Monsoon Updates

What is Global Warming Hiatus (GWH)?


From UPSC perspective, the following things are important :

Prelims level: Mascerene High, Global Warming Hiatus (GWH)

Mains level: Impact of global warming on Indian Monsoon

A new study on variability in the Mascarene High (MH) in the Southern Indian Ocean during global warming hiatus (GWH) has revealed that the region experienced significantly increased sea surface temperature (SST) during this period (1998-2016).

Try this PYQ:

Q.With reference to Ocean Mean Temperature (OMT), which of the following statements is/are correct? (CSP 2020)

  1. OMT is measured upto a depth of 26 degree Celsius isotherm which is 129 meters in the south-western Indian Ocean during January-March.
  2. OMT collected during January-March can be used in assessing whether the amount of rainfall in monsoon will be less or more than a certain long-term mean.

Select the correct answer using the code given below:
(a) 1 only
(b) 2 only
(c) Both 1 and 2
(d) Neither 1 nor 2

What is Global Warming Hiatus (GWH)?

  • A global warming hiatus is referred to a global warming pause, or a global warming slowdown, which is a period of relatively little change in globally averaged surface temperatures.
  • The hiatus, however, can result in an increase in the SST.

What is Mascarene High (MH)?

  • The Mascarene High (MH) is a semi-permanent subtropical high-pressure zone in the South Indian Ocean.
  • It is also called the Indian Ocean subtropical high, which is a high-pressure area located between 20° to 35° South latitude and 40° to 90° East longitude.
  • It is a region from where the cross-equatorial winds blow to India.
  • It has been named after the Mascarene Islands, in the Indian Ocean east of Madagascar consisting of the islands belonging to Mauritius as well as the French Réunion Islands.
  • Apart from its large influence on African and Australian weather patterns, it also helps in driving the inter-hemispheric circulation between the Indian Ocean in the south and subcontinental landmass in the north.

Role of MH

  • The warming in SST due to global warming has resulted in a decrease in the pressure gradient between the MH and the Indian landmass.
  • This in turn suppressed the intensity of low-level cross-equatorial winds over the western Indian Ocean affecting the onset of the monsoon over the Indian subcontinent and rainfall over East Asia.

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