科学家花费了大量时间来计算世界可以发出的二氧化碳量，同时将变暖限制在国际上达成的温度目标（远低于2°C（3.6°F）），并努力将进一步的变暖限制在1.5°C（2.7°F）（2.7°F））。这是我们的“碳预算”。

政府间气候变化的面板（IPCC）必威官网是真的吗新报告takes stock of the most recent literature on the carbon budget. The底线? We’re on track to blow through it over the next decade.

如果我们将变暖限制为1.5°C，剩余的碳预算是多少？

To have a medium chance of limiting warming to 1.5°C, the world can emit 770 gigatonnes of carbon dioxide (GtCO2). To have a likely chance (67 percent), the remaining budget drops to 570 GtCO2.

Even if countries fulfill their current unconditional emissions-reduction pledges,我们正在步入正轨吹入整个剩余的碳预算，以便到2030年将变暖限制为1.5°。

即使在过度乐观的情况下，当前二氧化碳排放量的水平恒定，我们仍然会在2030年耗尽预算（有可能将变暖限制为1.5°C）。这清楚地说明了需要全球峰值排放在2030年之前，有更好的机会避免最严重的气候影响。必威官网是真的吗

为了在长期内将变暖保持在1.5°C时，世界将需要在25年内达到零排放。

What about for 2°C?

剩余的预算要高得多，以将变暖限制为2°C：1690 GTCO2的机会为50％，或1320 GTCO2的机会为67％。

在当前二氧化碳排放水平的过于乐观的情况下，该预算将在2049年耗尽（有可能将变暖限制在2°C）。

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去除碳在达到1.5°C中的作用是什么？

The report also finds that if we exceed the carbon budget, meeting the 1.5 ˚C goal will require carbon removal, a process where we’re actually taking carbon from the atmosphere and storing it. Almost all of the models used in the IPCC report rely on carbon removal to some extent.

There are a number of different ways to remove carbon, such asbioenergy with carbon capture and storage (BECCS),afforestation并直接捕获和存储（DACS）。重要的是，温度升高之前的模型在退缩之前更大程度地依赖于碳去除。

Deploying carbon removal at the scale that climate models assume is untested. Given the risks and uncertainties related to various carbon removal approaches, scaling would have to be以安全和谨慎的方式追求。如果部署的速度和规模受到限制，这将为我们依靠这种策略来满足1.5度目标，特别是对于那些超出1.5°C的途径，这将留下很多问题。

为什么剩余的碳预算大于IPCC第五次评估报告中的估计？

A significant body of literature has emerged since the Fifth Assessment Report was released in 2014, and, as a result, the IPCC’s report on 1.5°C includes a larger carbon budget. More recent estimates have adjusted for the difference between recent observations of historical warming and cumulative emissions with those used in the IPCC’s Fifth Assessment Report’s Earth system modeling. (Others已经注意到了一旦纠正了各种偏见的比较，就没有这种差异。）

最近的努力试图纳入过去排放和变暖的最新观察结果。这样做之后，这些估计值研究了迄今为止的当前变暖与1.5°C之间的差异，然后计算出我们可以相应地发射多少。

尽管鉴于与1.5°C相关的预算非常小，但与旧建模结果的差异相对较小，但这可能导致计算预算的显着差异。因此，与1.5°C相关的预算对不同的假设和不确定性特别敏感。

关于预算计算的主要差异和不确定性是什么？

Scientists’ estimations of the remaining carbon budget vary. Key differences include the choice of model used, methodological choices, assumptions regarding historical emissions and the warming realized to date, and the extent of overshooting temperature targets, among other factors. Also, some carbon budgets are CO2-only, while others include all greenhouse gases and aerosols. Budgets that don’t take into account non-CO2 gases overestimate the carbon budget.

There are many uncertainties regarding the calculation of the remaining carbon budget, including the Earth’s climate response to carbon emissions, the role of non-CO2 emissions, climate feedbacks and more. In fact, the IPCC states that uncertainties in the climate budget contribute ±400 GtCO2, and uncertainties regarding the level of historic warming contributes ±250 GtCO2 to the budget. And as a result, the timing of bringing carbon dioxide emissions down to net-zero can vary by ±15–20 years.

一个重要的不确定性是climate feedbacks, or a cascade of impacts that can result in greater warming. For example, if the remaining budget was stretched out to 2100, it would be roughly 100 GtCO2 lower because of the potential release of methane from wetlands and thawing permafrost.

Staying Within the Carbon Budget

We have already burned through a large portion of our carbon budget, and recently at an alarming rate. It is clear from the report that if emissions continue unabated, even with countries’ current climate commitments being fully implemented, we blow through the budget in just about a decade’s time for a likely chance of limiting warming to 1.5°C. Doing so would揭露世界to even more severe heat waves, sea level rise, extreme rainfall and other climate impacts. The IPCC makes it clear that we can no longer emit at our carbon-intensive rate if we are to avoid the worst climate impacts. We must instead rapidly turn around our emissions trajectory.