Hyderabad: A sudden rise in the global-mean surface temperature of Earth in 2023 has alarmed scientists. The paper published in European Geosciences Union - Atmospheric Chemistry and Physics, notes an increase of nearly 0.3 degrees celsius from 2022 to 2023. The study led by Shiv Priyam Raghuraman at the University of Illinois Urbana-Champaign credits this sudden rise in global-mean surface temperature to the El Nino-Southern Oscillation.
While such a large global warming spike is not unprecedented, with previous instance occurring in 1976-1977, the recent phenomenon led researchers to believe that it could have been externally driven.
“When a prolonged La Nina immediately precedes an El Nino in the simulations, as occurred in nature in 1976–1977 and 2022–2023, such spikes become much more common,” the study reveals, adding that nearly all simulated spikes are associated with El Nino occurring that year.
This is why the results underscore the importance of the El Nino–Southern Oscillation in driving the occurrence of global warming spikes, without needing to invoke anthropogenic forcing, such as changes in atmospheric concentrations of greenhouse gases or aerosols, as an explanation.
To put it simply, the results of this study show that global warming spikes can happen without any human influence.
When unconditioned on ENSO history, such global warming spike events may seem uncommon. However, they become much more common when conditioned on the occurrence of a long La Nina–El Nino transition, the study explains.
However, the study also emphasises that its findings (regarding the association of global warming spikes with ENSO) do not undermine the “vast body of literature on how anthropogenic activities are causing long-term global warming”. Instead, it says that the ENSO variability against a background warming trend may lead to year-on-year spikes that are also historical temperature records.
