COP28: Why Bhutan fears 'a tsunami in the sky'

Nestled between 1,500 and 3,000 metres above sea level in the east of the Himalayan mountain range, Bhutan is an enclave with extremely varied landscapes, between forests, green valleys and several hundred glaciers. Karma Toeb is a glaciologist, head of the cryosphere department at the National Center for Hydrology and Meteorology. He has been working for twenty years to reduce the risk of glacial lake ruptures. We met him at his country's pavilion at Expo City in Dubai.

Karma Toeb, a Bhutanese glaciologist, at his country's pavilion at COP28. © Géraud Bosman-Delzons/RFI

By: Géraud Bosman-Delzons Follow


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From our special correspondent in Dubai,

Bhutan was the world's first carbon-negative country. What does this mean?

More than 60% of Bhutan's land area is covered by forests. These absorb and sequester carbon from the atmosphere. Their sequestration capacity is greater than what we emit in greenhouse gases. And the forest cover continues to expand because our Constitution imposes this minimum of 60% of our territory.

We are proud because only Suriname has achieved carbon neutrality, and Bhutan is the first to have a negative balance sheet, as we announced at COP15 [in 2009]. We now hope that the big countries will follow us.

What is the climatic situation in Bhutan, especially that of the glaciers?

There are about 700 glaciers in Bhutan. All of them are in recession. They lose a lot of mass every year: 16 meters per year for the smallest, and 30 to 35 meters for the really big glaciers.

This melting ice causes the level of glacial lakes to rise, and they grow larger and larger. There are 517 such lakes in Bhutan. Seventeen are classified as potentially hazardous, and four or five are critical. These are huge lakes with a reservoir moraine [natural dam] that is more than 100 metres deep. We fear that these moraines will break up and cause a Glof (Glacier Lake Outburst Floods), a "sudden emptying of a glacial lake", what we call a "tsunami of the sky", with huge floods. We are particularly monitoring Thorthomi and Raphstreng lakes in Lunana, northern Bhutan. They are separated only by a thin moraine that contains ice cores. Lake Thorthomi is located above the Raphstreng.

What would be the consequences of such an explosion?

First of all, we know for sure that it will happen, but we don't know when. The glaciers are growing and the hydrostatic pressure against the moraine is increasing. Studies conducted in the 80s and 90s predicted that this could happen as early as 2010.

If this moraine were to break, 53 million cubic metres would flow into the valley. About 1,000 people could be in the path where 70% of the villages are located, as these are the only fertile places to farm. The communities closest to the lake are only 3 or 4 km away, so they might only have 15 minutes to escape and 5 to 6 hours for those 100 km below. This is a problem that is taken very seriously in Bhutan.

Lake Raphstreng, in Lunana, is located below Thorthomi (right, outside the photo). A break in the thin moraine between the two would be catastrophic, warns Karma Toeb. © Flickr

What solutions are being considered?

There was a project to lower the level by five metres. This lasted five years, from 2009 to 2012. Nearly 17 million cubic metres of water were artificially discharged. It was quite risky, because in this area, the terrain is made up of ice, so no backhoe loaders, no machines were used. 300 people were mobilized to dig a natural drainage channel. We are now in 2023, these lakes have not given way. Maybe it's because of our adaptation work.

Another tool is the Glof risk mapping established for local and regional authorities. Finally, we are developing early warning systems. If something abnormal happens up there, the sensors, we will transmit the information and we will be able to warn the people in the valley to evacuate.

How did you work to understand this?

It is essentially data collection work in the field, on the Thana, Gangju La and Shodug glaciers. Mass balance measurements are made to estimate the thickness of ice lost or gained per year. We also look at how many metres the front of the glacier is receding, how fast. The same goes for lakes: we measure their widening, their depth and the condition of the moraines.

► Understanding glacier measurements: Martial Bouvier, from La Poste to glacier monitoring

And then the Bhutanese are dependent on these glaciers for fresh water...

Yes, and not just for drinking and washing, but for agriculture, electricity...

What do you think of these negotiations? Do you think that the States have taken the measure of the urgency?

This is the first time that a global stocktaking has been carried out. The problem of mountains will be mentioned in the declaration on the Global Stocktake. This will be a very important document for us. We are also working to get mention of the need for an international dialogue on mountains.

If your priorities are not reflected in this text, the impacts of climate change in your environment will not be taken into account at the international level. It is therefore essential to secure our protection and adaptation, for which we are particularly worried.

I believe that the States have taken the measure of the urgency. They negotiate night and day to find a compromise and there are 200 of them. The first step is to agree on paper. But it's true that people are waiting to see concrete actions implemented.

► Listen again: Melting glaciers, a danger for the planet

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