Among the few silver linings in the Intergovernmental Panel on Climate Change's recent report on the dire state of the planet under the yoke of climate change is that scientists miscalculated the fate of Himalayan glaciers. Rather than the icy reservoirs disappearing by 2035, as had been reported in 2007, science done since that time suggests that most should last through the end of this century and beyond.

That's not to say many will not continue to shrink, or that this will not be a big concern for the 2 billion people currently living downstream.

"It certainly marked a big change," said Himalayan glacier researcher Walter Immerzeel of Utrecht University in The Netherlands. "The Himalayan glaciers suddenly received lots of attention, and also from funding agencies...and the amount of research into Himalayan glaciers and hydrology has increased significantly."

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So in the years since the 2007 IPCC assessment a lot of important work was done to figure out the importance and quantities of glacier and snow melt for the water supply downstream. Several monitoring programs were also started on mass balances and length changes of glaciers programs to study the water cycle of Himalayan watersheds in general.

Still, there is a lot to learn, and it's not an easy place to learn it. Not only are the glaciers remote, but they are politically and socially sensitive, sometimes crossing international borders.

"Folks are getting tired of western scientists coming and saying Armageddon is happening, then leaving," said Ann Rowan of the British Geological Survey. "It's not like studying glaciers in Antarctica."

A lot of work up to now has necessarily been done using remote sensing from space, said Rowan. But remote sensing -- both imagery and gravity measurements of the mass of glaciers -- has a lot of limitations. For instance, debris covered glaciers are hard to measure from space. It's also hard to see from above whether a glacier has shrunk vertically -- or lost height.

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"There is very little field data," said Rowan. "We are talking about a very big area with a massive amount of ice." And it's not like scientists can extrapolate from what is going on in the more accessible, better understood and smaller Alps.

Those Himalayan glaciers covered with sand and rock, pose another set of problems."They are decoupled from climate somewhat," Rowan said.

"Debris thicker than a few centimeters has an insulating effect, yet they seem to loose mass similar to clean ice glaciers," Immerzeel added. "Possibly ice cliffs and supra-glacier ponds play an accelerating role. We used drones to investigate this in a pilot project and we would like to extend this to other regions."

Mt. Everest - the pinnacle of the Himalayan Mountains.iStock

Another unknown is the high altitude snowfall rates.

"We know almost nothing about precipitation at high altitude and its spatial variation," said Immerzeel. "We installed several gauges at 5,000 meters (16,400 feet), but maintenance and getting accurate long-term records remains a challenge."

Then there is the big difference between the glaciers in the Eastern Himalaya -- which receive moisture from the Indian Monsoon -- and the western Himalayan glaciers the Karakoram.

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But climate models have great difficulty simulating the monsoon.

"They can hardly reproduce the past, and the future is an even larger challenge," said Immerzeel. Better high-resolution models validated with ground data are required to solve this, but this is not something that is done overnight.

"We had an acceleration of mass loss since the 90s in the Eastern Himalaya, where the monsoon is the main control," said Rowan. Over the next century they could continue to lose mass, but changes in the monsoon could offset that, she said. "So glacier melt [in the eastern Himalaya] may not be a problem."

On the other hand, glaciers in the Karakoram seem to be gaining mass. Which just goes to show, again, how complicated the Himalaya climate picture is and how poorly understood it is.

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Still, while there is still a long way to go, the new assessment is a huge improvement over the 2007 report, which was based on the little information that was then available.

"There were very limited peer reviewed publications and conclusions were drawn on grey literature sources, because of the lack of properly published studies," said Immerzeel. "This has now all changed and a body of literature has developed over the past years on which AR5 (Assessment Report 5) is based."

To move ahead further, one thing is clearly needed: more field work to study what exactly is happening to the glaciers on the world's premiere mountains.