Dr Moses Amweelo

The ocean has long taken the brunt of the impacts of human-made global warming, according to United Nations Climate Change. As the planet’s greatest carbon sink, the ocean absorbs excess heat and energy released from rising greenhouse gas emissions trapped in the Earth’s system. 

Today, the ocean has absorbed about 90% of the heat generated by rising emissions. As excessive heat and energy warms the ocean, the change in temperature leads to unparalleled cascading effects, including ice melting, sea-level rise, marine heat waves, and ocean acidification. 

These changes ultimately cause a lasting impact on marine biodiversity and the lives and livelihoods of coastal communities beyond, including around 680 million people living in low-lying coastal areas, almost 2 billion who live in half of the world’s coastal megacities, nearly half of the world’s population (3.3 billion) that depends on fish for protein, and almost 60 million people who work in fisheries and the aquaculture sector worldwide. 

Extreme sea level events that used to occur once a century will strike every year on many coasts by 2050, no matter whether climate heating emissions are curbed or not, according to a landmark report by the world’s scientists. 

The stark assessment of the climate crisis in the world’s oceans and ice caps concludes that many serious impacts are already inevitable, from more intense storms to melting permafrost and dwindling marine life. But far worse impacts will hit without urgent action to cut fossil fuel emissions, including eventual sea level rise of more than four meters in the worst case, an outcome that would redraw the map of the world and harm billions of people. 

The report from the Intergovernmental Panel on Climate Change (IPCC), approved by its 193 member nations, says, “All people on Earth depend directly or indirectly on the ocean” and ice caps and glaciers to regulate the climate and provide water and oxygen. 

But it finds unprecedented and dangerous changes being driven by global heating. Sea level rise is accelerating as losses from Greenland and Antarctica increase, and the ocean is getting hotter, more acidic, and less oxygenated. 

All these trends will continue to the end of the century, the IPCC report said. Half the world’s megacities, and almost two billion people, live on coasts. Even if heating is restricted to just 2°C, scientists expect the impact of sea level rise to cause several trillion dollars of damage a year and result in many millions of migrants. 

“The future for low-lying coastal communities looks extremely bleak,’’ said Prof. 

Jonathan Bamber at Bristol University in the UK, who is not one of the authors of the report. 

“But the consequences will be felt by all of us. There is plenty to be concerned about for the future of humanity and social order from the headlines on this report.” 

The new IPCC projections of likely sea level rise by 2100 are higher than those it made in 2014, due to unexpectedly fast melting in Antarctica. Without cuts in carbon emissions, the ocean is expected to rise between 61cm and 110cm, about 10cm more than the earlier estimate. 

A 10cm rise means an additional 10 million people are exposed to flooding, research shows. 

The IPCC considers the likely range of sea level rise but not the worst-case scenario. Recent expert analysis led by Bamber concluded that up to 238cm of sea level rise remains possible by 2100, drowning many megacities around the world.

 “This cannot be ruled out,” said Zita Sebesvari at the United Nations University, a lead author of the IPCC report. 

Even if huge cuts in emissions begin immediately, between 29cm and 59cm of sea level rise is already inevitable because the ice caps and glaciers melt slowly. Sea levels will rise for centuries without action, Sebesvari warned. 

“The dramatic thing about sea level rise is if we accept one meter happening by 2100, we accept we will get about four meters by 2300. That is simply not an option we can risk.’’ 

The heating oceans are causing more intense tropical storms to batter coasts, the IPCC report found, with stronger winds and greater deluges of rain. 

For example, Hurricane Harvey’s unprecedented deluge, which caused catastrophic flooding, was made three times more likely by climate change. Ocean heating also harms kelp forests and other important ecosystems, with the marine heatwaves that sear through them like underwater wildfires having doubled in frequency in the last 40 years. 

They are projected to increase by at least 20 times by 2100, the IPCC reported. Extreme El Nino events, which see heatwaves in some regions and floods in others, are projected to occur twice as often this century whether emissions are cut or not, coral reefs, vital nurseries for marine life, will suffer major losses and local extinctions. 

Across the ocean, heat, acidification and lower oxygen are set to cut fisheries by a quarter and all marine life by 15% if emissions are not slashed. 

The IPCC report also records the large reduction in Arctic ice. This loss exacerbates global heating because the exposed darker ocean absorbs more heat from the sun than highly reflective ice, scientists announced that the Arctic Sea ice in 2019 shrank to its second lowest extent in the 41-year Satellite record. 

Rising temperatures increase the risk of irreversible loss of marine and coastal ecosystems. Currently, widespread changes have been observed, including damage to coral reefs and mangroves that support ocean life, and migration of species to higher latitudes and altitudes where the water could be cooler. 

Latest estimates from the UN Educational, Scientific and Cultural Organisation warn that more than half of the world’s marine species may stand on the brink of extinction by 2100. 

At a 1.1°C increase in temperature nowadays, an estimated 60% of the world’s marine ecosystems have already been degraded or are being used unsustainably. A warming of 1.5°C threatens to destroy 70% to 90% of coral reefs, and a 2°C increase means a nearly 100% loss – a point of no return.

*Dr Moses Amweelo is a former minister of works, transport and communication. He earned a doctorate in Technical Science, Industrial Engineering and Management from the International Transport Academy (St Petersburg, Russia).