Effects of global warming on El Niño in the 21st Century
El Niño remains the largest climate phenomenon that occurs frequently producing droughts, floods, wildfires, dust and snow storms, fish kill, and even elevated risks of civil conflicts.
El Niño’s occur every two-to-seven years with very strong El Niño’s occurring about every 15 years. How the its frequency or the time between two events and strength will change because of global warming remains a grand challenge for climate models.
- A study, published in Journal nature, has thrown some light on the effects of global warming on El Niño in the 21st Century.
- El Niño is measured by an index that averages sea surface temperature anomalies over the central-eastern tropical Pacific.
- The theatre of action for El Niño is the tropical Pacific Ocean but its global reach costs the global community tens of billion dollars each time.
- This has been an issue in finding a consensus among models as far as the El Niño response to global warming is concerned.
- The results should serve as a warning to the 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 mean state of the tropical Pacific has cold temperatures in the east around the Galápagos Islands because the trade winds blowing from the east to west diverge waters away from the equator and push them westward.
- The atmosphere warms westward, moving waters and piling it in the west. Warm waters favour atmospheric convection and produce over 5 meters of rain per year to the west of the Dateline to New Guinea.
- El Niño is a perturbation of this background state of cold east – warm west ocean with air rising in the west and sinking in the east.
- In this context, it is imperative that models be held to very stringent standards on their performance of El Niño behaviour during historic periods, especially the 20th century, as a test of 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 in their historic depiction of El Niño’s as well as monsoons and how reliably they can project El Niño response to global warming in addition to how the models perform in reproducing floods and droughts of 20th century.