British researchers have modelled the immediate phase out of fossil fuel.

Immediately starting to phase out fossil fuel infrastructure as it reaches the end of its expected lifetime would result in about a 64 per cent chance that global mean temperature rise will remain below 1.5°C relative to pre-industrial levels.

The immediate phase-out, with a continuously steady rate, would accomplish near-zero emissions by 2050.

But researchers at the University of Leeds say that delaying mitigation until 2030 reduces the likelihood that 1.5°C would be attainable, even if the rate of retirement was accelerated.

The modelling study is published in Nature Communications.

The study modelled climate outcomes under different scenarios to determine what would happen to global temperature rise if CO2 emissions were phased out from the end of 2018 at a close to linear rate, becoming near-zero after 40 years.

In these scenarios, fossil fuel power plants, cars, aircraft, ships, and industrial infrastructure would be replaced with zero-carbon alternatives at the end of their life.

Based on their results, the authors suggest that starting to phase out existing CO2-emitting infrastructure immediately means there is a 64 per cent probability warming could be kept below 1.5°C, whereas delaying action until 2030 reduces this probability to below 50 per cent.

However, their results rely on no large-scale climate tipping points being breached in the coming decades, for example from extensive melting of permafrost.