Carbon dioxide in the Earth's atmosphere is now 50 per cent higher than the pre-Industrial Revolution era, reaching levels not seen in more than four million years, according to a study.
Emissions peaked at 421 parts per million in May, an increase of 1.8 ppm since 2021, scientists from the US National Oceanic and Atmospheric Administration said in a report released on Friday. Parts per million, or ppm, is a weight-to-weight ratio used to describe concentrations.
The Scripps Institution of Oceanography at the University of California San Diego, the NOAA's partner in the report, calculated a monthly average of 420.78 ppm.
The NOAA noted that prior to the Industrial Revolution, carbon dioxide levels were consistently around 280 ppm for almost 6,000 years of human civilisation. Since then, humans have generated an estimated 1.5 trillion tonnes of carbon dioxide pollution – much of which will continue to warm the atmosphere for thousands of years.
“The science is irrefutable: humans are altering our climate in ways that our economy and our infrastructure must adapt to,” Rick Spinrad, the administrator of the NOAA, wrote in the report.
“We can see the impacts of climate change around us every day. The relentless increase of carbon dioxide is a stark reminder that we need to take urgent, serious steps to become more climate-ready.”
Governments, businesses and societies have been joining hands to temper global warming with several initiatives to promote the use of more sustainable alternatives.
The International Energy Agency had already reported that global carbon dioxide emissions reached their highest annual level in 2021, rising 6 per cent to 36.3 billion tonnes.
Almost all regions posted an increase in emissions last year, with the annual change ranging from growth of more than 10 per cent in Brazil and India, to less than 1 per cent in Japan, the Paris-based agency said. Emissions in China rose by 5 per cent, while the US and EU both registered increases of around 7 per cent, it added.
The clock, however, is ticking, and immediate action is needed. US climate change envoy John Kerry, at a London summit last month, urged the world to implement green changes "up to 20 times faster" if it is to meet climate commitments made at the Cop26 gathering in Glasgow last year.
Industries are taking note. The transport sector, for instance, is increasingly shifting towards greener means of transport as more consumers realise their benefits and become responsible towards the environment.
To become a net-zero global fleet by 2050, zero-emission vehicles must account for 61 per cent of global new passenger vehicle sales by 2030 and 93 per cent by 2035, BloombergNEF said in a report this week. The last internal combustion engine vehicle of any segment must be sold by 2038, it added.
The NOAA explained that pollution from carbon dioxide is generated by burning fossil fuels for transportation and electrical generation, and by several other practices including manufacturing, deforestation and agriculture, among others.
Along with other greenhouse gases, carbon dioxide traps heat radiating from the Earth's surface that would otherwise escape into space, causing the planet’s atmosphere to warm steadily.
This, in turn, unleashes a domino effect of weather impacts, including episodes of extreme heat, drought and wildfire activity, as well as heavier precipitation, flooding and tropical storm activity.
"CO2 levels are now comparable to the Pliocene Climatic Optimum, between 4.1 and 4.5 million years ago, when they were close to, or above 400 ppm," the NOAA said.
At that time, sea levels were between 5 and 25 metres higher than at present — which were high enough to drown many of the world’s largest modern cities — and temperatures averaged 7 degrees Fahrenheit higher than in pre-industrial times, it added.
“It's depressing that we've lacked the collective will power to slow the relentless rise in CO2. Fossil-fuel use may no longer be accelerating, but we are still racing at top speed towards a global catastrophe," Ralph Keeling, a geochemist who runs the Scripps programme at Mauna Loa, wrote in the study.
The NOAA began measurements in 1974, and along with Scripps have since made co-ordinated and independent observations.