Explained | March 2023 was the second-warmest March, not the first. What does this mean? Premium

Climate scientists need to provide the proper context when they compare individual months’ climate-related superlatives against each other, or they risk normalising global warming when they don’t seed complacency.

It has become a standard routine now to rank each month in terms of how warm it is compared to the same month in previous years in the instrumental record.

The most recent news to flash across all media was that March 2023 was the second warmest month on record. What does this actually mean in terms of impact on the planet, on the local weather, and on the human psyche? Do such headlines help or are they likely to render people numb to the idea of global warming by normalising the warming as a part of everyday life?

Many agencies across the world produce global climate anomaly reports regularly. The monthly report and the subsequent end-of-the-year annual summary by the U.S. National Oceanic and Atmospheric Administration serves as an excellent resource to contextualise the individual month’s ranking by temperature anomalies.

March 2023 was indeed the second warmest in the instrumental record. The warmest March occurred just a few years ago in 2016, when the biggest El Niño of the 21st century triggered a ‘mini’ global warming. But the January-to-March average temperature anomaly ranks 2023 as the fourth warmest such period on record. This raises obvious questions. Why was March 2023 the second warmest and not the warmest?

As seen in the figure below, each year’s March can be warmer or cooler than the March of the year before. Natural climate variability, including events like El Niño, can temporarily spike temperatures.

The old adage (often mistakenly attributed to Mark Twain) says that climate is what we expect and weather is what we get. In India, we expect March to be the beginning of the scorching summer season. But a particular year’s March may be cooler due to some other climate factors, such as a La Niña, and especially when averaged over a region as large as India or even an Indian state.

A year is an ‘El Niño year’ if warmer water spreads in a band from west to east over the equatorial Pacific Ocean. In a ‘La Niña year’, cooler water spreads east to west in the same region. Both phenomena have distinct and significant effects on the global climate.