Plus 1.5 degrees C – a realistic goal?
I am sure many of you have read reviews and extracts from the Sixth Assessment Report (AR6) published earlier this month by the IPCC. This expansive document – 3949 pages in all – gives budgets for carbon emission reductions that will be needed in order to limit global warming to +1.5˚ Celsius. The human-caused increase in global surface temperature is now estimated to have reached an average of 1.07˚C during the 10-year period from 2010 through 2019 – about 0.1˚ higher than temperature assumptions in the IPCC’s AR5 report released in 2014 – leaving only 0.43˚ to spare before reaching the 1.5˚ threshold. However, this change of view of historical temperature development was actually established by the IPCCs three years ago in its 2018 special report on 1.5˚ global warming (SR1.5). The carbon budgets for 1.5˚ have not changed since the SR1.5 report was released when adjusting for the starting point for measuring emissions, which now is set at 1 January 2020.
The IPCC conclusions are clear: we need to act and speed is of the essence. To reach the 1.5˚ objective with 50% probability, net zero must be reached before accumulated global CO2 emissions exceed 500 gigatonnes (Gt). A key element in the IPCCs climate model is a linear relationship between accumulated CO2 emissions and temperature increase. Actually, the linearity is a combination of two nonlinear effects cancelling each other out – namely that increased concentrations of CO2 in the atmosphere lead to a declining temperature effect per additional molecule, but increased CO2 in the sea reduces the CO2 sink in oceans, meaning that a greater volume of emissions remains in the atmosphere.
The linear relationship is 0.45˚ per 1000 Gt of CO2 emissions. Human-induced emissions since 1850 are calculated to have reached 2390 Gt, which, when multiplied by 0.45, gives the 1.07˚C figure mentioned above. From this logic, the remaining budget for limiting the increase in global temperature to another 0.43˚C should be 956 Gt. The reason why it is only 500 Gt, rather than 956 Gt, is that the IPCC has accounted for significant methane and nitrous oxide emissions after carbon dioxide has reached net zero, as well as some Earth System Feedback emissions like the release of methane from permafrost in Siberia.
In the same report, the IPCC reveals that a 2˚ scenario could become a grim reality if accumulated emissions climb to 1350 Gt by the time net zero is achieved. As we see it, technologies like solar PV, li-ion batteries and electric cars will lay the foundation for rapid change and will limit emissions to well below 1350 Gt. However, strong policy support will be vital in order to achieve a cap of only 500 Gt, including carbon taxes and legally-binding emission reduction requirements. Limiting emissions to between 650 and 850 Gt, on the other hand, seems quite achievable given the pace of development for green technologies along with emerging legalization and carbon pricing. All in all, our view in Rystad Energy is that the likely outcome lies in the range between 1.5 and 1.7˚C.
We look forward to sharing our insights on these and other topical energy-related issues at the upcoming Rystad Talks Energy webinar, which will be hosted by our Americas team from Houston on Thursday 26 August. Please be sure to tune into this session and other Rystad Energy digital events that will provide high-level updates from our teams on the latest developments within the global energy agenda.