World saw record-high greenhouse gases, sea levels and ocean heat in 2021, report finds

Global heating shows no sign of abating as key measures such as greenhouse gas concentrations, sea levels and ocean heat reached record highs last year, according to an international review of the world’s climate.

The concentrations of carbon dioxide, methane and nitrous oxide which all heat the planet each rose to a new record, according to the annual State of the Climate report, which is based on contributions from more than 500 scientists in over 60 countries and led by scientists at the United States’ National Oceanic and Atmospheric Administration.

The global annual average atmospheric carbon dioxide concentration, for example, was 414.7 parts per million. That is 2.3 ppm greater than the 2020 amounts, and was the highest recorded in modern observational records as well as the highest in the last million years, based on paleoclimatic records.

A similar picture can be found for global sea level rise and ocean heat. Global ocean heat reached new record highs as the ocean takes in the vast majority of the excess energy trapped in the earth’s atmosphere, according to the study which is published by the bulletin of the American Meteorological Society.

Meanwhile, for a tenth consecutive year, global average sea level rose to a new record high and was about 3.8 inches higher than the 1993 average – the year when the satellite measurement record began, according to the report.

"The data presented in this report are clear – we continue to see more compelling scientific evidence that climate change has global impacts and shows no sign of slowing,” said NOAA administrator Rick Spinrad.

Global heating can be measured in a number of different ways.

Measuring the earth’s surface temperature is one of the better known examples, and is the one used by the United Nations when encouraging action to combat climate crisis.

The report found that annual global surface temperatures last year were 0.21-0.28C above the 1991-2020 average.

This puts 2021 as among the six warmest years since records began in the mid to late 1800s. The last seven years have been the seven warmest years on record, it said.

The UK Met Office’s Rober Dunn, who is the lead editor of the report’s global climate chapter, said natural variations can mask some of the detail of climate change when using only the surface temperature as a metric.

“When you look at how much the deep ocean is warming and how much sea levels are rising it is easier to obtain a clearer trend of ongoing climate change, as the majority of the excess energy trapped in the climate system by increases in greenhouse gases goes into heating the oceans,” he said. “For these two measurements 2021 was a record-breaking year.”

“The evidence of climate change becomes more stark with the publication of every annual State of the Climate report,” he added. “If we can get to a point where atmospheric greenhouse gas concentrations start to flatline or even reduce, we would in time start to see a much more positive picture of our climate and our future from these reports.”