As global warming continues its onward march there are key metrics scientists are watching closely to gauge the degree of change gripping our planet. The latest climate change report from the World Meteorological Organization (WMO) shines the spotlight on some of these important markers, detailing a string of alarming new records set across 2021.
The newly released State of the Climate report from the WMO follows similarly alarming publications from the world's top climate scientists to land this year, and continues to fill in important details of an increasingly grim picture. Compiled by dozens of experts, the report focuses on the ways key indicators of climate change are continuing to unfold, and charts the course of several in particular throughout 2021 that ventured into uncharted territory.
Despite the La Niña cooling effect, the average global temperature in 2021 was around 1.11 °C (1.99 °F) above pre-industrial levels, evidence that we're well on our way to the 1.5 °C (2.7 °F) limit laid out in the Paris Agreement to stave off climate change's most disastrous effects. The past seven years have been the warmest seven years on record, according to the authors, highlighting an overall warming trend that has seen each decade since the 1980s warmer than the last.
“It is just a matter of time before we see another warmest year on record,” said WMO Secretary-General Petteri Taalas. “Our climate is changing before our eyes. The heat trapped by human-induced greenhouse gases will warm the planet for many generations to come. Sea level rise, ocean heat and acidification will continue for hundreds of years unless means to remove carbon from the atmosphere are invented. Some glaciers have reached the point of no return and this will have long-term repercussions in a world in which more than 2 billion people already experience water stress.”
Among the striking findings outlined in the report is a new global high for the concentration of greenhouse gases in the atmosphere, with carbon dioxide now listed at 413.2 parts per million (ppm) globally, 149 percent of the pre-industrial level. Scientists have previously warned that this accumulation is accelerating at a dangerous rate, from low 300s ppm in the 1960s and increasing at around 0.9 ppm per year, to around 2.4 ppm each yeah between 2010 and 2019 – 350 ppm is a level experts consider to be safe. Early data from a monitoring station in Hawaii indicates the concentration actually reached 420.23 ppm in April 2022.
"The report highlights that atmospheric CO2 has now surpassed 420 ppm in 2022," commented Dr Tom Mortlock, an Adjunct Fellow at Australia's Macquarie University. "To put this into perspective, ice core records in Antarctica suggest that atmospheric CO2 naturally fluctuates between 150 and 300 ppm. We are now probably 40 per cent above natural levels of CO2 experienced over the last million years of Earth’s history, and this has all happened in the past 150 years. It is now unequivocal that this recent period of warming has been driven by human-produced greenhouse gas emissions. If we want to avoid the worst impacts of climate change, we must limit warming to 1.5 °C in line with the Paris agreement."
While climate change has many impacts across the terrestrial environment, much of its effects can be seen through the way the ocean responds and the State of Climate report shines a light on this in a number of ways. Global mean sea levels increased at an average of 4.5 mm (0.18 in) per year between 2013 and 2021, around double the rate of 1993-2002 due to increasing melt rate seen in the ice sheets, bringing them to record levels in 2021.
The ocean absorbs around 23 percent of CO2 generated by human activity, and when it does chemical reactions take place that acidifies the seawater. Not only does this pose grave threats to marine environments like the Great Barrier Reef where severe bleaching continues to take place, but as pH levels decline so too does the ocean's ability to soak up this CO2, and they've now reached record lows, according to the authors.
"There is very high confidence that open ocean surface pH is now the lowest it has been for at least 26,000 years and current rates of pH change are unprecedented since at least that time," they write.
In addition to these impacts, the ocean, like the planet, is also growing warmer. The data paints a picture of a particularly strong increase in ocean temperatures across the past two decades and a record high in 2021. Strong marine heatwaves were seen across much of the ocean in 2021, with the upper 2,000 meters (6,500 ft) continuing to warm and that warmth penetrating to increasingly deeper levels.
In addition to these new benchmarks, climate change continued to drive extreme weather events such as record-breaking heatwaves in North America and the Mediterranean, severe flooding in China and Western Europe and heavy droughts in Africa and Asia. The authors also note that amid accelerated melting of the Greenland ice sheet, the first ever recorded rainfall occurred at Summit Station, the sheet's highest point.
"The new WMO report makes grim reading," said Ian Lowe Emeritus professor of science, technology and society at Australia's Griffith University. "It documents the acceleration of climate change. The last seven years are the seven warmest ever, sea-level rise is speeding up as the oceans become warmer and the world’s seas are becoming more acidic. Unless we take urgent action to reduce the burning of fossil fuels, there will be no chance of saving the Great Barrier Reef. With worse heat waves, flood events and wildfires, the world is already paying a high price for the decades of inaction since the science became clear."
The WMO State of the Global Climate report is put forward as a complement to the IPCC Sixth Assessment report due to be completed this year. It will also serve as an official document and resource for negotiations at COP27, the United Nations Climate Change Conference set to take place in Egypt later this year.
Source: WMO