In a new briefing following the COP21 climate negotiations in Paris, Professor Myles Allen of the Oxford Martin Net Zero Carbon Initiative looks at whether the target of a global average temperature rise of no more than 1.5°C is realistic.
Human induced warming is already likely to be over 0.9°C and is increasing at almost 0.2°C per decade, says Professor Allen, with cumulative emissions of CO2 the dominant driver of long-term temperatures.
In the briefing, he explains that past emissions, amounting to about 2 trillion tonnes of CO2, have already committed us to about 1°C of warming, adding: "If we limit net future emissions to another trillion tonnes of CO2, which the IPCC 5th Assessment Report considers to be technically feasible, that gets us close to 1.5°C of warming due to CO2 alone."
He details the action that needs to be taken on both CO2 and short-lived climate pollutants such as methane, arguing that emissions need to fall to net zero in order for temperatures to eventually stabilise.
Professor Allen says that while far from guaranteed, limiting warming to 1.5°C is "clearly not out of the question". But, he says, it will require the aggressive mitigation detailed in the IPCC's RCP3PD scenario, which involves a "substantial element of industrial-scale CO2 disposal" and reducing CO2 emissions to zero and below in the second half of the 20th century.
Follow the links below for opinion pieces by Professor Allen: