A useful source of data for both EEs and IAs is the Greenhouse Gas Bulletin which is published annually.

The latest publication (which came out today, just one week before the start of COP26 in Glasgow) covers the state of greenhouse gases in the atmosphere based on global observations through 2020. It contains sobering reading. Despite a fall in carbon dioxide emissions during the pandemic, the atmospheric concentration of carbon dioxide has continued to rise and is now at 413 ppm which is 149% greater than its pre-industrial level. There are several reasons for this increase. About half of the carbon dioxide produced by human activity is taken up by other sources such as trees, lands and oceans but the ability of these carbon ‘sinks’ to take up carbon dioxide depends on several factors including temperature and rainfall. The effect of global warming is to also increase the concentration of other greenhouse gases with greater warming potential such as methane. This is in part due to increased activity of microbes in natural sources such as wetlands and melting permafrost which account for about 40% of the methane in the atmosphere. Methane has a global warming potential (GWP) about 50 times greater than that of carbon dioxide and its concentration has risen by 262% since pre-industrial times. The rise in the concentration of atmospheric sulfur hexafluoride is also extremely worrying as it has more than doubled in the past twenty five years. Sulfur hexafluoride is an highly potent greenhouse gas with a GWP over 20,000 times that of carbon dioxide.

The concern now is that at the current rate of increase in greenhouse gas concentrations, the temperature rise will be far in excess of the 2015 Paris Agreement target to limit global warming to 1.5 to 2.0 ^oC above pre-industrial levels. A positive outcome leading to real action from the COP26 talks next week is absolutely crucial.