5.1 Global warming ‘well below 2 ˚C’

Section 2 showed how the concentration of carbon dioxide in the atmosphere has been rising over time (the Keeling Curve). In 2023 it passed 420 ppm, which is 50% higher than pre-industrial levels. It also explained how rising greenhouse gas emissions from human activity have led to the enhanced greenhouse effect and a warming of the Earth. The long-term trend shows that the global mean surface temperature was 1.1 °C warmer in 2011–20 compared to the last half of the 19th century, and is rising (IPCC, 2023).

Although carbon dioxide (CO₂) is not the only greenhouse gas – methane (CH₄) and nitrous oxide (N₂O) are also important – it is estimated to account for around two-thirds of global warming since pre-industrial levels. Whilst governments and fossil fuel producers have started to make commitments to reduce methane emissions, the main focus of climate change policies and action to date has been to reduce CO₂ emissions. These initiatives are yet to see global CO₂ emissions fall significantly, but there is some progress.

As shown earlier in Figure 7, between 1950 and 2010, global emissions from fossil fuel burning increased at a rate of about 500 million tonnes per year. However, the rate of increase has slowed since 2010 and the world may now be at, or close to, its peak of CO₂ emissions from the combustion of fossil fuels.