Mains Paper 1: Geography | Salient features of World’s Physical Geography
From UPSC perspective, the following things are important:
Prelims level: El Nino, La Nino and ENSO
Mains level: Impact of El-Nino
- El Niño is the largest climate phenomenon that occurs frequently, producing droughts, floods, wildfires, dust and snow storms, fish kill, and even elevated risks of civil conflicts.
- The theatre of action for El Niño is the tropical Pacific Ocean but its global reach costs the global community tens of billions of dollars each time.
Why study El Nino occurrence?
- El Niños occur every two-to-seven years, with very strong El Niño’s occurring about every 15 years.
- How the frequency, time and strength between two events will change because of global warming remains a grand challenge for climate models.
- This also impacts projections of future climate since El Niños redistribute the heat gathered by the ocean between two El Niño events to cause a mini global warming.
Measuring El Nino
- El Niño is measured by an index that averages sea surface temperature anomalies over the central-eastern tropical Pacific.
- This has been an issue in finding a consensus among models as far as the El Niño response to global warming is concerned.
- But by using a model-specific El Niño index to make room for the inter-model differences, the latest projection shows that strong El Niños and extreme weather events associated.
- The results should serve as a warning to countries on all continents that suffer from these extreme weather events during strong El Niño events such as the ones during 1982-83, 1997-98 and 2015-16.
- The first caveat is that the eagerly-awaited winter rain and snow storms over California did not occur over California during the latest extreme El Niño.
- It is thus unclear if global warming is already affecting El Niño and its remote impacts.
- Secondly, the models used for making future projections have not stood the test of time for their depiction of El Niño during the 20th century.
Lack of consensus
- Some models warm the eastern tropical Pacific more than the west while others produce a faster warming in the west.
- Whether the east warms faster or the west has serious consequences for global warming itself since the cold eastern Pacific soaks up a lot of heating from the atmosphere.
- A slower warming of the east would imply more heat uptake by the ocean and a slower global warming.
- Available data is not sufficient to say with confidence how the tropical Pacific has responded to global warming till now.
- All available evidences indicates that El Niño is highly variable and its variability depends on weather noise over the western Pacific, volcanoes, impact of phytoplankton on penetration of solar radiation into the ocean, aerosols and so on.
- It is unclear if the impact of global warming on El Niño can easily be extracted.
- It is imperative that models be held to very stringent standards on their performance of El Niño behaviour during historic periods for their reliability for future projections.
- This would also be necessary for projecting other events such as droughts and floods.
- For example, droughts over India are closely tied with El Niño and any projections of how droughts will respond to global warming will depend on how models perform.
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