The earth has lost 28 trillion tonnes of ice. Here's what that means for our future

A sea level rise of two metres would render the current Thames Flood Barrier obsolete and would require consideration of alternative ways to protect the capital

August 26, 2020
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As human activities continue to roast the planet, so its once stable climate is being knocked seriously out of kilter. Unprecedented changes are taking place at great speed, not least in those parts of the world covered with ice. Colossal changes are often described using big numbers. The trouble is that these very large numbers are impossible for the mind to grasp. So, the standard response to the recent news that our world has lost a mind-blowing 28 trillion tonnes of ice since 1994 is a shrug and perhaps a muttered “so what.”

This is a problem, because at a time when we all need to be fully engaged in the battle to stop further climate breakdown, there remains an unhelpful tendency to turn away from facts that seem either meaningless or unpalatable, or both.

Let's look at things another way. Consider the amount of water held in seven average-sized public swimming pools. Then imagine that amount of water pouring off the Greenland ice sheet and into the North Atlantic—for every single second of 2019.

This is just one snapshot of what is happening to the world's ice, from the glaciers of the Alps and the Himalayas, to the ice caps of Svalbard and Iceland, and the prodigious ice sheets that bury Greenland and Antarctica. The Earth's cryosphere—our world's stock of frozen water—is vanishing at a rate not seen since the end of the last Ice Age around 10,000 years ago.

For those whose livelihoods depend upon the winter sports industry, this sounds a death knell. For those in Asia, who rely for energy and irrigation upon the great rivers that drain the Himalayan glaciers, it means dwindling power supplies and plunging crop yields as the century progresses. And for all those who live anywhere near a coastline, it promises ever-growing flood risk and eventual inundation.

For wherever ice melts on our world it will, ultimately, find its way to the ocean. Where the sea touches the land really is climate breakdown's front line, and it is a front line that is only moving one way—inland. During the 20th century, global sea levels rose by around 20cm, but over the last few decades the rate of rise has increased alarmingly. From around 1.4mm a year for much of the 20th century, it shot up to 5mm annually between 2015 and 2019. With ice loss accelerating fast, it is unlikely to stop there.

While such numbers might seem small, it is worth recording that every centimetre rise sees an additional one million people living in the coastal zone come under threat from permanent inundation. It may also not take long for such apparently trivial numbers to become far larger.

According to the Intergovernmental Panel on Climate Change, a worst-case scenario would result in the global sea level climbing 110cm higher by the century's end. This is bad enough in its own right, and sufficient to displace many tens of millions of people from low-lying coastal areas. A number of peer-reviewed studies, however, point to a much more rapid rise, which could hike the sea level by more than 250cm in the next 80 years.

Increasingly, observations suggest that these more pessimistic scenarios could well be right. If the rate of sea level rise doubles every 20 years—and recent measurements suggest that this is perfectly reasonable—then by 2100 the oceans would be rising by a staggering 8cm a year, swamping the world's coastal towns and cities so rapidly that defence would be impossible.

And that wouldn't be the end either. The UK government's target to achieve net-zero emissions by 2050 will come far too late, and there is as yet little interest from most governments in slashing greenhouse gas emissions at the rate the science demands. The corollary of this is that keeping the global average temperature rise (compared to pre-industrial times) below 2°C seems increasingly unlikely.

Disturbingly, the last time our world was a couple of degrees warmer—during the Eemian interglacial 125,000 years ago—sea level was between six and nine metres higher than it is today. To put this into perspective, a sea level rise of two metres would render the current Thames Flood Barrier obsolete and would require consideration of alternative ways to protect the capital, while a four metre rise would leave the city of Miami stranded nearly 100km offshore.

The message then is clear. Either we take immediate action to drastically curtail emissions, or we leave our children and their children to face a broken world. Without decisive action, we will soon see a world where previously ice-fed rivers are reduced to mere trickles, bringing harvest failure and famine. Oceans bloated by ice melt will continue to climb remorselessly well into the next century, until every coastal town and city is gone.