Responding effectively to climate change is both urgent and long term. It is urgent in that our actions and responses in the next 5 to 15 years may effectively lock in large-scale and irreversible planetary changes over this and subsequent centuries. The 2015 Paris Agreement sets the international agenda for addressing this challenge by setting clear temperature goals. The pathways to these goals will need to be addressed at national and sub-national levels and by cities, businesses and communities.

The accumulation in the atmosphere of relatively stable and inert gases, such as carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) that trap energy are the key threats to our climate.

Carbon dioxide concentrations have increased by 40 per cent since pre-industrial times. The global average atmospheric carbon dioxide in 2019 was 409.8 parts per million (ppm), with a range of uncertainty of plus or minus 0.1 ppm. Carbon dioxide levels today are higher than at any point in at least the past 800,000 years. This is primarily due to fossil fuel emissions but also land use changes, which release carbon from biomass and soils.