming of the sea surface near the asset. It does not use an absolute temperature threshold, but counts how many months per year the sea temperature exceeds the level considered anomalous for that month relative to the historical record: the more anomalous months, the higher the risk. It is computed at the marine grid point closest to the site, only for coastal sites, within 30 km of the coast and below 20 m of elevation: for an inland, non-coastal site the risk does not apply.
Indicator. Number of marine heatwave months (Marine Heatwave Months, MHM), 0–12 per year. It is a simplified monthly approximation of the marine heatwave concept (not the rigorous daily Hobday definition). Computed only for coastal sites, within 30 km of the coast and below 20 m of elevation, at the nearest marine grid point; for an inland, non-coastal site the risk does not apply and is shown as N/A.
Data. Monthly mean of the sea surface temperature (SST), in °C, from the Copernicus Climate Data Store (CDS). The 1950–1970 historical period is used to compute the thresholds. Scenarios: SSP1-2.6 / SSP2-4.5 / SSP3-7.0 / SSP5-8.5.
Calculation.
(1) From the monthly historical SST series the 90th percentile (P90) is computed for each calendar month, over all available historical years.
(2) For each future year and scenario the months in which the projected SST reaches or exceeds the P90 threshold of the respective month are counted: this count is the MHM.
(3) Thresholds on the MHM are applied to assign the level 0–5.
Thresholds → level A–F.
• F: = 12 (all months above P90)
• E: ≥ 9
• D: ≥ 6
• C: ≥ 3
• B: ≥ 1
• A: = 0.
The 1 / 3 / 6 / 9 / 12-month thresholds and the 1950–1970 reference period are a xNatura choice without a published source.
From physical to impact. The physical level (A–F) is combined with the production process's sensitivity through the risk matrix (6 physical levels by 5 sensitivity bands) → impact level; the damage curve converts the level into a damage factor, from which the Version 2025 value at risk is derived. The damage factor per class is an xNatura estimate without a published source: the value is indicative.
Sources.
• [Copernicus Climate Data Store (CDS)](Copernicus Climate Data Store (CDS))
• [A hierarchical approach to defining marine heatwaves](A hierarchical approach to defining marine heatwaves)
• [Special Report on the Ocean and Cryosphere in a Changing Climate](Special Report on the Ocean and Cryosphere in a Changing Climate)
• [Global warming and recurrent mass bleaching of corals](Global warming and recurrent mass bleaching of corals).
Indicator. Number of marine heatwave months (Marine Heatwave Months, MHM), 0–12 per year. It is a simplified monthly approximation of the marine heatwave concept (not the rigorous daily Hobday definition). Computed only for coastal sites, within 30 km of the coast and below 20 m of elevation, at the nearest marine grid point; for an inland, non-coastal site the risk does not apply and is shown as N/A.
Data. Monthly mean of the sea surface temperature (SST), in °C, from the Copernicus Climate Data Store (CDS). The 1950–1970 historical period is used to compute the thresholds. Scenarios: SSP1-2.6 / SSP2-4.5 / SSP3-7.0 / SSP5-8.5.
Calculation.
(1) From the monthly historical SST series the 90th percentile (P90) is computed for each calendar month, over all available historical years.
(2) For each future year and scenario the months in which the projected SST reaches or exceeds the P90 threshold of the respective month are counted: this count is the MHM.
(3) Thresholds on the MHM are applied to assign the level 0–5.
Thresholds → level A–F.
• F: = 12 (all months above P90)
• E: ≥ 9
• D: ≥ 6
• C: ≥ 3
• B: ≥ 1
• A: = 0.
The 1 / 3 / 6 / 9 / 12-month thresholds and the 1950–1970 reference period are a xNatura choice without a published source.
From physical to impact. The physical level (A–F) is combined with the production process's sensitivity through the risk matrix (6 physical levels by 5 sensitivity bands) → impact level; the damage curve converts the level into a damage factor, from which the Version 2025 value at risk is derived. The damage factor per class is an xNatura estimate without a published source: the value is indicative.
Sources.
• [Copernicus Climate Data Store (CDS)](Copernicus Climate Data Store (CDS))
• [A hierarchical approach to defining marine heatwaves](A hierarchical approach to defining marine heatwaves)
• [Special Report on the Ocean and Cryosphere in a Changing Climate](Special Report on the Ocean and Cryosphere in a Changing Climate)
• [Global warming and recurrent mass bleaching of corals](Global warming and recurrent mass bleaching of corals).