Ocean warming to reach record levels in 2021 due to greenhouse gas emissions

National

“We’ve built up so much greenhouse gas that the oceans have started to take in an increasing amount of heat compared to before.”

The first few kilometers of National Road 1, eroded by erosion by rising Atlantic Ocean waters, near the city of Munda in the extreme southwest of the Democratic Republic of the Congo. Alexis Huguet / AFP via Getty Images

The heat of the world’s oceans has broken records. again.

A new analysis published Tuesday in the journal Advances in Atmospheric Sciences showed that the oceans had the most thermal energy in 2021 since measurements began six decades ago – accelerating at a rate possible only due to human-excreted greenhouse gases.

Since the late 1980s, Earth’s oceans have warmed at a rate eight times faster than in previous decades.

“When you have this long-term upward trend, you’re breaking records almost every year and it’s a monotonous increase,” said John Abraham, co-author of the study and professor at St. Thomas University in Minnesota. “We’ve built up so much greenhouse gas that the oceans begin to take in a greater amount of heat than previously thought.”

Team a. analyzed data from worldwide network of buoys in seven ocean basins. Overall, it was found that the upper 2,000 m of Earth’s oceans absorbed more than 227 additional zetajoules of energy compared to the 1981–2010 average. Last year broke the previous record set in 2020 by at least 14 zettajoules.

Additionally, the team found that ocean waters have been warming steadily since 1958, each decade warmer than the previous. Warming increased significantly in the 1980s. In recent decades, parts of the Atlantic Ocean, Pacific Ocean and Indian Ocean have warmed the most.

Through climate model experiments, the researchers showed that warming patterns since 1979 were primarily attributed to increases in anthropogenic greenhouse gas concentrations. Long-term trends brought on by human activity are also dominating short-term climate fluctuations, such as La Nia and El Nio, which may have regional implications.

“The ocean stores more than 90% of Earth’s net heat gain due to greenhouse gases, thus ocean warming is a fundamental factor in climate change,” lead author and associate professor Lijing Cheng of the Chinese Academy of Sciences wrote in an email. indicator.” , “Record ocean warming in 2021 is strong evidence that global warming is continuing.”

The 2021 record is not surprising, said ocean researcher Linda Rasmussen, who was not involved in the study. Mainly, Rasmussen said, because the key driver of ocean warming hasn’t changed.

“Anthropogenic greenhouse gases that warm the atmosphere continue to rise rapidly,” Rasmussen wrote in an email. “Since the ocean still absorbs the vast majority of excess heat, it would be surprising that this trend did not continue.”

Last year, several extreme weather events saw record heat. Warmer water provides more energy or fuel for tropical storms, increasing intensity and lifespan. After a record-breaking 2020 Atlantic hurricane season, 2021 experienced another intense pull of storms.

Hurricane Ida caused intense flooding and thunderstorms, ranking as the fifth costliest hurricane on record with damage. $75 billion cost, Hurricanes Nicholas and Tropical Storms Elsa and Fred also caused billions of dollars in damage.

The increase in ocean heat also increases the air temperature, allowing more moisture to enter the warmer atmosphere. For every 1.8 degrees of warming, heavy rain events will intensify by about 7 percent. 2021 marked one of the warmest years on record for the East Coast, thanks to tropical storms and summer thunderstorms.

Extraordinary december tornado Can also be traced back to warm water. In December, record warm temperatures in the Gulf of Mexico created an environment more reminiscent of spring than winter. As such, two tornado outbreaks occurred in the southern and central United States in the same week.

Rasmussen said the influx of ocean heat is also affecting the frequency and severity of ocean heat waves or the duration of abnormally high sea temperatures. For example, a series of ocean heat waves have occurred in the North Pacific—including the infamous “blob” that disrupted food chains by reducing phytoplankton productivity, while starving many animals. The North Pacific will host another warm “blob” in 2021, continuing from an anomaly into 2020.

Like hurricanes or droughts, it can be difficult to tie ocean heat waves to a specific cause. However, Rasmussen said, observations and analysis of more than 100 years of data in Southern California have shown that ocean heat waves in the region have become more severe over time.

“The coastal ocean temperatures that have repeatedly broken records in recent years would not have broken records without an underlying warming trend,” wrote Rasmussen, a retired researcher at the Scripps Institution of Oceanography. “Oceanic heat waves are one of those events that are expected to increase as an ocean as a whole.”

In addition to extreme weather events, ocean warming is also affecting sea level rise. Last year, sea ​​rose to its highest level on record. Global sea level rise is expected to continue at a rapid rate in the coming decades.

“Ocean warming is destabilizing the Antarctic ice shelves from below, causing large pieces of ice sheet to collapse such as the Thwaites Glacier, threatening a massive (metre) rise in sea level,” says Michael Mann. , is a co-author of. study and a climate scientist at Pennsylvania State University wrote in an email. “This finding really underscores the urgency to act on climate now.”

Despite ocean’s record heat, scientists Copernicus Climate Change Service The European Union announced that the global surface air temperature in 2021 was the fifth warmest on record. Surface air temperatures were the warmest on record for the past seven years, with 2020 and 2016 being the warmest.

Abraham said that air and land temperatures fluctuate much more than at sea. Just as the air temperature around your home fluctuates on a day-to-day or weekly basis, there are similar changes in the air temperature around the planet. To tease out larger climate trends against natural variability, scientists analyze surface air temperatures on a scale of decades.

However, water is much denser than air and retains heat much better than the atmosphere. Water takes longer to either cool down or heat up. Abraham and his colleagues were able to understand climate trends from natural variability, with a minimum of four years of data,

“If you want to know how fast the Earth is warming, you have to measure the oceans,” Abraham said. “Since most of the global warming heat ends up in the oceans, we like to say ‘global warming is ocean warming’.”