As humanity was forced to sit at home for a considerable part of 2020 to help prevent the spread of the worldwide coronavirus outbreak, the world's space agencies and research institutes were quick to point out the positives: the dissipating air pollution clouds over major cities, visible in satellite images, and widespread reductions in concentrations of pesky pollutants such as nitrogen dioxide. In fact, so we were told, nature was healing as humankind struggled, and dolphins spotted in the canals of Venice were supposed to be the proof.
The State of the Global Climate 2020 report released on Monday (April 19) by the World Meteorological Organization (WMO), the United Nations body promoting international cooperation in atmospheric science, climatology, and hydrology, shows the optimism was rather premature. In fact, concentrations of greenhouse gases in Earth's atmosphere continued to rise in 2020. The concentrations of carbon dioxide, the most notorious climate warming agent, reached 410 parts per million, up from 408 in 2018, the report states.
Moreover, 2020 was one of three warmest years on record despite the developing La Niña effect, a climate pattern in the Pacific Ocean that usually cools the climate. Average global temperatures climbed 2.16 degrees Fahrenheit (1.2 degrees Celsius) above pre-industrial levels, inching closer to the 2.7 degrees F (1.5 degrees C) limit set out in the Paris Agreement, signed at the 2015 United Nations Climate Change Conference in Paris. Just as in previous years, the warming proceeded twice as fast in the Arctic as in the rest of the world, causing record shrinkage of Arctic sea ice in the period between July and October 2020.
As Maxx Dilley, the director of the Climate Program at WMO, told Space.com, the COVID-19 economic slowdown didn't make much of a dent in the data.
"The greenhouse gas concentrations continued to rise at an increasing rate even though there was a measurable reduction in the emissions," Dilley said. "The COVID-19 slowdown was too short and too little to make any measurable difference to the concentrations."
Carlo Buontempo, director of the European Union's Copernicus Climate Change Service, which processes data from Europe's environment-monitoring Copernicus satellite constellations and contributed to the report, told Space.com that while in Europe the pandemic led to a decrease in emissions of around 8%, it only slightly slowed down the rate at which the greenhouse gas concentrations were growing.
The concentrations, Dilley explained, are cumulative. New emissions add to the concentrations already in the atmosphere unless the natural carbon sinks, which the planet uses to maintain balance, absorb more carbon than humans emit.
But as the report pointed out, these natural greenhouse gas removal mechanisms might be getting less efficient because of the rising concentrations of greenhouse gases in the atmosphere.
The ocean absorbs about 23% of all human-made CO2 emissions, but as this CO2 reacts with seawater, the water becomes more acidic. The more acidic the water, the worse its ability to absorb CO2 from the atmosphere, the report states. The trend of increasing acidity (decreasing pH), first detected in the 1980s, continued in 2019 and 2020 unabated, according to the report.
"The emissions are coming more quickly than the [carbon] sinks are reacting to them," Dilley said. "There are still many scientific unknowns about the absorption capacity of the oceans and when that is expected to plateau. In fact, a lot of methane is trapped in the sea floor, frozen by the combination of high pressure and low temperature, and at some point, that might be released as well."
The report also found that the temperature of the global ocean was the highest on record in 2019 in depths up to 2,000 meters (1.2 miles). Although the 2020 data have not yet been fully processed, a preliminary analysis suggested that 2020 was on a trajectory to set a new record, the report stated.
The report, according to Dilley, sends a strong signal that the world is nowhere near to meeting the goals of the Paris Agreement, which binds countries to work towards keeping the global average temperature rise below 3.6 degrees F (2 degrees C), but preferably below 1.5 degrees C (2.7 degrees F), compared to pre-industrial levels.
"The report shows that we are already 1.2 °C on pre-industrial levels and the CO2 concentrations are still going up," Dilley said. "WMO is calling on the countries to raise their ambitions so that we change the trajectory, that the emissions start going down and the concentrations start to level off and we start moving away from this abyss."
The report also stated that six warmest years on record have all taken place since 2011, making the 2011-2020 decade by far the warmest since measurements began.
"These findings highlight the need to strengthen our efforts to reduce emissions and meet the targets of the 2015 Paris Agreement," Buontempo said. "This report highlights how sustained effort is needed to curb the concentration of greenhouse gases in the atmosphere and consequently minimise the changes in global climate."
A temperature rise above the levels recommended by the Paris Agreement would result in dangerous shifts in the Earth's equilibrium, an increase in frequency and severity of devastating weather events, unsafe sea level rise, widespread disruption to agriculture and erosion of biodiversity, according to the Intergovernmental Panel on Climate Change.