What the tiny remaining 1.5C carbon budget means for climate policy

By | November 11, 2022

Prof Piers Forster, Dr Debbie Rosen, Dr Robin Lamboll,and Prof Joeri Rogelj, write:

The latest estimates from the Global Carbon Project (GCP) show that total worldwide CO2 emissions in 2022 have reached near-record levels.

The GCP’s estimates put the remaining carbon budget for 1.5C – specifically, the amount of CO2 that can still be emitted for a 50% chance of staying below 1.5C of warming – at 380bn tonnes of CO2 (GtCO2). At the current rate of emissions, this budget would be blown in just nine years.

While that is a disconcertingly short amount of time, the budget for 1.5C may actually be even tighter.

Combining the latest insights from the Intergovernmental Panel on Climate Change (IPCC) with the GCP’s data, we estimate that the remaining 1.5C carbon budget could be just 260GtCO2 – around 120GtCO2 smaller. If emissions continued at current levels, this budget would run out in around six and half years.

However, reducing the remaining carbon budget to a single number means that many of the factors and uncertainties involved in calculating it – and their implications for decision-making – are missed.

With the immense efforts of the GCP, we know that there is still no sign of the sustained fall in global CO2 emissions needed to meet the Paris Agreement warming limits.

Cutting global CO2 emissions to zero by 2050, in line with limiting warming to 1.5C, would require them to fall by about 1.4GtCO2 every year, comparable to the drop in 2020 as a result of Covid-19 lockdowns around the world, but this time driven by a long-term, structural change of the economy.

This highlights that the scale of the challenge is immense, no matter the precise figure of the rapidly shrinking carbon budget. [Continue reading…]

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