Number Theory: 2022 was the warmest summer on the planet

An HT analysis of global temperature database maintained by NASA shows that the June-July-August (JJA) period might indeed have been the warmest the world has seen since 1880.

From a premature heat wave in India in March to severe heat waves, even drought in many European countries, this year’s summer has made headlines across the world. An HT analysis of global temperature database maintained by NASA shows that such headlines were not blowing things out of proportion and the June-July-August (JJA) period -- it is officially treated as the summer season in the northern hemisphere (although India’s summer is more April-May-June), might indeed have been the warmest the

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The NASA database treats the 1951-1980 average as the normal for making long-term temperature comparisons. The database gives deviations from this normal rather than absolute temperatures. One can use these deviations to measure how hot or cold the planet has been since 1880, the earliest period for which the database has these deviation estimates. A long-term analysis of this deviation trend shows that the planet has been getting consistently warmer.

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What does this database tell us about 2022 JJA period?

The earth was 0.97 degrees Celsius (°C) warmer than the 1951-1980 average in 2022. This the warmest the earth has been in this season since 1880. Because the deviation from normal measures difference with a fixed value (1951-1980 average) it can be used to rank years by absolute temperatures.

Ironical as it sounds, the hottest planet is more a result of the hottest winter in southern hemisphere than the hottest summer in the north

To be sure, what is summer season for the northern hemisphere is winter in the southern. HT’s analysis of the NASA database shows that the planet reaching its highest ever temperature in JJA 2022 has somewhat more to do with the southern hemisphere recording its hottest winter than the northern hemisphere recording its hottest summer. To be sure, a month-wise breakup shows that the none of the three months in the southern hemisphere was the warmest ever. However, the fact that the JJA average is the highest ever, means that winter was never cold enough. The northern hemisphere, on the other hand, recorded the hottest August, the third hottest July, and the fourth hottest June. The overall JJA period was the second hottest in 2022; 2020 was the hottest.

This JJA season was the hottest in 12 countries, and among the top three hottest in 52

Averages hide variations. For example, although the northern hemisphere did not experience its hottest summer as a whole, 11 countries (China, Nepal, Bangladesh in Asia; Spain, Portugal, Ireland, Finland, and Svalbard and Jan Mayen Islands in Europe; Canada in the North America; and Morocco and Tunisia in Africa) did. In the southern hemisphere, only New Zealand experienced its warmest winter. To be sure, when the earth is warming at an unprecedented rate, a second or third warmest rank is not going to be pleasant either as 40 countries experienced this. A map of temperature’s deviation from normal shows that almost all of the land on earth was warmer than usual.

How hot was the JJA season for India?

India, which was in the news for its heat wave before Europe and China, is conspicuous by its absence among the places that warmed the most this JJA season. There are reasons for this. One of them is India’s size, which is bigger than most European countries. Even if parts of India are experiencing one of their warmest years, the average for the country can be dragged down by parts that are not, especially when JJA months are the wettest in India. A state-wise analysis shows that this divergence between regions played a role in India appearing to be not as hot as the rest of the world in this season. Among 24 states for which this analysis is possible using NASA data, the JJA season was among the top three hottest since 1880 in six : Bihar, West Bengal, Assam, Arunachal Pradesh, Manipur, and Ladakh. Yet, for the country as a whole, this was only the sixth hottest JJA season. A month-wise breakup further shows India got this sixth rank on the strength of August temperatures alone, which was the 5th warmest since 1880, while June and July were only the 15th and 16th hottest. This is reflected in the regional spread of a hot monsoon. While the JJA season as a whole was the warmest ever only in Assam, Manipur, and Arunachal; August was the warmest ever in six states: Jharkhand, Bihar, West Bengal, Assam, Manipur, and Arunachal.

To be sure, taking April, May and June into account, India experienced its fourth hottest summer, after 2010, 2019, and 2016. April, however, was the hottest ever in India.

Note: All analysis in this story has been done using the GISTEMP gridded data (Land-Ocean Temperature Index, ERSSTv5, 1200km smoothing) from NASA. Ranks for different regions can be slightly different in other datasets.