Heat trapped by greenhouse gases peaked in 2021, scientists say

Greenhouse gases emitted by human activities have trapped far more heat in 2021 than three decades ago, scientists say.

The National Oceanic and Atmospheric Administration has released an update to its Annual greenhouse gas index Monday. The index is used to provide a measure of the amount of greenhouse gases causing warming.

In 2021, the index reached a value of 1.49, 49% higher than the value assigned to 1990 – the year of the Kyoto Protocol, one of the first binding agreements on climate change signed by 192 countries. . The value 0 is attributed to the beginning of the industrial revolution in 1750.

Carbon dioxide levels

According to scientists, carbon dioxide is the most abundant of the green greenhouse gases and increased by 2.6 parts per million last year. The level has increased by 61 ppm since 1990 and represents 80% of the increase in heat shown in the AGGI.

“CO2 is the biggest contributor because it stays in the atmosphere and oceans for thousands of years and is by far the biggest contributor to global warming,” said Pieter Tans, senior scientist at the Global Monitoring Laboratory of the NOAA.

CO2 graph
Carbon dioxide increased by 2.6 parts per million last year.
NOAA Global Monitoring Laboratory

The sources of methane are still unclear

Methane, or CH4, is another greenhouse gas that drives climate change, but scientists are still trying to figure out what’s causing it to rise.

Scientists said CH4 levels rose by 16.9 parts per billion in 2021 – the fastest rise seen since the early 1980s.

The nature of its increase is important to understand because it warms the earth 30 to 90 times more than an equivalent amount of carbon dioxide. However, it stays in the atmosphere much shorter than CO2 – decades versus millennia.

Scientists say the rise in methane may come less from fossil fuels and more from wetlands, agriculture and landfills.

“We definitely need to target man-made methane emissions – especially those from fossil fuels – because it is technologically possible to control them,” said Xin Lan, a scientist from the Cooperative Research Institute of Life Sciences. environment. “If wetlands are emitting more methane due to warming and changes in global rainfall caused by rising CO2 levels, that’s something we can’t directly control, and that would be of great concern.”

Other Gases Monitored

A total of 19 greenhouse gases are monitored by scientists. While carbon dioxide and methane make up the bulk of these gases in the atmosphere, another called nitrous oxide, or N2O, comes in third.

According to scientists, N2O levels are mainly the result of the use of fertilizers for agriculture.

“We can find alternative energy sources to replace fossil fuels, but reducing the emissions associated with food production is a very difficult task,” said Stephen Montzka, the GML scientist who leads the AGGI report each year.

The remaining 16 greenhouse gases account for about 4% of the heat trapped since 1750, scientists say.

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