Understanding the “Emissions Gap” in 5 Charts

2017年11月6日经过凯利·莱文（Kelly Levin）andTaryn Fransen

Topic

每年，联合国环境计划（UNEP）都会汇集来自世界各地的科学家to measurethe size of the greenhouse gas (GHG) “emissions gap,” the difference between the emissions level countries have pledged to achieve根据国际协议and the level consistent with limiting warming to well below 2 degrees C (3.6 degrees F). That benchmark exists because warming above 1.5-2 degrees C would bring increasingly catastrophic impacts. (Learn more in our post describing世界的“碳预算”。）

So what doesthe Gap Report表演2017年？这五个图表解释了。

1.全球温室气体排放仍在增加。

2016年，全球温室气体排放量约为52 Gigatonnes（GT CO2E/年）。自1970年以来，全球全球温室气体排放量大约翻了一番，即使自2000年以来，二氧化碳的排放量也急剧增长。化石燃料燃烧，水泥和其他过程的二氧化碳排放量最大，总计约为总数的70％。

Encouragingly, the growth in global emissions in 2015 and 2016 is the slowest since the early 1990s (except years of global economic recession), and global CO2 emissions from fossil fuel use and cement production remained stable in both 2015 and 2016. However, it remains to be seen whether these trends will be permanent.

2. The world's largest emitters are collectively on track to achieve their promised emissions reductions for 2020, but several countries need to step up.

In 2009 and 2010, 73 Parties to the UN Framework Convention on Climate Change (UNFCCC) made GHG emissions pledges for 2020. For the G20 countries – responsible for roughly three quarters of global emissions – the Gap Report compares their projected 2020 emissions with their pledges. It found that seven G20 members (Australia, Brazil, China, the EU, India, Japan and Russia) are on track to meet their 2020 pledges; five (Canada, Mexico, the Republic of Korea, South Africa and the United States) are likely to require further action or will have to purchase offsets; and the remaining three (Argentina, Saudi Arabia and Turkey) did not make pledges for 2020. While not all members are on track to meet their pledges, collectively, 2020 emissions are expected to fall within the pledged range.

3. To keep warming between 1.5 and 2 degrees C, emissions in 2030 need to be far lower than they are expected to be.

为了衡量排放差距的规模，专家审查了科学文献中可用的方案，显示了如何减少排放以将变暖限制为2和1.5摄氏度，这是《国际巴黎气候变化协定》中规定的温度目标。必威官网是真的吗专家将这些范围与根据《巴黎协定》中166个当事方制定的承诺以及预期如果当前政策继续进行的排放（而无需加强以符合承诺）而预期发生的排放量将这些范围与预计发生的排放量进行了比较。他们发现，在2030年与巴黎协议兼容的排放和这两种情况之间存在很大的差距。

使用可能有2度C的机会的基准，巴黎目标与承诺之间的差距为11-13.5GTCO2E。使用中位数或1.5度C的可能性的基准，差距为16-19GTCO2E。鉴于许多国家尚未有望实现减少排放的承诺，巴黎温度目标与当前的政策情况之间的差距更高，但鉴于延伸到2030年的承诺仍然相当新。

4. Existing solutions can close the gap, if they are embraced quickly.

The report finds that proven technologies, even with conservative assumptions, could reduce emissions 33 Gt CO2e/year by 2030. And if you add in newer technologies, that potential grows to 38 Gt CO2e/year in 2030. That’s more than what’s needed to close the emissions gap and keep warming below 1.5 degrees C.

超过一半的潜力来自少数类别（极性和风能，高效的乘用车，造林和停止森林砍伐），并且需要迅速降低依赖并很快逐步淘汰，燃煤功率不配备碳捕获和存储。

5.将变暖限制为1.5-2摄氏度也依赖于二氧化碳的去除和负排放方法。

The report notes that the rate at which we are depleting the carbon budget will force us to increasingly rely upon carbon dioxide removal technologies and approaches, which remove and sequester carbon dioxide. There are significant risks, however, associated with these technologies and approaches, including uncertainty in their carbon retention, the consequences of large-scale deployment, and costs and feasibility.

Scenarios that meet the 1.5 degrees C target in 2100 assume large-scale availability of negative emissions technologies, such as bioenergy combined with carbon capture and storage. These technologies would be scaled up quickly. By 2100, the average removal of carbon dioxide through negative emissions technologies would be 810 GtCO2e, which is equal to almost two decades' worth of global emissions at current rates. Few scenarios can also meet the 2 degrees C target without using negative emissions technologies.

如果无法以这些速度和规模部署此类技术，这尚未得到证明，那么我们满足这些温度目标的能力将受到重大损害。