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Climate change threatens the world’s oceans

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The Intergovernmental Panel on Climate Change (IPCC) recently released its 5th climate assessment report and it spells bad news for our oceans. The IPCC is the principal international body responsible for assessing information on climate change. Since their last report in 2007, evidence for human influence on atmospheric and oceanic warming and sea level rise has increased. The IPCC consider it ‘extremely likely’ that the dominant cause of atmospheric and oceanic climate warming is a result of human influence.

The report includes information on changes in ocean temperatures from 1971 to 2010, as well as future predictions. Work has been done to compensate for problems in historic records of ocean temperatures, lending support to the IPCC’s findings.

It is ‘virtually certain’ that the upper ocean, from 0-700m, has warmed over the last 40 years. The temperature of the upper 75m of the ocean increased by 0.11°C per decade over this period. Furthermore, the IPCC findings indicate that it is ‘very likely’ that human actions have contributed significantly to the warming observed in this part of the ocean. The report also predicts continued ocean warming globally throughout the 21st century, with an increase of up to 2°C in the top 100m of the ocean. This increase will result in higher ocean temperatures than have been seen in the past 420,000 years, threatening to make extinct species that are sensitive to temperature changes, such as corals.

Ocean warming combines with other consequences of climate change such as ocean acidification, changes in ocean circulation and sea level rise, to affect the oceans’ ecosystems. The trends shown by the IPCC are already extremely worrying, but a report published by the International Union for Conservation of Nature (IUCN) and International Programme on the State of the Ocean (IPSO) states that the severity of the risks presented by climate change to the ocean and its supported ecosystems remain underestimated. Combined interactions between various aspects of climate change are likely to result in a greater threat to the health of the oceans than individual impacts.

Changes in the climate affect the lifestyle of many marine species. In terms of fish populations, the changes predicted by the IPCC report may result in changes to stock abundance or stock location. IPSO Scientific Director Alex Rogers says: “The IPCC’s findings reflect exactly what we are seeing in the ocean: massive changes in the distribution of marine organisms and marine ecosystems globally.”

It is not certain exactly how fish populations will change around the UK but some effects of climate change have already been seen. Scientists have observed that two-thirds of North Sea fish have shifted distributions in the past 25 years in response to warming sea temperatures.

Climatic variation may also hinder recovery of species vulnerable to over-fishing. This makes promoting sustainability in fisheries even more important. The declining trend of many of the world’s fisheries demands innovative action to counteract the combined pressures of climate change and overfishing. The SSC is working towards a sustainable future by creating voluntary codes of conduct to standardise labelling and encourage responsible sourcing of seafood. Find out who is a member of the SSC.

Article: Rebecca Giesler  Image: Alex LA
This blog was updated on 14/12/2016.