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Why Climate Matters

The Hindu Kush Himalaya:
An Endangered "Water Tower" in a Warming World

 Mountain systems, such as the Hindu Kush Himalaya, European Alps and the Andes, play a critical role for the 1.3 billion people who live either within or downstream from their ranges, but also half the Earth’s biodiversity. This is a consequence of the water storage and supply capacity of the glaciers in these regions.
A copy of this article was published in Global Geneva.

Paul Andrew Mayewski
Professor/Director Climate Change Institute, University of Maine
Alexander More
Assoc. Professor of Environmental Health LIU, Research Assoc. at Harvard – Climate Change Institute
Charles H. Norchi
Benjamin Thompson Professor of Law, University of Maine School of Law
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Mountain systems have long played a vital role for ensuring replenishable water resources for both human survival and natural ecosystems, for drinking, farming, hydroelectrical power, irrigation, transportation and fishing, among other human activities.  Inhabitants of Asia and South America are particularly vulnerable to the impacts of climate change, population growth and rapid economic development. 

According to the 2019 Intergovernmental Panel on Climate Change (IPCC) Special Reporton the Ocean and Cryosphere in a Changing Climate, global warming is already causing dramatic negative changes to mountain environments, a trend that we can expect to worsen in the years ahead. For example, as Swiss scientists point out, the southern Alps of the Valais region can expect to be completely free of summer snow by 2050. This raises the possibilities of less water feeding into Switzerland’s rivers and lakes eventually affecting the ability to respond to rising energy requirements. It also means a thawing of permafrost which may require a refurbishing of mountain dams, roads and tunnels amongst Europe’s Alpine countries. (See Global Insights article on Tolkien and the Aletsch Glacier in the Swiss Alps).

Based on the IPCC findings, the report specifically notes the serious loss of ice amongst almost all of the world’s mountain glaciers. Snow cover declines of five days per decade are projected to double in coming years, coupled with a significant decrease in the extent of frozen ground. We can expect this to result in serious impacts for both humans (agriculture, drinking water, hydropower, slope stability, mass water discharges from melting glaciers, tourism, migration) and ecosystems (habitat suitability, biodiversity, food sources).

IPCC 2019 as well as other government and non-governmental reports stress the essential role of science-based decision making if societies are to coordinate rural and urban water planning more effectively, plus introduce more targeted and responsible legislation. This also means the implementation of international agreements across borders to ensure the sustainability of humans and ecosystems in these fragile regions. Such approaches also highlight the necessity for reducing uncertainty in the prediction of future climate change scenarios as a means of formulating approaches for dealing with mitigation, adaptation and overall sustainability.


The Hindu Kush Himalyan region and major river basins and rivers. Map source: Mukherji et al. 2015 (Creative Commons).

The Hindu Kush Himalaya Water Tower: Earth's "Third Pole"

One of the world’s most important mountain regions is what is now often referred to as the Hindu Kush Himalaya (HKH) Water Tower. Some 4.3 million square kilometers in size, this massive range includes Afghanistan, Bangladesh, Bhutan, China, India, Myanmar, Nepal and Pakistan. It is the source for major river basins such as the Indus and Ganges-Brahmaputra and contains more snow and ice than any other place outside of the polar regions, hence its description as the “Third Pole.” 

A defining aspect of HKH sustainability is the current and projected state of glacier health and therefore water storage.  People and ecosystems dependent on the HKH are facing increasing, interconnected challenges as a consequence of climate change. These affect water availability, which in turn trigger human, animal and plant migrations through the degradation of grasslands and wetlands, glacier recession, resource depletion (forests and mining). They also lead to distant and local source pollution as well as undermining tourism, often a major form of sustainable revenue.

As the glaciers decrease in volume – an estimated 15 per cent since the 1970s – the elevation of year-round snow is constantly rising. This is resulting in the expansion of meltwater lakes. The warming responsible for this massive ice loss has only been 0.5 to 1oC, mostly since the late 1990s. Yet the loss of white, highly reflective snow that can be up to 100 per cent effective in reflecting incoming solar radiation is being replaced by exposed soil and rock that absorb energy from the sun much more easily and therefore result in warming and increased loss of snow and ice through melting.

Temperature surges: an important indicator of global warming

To understand how temperatures have risen over Asia, we need to compare the period of greatest temperature change (since 1998 as seen below) with the earlier portion of the instrumental record (1950 to 1997) demonstrating that recent temperature increases over the HKH and Tibet exceed those to the south. The most marked temperature rises are over the eastern Arctic, potentially playing a pivotal role in the availability of water for rain and snow in Asia by opening up a formerly ice-covered Arctic Ocean source, but also by impacting the shape and intensity of airmasses that provide the western and northern moisture sources to the HKH.


Time-series for surface (2m) annual temperature (oC) (1950-2020) for the area bounded by the red box as an anomaly relative to the period 1981-2010 using data from ECMWF ERA5 (0.5×0.5 degree resolution) (Hersbach et al., 2020) plotted using the Climate Change Institute’s Climate Reanalyzer software (CCI, 2021).

The primary sources of moisture for South Asia and the HKH, however, come from the Indian Ocean and Bay of Bengal during the summer monsoon. As sea surface temperatures continue to rise in coming decades, more precipitation is expected over South Asia. How far these moisture-bearing winds will penetrate the HKH remains a question. 

In addition, as warm summer monsoon rains penetrate northward from Southeast Asia, they can be expected to add to further glacier loss by melting snow and ice. Projected warming under both low and high greenhouse gas emission scenarios suggests that by 2040-2050 the HKH could produce an increase of ~1.5oC and 2-2.5oC, respectively, spreading to lower elevations (compared to 1998-2020, see Figure 6). Projections for 2050 suggest a further loss of one-third to one half of current HKH ice volume.


Annual surface (2m) temperature (oC) anomaly (2040-2050 minus 1998-2020) under the IPCC low emission scenario (top) and high emission (bottom) scenario over Asia using data from CMIP5 RCP4.5  and RCP 8.5 Ensemble Averages provided by the World Meteorological Organization plotted using the Climate Change Institute’s Climate Reanalyzer software (CCI, 2021).

The ability to understand and predict future changes in the HKH are complicated by the complexity of the terrain, particularly the logistical challenges of doing scientific field work in the world’s highest region. The most recent contributions to understanding climate change at the roof of the world were produced by the 2019 National Geographic and Rolex Perpetual Planet Everest Expedition. This established a scientific framework for assessing recent and future change based on high resolution imagery to monitor glacier loss and changes in water quality and biodiversity. The expedition also took the world’s highest ice core (8020m) revealing glacier mass losses even at this elevation. 

The expedition also established a suite of automatic weather stations including the two highest on Earth, installed along the southern climbing route of Mt. Everest at 7945m and 8430m, providing data capable of verifying and calibrating forecasts based primarily on modeling. Finally, it undertook biological monitoring, including species identification utilizing environmental DNA, as well as water, snow and ice sampling to analyze the levels of toxic trace elements such as lead in some regions. This included identification of microplastics and PFAS (forever) chemicals at the highest altitude so far, and related geological, atmospheric, biological and health risks.

The impact of man-made climate change on health

The impact of climate change on the health of human populations and ecosystems is ever more apparent as the world faces higher rates of vector-borne diseases, catastrophic weather events, and continued migration of people and animals. The HKH region is no exception.

As people become more aware of the vulnerability of pandemics, current research is linking the instability of climate, water and food sources to disease outbreaks worldwide. Extreme and erratic precipitation coupled with glacier melting, for example, have caused more frequent contamination of water sources. Climate anomalies have also been tied to increased outbreaks of vector-borne diseases. In the HKH region, this includes Dengue and Chikungunya (Figure 7). Despite the need for more in-depth studies, this already stands out as one of the key zones where climate change is creating the highest risks for increased disease outbreaks. Changes are emerging in the availability and distribution of water, which in turn affect the spread of both insect and animal vectors as well as their food sources. 


Dengue (A) and Chikungunya (B) cases in in the Hindu Kush Himalaya region from 61 different studies with average annual temperature, from Phuyal et al. 2020 (Creative Commons).

One common example is the outbreak of water-borne diseases that almost invariably follow ever more destructive tropical storms, especially in areas where water supplies are limited or dependent on a single source such as in southern Afghanistan and Pakistan. Scientists have detected antibiotic-resistant strains of several bacteria, especially in water-stressed areas where sanitation infrastructures are not readily available. 

Air pollution originating mainly from the use of solid, organic fuels in inefficient stoves is one of the leading causes of death for South Asia. Regarded as the leading silent killer, air pollution causes 6.5 million casualties every year according to two major independent studies. Air pollution in the HKH follows seasonal and daily patterns and is dependent on the human use of fossil fuels, biofuels and other organic matter for heating homes, cooking and industrial production. 

In recent years, the use of inefficient fuels as well as the burning of trash – which in turn causes the release of toxic aerosols, dust and black carbon – has generated persistent fogs or smog. This pollution dims the sun’s ability to heat the ground, strengthening a phenomenon called “inversion” which causes polluted air to remain trapped in a cold layer near the ground cushioned below a warmer cover, preventing the smog from rising. Air pollution is greatest in the winter months, when heating needs rise, particularly in cities such as Lahore, Kabul or Kathmandu, with terrible consequences for the health of urban populations. Air pollution also affects rainfall patterns by changing the chemistry of the atmosphere, becoming acidified and producing significant negative consequences for agriculture and drinking water.

Since the 1960s, black carbon, dust and other toxic air pollution from human activities have resulted in a 150 per cent increase of deposits on HKH glaciers when compared to the previous 50 years. Toxic pollutants are also reaching high elevations, as noted. Apart from changing the chemistry of the ice, staining the white glaciers in the process, air pollutants also increase how much sunlight ice and snow can absorb, especially above 6000m(18,000 feet). The more sunlight is absorbed, the more heat is available to melt the ice. All this creates even more instability for the survival, health and economies of the HKH region.


Dengue and Chikungunya viruses. Image: Pixabay/Creative Commons License.

In addition to rising viral, bacterial, and parasitic threats due to manmade climate change, glacier-lake and flash floods have caused enormous damage to homes and other infrastructures in the HKH region. The steep, climate-driven increase in destructive flooding is often followed by a sharp decrease in the availability of potable water. This will continue as glaciers continue to retreat. 

Water scarcity has led to the migration of human populations throughout history, most recently in the Middle East, Africa and South America. Diseases tend to travel with people as they migrate, increasing the risk of additional global outbreaks. Similarly, food and water scarcity cause animal populations to move outside of their normal habitats, often crossing into human environments. Shifts in these migrations, too, are likely to increase the risk of outbreaks of disease, some unknown to science, thus presenting a serious public-health challenge.

Quantifying the climate-change risks caused by food and water insecurity, flooding, or water and vector-borne diseases requires prompt additional, highly interdisciplinary analysis. This needs to focus on past continent-wide phases of transition, when similar climatic instability may have influenced the same ecological and hydrological cycles that we are witnessing today. In order to mitigate these risks effectively, we will need immediate reductions in greenhouse gas emissions and associated toxic pollutants.

International Law: the need for a substantive Hindu Kush-Himalaya Treaty

The countries of the HKH region are confronting varying degrees of insecurity and conflict. Afghanistan is on the brink of civil war, while Bangladesh struggles with floods and famine. Bhutan is suppressing civil society, while China is curtailing the human rights of Uighurs and Tibetans. Myanmar, also known as Burma, is in turmoil and Nepal is confronting insurgency, Pakistan supports militants in Kashmir and skirmishes with India, while India skirmishes with Pakistan and China.

And a vast number of people within these states are water-tower dependent. Would a region-wide scramble for resources exacerbate existing conflicts or catalyze a common interest in water conservation and allocation? Either way, HKH water flows have implications for interstate claims, transnational management, and international law. 

States enter into international agreements when it is in their shared interests.  The 1997 United Nations Convention on the Law of Non-Navigational Uses of International Water Courses (Watercourse Convention) is a model for the trans-border management demands of the HKH region. It obligates equitable sharing and consideration of impacts upon other state parties, requiring reasonable utilization, cooperation and information sharing.  It also requires that state parties not cause significant harm and potentially to compensate state parties for any damages caused.  These are sound water management policies. Yet not a single HKH state has ratified the Watercourse Convention. Either ratification is not in their common interest, or they have set such interests aside.

One international agreement has a particular bearing on the HKH water towers: The Indus River Treaty of 1960, which was brokered by the World Bank. Its goal is to manage and allocate the waters of a major river and the basin it feeds. The Indus River, with sources in the mountains of Tibet (China), traces an east-west arc traversing India, Kashmir, Afghanistan and Pakistan into the Arabian Sea. The HKH feeds the Indus River Basin, an area of 1,165,000 square kilometers dispersed across Pakistan (60 per cent), India (22 per cent) China (10 per cent) and Afghanistan (7 per cent). Kashmir, which straddles Pakistan, India and China, has been engulfed in varying degrees of conflict. The once Princely State became caught up in a conflict that has persisted since partition, causing the United Nations Security Council to adopt a resolution on January 17, 1948 forming the United Nations Commission for India and Pakistan (UNCIP), calling for a plebiscite that remains unfulfilled to this day. 

Although the Kashmir dispute is an ongoing threat to the agreement triggering party review and near suspension, the Indus River Treaty has remained in force. It allocates river waters, preserves agricultural uses, permits specified hydro-electric power uses, recognizes lower riparian state rights, establishes an oversight commission and provides for dispute settlement. 

But in an era of glacier retreat and shifting surface and groundwater, is this 1960 agreement an effective tool for 2021 conditions?  The treaty does not account for contemporary factors, especially climate change. It is predicted that by 2040, the Indus will be a seasonal river. Further, Himalayan glacier melt is carrying silt into the Indus basin, reducing the capacity of the Tarbela, Trimnu and Mnagla reservoirs in Pakistan and the Salal reservoir in India. Such changing conditions will bear on different interpretations of water allocation. Furthermore, key HKH states—Afghanistan, Bangladesh, China and Nepal—are not parties to the Indus River Treaty.


Afghanistan, whose Kabul River flows into the Indus, relies heavily on water from the Hindu Kush for much of its irrigated farming. (Photo: UNAMA)

Addressing climate-induced decline in water towers will require a Hindu Kush-Himalaya Treaty for all regional states. It could incorporate the functional elements of the Indus River Treaty and the Watercourse Treaty while accounting for consumptive land use and patterns and scientific understandings of the interactions of climate conditions, geology, geohydrology. It would guarantee data sharing and include a mechanism for inter-state HKH planning, conservation and allocation. 

This is imperative, as science-based projections suggest an HKH future potentially fraught with the possibility of water wars. Achieving an alternative and preferred future will require a return to policy fundamentals and effective implementing of international law. 


As is abundantly clear, climate change conditions are impervious to international borders. Policy approaches should therefore incorporate science-based decision-making. Only then can tools­ – legislation, planning and coordination mechanisms, international agreements ­– be effectively designed to achieve optimal outcomes. 

Sound policies also generate effective law, a process of human beings making choices. The combined law and policy must facilitate transnational water management but also community-level management conducted by people informed by scientific expertise. The question is what are the available instruments and mechanisms that could best ensure water security for the HHK community? The fundamental policy goal is sustainable access to a dwindling resource across national borders of an interconnected and often contested region.  

HKH climate change: a water future with even less capacity?

As the climate continues to warm, mountain glaciers will decrease in volume leading to an even more acute lack of water storage in natural reservoirs such as glaciers. The consequences for humans and ecosystems are clear and will play a critical role in our collective future. Mountain glaciers worldwide are the proverbial “canary in the mine” for the mid to low latitudes of the planet. Any prospect of fulfilling the UN’s Sustainable Development Goal number six, notably to “ensure availability and sustainable management of water,” will require close attention to mountain glaciers of the Hindu Kush Himalaya region and beyond.

Research on Mt. Everest referred to in this article was conducted through a partnership with National Geographic Society, Rolex, and Tribhuvan University, with approval from all relevant agencies of the Government of Nepal. We wish to thank Jiban Ghimire and team from Shangri-La Nepal Trek Pvt. Ltd., Panuru Sherpa and team from Xtreme Climbers Treks and Expedition P. Ltd, and the United States Embassy of Kathmandu for all of their support.



Paul Andrew Mayewski

is an internationally acclaimed glaciologist, climate scientist and polar explorer who has led more than 60 expeditions throughout the remotest polar and high mountain regions of the planet. His scientific and exploration achievements have been recognized by numerous awards such as: the first-ever international Medal for Excellence in Antarctic Research and the Explorers Club Lowell Thomas Medal. He has appeared many times in major media including: National Geographic, CBS 60 Minutes, and the Emmy Award Winning Showtime series “Years of Living Dangerously.”

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Alexander F. More 

is a leading climate & health scientist and economic historian at Harvard, the Climate Change Institute & LIU. His research spans multiple continents and centuries, focusing on the impact of climate change on population and ecosystem health and the economy, as well as the human impact on climate and the environment. He has worked in the US Senate for Ted Kennedy and is actively involved in conservation efforts with multiple non-profit organizations. His work and interviews have been featured by CNN, The Washington Post, Forbes, CBS, ABC, Newsweek and many other news media worldwide.

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Charles H. Norchi

is the Benjamin Thompson Professor of Law in the University of Maine School of Law and Director of the Center for Oceans and Coastal Law. He teaches and researches international law, law of the sea, international human rights, law and science, and Arctic Law. He is co-President of the Arctic Futures Institute, Chair of the Admiralty and Maritime Law section of the Association of American Law Schools, Fellow of the Explorers Club, the Royal Geographic Society and the World Academy of Arts and Sciences and was Fulbright Arctic Scholar in Iceland.

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