Oceans cover about 71 per cent of the Earth’s surface and frozen land – the cryosphere – 10 per cent of the land surface. As global warming raises temperatures, those areas act as a buffer for heating on land. However, that process is melting the ice and making the seas hotter, and there are deep linkages between the oceans and all life on Earth.

Human-induced climate change is thus negatively affecting this delicate balance.

The Earth is getting warmer as more greenhouse gases in the atmosphere trap heat energy. This heat energy is unevenly spread though: while the overall surface temperature has increased by 0.87°C, the average land temperature has risen by 1.53°C, according to the Intergovernmental Panel on Climate Change.

This United Nations body says that the oceans have taken up 90 per cent of the excess heat in the climate system. But as they continue to warm, there will be profound impacts for marine life and ecosystems.

Marine heatwaves have already doubled in frequency and are longer lasting as well as more intense and extensive, but a new IPCC special report says that up to 90 per cent are very likely caused by human-induced warming. By 2080-2100, they could be 20-times more frequent than in the second half of the 19th century.

Meanwhile temperatures of permafrost areas are at record levels with average polar and high-mountain regions rising by 0.29°C since 2007 and much more greenhouse gases could be released into the atmosphere as frozen areas thaw. The IPCC says warming has led to widespread shrinking of the cryosphere, reducing the mass of ice sheets, glaciers, snow cover and the thickness of Arctic sea ice.

Sea levels rise not only because of the melting ice, but because thermal expansion changes the water’s density – but human-induced warming is now the main driver of rising sea levels. With the thawing of the Greenland and Antarctic ice sheets accelerating, sea levels could rise up to 110cm by 2100 with an increased frequency of major floods and storm surges.

Such extreme floods usually occur once every 100 years but could become annual in tropical locations by 2050 and may happen at least once a year in most locations by 2100. The consequences could be devastating for small island-states and low-lying cities.

Coral growth is hit by increased acidification and warmer oceans hold less oxygen, which can disrupt marine ecosystems, changing where different species grow or decline. That can affect food security and nutrition, with indigenous communities in the Arctic and coastal communities most at risk.

Almost half of coastal wetlands have been lost because of climate change or localised human action, according to the IPCC, and up to 90 per cent of wetlands could be lost by 2100. The potential catch of fisheries could fall by more than 20 per cent by then too.

There are many ways to respond to warming and rising sea levels. Co-operation and long-term planning could stave off some of the worst effects, but growing public dissatisfaction with the global policy response may stoke political pressure for much more ambitious action as countries consider strengthening their climate pledges.

We think adaptation is vital, even though this could become increasingly challenging because the more the Earth warms, the less opportunity there is to adapt.

Would you like to find out more? Click here to read the full report (you must be a subscriber to HSBC Global Research).

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