Last year was Earth’s fifth hottest on record, European scientists announced on Monday. But the fact that the worldwide average temperature didn’t beat the record is hardly reason to stop worrying about global warming’s grip on the planet, they said.
Not when both Europe and the United States had their warmest years. Not when higher temperatures around the Arctic caused it to rain for the first time at the Greenland ice sheet’s normally frigid summit.
Not when the seven hottest year ever recorded were, by an overwhelming margin, the previous seven.
The events of 2021 “are a stark reminder of the need to change our ways, take decisive and effective steps toward a sustainable society and work toward reducing net carbon emissions,” said Carlo Buontempo, director of the Copernicus Climate Change Service, the European Union program that conducted the analysis made public on Monday.
Globally, the average temperature last year was 1.1-1.2 degrees Celsius (2-2.2 degrees Fahrenheit). This is higher than it was before industrialization.
The year was fifth warmest by a slight margin over 2015 and 2018, by Copernicus’s ranking. 2016 and 2020 are the hottest years ever recorded, in a virtual tie.
Consistent warming is consistent with the scientific consensus that rising levels of greenhouse gases are causing long-lasting changes to the global climate. Copernicus stated that its preliminary analysis of satellite measurements showed that heat-trapping gas concentrations continued to rise last season, thanks to 1,850 megatons of carbon dioxide from wildfires around the world.
One big reason for 2021’s lower mean temperature was the presence during the early part of the year of La Niña conditions, a recurring climate pattern characterized by lower surface temperatures in the Pacific Ocean. (La Niña has returned in recent months, which could presage a drier winter in the Southern United States but wetter conditions in the Pacific Northwest.)
Copernicus stated that these effects were neutralized by the 2021 average due to higher temperatures in many places of the globe between June and Oct.
“When we think about climate change, it’s not just a single progression, year after year after year being the warmest,” said Robert Rohde, the lead scientist at Berkeley Earth, an independent environmental research group.
“The preponderance of evidence — which comes from looking at ocean temperatures, land temperatures, upper atmospheric temperatures, glaciers melting, sea ice changes — are telling us a coherent story about changes in the earth system which points to warming overall,” Dr. Rohde said. “Slight variations up or down, a year or two at a time, don’t change that picture.”
Berkeley Earth and two U.S. government agencies (NASA and the National Oceanic and Atmospheric Administration) are expected to release their own analyses of 2021 temperatures this month.
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Copernicus uses a technique called reanalysis to create a portrait of global weather conditions. It uses a computer model to fill in the gaps between temperature measurements. Even so, the different groups’ conclusions usually line up quite closely.
As usual, temperatures that were higher than average did not occur uniformly across the globe last year. Many parts of Australia, including Antarctica, experienced below-normal temperatures in 2021. Western Siberia also experienced below-normal temperatures.
Europe’s summer last year was the warmest on record, though 2010 and 2018 were not far behind, according to Copernicus. Flooding and severe rainfall caused havoc in the Netherlands, Belgium, Germany, Luxembourg, and Luxembourg. The Mediterranean’s Mediterranean wildfires were fueled by heat and dryness.
Last summer, the western side of North America was hit with extreme heat, drought, and wildfires. Canada’s maximum temperature record was broken in June when the mercury in a small town in British Columbia hit 121.3 degrees Fahrenheit, or 49.6 Celsius.
Scientists have concluded the Pacific Coast heat wave would not have been possible in a world without human-induced global warming. The question is whether this event is consistent with meteorological knowledge, even though it is not precedent, or a sign that climate change is occurring in ways scientists do not fully understand.
“From where I sit right now, I would tend to think that this was probably still a very rare event, even in the modern climate,” Dr. Rohde said. “But there’s a degree of ‘wait and see’ involved.”
Scientists will likely look back at 2021 and consider it an extreme fluke if the planet doesn’t experience heat events of the same intensity in the next decades, he said. “If we do, it’s telling us that something is changed in a more fundamental way.”
Source: NY Times