Credit: DH Illustration
The World Meteorological Organisation (WMO) predicted a 60 per cent chance for La Nina to arrive between December and February. The wet and cold weather in north India; snowfall in western Himalayas bringing an influx of tourists to Gulmarg and Kulu-Manali; the disruption of life in Europe due to heavy snow; and the devastating wildfires in Los Angeles continuing since January 7 are a confirmation of the arrival of La Nina.
Wildfires in California are common in summers, but their occurrence at such scale in winters is unheard of. We must cut down on pumping greenhouse gases into the atmosphere.
The fires that have broken out across the Los Angeles area killed at least 25 people, destroyed more than 12,000 structures and scorched an area of 150 square km. More than 60,000 people have left their homes for safety. The Palisades and Eaton fires– the largest by far—are continuing to burn even after 10 days.
La Nina is one among many factors in dry southern California. During winters, La Nina tends to push storms back to the northern part of the US, making the northern part wetter than usual and the southern part drier than usual.
Further, the extreme Santa Ana winds common in January and February in the region have been brutal, with wind speeds up to 120 km per hour, making firefighting tricky. The temperature contrast between cooler inland areas (southern California deserts) and warmer coastal areas is the reason for these winds.
The extent of dryness of the area can be understood with the fact that the last half-inch rain received was only a year ago.
The Pacific Ocean is the biggest water body and occupies nearly one-third of the area of the globe. It influences the climate and temperature considerably. Earth’s rotation is faster in areas near the equator as compared to the polar regions, and such strong rotation in the equatorial region, also termed the Coriolis force, has a high influence on the wind pattern.
The wind crossing the equator into the northern hemisphere gets deflected to the right owing to the strong force of rotation and the wind crossing to the southern hemisphere deflects to the left. This is known as Ferrel’s Law.
El Nino and La Nina are warm and cool phases of the natural climate patterns across the tropical Pacific. A recurring climate pattern involving changes in the temperature of the water in the region is called the El Nino Southern Oscillation (ENSO).
Historically, the Pacific Ocean in the southern hemisphere has provided major trade routes for the sailing of ships. The strong winds from east to west in the region have also influenced the speed of sailing and sailors have called it ‘trade winds’.
The speed of the trade winds is dependent on the sea surface temperature. When the temperature is normal, the winds are absent and neutral climate conditions prevail. When trade winds are strong, the resultant climatic condition is known as La Nina; when they are weak, the conditions are for El Nino.
In the south-western Pacific, trade winds from east to west have the potential to carry water from the sea surface along. When these winds are strong, warm water is pushed from the surface towards the west, making the sea surface temperature cooler in the east and warmer in the west.
This leads to the development of low-pressure areas in the west of the Pacific, i.e. the Indian sub-continent, causing heavy rains, flooding and cold weather. As opposed to this, there are heat waves, drought conditions and wildfires in the east of the Pacific, i.e. American continents.
In the El Nino phase that ended in May 2024, India has faced extreme heatwave conditions and wildfires that disrupted lives considerably. Forest fires in Uttarakhand and other Himalayan states have claimed human lives and destroyed forests.
Thereafter, the neutral phase persisted longer and La Nina was delayed, impacting the monsoon in many parts of the country. Prices of vegetables and food soared, with inflation breaching the RBI’s comfort level of 6 per cent in the quarter ending September; even the GDP growth of the quarter was a dismal 5.4 per cent.
Even without La Nina showing signs of arrival, cyclones Dana and Fengal menaced India’s east coast. The south-eastern region of Asia, especially the Philippines and Indonesia, too, faced several sea surges, which caused heavy rains and flooding. Malaysia and Thailand have also faced cyclones and heavy flooding.
Scientists from the WMO predict that the sea level in Indonesia is rising at an alarming rate of 10 cm per year and by 2050, a large part of Indonesia will submerge in sea.
The worst impact of La Nina is in South America, where hot-weather conditions have caused droughts and wildfires. Amazon forests, a global lung space, have burned for months and reports suggest that 25 per cent of this lung space was in flames. The assessment made at the end of November indicates that 32 lakh acres of Brazil’s Amazon, 1.7 crore acres in Bolivia, 5 lakh acres in Paraguay and 8 lakh acres in Argentina have been ravaged by fire, even prior to La Nina conditions.
Reports say that the water level in the rivers in Amazon forests has hit an all-time low, indicating the extent of degradation. Some of these rivers feed water to reservoirs, where maintaining a proper water level is essential for a smooth crossing of ships from the Atlantic Ocean to the Pacific Ocean through the Panama Canal.
Created in 1913 by damming the Cagres River, the Gatun Lake is a key part of the Panama Canal, supplying millions of litres of water. With the flow of water into the rivers depleting, the number of ships crossing the canal is reduced to half, thereby impacting the trade considerably.
(The author is retired principal chief conservator of forests (Head of Forest Force), Karnataka)