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The world’s remotest water towers are in retreat. The snows of Kilimanjaro in Africa are diminishing: between 1986 and 2017 the area of ice that crowns the most famous mountain in Tanzania has decreased by 71%. A tropical glacier near Puncak Jaya in Papua in Indonesia has lost 93% of its ice in the 38 years from 1980 to 2018. Melting tropical glaciers are together sounding an ominous warning.

Indonesia’s Puncak Jaya, known also as Carstensz Pyramid, has lost more than 90% of its ice since 1980. Image: By Alfindra Primaldhi, via Wikimedia Commons

The frozen summit of Huascarán, the highest peak in the tropics, in Peru has decreased in area by 19% between 1970 and 2003. In 1976, US scientists first took cores from the ice cap of Quelccaya in the Peruvian Andes: by 2020, around 46% had gone.

The darkening summits of the highest tropical mountains have a message for the world about the rate of climate change. “These are in the most remote parts of our planet − they’re not next to big cities, so you don’t have a local pollution effect,” said Lonnie Thompson of Ohio University.

“These glaciers are sentinels, they’re early warning systems for the planet and they are all saying the same thing.”

Millennial climate records

He and colleagues report in the journal Global and Planetary Change that they analysed the impact of warming on what they call “rapidly retreating high-altitude, low-latitude glaciers” in four separate regions of the planet: Africa, the Andes in Peru and Bolivia, the Tibetan Plateau and Himalayas of Asia, and the mountains of Papua province in Indonesia on the island known as New Guinea in the southwestern Pacific.

Each of the sample glaciers has yielded cores of ice that preserve, in their snow chemistry and trapped pollen, a record of many thousands of years of subtle climate change. And, since 1972, Earth observation satellites such as Nasa’s Landsat mission have monitored their surfaces.

In a world now heating as a response to greenhouse gas emissions into the atmosphere, where once snow had fallen, there is now rain to wash away the high-altitude ice. Glaciers serve as sources of fresh water for farmers and villagers in the tropical mountain zones: they also provide the river melt for many millions downstream.

The latest research confirms something climate scientists already knew: that almost everywhere, mountain ice is in retreat, with potentially devastating consequences for local economies. And the culprit is climate change driven by profligate fossil fuel combustion.

“These glaciers are sentinels, they’re early warning systems for the planet and they are all saying the same thing”

The Ohio researchers say: “Since the beginning of the 21st century the rates of ice loss have been at historically unprecedented levels.”

Within two or three years, the high snows near Puncak Jaya − these have powerful religious and cultural significance for the local people − will have gone.

But, the scientists argue, it is not too late to slow or stop the rate of greenhouse gas emissions into the atmosphere, and to slow or stop the retreat of many tropical glaciers.

“The science doesn’t change the trajectory we’re on,” said Professor Thompson. “Regardless of how clear the science is, we need something to happen to change that trajectory.” − ClimateNewsNetwork.net

Tim Radford, a founding editor of Climate News Network, worked for The Guardian for 32 years, for most of that time as science editor. He has been covering climate change since 1988.