{"id":22503,"date":"2019-08-06T05:03:44","date_gmt":"2019-08-06T10:03:44","guid":{"rendered":"http:\/\/www.realclimate.org\/?p=22503"},"modified":"2019-08-12T10:11:29","modified_gmt":"2019-08-12T15:11:29","slug":"how-much-co2-your-country-can-still-emit-in-three-simple-steps","status":"publish","type":"post","link":"https:\/\/www.realclimate.org\/index.php\/archives\/2019\/08\/how-much-co2-your-country-can-still-emit-in-three-simple-steps\/","title":{"rendered":"How much CO2 your country can still emit, in three simple steps"},"content":{"rendered":"<div class=\"kcite-section\" kcite-section-id=\"22503\">\n\n<p><strong>Everyone is talking about emissions budgets \u2013 what are they and what do they mean for your country? <\/strong><\/p>\n\n\n\n<p>Our CO2 emissions are causing global heating. If we want to stop global warming at a given temperature level, we can emit only a limited amount of CO2. That\u2019s our emissions budget. I explained it here at RealClimate a couple of years ago:<\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\"><p> First of all \u2013 what the heck is an \u201cemissions budget\u201d for CO2? Behind  this concept is the fact that the amount of global warming that is  reached before temperatures stabilise depends (to good approximation) on  the <em>cumulative emissions<\/em> of CO2, i.e. the grand total that  humanity has emitted. That is because any additional amount of CO2 in  the atmosphere will remain there for a very long time (to the extent  that our emissions this century will <a href=\"http:\/\/www.nature.com\/nature\/journal\/v534\/n7607_supp\/full\/nature18452.html\">like prevent the next Ice Age<\/a>  due to begin 50 000 years from now). That is quite different from many  atmospheric pollutants that we are used to, for example smog. When you  put filters on dirty power stations, the smog will disappear. When you  do this ten years later, you just have to stand the smog for a further  ten years before it goes away. Not so with CO2 and global warming. If  you keep emitting CO2 for another ten years, CO2 levels in the  atmosphere will increase further for another ten years, and then <em>stay higher for centuries to come<\/em>.  Limiting global warming to a given level (like 1.5 \u00b0C) will require  more and more rapid (and thus costly) emissions reductions with every  year of delay, and simply become unattainable at some point. <\/p><\/blockquote>\n\n\n\n<p>In her recent speech at the French National Assembly, Greta Thunberg rightly made the emissions budget her central issue.<\/p>\n\n\n<p><iframe title=\"Greta Thunberg speech in Assembl\u00e9e Nationale\" width=\"500\" height=\"375\" data-src=\"https:\/\/www.youtube.com\/embed\/J1yimNdqhqE?feature=oembed\" frameborder=\"0\" allow=\"accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture; web-share\" referrerpolicy=\"strict-origin-when-cross-origin\" allowfullscreen src=\"data:image\/svg+xml;base64,PHN2ZyB3aWR0aD0iMSIgaGVpZ2h0PSIxIiB4bWxucz0iaHR0cDovL3d3dy53My5vcmcvMjAwMC9zdmciPjwvc3ZnPg==\" class=\"lazyload\" data-load-mode=\"1\"><\/iframe><\/p>\n\n\n<p>So let&#8217;s look at how the emissions budget concept can be used to guide policy on future emissions trajectories for countries. <\/p>\n\n\n\n<!--more-->\n\n\n\n<p><strong>Step 1: The temperature goal<\/strong><\/p>\n\n\n\n<p>First we need to determine at what level we want to stop global warming. That&#8217;s quite simple because it has already been agreed in 2015 by all nations in the <a href=\"https:\/\/unfccc.int\/process-and-meetings\/the-paris-agreement\/what-is-the-paris-agreement\">Paris Agreement<\/a>. That has taken decades of discussion and negotiations, ever since nations <a href=\"https:\/\/unfccc.int\/process-and-meetings\/the-convention\/what-is-the-united-nations-framework-convention-on-climate-change\">agreed in 1992 at the Rio Earth Summit<\/a> to stabilize greenhouse gas concentrations &#8220;at a level that would  prevent dangerous anthropogenic (human induced) interference with the  climate system.&#8221; In Paris a consensus was finally reached on <strong>&#8220;limiting global temperature increase to well below 2 degrees Celsius,  while pursuing efforts to limit the increase to 1.5 degrees&#8221;<\/strong>. <\/p>\n\n\n\n<p>Last year, the IPCC special report <a href=\"https:\/\/www.ipcc.ch\/sr15\/\">Global Warming of 1.5 \u00b0C<\/a> (in short SR15) detailed strong reasons for why limiting to 1.5 \u00b0C would be much more sensible than to 2 \u00b0C. <\/p>\n\n\n\n<p><strong>Step 2: The global CO2 budget<\/strong><\/p>\n\n\n\n<p>Once the temperature limit has been agreed, we need to know the corresponding CO2 budget. That is a question for science, and the IPCC SR15 answers that, including the uncertainties as always is a hallmark of good science. The following shows the budget table from IPCC.<\/p>\n\n\n\n<figure class=\"wp-block-image\"><img decoding=\"async\" width=\"600\" height=\"433\" data-src=\"http:\/\/www.realclimate.org\/images\/\/IPCC-SR15-budget-table-600x433.png\" alt=\"\" class=\"wp-image-22504 lazyload\" data-srcset=\"https:\/\/www.realclimate.org\/images\/IPCC-SR15-budget-table-600x433.png 600w, https:\/\/www.realclimate.org\/images\/IPCC-SR15-budget-table-300x217.png 300w, https:\/\/www.realclimate.org\/images\/IPCC-SR15-budget-table.png 788w\" data-sizes=\"(max-width: 600px) 100vw, 600px\" src=\"data:image\/svg+xml;base64,PHN2ZyB3aWR0aD0iMSIgaGVpZ2h0PSIxIiB4bWxucz0iaHR0cDovL3d3dy53My5vcmcvMjAwMC9zdmciPjwvc3ZnPg==\" style=\"--smush-placeholder-width: 600px; --smush-placeholder-aspect-ratio: 600\/433;\" \/><figcaption>CO2 emission budget left from the beginning of 2018 in order to remain below a certain warming limit. Example: in order to remain below 1.5 degrees with a 67% probability, we can still blow 420 billion tons into the air from the beginning of 2018. From the beginning of 2019, that is only 380 billion tons, since around 40 billion tons are currently emitted annually. Source: IPCC SR15, Table 2.2 <\/figcaption><\/figure>\n\n\n\n<p>The uncertainties to a large extent result from the fact that CO2 is the main but not the only cause of human-caused climate change, so the CO2 budget depends on how we will deal with non-CO2 climate forcings such as aerosol pollution. There are also different methodologies to estimate the CO2 budget. A thorough analysis of the uncertainties is found in a recent paper by <a href=\"https:\/\/www.nature.com\/articles\/s41586-019-1368-z\">Rogelj et al. in Nature<\/a>. The bottom line, as one of the co-authors (Elmar Kriegler) told me, is that the SR15 estimates in the table above are still the best we have.<\/p>\n\n\n\n<p>Some have argued that the uncertainties make the budget approach a poor guidance for policy. I disagree. First of all, practically all of politics operates under high levels of uncertainty about the outcome of policy decisions; that is inevitable. In fact it is rare that politics has a clear guidance like the well-established linear relationship between cumulative emissions and global temperature. Those who criticise using this as policy guidance must come up with a better guidance providing less uncertainty, then we can discuss.<\/p>\n\n\n\n<p>Second, some of the uncertainty is captured by the probabilities for reaching a certain temperature limit, shown in the table, so society can simply decide what level of risk of overshooting a temperature level they are willing to take. <\/p>\n\n\n\n<p>And finally, all policy is to a large extent learning by doing. You start with the best scientific advice now (especially since we cannot afford to wait any longer), and if we know more in ten years time we can adjust policy then. Given that climate change is largely irreversible it is best to err on the safe side, i.e. the uncertainty, if anything, is a reason to apply the precautionary principle and reduce emissions fast.<\/p>\n\n\n\n<p>Greta has argued in her speech to use 67% probability for staying below 1.5 \u00b0C, i.e. a 420 Gt budget from the start of 2018. Subtract 2 years of emissions, i.e. 80 Gt, then we&#8217;re left with 340 Gt from the start of next year. That is 8.5 years of current emissions &#8211; or 17 years until zero emissions in case of a linear rampdown.<\/p>\n\n\n\n<p>If you translate the &#8220;efforts to limit the increase to 1.5 degrees&#8221; promised by all nations in the Paris Agreement as a policy that gives us 50:50 chance to actually achieve that goal, that&#8217;s 500 Gt from the start of next year. That&#8217;s 12.5 years of current emissions, or 25 years for a linear rampdown, i.e. halving emissions in 12.5 years to reach zero by the end of 2044.<\/p>\n\n\n\n<p>But <strong>beware of using those end dates instead of budgets<\/strong>, because it is not the end date but the cumulative emissions that count! A simple illustration: if you don&#8217;t achieve reductions in the next ten years but keep emissions constant, and reduce linearly after that, the result is that you have to reach zero ten years earlier! See the next figure.<\/p>\n\n\n\n<figure class=\"wp-block-image\"><img decoding=\"async\" width=\"600\" height=\"448\" data-src=\"http:\/\/www.realclimate.org\/images\/\/budget-example-600x448.jpg\" alt=\"\" class=\"wp-image-22508 lazyload\" data-srcset=\"https:\/\/www.realclimate.org\/images\/budget-example-600x448.jpg 600w, https:\/\/www.realclimate.org\/images\/budget-example-300x224.jpg 300w, https:\/\/www.realclimate.org\/images\/budget-example.jpg 949w\" data-sizes=\"(max-width: 600px) 100vw, 600px\" src=\"data:image\/svg+xml;base64,PHN2ZyB3aWR0aD0iMSIgaGVpZ2h0PSIxIiB4bWxucz0iaHR0cDovL3d3dy53My5vcmcvMjAwMC9zdmciPjwvc3ZnPg==\" style=\"--smush-placeholder-width: 600px; --smush-placeholder-aspect-ratio: 600\/448;\" \/><figcaption>Detrimental effect of wait-and-see policy. The blue emissions path stays within a 500 Gt budget, but the solid red path emits 700 Gt. To stick to the 500 Gt budget despite ten years of waiting, emissions need to reach zero by 2035 rather than 2045 (dashed line).<\/figcaption><\/figure>\n\n\n\n<p>This is why one should not attach much value to politicians setting targets like &#8220;zero emissions in 2050&#8221;. It is immediate actions for fast reductions which count, such as actually halving emissions by 2030. Many politicians either do not understand this &#8211; or they do not want to understand this, because it is so much simpler to promise things for the distant future rather than to act now. Greta asked the pertinent question in her Paris speech: <\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\"><p> \u201dWhat I would like to ask all of those who question our so called \u2018opinions\u2019, or think that we are extreme, is: Do you have a different budget for at least a reasonable chance of staying below a 1,5\u00b0 of warming? Is there another, secret Intergovernmental Panel on Climate Change?\u201d <\/p><\/blockquote>\n\n\n\n<p><strong>Step 3 Computing a budget for your country<\/strong><\/p>\n\n\n\n<p> How do you divide up the remaining budget amongst humankind?  This is a crucial step since most climate policy is made at the national level. Yet, this is not a scientific question but one of climate justice. Who gets how much?<\/p>\n\n\n\n<p>I can&#8217;t solve this question but I am going to propose a starting point, based on the idea that a principle of fair distribution needs to be universal and simple. The most simple one clearly is an equal per capita distribution. Anyone who wants more of the budget than someone else would need to provide a good reason. There could be many reasons &#8211; cold countries might claim they need more emissions for heating, hot countries for air conditioning, large countries for transport over long distances, developing countries to eradicate poverty, rich countries because they are already developed.<\/p>\n\n\n\n<p>A tricky question is: at what point in time do you distribute the budget? This is important because rich countries are eating up the remaining CO2 cake much faster than poor countries. I would propose: from the time of the Paris Agreement, i.e. from the start of 2016. Of course developing nations will argue (and have argued) for a much earlier start date, to account for the historic emissions of developed nations. That may be justified but has the practical problem that the remaining budget for countries with large per-capita emissions is then already zero or rather: overdrawn. <\/p>\n\n\n\n<p>So just to be practical, let&#8217;s take 2016. So you compute the remaining global budget at the start of 2016 by adding 80 Gt to the IPCC budget table numbers shown above. Then you multiply that number by the population of your country, divide by the global population, and then subtract the emissions of your country from the start of 2016 until now. I have done this for Germany (in a <a href=\"https:\/\/scilogs.spektrum.de\/klimalounge\/wie-viel-co2-kann-deutschland-noch-ausstossen\/\">German blog post<\/a>) using a global budget of 800 Gt from the table, just to be generous, for a 67% chance to stay below 1.75 \u00b0C (my interpretation of &#8220;well below 2 \u00b0C&#8221;). The result was a remaining emissions budget of  7.3 Gt from the start of 2019 or 6.5 Gt from the start of 2020. That is 8 more years at current emissions. The next figure shows a linear reduction trajectory compatible with this budget.<\/p>\n\n\n\n<figure class=\"wp-block-image\"><img decoding=\"async\" width=\"600\" height=\"328\" data-src=\"http:\/\/www.realclimate.org\/images\/\/budget-example-germany-600x328.jpg\" alt=\"\" class=\"wp-image-22510 lazyload\" data-srcset=\"https:\/\/www.realclimate.org\/images\/budget-example-germany-600x328.jpg 600w, https:\/\/www.realclimate.org\/images\/budget-example-germany-300x164.jpg 300w, https:\/\/www.realclimate.org\/images\/budget-example-germany.jpg 1383w\" data-sizes=\"(max-width: 600px) 100vw, 600px\" src=\"data:image\/svg+xml;base64,PHN2ZyB3aWR0aD0iMSIgaGVpZ2h0PSIxIiB4bWxucz0iaHR0cDovL3d3dy53My5vcmcvMjAwMC9zdmciPjwvc3ZnPg==\" style=\"--smush-placeholder-width: 600px; --smush-placeholder-aspect-ratio: 600\/328;\" \/><figcaption>Emissions budget example for Germany<\/figcaption><\/figure>\n\n\n\n<p>I&#8217;m not so concerned about the exact numbers, given the uncertainties discussed above. But there are at least three important conclusions from the budget approach. <\/p>\n\n\n\n<p>First of all, nations with high per-capita emissions need to reduce faster than others, based on the limited budget and simple justice considerations. If some reduce faster and some slower, even if every nation reduces linearly global emissions will not decline linearly, but more rapidly at first from the reductions of wealthy nations, with a longer tail of emissions from developing nations reaching zero later.<\/p>\n\n\n\n<p>Second, even with generous assumptions (like an 800 rather than 420 Gt  global budget and a 2016 start date for dividing up the cake) emissions from developed nations need to drop much faster than almost all politicians think, in order to honour the Paris agreement.  <\/p>\n\n\n\n<p>Third, it is not some end date that counts but rather very rapid reductions starting right now. The end date is a moving target &#8211; every year we wait we lose two years: the year we waited, and a year at the end because the required end year moves towards us.<\/p>\n\n\n\n<p>Finally, unprecedented global cooperation is needed to tackle the climate crisis. This may involve deals that make the tight budgets more palatable to countries with high per-capita emissions &#8211; for example they might find partners with low emissions and negotiate to use some of their budget in exchange for technological and financial support in climate adaptation and mitigation.<\/p>\n\n\n\n<p><strong>p.s. (7 August):<\/strong> I have posted <a href=\"http:\/\/www.pik-potsdam.de\/~stefan\/Country CO2 emissions 2016 calculator.xlsx\">a spreadsheet<\/a> where you can look at this budget estimate and the budget reach in years for any country. Someone suggested on twitter I should provide a site which automatically produces the figure above for any country &#8211; I don&#8217;t have the time to do this but it is not a bad suggestion, perhaps there is a volunteer?<\/p>\n\n\n\n<figure class=\"wp-block-image\"><img decoding=\"async\" width=\"600\" height=\"285\" data-src=\"http:\/\/www.realclimate.org\/images\/\/emissions-calculator-600x285.jpg\" alt=\"\" class=\"wp-image-22527 lazyload\" data-srcset=\"https:\/\/www.realclimate.org\/images\/emissions-calculator-600x285.jpg 600w, https:\/\/www.realclimate.org\/images\/emissions-calculator-300x143.jpg 300w, https:\/\/www.realclimate.org\/images\/emissions-calculator.jpg 1469w\" data-sizes=\"(max-width: 600px) 100vw, 600px\" src=\"data:image\/svg+xml;base64,PHN2ZyB3aWR0aD0iMSIgaGVpZ2h0PSIxIiB4bWxucz0iaHR0cDovL3d3dy53My5vcmcvMjAwMC9zdmciPjwvc3ZnPg==\" style=\"--smush-placeholder-width: 600px; --smush-placeholder-aspect-ratio: 600\/285;\" \/><\/figure>\n\n\n\n<p><strong>Reference<\/strong>s<\/p>\n\n\n\n<p><a href=\"http:\/\/www.pik-potsdam.de\/~stefan\/Publications\/Journals\/messner_etal_2010.pdf\">Messner et al. 2010: The budget approach: A framework for a global transformation toward a low-carbon economy (PDF)<\/a><\/p>\n\n\n\n<p>For a more complex formula to share the budget: Raupach et al. 2014, <a href=\"https:\/\/www.nature.com\/articles\/nclimate2384\">Sharing a quota on cumulative carbon emissions<\/a>. <\/p>\n<!-- kcite active, but no citations found -->\n<\/div> <!-- kcite-section 22503 -->","protected":false},"excerpt":{"rendered":"<p>Everyone is talking about emissions budgets \u2013 what are they and what do they mean for your country? Our CO2 emissions are causing global heating. If we want to stop global warming at a given temperature level, we can emit only a limited amount of CO2. That\u2019s our emissions budget. I explained it here at [&hellip;]<\/p>\n","protected":false},"author":10,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_exactmetrics_skip_tracking":false,"_exactmetrics_sitenote_active":false,"_exactmetrics_sitenote_note":"","_exactmetrics_sitenote_category":0,"_genesis_hide_title":false,"_genesis_hide_breadcrumbs":false,"_genesis_hide_singular_image":false,"_genesis_hide_footer_widgets":false,"_genesis_custom_body_class":"","_genesis_custom_post_class":"","_genesis_layout":"","footnotes":""},"categories":[1],"tags":[65,58,64],"class_list":{"0":"post-22503","1":"post","2":"type-post","3":"status-publish","4":"format-standard","6":"category-climate-science","7":"tag-budget","8":"tag-co2","9":"tag-emissions","10":"entry"},"aioseo_notices":[],"post_mailing_queue_ids":[],"_links":{"self":[{"href":"https:\/\/www.realclimate.org\/index.php\/wp-json\/wp\/v2\/posts\/22503","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.realclimate.org\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.realclimate.org\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.realclimate.org\/index.php\/wp-json\/wp\/v2\/users\/10"}],"replies":[{"embeddable":true,"href":"https:\/\/www.realclimate.org\/index.php\/wp-json\/wp\/v2\/comments?post=22503"}],"version-history":[{"count":19,"href":"https:\/\/www.realclimate.org\/index.php\/wp-json\/wp\/v2\/posts\/22503\/revisions"}],"predecessor-version":[{"id":22553,"href":"https:\/\/www.realclimate.org\/index.php\/wp-json\/wp\/v2\/posts\/22503\/revisions\/22553"}],"wp:attachment":[{"href":"https:\/\/www.realclimate.org\/index.php\/wp-json\/wp\/v2\/media?parent=22503"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.realclimate.org\/index.php\/wp-json\/wp\/v2\/categories?post=22503"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.realclimate.org\/index.php\/wp-json\/wp\/v2\/tags?post=22503"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}