A Cold Controversy: Himalayan Glaciers
05/01/10 16:17
A controversy has
been brewing over glaciers and climate change,
especially the glaciers of the Himalayas and the
Tibetan plateau, a vast region that spans India,
Pakistan, Bhutan, Nepal, the Tibetan region of
China, and other parts of China too. The conflict
began last November after the Indian
government produced a report on their part
of the Himalayas, focusing on how the leading
edges of their glaciers (called the
snout) have been trending over the
past century or so. Were the snouts advancing?
Retreating? Using many lines of evidence, the
report stated that the snouts of their glaciers
were mostly retreating, but some were advancing.
The most important conclusion of the report was
that the movement of the snouts did not seem to
be related to climate change.
A strong negative
reaction to the India report came from
Rajenda Pachauri,
who is the head of
the IPCC, the UN scientific and
technical branch charged with delivering the
best available research on how climate change is
affecting the planet. He’s also head a group
based in India called TERI. He’s very famous and widely
respected in climate change circles, and on
behalf of the IPCC he received a Nobel Peace
Price a few years ago (and I made a
video
in December 2009
that includes Pachauri).
Pachauri disputed the conclusion that global warming was not affecting the snouts of these glaciers in India. His reaction was strong and vociferous and covered by a number of major media outlets, several of which picked up on a major 2007 IPCC report (Working Group 2, Fourth Assessment Report) that stated that Himalayan glaciers could disappear by 2035.
I’ve long thought that this was an extreme and alarmist date, but several media outlets are now reporting that this reference is probably a typographical error, and that original paper referred to the Himalayan glaciers disappearing by 2350, or 315 years after 2035.
This is a stupid argument. The Indian government report really states that the movement of the snouts of the glaciers they studied don’t seem that related to broader climate trends. However, the report clearly states that the overall mass of these glaciers is declining and has been declining for over a century. They did not see evidence of an acceleration in mass loss as has been seen in Alaska and Greenland over the past 20 years, but those glaciers are quite different regionally and latitudinally. In other words, global warming is making us lose glaciers in the Himalayas, but the loss is not as fast as in some other places.
The report clearly shows that the link between the movement of the snout and the overall change is mass is very weak at best. Most of the ice in a glacier, of course, is not at the edge but in the middle. And trying to look for signals for changes in the interior is like trying to read a letter by looking at the side of the paper. It won’t tell you very much. Thus, Pachauri’s condemnation of the government report is unfortunate, and I think that the negative response really missed the point of the report.
So what do we know is happening to these glaciers?
It is important to recognize at the outset that these are tropical glaciers, like those of the Andes in South America or the high peaks of eastern Africa. There are also lots of glaciers in temperate regions, such as the Alps in Europe and the Sierra Nevada and Cascades of North America. And of course there are high-latitude glaciers, such as those of Alaska, northern Canada and Russia, the Arctic, Greenland, and Antarctica. It’s also worth pointing out that glaciers do not contribute much to the water in rivers and lakes downstream. That water comes from seasonal snowpack, which normally lasts one year or less. Snow falls on top of the glacier in winter and melts over the warm summer, entering the surface and groundwater portions of the hydrological cycle. Glaciers are like the savings account for freshwater ecosystems. Snowpacks are the checking account — they get drained far more rapidly than savings accounts (at least, like my personal checking account).
Globally, the majority of glaciers are losing volume, usually referred to as their mass (or mass balance). However, there are patterns in glacial loss that vary by latitude (tropics vs temperate vs high latitude) and by region (Himalayas vs Andes).
Recent reports by groups such as WWF-India suggest that smaller glaciers may be the most vulnerable to climate change. And a video report from WWF-Nepal shows very significant impacts that are occurring on their side of the Himalayas and some powerful responses to adapt to the emerging conditions in the Gokyo region. A new video from the Asia Society called On Thinner Ice is another good demonstration of the undeniable shifts that are occurring with glaciers in the Himalayas.
I am personally afraid that there may be some attempts to use this controversy as a means of discrediting Pachauri, the IPCC, TERI, or climate science more generally. These would be foolish conclusions to draw from the incident. The real story as I see it is that we’ve been focused on the wrong data points. We should be looking at what’s happening in the interior of glaciers in addition to their edges.
The data about the overall mass balance of Himalayan glaciers is terribly concerning. There are several trends that should be noted:
1. A 2008 paper by Kehrwald et al. in Geophysical Research Letters looks in the middle of many glaciers using ice cores. Glaciers are laid down in layers, with the most recent layers on the top. Using some very clever techniques to date particular layers to radioactive debris from old nuclear bomb explosions, the authors were able to show that the top layers for a lot of glaciers have disappeared — the outer wrapping, in effect, may date back to the 1950s, the 1930s, or even older. These glaciers are thinning from the top down, and they are certainly not accumulating new layers. This is a scary trend because it suggests that we’ve been watching the wrong parts of glaciers for the past century — the snouts — and missed the loss of the bulk of the ice.
2. What’s happening to the water? Perhaps the most concerning aspect of recent research is the suggestion that these glaciers are not simply melting. They are sublimating, which means that more frozen water may be disappearing directly into the atmosphere as water vapor rather than going through a transition to liquid water, which would presumably cause flooding — or at least enter the network of rivers and streams throughout South Asia. The Kehrwald author team call this process “surface wasting.” This distinction is important because it implies that the bulk of the glacial mass may not be lost in a way that would be of even temporary benefit to farmers or cities in what is actually the semi-arid region South Asia. I have heard anecdotal reports of extreme surface wasting occurring in the Sierra Nevada of California in recent years, which would affect the urban water supply of many important US cities.
3. Finally, we know a great deal about the historical degree of change that the current period of warming represents for tropical glaciers. In a 2006 PNAS paper, Lonnie Thompson and colleagues argue that the current period of warming for all tropical glaciers is unprecedented for at least 5200 years. He uses multiple lines of evidence (ice cores, plant records, geological and chemical analyses). All point in the same direction. Their conclusion is that low latitude, high altitude glaciers are at risk of disappearing in the near future, but that does not mean by 2035. He means over a timescale of centuries (that is, “near” in a geological timescale).
Pachauri disputed the conclusion that global warming was not affecting the snouts of these glaciers in India. His reaction was strong and vociferous and covered by a number of major media outlets, several of which picked up on a major 2007 IPCC report (Working Group 2, Fourth Assessment Report) that stated that Himalayan glaciers could disappear by 2035.
I’ve long thought that this was an extreme and alarmist date, but several media outlets are now reporting that this reference is probably a typographical error, and that original paper referred to the Himalayan glaciers disappearing by 2350, or 315 years after 2035.
This is a stupid argument. The Indian government report really states that the movement of the snouts of the glaciers they studied don’t seem that related to broader climate trends. However, the report clearly states that the overall mass of these glaciers is declining and has been declining for over a century. They did not see evidence of an acceleration in mass loss as has been seen in Alaska and Greenland over the past 20 years, but those glaciers are quite different regionally and latitudinally. In other words, global warming is making us lose glaciers in the Himalayas, but the loss is not as fast as in some other places.
The report clearly shows that the link between the movement of the snout and the overall change is mass is very weak at best. Most of the ice in a glacier, of course, is not at the edge but in the middle. And trying to look for signals for changes in the interior is like trying to read a letter by looking at the side of the paper. It won’t tell you very much. Thus, Pachauri’s condemnation of the government report is unfortunate, and I think that the negative response really missed the point of the report.
So what do we know is happening to these glaciers?
It is important to recognize at the outset that these are tropical glaciers, like those of the Andes in South America or the high peaks of eastern Africa. There are also lots of glaciers in temperate regions, such as the Alps in Europe and the Sierra Nevada and Cascades of North America. And of course there are high-latitude glaciers, such as those of Alaska, northern Canada and Russia, the Arctic, Greenland, and Antarctica. It’s also worth pointing out that glaciers do not contribute much to the water in rivers and lakes downstream. That water comes from seasonal snowpack, which normally lasts one year or less. Snow falls on top of the glacier in winter and melts over the warm summer, entering the surface and groundwater portions of the hydrological cycle. Glaciers are like the savings account for freshwater ecosystems. Snowpacks are the checking account — they get drained far more rapidly than savings accounts (at least, like my personal checking account).
Globally, the majority of glaciers are losing volume, usually referred to as their mass (or mass balance). However, there are patterns in glacial loss that vary by latitude (tropics vs temperate vs high latitude) and by region (Himalayas vs Andes).
Recent reports by groups such as WWF-India suggest that smaller glaciers may be the most vulnerable to climate change. And a video report from WWF-Nepal shows very significant impacts that are occurring on their side of the Himalayas and some powerful responses to adapt to the emerging conditions in the Gokyo region. A new video from the Asia Society called On Thinner Ice is another good demonstration of the undeniable shifts that are occurring with glaciers in the Himalayas.
I am personally afraid that there may be some attempts to use this controversy as a means of discrediting Pachauri, the IPCC, TERI, or climate science more generally. These would be foolish conclusions to draw from the incident. The real story as I see it is that we’ve been focused on the wrong data points. We should be looking at what’s happening in the interior of glaciers in addition to their edges.
The data about the overall mass balance of Himalayan glaciers is terribly concerning. There are several trends that should be noted:
1. A 2008 paper by Kehrwald et al. in Geophysical Research Letters looks in the middle of many glaciers using ice cores. Glaciers are laid down in layers, with the most recent layers on the top. Using some very clever techniques to date particular layers to radioactive debris from old nuclear bomb explosions, the authors were able to show that the top layers for a lot of glaciers have disappeared — the outer wrapping, in effect, may date back to the 1950s, the 1930s, or even older. These glaciers are thinning from the top down, and they are certainly not accumulating new layers. This is a scary trend because it suggests that we’ve been watching the wrong parts of glaciers for the past century — the snouts — and missed the loss of the bulk of the ice.
2. What’s happening to the water? Perhaps the most concerning aspect of recent research is the suggestion that these glaciers are not simply melting. They are sublimating, which means that more frozen water may be disappearing directly into the atmosphere as water vapor rather than going through a transition to liquid water, which would presumably cause flooding — or at least enter the network of rivers and streams throughout South Asia. The Kehrwald author team call this process “surface wasting.” This distinction is important because it implies that the bulk of the glacial mass may not be lost in a way that would be of even temporary benefit to farmers or cities in what is actually the semi-arid region South Asia. I have heard anecdotal reports of extreme surface wasting occurring in the Sierra Nevada of California in recent years, which would affect the urban water supply of many important US cities.
3. Finally, we know a great deal about the historical degree of change that the current period of warming represents for tropical glaciers. In a 2006 PNAS paper, Lonnie Thompson and colleagues argue that the current period of warming for all tropical glaciers is unprecedented for at least 5200 years. He uses multiple lines of evidence (ice cores, plant records, geological and chemical analyses). All point in the same direction. Their conclusion is that low latitude, high altitude glaciers are at risk of disappearing in the near future, but that does not mean by 2035. He means over a timescale of centuries (that is, “near” in a geological timescale).
