Rockies, Alps, Himalayas: More rain, less snow in Northern hemisphere mountains as temperatures rise, says report

Rockies, Alps, Himalayas: More rain, less snow in Northern hemisphere mountains as temperatures rise, says report

Subject :Geography

Section: Places in news

Context:

• The Himalayas and other mountains across the Northern Hemisphere are likely to see 15 per cent more rain for every 1-degree Celsius rise in temperature due to climate change, according to a new study.
• Earlier, a report from International Centre for Integrated Mountain Development (ICIMOD) found that the Hindu Kush Himalayas have seen a 65 per cent faster loss of glacier mass.

Study findings:

• Researchers from Lawrence Berkeley National Laboratory, Berkeley and the University of Michigan used European Centre for Medium-Range Weather Forecasts atmospheric reanalysis (ERA527) for data between 1950 and 2019. They relied on computer models for future projections.
• Data from 1950-2019 already shows that this transition from snowfall to rainfall has already been set in motion in the mountain regions of the Northern Hemisphere.
• It will continue to increase at a rate of 15 per cent for every 1 degree Celsius rise in temperature. For 2 degrees and 3 degrees rise, the world would see a 30 per cent and 45 per cent increase in rain, respectively.
• This shift could amplify rainfall extremes lasting over a few hours to a day.
• This switch from snowfall to rainfall could increase the risk of disasters such as floods, landslides, and soil erosion.
• One-quarter of the global population will be affected directly as they live in or downstream from mountainous regions.
• Risk regions:
  • Not all mountain regions are at high risk. The Himalayas and the North American Pacific Mountain ranges, including the Cascades, Sierra Nevada, and coastal ranges (from Canada to Southern California) are more threatened than the Rockies or the Alps.
  • The Himalayas is one of those hotspot regions where we see an increased risk of rainfall extremes.

• Causes:
  • The higher risk might be due to changes in atmospheric dynamics.
  • The North American Pacific Mountain range sees a significant portion of snowfall at temperatures just below zero degrees Celsius. A change in air temperature will shift this snowfall to rainfall.
• Risk analysis in the southern hemisphere:
  • The research team did not consider mountain regions in Southern Hemisphere due to a paucity of data from the pre-satellite era (before 1979).

Physiology of Himalaya:

• Himalayas mountain ranges start from Pamir Knot in the west and extend up to Puruvachal [ Mizo hills] in the east.
• Geologically: Geologically the Himalayas is a young fold mountain and it is made up of granite sedimentary Rock.
• Structurally: Structurally Himalayas is a type of fold mountain that is made up by the convergence of the Indian Plate and Eurasian Plate.
• West to the east stretch of the Himalayas is in an arc form.

Physiography of the Himalayas can be understood better by dividing it into two parts:

• latitudinal division [north to south]
• Vertical/Longitudinal division [west to east]

Latitudinal division or “North to south divisions” of the Himalayas:

• The greater Himalayan range can be divided into the following four parts from north to south:
  1. Trans Himalayan range
  2. The Great Himalayas or Inner Himalayas or Himadri
  3. The Middle Himalayas or Himachal Himalayas or Lesser Himalaya
  4. Shiwalik Himalayas or the outer Himalayas

Vertical/longitudinal division or “West to East divisions” of Himalayas:

• From west to east, the Himalayas can be divided into the following parts:
  1. Punjab Himalayas or Kashmir Himalayas or Northwestern Himalayas
  2. Kumaon Himalayas
  3. Nepal Himalayas
  4. Assam Himalayas
  5. Puruvachal Himalayas