Glaciers are slow-moving rivers of ice that usually grow in winter and shrink in summer.

But with global temperatures rising, many glaciers are losing more ice than they're gaining, meaning the world's glaciers are shrinking.

Philippus Wester, a chief scientist at the International Centre for Integrated Mountain Development, called it "the climate crisis you haven't heard of."

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It's no longer unimaginable to have a world without glaciers.

In September, the Intergovernmental Panel on Climate Change released a report that said around the world, glaciers are losing hundreds of billions of tons of ice every year.

The report's scientists said if humans don't get carbon emissions under control, glaciers would continue to decline, causing "landslides, avalanches, rockfalls, and floods."

Another report found that a third of the icecaps in the Himalayas, which run from Afghanistan to Myanmar, were doomed.

The report's leader, scientist Philippus Wester, called it "the climate crisis you haven't heard of."

These 40 photos show glaciers that are disappearing or on the brink of collapse around the world.