Kategori : NATURAL GAS ENERGY NEWS, ENERGY AGENDA NEWS, COAL NEWS, OIL & FUEL SECTOR NEWS - Tarih : 09 September 2021
Parties to the 2015 Paris Agreement pledged to limit global warming to well below 2 °C and to pursue efforts to limit the temperature increase to 1.5 °C relative to pre-industrial times1.
However, fossil fuels continue to dominate the global energy system and a sharp decline in their use must be realized to keep the temperature increase below 1.5 °C (refs. 2,3,4,5,6,7). Here we use a global energy systems model8 to assess the amount of fossil fuels that would need to be left in the ground, 
regionally and globally, to allow for a 50 per cent probability of limiting warming to 1.5 °C.
By 2050, we find that nearly 60 per cent of oil and fossil methane gas, and 90 per cent of coal must remain unextracted to keep within a 1.5 °C carbon budget. This is a large increase in the unextractable estimates for a 2 °C carbon budget9, particularly for oil, for which an additional 25 per cent of reserves must remain unextracted. Furthermore, we estimate that oil and gas production must decline globally by 3 per cent each year until 2050. This implies that most regions must reach peak production now or during the next decade, rendering many operational and planned fossil fuel projects unviable.
We probably present an underestimate of the production changes required, because a greater than 50 per cent probability of limiting warming to 1.5 °C requires more carbon to stay in the ground and because of uncertainties around the timely deployment of negative emission technologies at scale.
Unextractable oil, fossil methane gas and coal reserves are estimated as the percentage of the 2018 reserve base that is not extracted to achieve a 50% probability of keeping the global temperature increase to 1.5 °C. We estimate this to be 58% for oil, 59% for fossil methane gas and 89% for coal in 2050. This means that very high shares of reserves considered economic today would not be extracted under a global 1.5 °C target. These estimates are considerably higher than those made by McGlade and Ekins9, who estimated unextractable reserves at 33% and 49% for oil and fossil methane gas, respectively (Supplementary Fig. 3). This reflects the stronger climate ambition assumed in this analysis, plus a more positive outlook for low-carbon technology deployment, such as zero-emission vehicles and renewable energy.
Continued use of fossil fuels after 2050 sees these estimates reduce by 2100. For oil, the global estimate drops to 43% in 2100. The reduction is smaller for fossil methane gas, reducing from 59% to 50%. The majority of fossil fuels extracted after 2050 are used as feedstocks in the petrochemical sector, and as fuel in the aviation sector in the case of oil. Feedstock use, which has a substantially lower carbon intensity than combustion, accounts for 65% and 68% of total oil and fossil methane gas use, respectively, in 2100 under a 1.5 °C carbon budget. However, it also reflects limited consideration of targeted actions to reduce feedstock use that, if available, would limit the dependence on CDR.
Unextractable shares vary substantially by region, relative to the global estimates (Fig. 1, Table 1). The largest reserve holders, such as the Middle East (MEA) (for oil and fossil methane gas) and Russia and other former Soviet states (FSU) (for fossil methane gas) have the strongest influence on the global picture, and therefore have estimates close to or marginally above the global average. For oil, Canada has much higher unextractable estimates than in other regions, at 83%. This includes 84% of the 49 billion barrels (Gb) of Canadian oil sands we estimate as proven reserves. By contrast, the FSU region has a relatively low unextractable share of total oil reserves (38% in 2050), reflecting their cost-effectiveness.
