Global warming is already happening as carbon emissions keep on rising, with effects from sea level rise to more and more extreme weather events worldwide
21 April 2021
Earth is warming. Globally, 2020 was the second-warmest year on record, with a mean temperature 1.2°C above the pre-industrial average. By that measure, this means we are already four-fifths of the way to the 1.5°C “safe” level to which the world committed to try to limit global warming.
The culprits are carbon dioxide emissions from burning fossil fuels and land use changes that reduce Earth’s ability to draw down greenhouse gases. The results are already being felt, not just through rising temperatures, but also through loss of ice cover, rising sea levels and more extreme droughts, floods and storms across the globe.
Greenhouse gas levels
In March 1958, climate scientist Charles David Keeling began measuring atmospheric carbon dioxide levels from a monitoring station atop Mauna Loa in Hawaii. The readings continue to this day, now carried out by the US National Oceanic and Atmospheric Administration. Together with measurements of air trapped in ice cores collected from the Antarctic and elsewhere, our record of the concentrations of this crucial greenhouse gas stretches back 800,000 years.
In March 2021, the average atmospheric CO2 concentration at Mauna Loa was 417.64 parts per million. Readings taken at other places around the globe confirm the picture at Mauna Loa: atmospheric CO2 concentration varies seasonally owing to differing levels of plant growth, but is trending upwards year on year. The average global concentration for 2020 was higher than at …