Every year, human activities release billions of tons of greenhouse gases into the atmosphere. These gases trap heat from the Sun, making the Earth warmer than it would be without them. Over 90% of the extra heat from greenhouse gases gets absorbed by the ocean, driving marine temperatures to alarmingly high levels. Some estimates suggest that oceans have warmed over 1.5°C since the Industrial Revolution started, more than 250 years ago.
Marine organisms are particularly sensitive to warming, partly because they have narrow “thermal safety margins”. This is the difference between the environmental temperature and the maximum temperature an organism can tolerate without experiencing harm.
A narrow thermal safety margin means there is little room for temperatures to rise before they start causing damage to marine life. To make matters worse, marine organisms have limited options for avoiding high temperatures. One option is for them to migrate to greater depths, which is not always possible.
