Are Earth’s natural climatic patterns changing?
- August 28, 2022
- Posted by: OptimizeIAS Team
- Category: DPN Topics
Are Earth’s natural climatic patterns changing?
An uncharacteristic La Nina may be a sign of the ongoing La Nina may become the longest on record.
- Petteri Taalas, secretary-general of WMO said – Human-induced climate change amplifies the impacts of naturally occurring events like La Niña and is increasingly influencing our weather patterns, in particular through more intense heat and drought and the associated risk of wildfires — as well as record-breaking deluges of rainfall and flooding.
- Climate change scientists have also predicted an impact of global warming on the El Niño-Southern Oscillation (of which La Nina is a part) phenomenon itself, especially the extremes.
- Michael McPhaden, a senior scientist with NOAA said – Extreme El Niño and La Niña events may increase in frequency from about one every 20 years to one every 10 years by the end of the 21st century under aggressive greenhouse gas emission scenarios,”
- The strongest events may also become even stronger than they are today.
La-Nina event and its characteristics-
- During a La Nina event, cooler-than-average sea surface temperatures prevail over the east and the central Pacific Ocean, due to which the trade winds above the sea surface change in character because of a difference in the wind pressures.
- This change in the character of the trade winds is then carried all around the world affecting different regions in different ways. Many regions become colder and wetter, while many others become hotter and drier.
- The character of La Nina – an ocean-atmosphere event that usually brings down global temperatures – is changing, indicating a shift in natural climatic patterns in a warming world.
- This is evidenced by La Nina’s strong continuation through the summer of 2022 and its involvement in the early, intense, and extensive heat waves in the northwest and central India.
Prolonged La Nina event in 2022-
- There are chances that the current La Nina could continue through the southwest monsoon season, winter of 2022, and even early 2023, and could lead to devastating and unpredictable consequences for India and many other regions worldwide.
- There is a 70 percent chance that the current La Nina will continue from June-August 2022, according to the World Meteorological Organisation (WMO), and thus complete 24 months.
- WMO predicted a 50-60 percent chance of it continuing from July-September.
- The weather agency also indicated chances of it continuing into the fall and winter seasons in the northern hemisphere but did not give specific probabilities for that happening.
- NOAA predicted that there was a 58 percent chance of La Nina for the August-October season and 61 percent for the winter season.
Are there any previous such experiences?
- The only other instances of such long La Nina events were during 1998-2001 and 1973-1976.
- The 1973-1976 event was 37 months long and the longest since 1950, according to the National Oceanic and Atmospheric Administration (NOAA).
- The longest La Nina on record was the one between 1998 and 2000 that lasted 24 months, according to a research paper published in the Journal of Meteorological Research in December 2018.
Cause of concern- Duration of the event or the changing character of La Nina?
- More than the length of the ongoing La Nina, it is its changing character that is a cause of great concern.
- La Nina usually brings wet and cold winter and spring seasons to India, but this time large parts of India did not experience a spring season at all.
- This happened as a north-south pressure pattern, which usually forms over India during the winter season and dissipates by spring, continued into March and April this year.
- The pattern interacted with warm waves coming in from the rapidly warming Arctic region to initiate and prolong heat waves in the country.
- The characteristics of the La Nina in March-May also indicate a stronger La Nina than usual.
- The month of May, for instance, was the second-strongest La Nina month on record, according to Emily Becker at the University of Miami, United States.
- If the three months are taken as a season, then the temperature anomaly of the eastern and central Pacific oceans was 1 degrees Celsius below normal. This is the second-lowest since the 1950s when the temperature was 1.2°C below normal.
- This was also only the second time since the 1950s that the La Nina became stronger (cooler) than the months of February-April.
Impact of changing characteristics of La Nina on India and the world-
- The stubborn nature of La Nina over the next many months can have devastating consequences for different regions of the world, including
- India can experience a prolonged monsoon season for the third year in a row, for instance.
- The monsoon seasons of 2020 and 2021 were also extended, leading to an increase in extreme rainfall events during the period and subsequent floods in many states. The extension had most likely happened because of the impact of La Nina, according to climate scientists.
- The ongoing drought conditions in 40 percent of the United States, and the years-long drought conditions in the Horn of Africa and southern South America would also likely continue and become more intense due to the continuation of the La Nina.
- NOAA has also factored in the impact of La Nina and forecasted an above-average hurricane season for the Atlantic Ocean, with a 65 percent
- During a La Nina event, the vertical wind shear (change in intensity of vertical winds from near surface to higher parts of the atmosphere) is low over the Atlantic Ocean and is conducive to the formation and intensification of hurricanes. A strong wind shear tears apart a hurricane from the top.
- The continuation and changing character of La Nina in an era of climate change have been highlighted by the WMO.