Energy companies and nations must leave nine-tenths of Earth鈥檚 coal and almost two-thirds of its known oil and gas in the ground if the world is to hold temperatures to below 1.5掳C of global warming, a target beyond which climate change鈥檚 impacts are dangerously amplified, researchers have calculated.
Their analysis of which fossil fuel reserves are effectively 鈥渦nextractable鈥� if we are to meet the Paris Agreement temperature pledge makes the situation look dire for petrostates. Globally, oil and gas production must fall by 3 per cent a year to meet the target.
鈥淲e鈥檙e painting quite a bleak picture for the future of the global fossil fuel industry,鈥� says at University College London (UCL), who was part of the team behind the analysis. Price and his colleagues built on an on how much of the world鈥檚 coal, oil and gas reserves must go unused to stay under 2掳C of warming, but this time looked at the 1.5掳C goal.
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The researchers assumed a 鈥渃arbon budget鈥� that was about half the size of the earlier study鈥檚, allowing the world to emit just 580 billion tonnes of carbon dioxide from fossil fuels between 2018 and 2100. They then updated energy system models to reflect the falling cost of renewables and calculated the carbon within global fossil fuel reserves using data from BP, the International Energy Agency (IEA) and others.
鈥淎 key output is we see near a doubling of unextractable oil reserves,鈥� says study author Dan Welsby, also at UCL, meaning that much more must go unused to remain under 1.5掳C instead of 2掳C. For a 1.5掳C future, 89 per cent of coal, 58 per cent of oil and 59 per cent of gas must stay in the ground by 2050.
However, the researchers say those figures are probably an underestimate. The first reason is that they only modelled scenarios with a 50 per cent chance of hitting 1.5掳C. 鈥淵ou wouldn鈥檛 get on a plane if you had a 50 per cent probability [of making it],鈥� says Welsby.
Secondly, the modelling is based on relatively high amounts of CO鈧� being removed from the atmosphere 鈥� about 6 billion tonnes of CO鈧� a year 鈥� to meet the temperature target. The technology to do this is still in its infancy, but even assuming it is developed in the coming years, the team was unable to model a scenario with a 66 per cent chance of hitting 1.5掳C without resorting to 鈥渕agic鈥� amounts of CO鈧� removals.
鈥淭here鈥檚 a good likelihood the rates of decline are going to have to be even larger, and the total amount of carbon that鈥檚 going to stay in the ground is also going to be larger. I feel that鈥檚 quite a stark outcome,鈥� says Price. 鈥淚t really puts into stark relief just how challenging conditions will be for countries that are reliant on [revenues] from oil and gas.鈥�
at Imperial College London says that the numbers are likely an underestimate because the scenario used by the team allows for warming to exceed 1.5掳C before dropping back below the milestone by 2100. 鈥淭hat results in weaker constraints on fossil-fuel phase-out. If the scenarios would be designed in a way that keeps warming below 1.5掳C, the amount of unextractable fossil fuels under these conditions would be even larger,鈥� he says.
Read more: Earth will hit 1.5掳C climate limit within 20 years, says IPCC report
The global figures mask regional differences. One similarity with the 2015 study is that Canada and Venezuela both have to leave an above average amount of oil reserves unused while the Middle East is more akin to the global average. But because of the sheer size of its oil and gas reserves, 鈥渢hat translates into huge volumes left in the ground鈥�, says Welsby.
Some oil companies, , have cut their future oil and gas plans as they attempt to transition to low-carbon energy. Earlier this year, by the IEA suggested no new oil and gas wells should be drilled if the world is to cut emissions to net zero by 2050. However, many national oil and gas companies, such as , plan to grow production. 鈥淲e need to reverse course. Where we are now is a long way away from where we need to be,鈥� says Welsby.
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