Watch: Warmest January on record, deadline for updated NDCs
| Video Credit: Zeeshan Akhtar
January 2025 kept up with the trend of recording hottest average temperatures ever. The month was 1.75 degrees Celsius above pre industrial levels.
January temperatures came as a surprise to scientists too. Samantha Burgess, Strategic Lead for Climate at ECMWF called it “surprising” and this was because La Nina trend, which creates a temporary cooling effect of global temperatures.
What is La Nina?: El Niño and La Niña are complementary atmospheric patterns that influence warming and cooling of sea surface temperatures in the Central and Equatorial Pacific. The two opposing patterns occur in an irregular cycle called the El Niño Southern Oscillation cycle. The study used mathematical models that analysed sea surface temperature from 1870 to 2019 to observe ENSO and make predictions.
While El Nino causes the warming of sea waters in Central-east Equatorial Pacific every few years, La Nina causes cooler than average sea surface temperatures in the equatorial Pacific region. Trade winds push warmer waters towards Asia, and colder Pacific waters lead to drier conditions in Southern U.S., and heavy rainfall in the northwest and Canada. La Niña also makes winter temperatures warmer in the south and cooler to the north of the U.S.
During El Nino, sea surfaces warm up, which leads to increased evaporation. This water vapour condenses to form water droplets that make up clouds, and the conversion of gaseous to liquid state of water is an exothermic process. Therefore, it releases heat into the atmosphere, increasing the atmospheric temperature.
The opposite happens during La Nina. The sea surfaces are cooler, so less evaporation happens, and reduced resultant heating of the atmosphere.
Because of these steps, the atmospheric heating is more during El Nino and lesser during La Nina. According to an older analysis by the National Oceanic and Atmospheric Administration of the United States, for 1°C cooling during La Niña, global average surface temperatures drop by about 0.07°C. https://www.climate.gov/news-features/blogs/enso/where-does-global-warming-go-during-la-nina
In India, El Niño causes weak rainfall and more heat, while La Niña intensifies rainfall across South Asia , particularly in India’s northwest and Bangladesh during the monsoon.
Stefan Rahmstorf, Professor of Physics of the Oceans at the University of Potsdam, said that this development despite La Nina is of serious concern and should call for urgent efforts to phase out fossil fuels.
Published – February 20, 2025 12:33 pm IST
