Timetable set on oceans’ struggle
"A warming climate could eventually cause changes in the ocean that have never happened before." Stephanie Henson, National Oceanography Centre
BRITAIN: More than half the world’s oceans could suffer multiple symptoms of climate change over the next 15 years, including rising temperatures, acidification, lower oxygen levels and decreasing food supplies, new research suggests.
By midcentury, without significant efforts to reduce warming, more than 80 per cent could be ailing - and the fragile Arctic, already among the most rapidly warming parts of the planet, may be one of the regions hit hardest.
The study, published yesterday in the journal Nature Communications, used computer models to examine how oceans would fare over the next century under a business-as-usual trajectory and a more moderate scenario in which the mitigation efforts promised under the Paris Agreement come into effect. In both scenarios, large parts of the ocean will be altered by climate change.
Nearly all of the open sea is acidifying because of greenhouse gas emissions. But the researchers found that cutting greenhouse gas emissions could significantly delay future changes, giving marine organisms more time to migrate or adapt.
‘‘Things that live in the ocean are used to regular variability in their environments,’’ said lead study author Stephanie Henson, a scientist at the National Oceanography Centre at the University of Southampton in Britain.
But she said a warming climate could eventually cause changes in the ocean that had never happened before - hotter temperatures, lower ph or less oxygen. When this happened, some organisms might no longer be able to tolerate the changed conditions and would be forced to migrate, evolve as a species or face possible extinction.
There is a large degree of uncertainty in the scientific community about how organisms will react. But there is evidence to suggest major challenges ahead. Mass coral bleaching events in the past few years have been largely attributed to unusually warm water temperatures. Large-scale coral death on the Great Barrier Reef last year is thought to be strongly linked to climate change.
The researchers focused on four climate-influenced ‘‘drivers’’ of marine ecosystems: temperature, ph, oxygen levels and ‘‘primary production’’, or how much food is available to a community. They noted that 99 per cent of the open ocean was experiencing a climatedriven change in ph, or ocean acidification. The subtropics and the Arctic are also experiencing sea surface temperatures beyond their natural ranges.
Under a business-as-usual climate scenario, the researchers have projected that by 2030, 55 per cent of the world’s oceans will experience changes in more than one of these factors - temperature and ph, most commonly - beyond the range of natural variability. By 2050, this number rises to 86 per cent.
Under the moderate climate scenario, the researchers predict that 34 per cent of the oceans will be affected by changes in multiple drivers, and 69 per cent by 2050. In general, they concluded that climate mitigation could delay climate-influenced changes by about 20 years. This delay could buy time for organisms to move or adapt to their surroundings.
- Washington Post