{"id":499,"date":"2015-01-12T12:30:47","date_gmt":"2015-01-12T12:30:47","guid":{"rendered":"http:\/\/blogs.sussex.ac.uk\/sussexenergygroup\/?p=499"},"modified":"2023-09-08T11:25:53","modified_gmt":"2023-09-08T11:25:53","slug":"unburnable-fossil-fuels-whose-limit-is-it-anyway","status":"publish","type":"post","link":"https:\/\/blogs.sussex.ac.uk\/sussexenergygroup\/2015\/01\/12\/unburnable-fossil-fuels-whose-limit-is-it-anyway\/","title":{"rendered":"Unburnable fossil fuels – whose limit is it anyway?"},"content":{"rendered":"

A research letter in Nature by Dr Christophe McGlade and Prof Paul Ekins\u00a0(McGlade & Ekins 2015<\/a>) has dared to go where policymakers and leaders across the globe have not: For a reasonable chance of limiting global warming to 2 degrees C; McGlade & Ekins provide not only the quantity of fossil fuels that should remain in the ground, but they also identify\u00a0where<\/em><\/strong>\u00a0in the world these should stay put.<\/p>\n

The findings state that in order to meet this generally accepted climate target then around 80% of coal, 50% gas and 33% oil reserves* are unburnable over the period 2010 to 2050. In reaching this result the IPCC cumulative<\/em> carbon budget was applied. This is an approach for\u00a0assessing how to meet\u00a0the 2 degrees C global warming target that has emerged in the last couple of years or so. Greenhouse gas emissions can persist in the atmosphere for a range of magnitudes up to thousands of years. It is therefore not the rate of greenhouse gas emissions, nor time of occurrence, but the cumulative total (for all time) that matters. In other words, it is the total cumulative greenhouse gas emissions that correspond with the long-term average increase in global temperature.<\/p>\n

McGlade & Ekins also took account of the relative economic cost of exploiting fossil reserves in different locations to determine the\u00a0unburnable proportion reserves for oil, gas and coal by region. Two alternative scenarios were considered; one where there was no deployment of Carbon Capture Storage (CCS) technology, and the other where CCS was widely deployed from 2025. Figure 1 shows the unburnable reserves for both CCS and \u201cnoCCS\u201d scenarios by region for oil, gas and coal.<\/p>\n

\"Coal,<\/a>Figure 1. Unburnable fossil fuels by region where CCS is widely deployed from 2025 (Oil_ccs, Gas_ccs, and Coal_ccs) and also where CCS is not deployed (Oil_noccs, Gas_noccs, Coal_noccs). Based on Table 1 in McGlade & Ekins 2015<\/em>. <\/em>CSA is Central and Southern America, FSU is the Former Soviet Union,<\/em> OECD Pacific includes Australia, Japan and South Korea, and ODA is Other Developing Asia.<\/em><\/p>\n

The levels of fossil fuels that are unburnable if we are to meet a 2 degrees C global warming target are startling, especially so for coal. Of the oil reserves, Canada has the highest unburnable proportion due to its comparatively high cost of exploitation of tar sands.<\/p>\n

What many may find surprising is that even if CCS is widely deployed, then for most regions the levels of unburnable reserves, even for coal, are not significantly\u00a0reduced.<\/p>\n

So how do these findings compare with other energy forecasts?<\/em><\/p>\n

In the International Energy Agency annual World Energy Outlook (WEO) report there is an energy forecast for what is called a \u201c450\u201d scenario. The purpose of this forecast is to project levels of energy supply and demand that are compatible with meeting the 2 degrees C climate target. \u00a0In this scenario rather than the cumulative carbon budget approach limiting\u00a0greenhouse gas emissions to levels that are in line with a concentration in the atmosphere that corresponds 2 degrees C global temperature increase are applied. Under this application emissions are allowed to peak and then are reduced to enable a stabilisation of atmospheric concentration beyond 2100 at a level of 450 parts per million. Emissions higher than this level are allowable provided the climate target is achievable.<\/p>\n

Production estimates for fossil and other types of resources for the years 2020, 2030, and 2040 under each\u00a0scenario is provided in Annex A in the IEA\u2019s World Energy Outlook 2014 report<\/a> (IEA 2014). To find the figures for interim years and to project to 2050 the equation-fitting tools in Excel was used. A cumulative production curve for coal, oil and gas was produced along with the proportion burnable implied by the McGlade & Ekins 2015 findings. The burnable reserve proportions\u00a0have been taken assuming that Carbon Capture and Storage is deployed as outlined in the article. It is\u00a0assumed that all production will be consumed i.e. burned.<\/p>\n

First lets take a look at coal: The burnable budget approximately equals the IEA WEO 450 scenario cumulative coal production projected out to 2050 as shown in Figure 2.<\/p>\n

\"\"<\/a> Figure 2. Coal production under IEA WEO 450 Scenario compared with burnable reserve derived from McGlade & Ekins 2015.<\/em><\/p>\n

This would suggest that the models give comparable results since the projected coal production in the IEA WEO 450 scenario seems to be in line with maximum burnable reserve 2010 to 2050 in McGlade & Ekins 2015. However the cumulative coal production curve does not appear to be markedly slowing down at 2050 and hence without drastic action the burnable coal budget will be overshot soon after\u00a02050.<\/p>\n

The picture for oil and gas is quite different as shown in Figure 3.<\/p>\n

\"Oil<\/a>Figure 3. Oil & Gas production under IEA WEO 450 Scenario compared with burnable reserve derived from McGlade & Ekins 2015.<\/em><\/p>\n

The burnable budget is overshot by 2035 for gas and 2036 for oil. This implies that more oil and gas is allowable under the IEA\u2019s 450 scenario than allowable by McGlade & Ekins.<\/p>\n

The IEA acknowledge in their report that under their central scenario \u201cNew Policies\u201d the carbon budget will be used up by 2040 however the budget appears to also be used up in their 2 degree C climate target \u201c450\u201d scenario too.<\/p>\n

These results imply that:<\/p>\n