Rising global temperatures are causing Earth’s glaciers and ice sheets to disappear at previously unprecedented rates. As this change accelerates it will affect ecosystems and the lives of billions of people – from those living in coastal regions at risk from sea level rise, to those who depend on mountain glaciers for their water supply.
The Greenland Ice Sheet Lost 532 Gigatonnes of Water in 2019
The cryosphere is the scientific term for the world’s repositories of frozen water – i.e. glaciers, ice sheets, sea ice and permafrost. In 2019, the United Nations’ Intergovernmental Panel on Climate Change (IPCC), which represents the global scientific consensus on climate change, published its latest special report on oceans and the cryosphere. The report states, unequivocally, that global heating has led to “widespread shrinking of the cryosphere”. Essentially, a warmer world means less ice.
All people on Earth depend directly or indirectly on the ocean and cryosphere.
IPCC Special Report
Ocean & Cryosphere in a Changing Climate, 2019
How much ice are we losing?
2006-2015
The IPCC’s latest Special Report on the Ocean & Cryosphere in a Changing Climate (SROCC) showed that between 2006 and 2015, the ice sheets covering Greenland lost ice at an average rate of 278 gigatonnes per year. The Antarctic ice sheet, meanwhile, was losing 155 gigatonnes per year, and glaciers outside of these ice sheets were losing ice at an average rate of 220 gigatonnes per year. Recent studies suggest these rates have increased since then.
The pace of change is incredibly fast already, within a generation. And it’s still accelerating.
Dr. Carolina Adler
Executive Director, Mountain Research Initiative (MRI) & IPCC Lead Author
To put this into perspective, each gigatonne is one billion metric tonnes – or roughly the same weight as 10,000 fully-loaded US aircraft carriers, according to NASA. The agency’s GRACE (Gravity Recovery and Climate Experiment) mission, which features in The Last Glaciers, found that a total of 5,641 gigatonnes of ice of was lost in Greenland and Antarctica in just 15 years between 2002 and 2017. This, NASA’s scientists point out, is enough to cover the entire state of Texas in a sheet of ice eight metres thick.
Is it just a result of rising temperatures?
Rising air and ocean temperatures are the main causes of the shrinking cryosphere, but there are other factors at play too. The length of time glaciers spend covered in snow is generally getting shorter. Any reduction in the amount of snow cover, or increase in the amount of dark debris can reduce their ability to reflect sunlight – something scientists refer to as their ‘albedo’. A reduced albedo can also speed up the process of glacial melt.
Earth’s glaciers are disappearing at previously unprecedented rates
Earth’s glaciers are disappearing at previously unprecedented rates
The melting of the Earth’s two major ice sheets – in Greenland and Antarctica – is currently the main contributor to sea level rise. Roughly 680 million people around the world live in coastal areas less than 10 metres above sea level, putting their homes and lives at risk.
As the world’s mountain glaciers disappear meanwhile, entire alpine ecosystems are being affected. This is disastrous for biodiversity, but also for the lives and livelihoods of the 670 million people who live in high mountain areas around the world.
Water scarcity & knock-on effects
Mountain glaciers act as natural water towers, regulating the flow of water to those living downstream. As they disappear, millions more who depend on glacial melt for their water supply will struggle. A comprehensive 2019 study suggested that the decline of glaciers in the Hindu Kush Himalaya region alone would affect the lives of some 1.65 billion people who live downstream.
The political consequences of water sources becoming less predictable could be equally catastrophic. The glacier-fed Indus river, for example, runs through the territory of three nuclear-armed powers – China, India and Pakistan. In a 2010 interview, veteran US diplomat Richard Holbrooke said that falling water levels in the Indus river “could very well precipitate World War III.
100 million farmers in India & Pakistan alone receive irrigation from the Indus and Ganges Rivers, which have significant inputs from glaciers and snowmelt.
IPCC Special Report
Ocean & Cryosphere in a Changing Climate, 2019
As mountain glaciers retreat & permafrost thaws, landslides, rockfalls, & flash floods will become more common
As mountain glaciers retreat & permafrost thaws, landslides, rockfalls, & flash floods will become more common
Retreating glaciers & melting ice sheets
Further reading
WIRED
Cold war – The grim fight to save Northern Italy’s glaciers
NASA
NASA’s interactive global ice viewer
The Guardian
World will lose 10% of glacier ice even if it hits climate targets
