Current climate heating cannot be explained by natural agents such as solar output or orbital cycles. Earth's habitable temperature is a consequence of its atmospheric make up and adjusting its compostion alters it's radiative properties and, in turn, the surface air temperature. By C(𝛿T/𝛿t)=[(1-α)S/4]-εσTs^4 to be exact.

Rises in CO₂ and other greenhouse gases since 1800 have brought Earth perilously close to breaching 'safe' warming levels of 1.5°C. According to climate model simulations human emissions of greenhouse gases must half by 2030 in order to keep heating below 2.0°C. Natural processes such as El-Nino may tip Earth temporarily beyond the 1.5°C target.

The socio-economic and biological consequences of failing to limit warming to 2.0°C will be severe. There is hope. Degradation of natural carbon sinks must stop now. Ecosystems must be restored immediately and integrated with human development. Energy production must stop repositioning carbon to the atmosphere. Our sucess by 2030 will determine what type of Earth we inhabit in 2100.