The Himalayas: Mitigation and adaptation
Till the 1960s, the Himalayas would witness rain for seven days in a row every July. The Saat Jaad season was a highly revered geographical phenomenon, as rains recharged groundwater reserves and fed the rice bowl of Southeast Asia. School children used to get leave for a week. The phenomenon began to fade away slowly, and by the 1980s, it had died an unnatural death. Scientists believe climate change has a part to play in this.
For over a century now, climate change has been affecting the Himalayas in more ways than one. Temperature rise is five to six times more than the global average. Of the 75 glaciers, 63 are shrinking. Climate change-induced disasters have become more frequent and several flora and fauna species are disappearing. Being one of the youngest mountain ranges in the world, it is vulnerable to climate change even without human intervention. Nearly two-thirds of Asia’s population is dependent on the Himalayas for its water requirements. It also sustains over 1.3 billion people, who are dependent primarily on subsistence agriculture.
There may be global data on climate change, but there is insufficient data on the impacts of climate change on the Himalayan region, says H S Dhami, Vice Chancellor of Kumaon University. The precise impacts on mountain ecosystems and the linkages with other drivers of global climate change are yet to be investigated. This can be attributed to poor accessibility of the complex Himalayan topography. Here, the weather changes every two to five kilometres (km), as opposed to the plains, where, even through a 100 km area, the climate is uniform. The climate varies not only in different parts of the Himalayas, but also on different slopes of the same range. “The information provided by global models is coarse and it cannot be applied to specific regions,” says J Sanjay, a scientist at the Indian Institute of Tropical Meteorology (IITM), Pune. Of late, some initiatives are trying to map these changes more accurately.
For instance, researchers who are part of the Coordinated Regional Climate Downscaling Experiment (CORDEX) archive and publish their data sets on a climate data portal for dissemination to climate change impact assessment groups. These groups then interpret raw data on how climate processes over the continent may change. The Intergovernmental Panel on Climate Change pointed out the need for regional downscaling. This can be done by two methods. In dynamical downscaling, scientists focus on a region and run a global model with high resolution or they zoom into a specific region.
On the other hand, statistical downscaling is a two-step process to develop statistical relationships between local climate variables (such as surface air temperature and precipitation) and large-scale predictors (such as pressure fields). They then apply such relations to the output of global climate model experiments to simulate local climate characteristics. Scientists have been successfully using both methods to study the climate in the Himalayas.
A P Dimri, a professor at the School of Environmental Sciences, Jawaharlal Nehru University (JNU), New Delhi, uses dynamical downscaling to evaluate precipitation and temperature change patterns. He found precipitation data points were sparse at medium elevation, but more localised at lower and higher elevations, though uncertainty in precipitation patterns is more pronounced at medium elevations.
While data from northeast Himalayas show a decrease in overall precipitation, data from the northwest Himalayas reveal an overall increase in precipitation. Such assessments of downscaled data can help build capacity and expertise for decision making. “Till now, we have interpreted downscaled data only to analyse present scenarios (1970-2000). We are also working to predict the future (2020-2049) and the far future (2070-2099) scenarios using this data,” adds Dimri.
Some researchers have used Indian Meteorological Department data to study changes in rainfall. For instance, S Sreekesh of the Centre for Social and Regional Development, JNU, focused on stations in Uttarakhand with varying altitudes—Munsiyari, Mukhteshwar, Mukhim, Joshi-math, Dharchula, and Dehradun—and found that though the number of rainy days has decreased since the 1960s, the amount of rainfall has remained the same. Rainfall over a short period of time could cause floods and other extreme-weather events, warns Sreekesh.
One of the biggest risks to the Himalayan ecosystem is caused by the melting of glaciers. To map the vulnerability of lakes, researchers are collecting data on the Glacial Lake Outburst Floods (GLOFs).
A K Lohani of the National Institute of Hydrology, Roorkee, and his team studied GLOFs in the Teesta basin using remote sensing to detect the most vulnerable lakes. They found Lake 140 and Lake 7 as the most vulnerable lakes. Using a one-dimensional equation of open channel flow, they computed the change in the area of Lake 140 to be about 28.66 per cent between April 2011 and March 2013. They say their experiment could help identify other vulnerable lakes in the Himalayas.
As the scientific community tries to find ways to assess the impact of a changing climate in the Himalayas, policymakers and local communities need to gear up to evolve appropriate mitigation and adaptive measures and integrate climate adaptation in development plans, felt experts at a recent conference on Climate Change: Impact and Adaptation in the Himalayas in Nainital.
They said that there is a need to take into account GLOF data on the number of glacial lakes in regions where hydropower projects are being planned to map their vulnerability, as pointed out by Lohani’s study of the Teesta basin. Similarly, analysis of rainfall patterns in Uttarakhand could be used to plan rainwater conservation projects, they said. Dimri’s analysis of decreasing preci-pitation in northeast Himalayas could enable the construction of water conservation projects and lead to effective flood management in the Himalayas. Mountains are transforming because their accessibility is being enhanced. “Therefore, mitigation is important, but adaptation has become vital, says J Bandhopadhyaya, a professor at JNU. We must save Asia’s water towers before it is too late.
(The views expressed are strictly personal)