The year 2021 was the sixth warmest on record, according to data released jointly on Thursday by NASA, the US space agency, and NOAA, the US ocean and atmospheric management agency.
“[O ano de] 2021 contributes to and is consistent with the observed long-term warming trend.”
The measurement published last Tuesday (11) by Copernicus, the European Union’s climate change service, pointed to 2021 as the fifth warmest year since records began.
Agencies use different models and baselines, which results in different numbers. NOAA points to an increase in the average global temperature in 2021 of 0.84 °C, while NASA reaches 0.85 °C (a value that is in line with that verified in 2018).
Copernicus, on the other hand, points to a warming of 1.1°C to 1.2°C. Comparisons are made against the temperature pattern of the period from 1850 to 1900, of the pre-industrial era.
Despite the numerical differences, the three research bodies confirm the global warming trend observed in this decade. They reveal the same graphic pattern and show that the last seven years were the hottest in history.
The historic records took place in the years 2016 and 2020, according to the three measurements. According to NASA data, the two record years tied, with a warming of 1.02ºC.
The trend of level change verified in the NASA graph is also shared by the measurements of NOAA and the European Copernicus: from 2014 to 2015, there is a jump in the global average temperature. The new level has been maintained ever since.
“Global temperatures are rising at a rate that the planet has not experienced in millennia. Although short-term climate cycles can affect the value measured in any year, the warming trends are very clear and increasing”, says the US space agency.
NASA’s temperature analysis shows that the Arctic is warming four times faster than the rest of the planet. “Satellites show a 13% decline in the extent of the region’s sea ice per decade,” the agency says in a statement.
NASA also points to ocean warming at unprecedented rates, with 2021 marking the warmest water temperatures and highest global sea levels on record.
“In addition to temperature and rainfall levels, we need to remember that the climate is integrated with all the other systems on Earth, like water and oceans and the entire biosphere. “, says researcher Suzana Kahn, deputy director of Coppe/UFRJ and one of the authors of several IPCC reports, the UN Scientific Panel on Climate Change.
The latest IPCC report last August revealed how rising average global temperatures increase the frequency and intensity of extreme weather events such as heavy rains, floods, droughts, hurricanes, cyclones and heat waves.
Extreme temperature swings that happened once a decade today can happen 2.8 times in the same period. The Northeast and Amazon are likely to suffer from longer dry periods, while the Center-South will face more rainy periods, with large volumes of water concentrated in up to five rainy days.
“There is a natural fluctuation in the average temperature from one year to the next, so the graphs show an upturned saw,” explains Kahn.
“The temperature records are not going to happen linearly, one year after the other. They also count natural factors such as the eruption of volcanoes, fluctuations in the incidence of the sun and the phenomena in the oceans, which are the most influential, although they receive less attention”, she quotes.
Among the influences best known for causing variations in the average temperature each year is the duo of natural phenomena El Niño and La Niña. The former warms the waters of the Pacific Ocean and causes temperature and precipitation fluctuations across the world, while La Niña does the opposite and leads to weather patterns that lower the Earth’s average temperature.
“Today, mathematical models are already able to separate natural and human causes to explain temperature variations”, explains Kahn.
NASA measured the influence of the pair of phenomena on the global average warming and cooling each year. Although 2016 and 2020 tied for the record for the warmest years in history, with an average temperature of 1.02°C, El Niño’s influence accounted for 0.11°C of the average warming in 2016, while in 2020 its impact was just 0. 03ºC.
In the last seven years, La Niña contributed to the cooling in the years 2017 (-0.01°C), 2018 (-0.03°C) and 2021 (-0.03°C).
According to NASA, the effect of La Niña on average global temperature occurs a few months after the phenomenon appeared in the Pacific.
“A La Niña event in early 2021 led to a year colder than it would have been otherwise, in particular colder than 2020 or 2016 – the warmest years on record,” NASA said in a statement.
“Scientists are predicting that as La Niña reappeared in late 2021, its cooling influence will likely affect temperatures in 2022,” the agency says.
.
