Earth temporarily breached 2°C threshold this month, scientists express concerns

By, Jayashree Nandi, New Delhi
Nov 21, 2023 04:44 AM IST

While the breach is temporary, it is expected that 2023 will be the warmest year on record due to record levels of greenhouse gas concentrations and the El Nino

Global temperatures may have temporarily breached a threshold on November 17 and November 18 that scientists believe could cause irreversible damage to Earth if it persists for longer periods. Average global daily temperature was around 2°C warmer than the 1850-1900 average for the first time in history on the two days last week, according to estimates. The Paris Agreement of 2015 set the goal of limiting global warming to well below 2°C and possibly not more than 1.5°C.

The data for November 17 and November 18 is from the ERA5 reanalysis dataset of the Copernicus Climate Change Service (C3S) run by the European Centre for Medium-Range Weather Forecasts (ECMWF). (Rep image)
The data for November 17 and November 18 is from the ERA5 reanalysis dataset of the Copernicus Climate Change Service (C3S) run by the European Centre for Medium-Range Weather Forecasts (ECMWF). (Rep image)

To be sure, the Earth warming by 2°C on two days does not mean failure to achieve the goals of the Paris Agreement. All such goals are for longer-term climate, which is the aggregate of weather (such as the temperatures on a particular day or month) over decades, and there is consensus that in these terms, the world is around 1.15°C warmer than pre-industrial levels. However, the breach shows how extreme weather can get even when the climate has changed by a smaller degree. The 2013-2022 global average temperature remains around 1.15°C warmer than the 1850-1900 average, still well below the 1.5°C threshold.

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The data for November 17 and November 18 is from the ERA5 reanalysis dataset of the Copernicus Climate Change Service (C3S) run by the European Centre for Medium-Range Weather Forecasts (ECMWF). ECMWF shared the data on November 20 on X (formerly Twitter). “ERA5 data from @CopernicusECMWF indicates that 17 November was the first day that the global temperature exceeded 2°C above pre-industrial levels, reaching 2.07°C above the 1850-1900 average and the provisional ERA5 value for 18 November is 2.06°C,” the organisation posted on X.

The ERA5 dataset uses model data in combination with observations to generate an estimate of global temperature before observations from across the globe are compiled. This is what makes the November 18 data provisional. For example, the provisional estimate for November 17 was 2.06°C, which has been revised to 2.07°C. To be sure, most long-term temperature data are estimates and the warming seen in ERA5 data is not very different from them.

Moreover, whether or not November 17 and November 18 are confirmed to have breached the 2°C threshold eventually, there is little doubt that they will be the warmest ever November 17 and November 18 dates. The chart shared by ECMWF shows the day’s temperature around 0.5°C above all previous temperature records for the day. In comparison, the monthly averages of the warmest and second warmest November months so far (observed in 2020 and 2015 respectively) are just 0.04°C apart in observed data from Nasa’s Goddard Institute for Space Studies (GISS).

The unprecedented warming on the two November days last week also comes after several months of already high warming. For example, the monthly average for October released by GISS on November 15 shows that October was the warmest ever this year and 0.25 degrees warmer than the second-warmest October — that of 2015. This makes October the fifth consecutive month when a month’s average temperature has been the warmest ever this year. The five months from January to May were not cool either. They were seventh, fourth, second, fourth, and third warmest this year. Overall, the January-October average this year is 1.12 degrees warmer than the 1951-1980 baseline in GISS, the warmest ever for the first 10 months of the year. This, coupled with unprecedented warming continuing in November, seals the fate of 2023 as the warmest ever year when December ends; the warmest year on record (2016) so far is just 1.02 degrees warmer than 1951-1980 average.

A senior scientist from the World Meteorological Organisation said that while the breach of the 2°C threshold was temporary, it is almost certain that 2023 will be the warmest year on record. “These data are from Copernicus Climate Change Service - this is one of the datasets WMO uses for its State of the Global Climate monitoring. We have not yet verified this independently. It should be stressed that this is temporary - there have been a number of days in 2023 which temporarily topped 1.5°C,” said the person who asked not to be named.

“WMO will release its State of the Global Climate provisional report on 30 November. This year is virtually certain to be the hottest year on record — the result of record levels of greenhouse gas concentrations and the El Niño event. The impacts on the cryosphere, ecosystems and the ocean are far reaching. We will provide more details on 30 November,” he added.

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What is perhaps worse about 2023 becoming the new warmest ever year is that it is likely to become the second warmest year as soon as 2024. This is because a periodic warming of the equatorial Pacific called El Nino is adding heat on top of human-induced warming. “Global warming is (proceeding) at a fast rate as emissions continue unabated. Along with that, we have a mature El Nino in place, which acts as a mechanism to transfer the heat from the ocean to the atmosphere across the globe. This adds to the global average temperatures. Since the El Nino will peak in December and continue to the next year, we might see more of these record-breaking temperatures,” Roxy Mathew Koll, climate scientist, Indian Institute of Tropical Meteorology had said last month referring to several months hitting record temperatures this year.

El Nino is the warming of waters in the Pacific Ocean, which creates a cascade of weather effects across the world — in India, this leads to the monsoon being drier than usual. The La Nino manifests in an exactly opposite phenomenon, leading to heavier rains in India.

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    Abhishek Jha is a data journalist. He analyses public data for finding news, with a focus on the environment, Indian politics and economy, and Covid-19.

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