Greenhouse gas emissions là gì

Editor"s Note: This blog was updated on August 12, 2020 lớn include"s recent paper on designing and communicating net-zero targets. You can read the paper here.

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The lakiểm tra retìm kiếm is clear: To avoid the worst climate impacts, global greenhouse gas (GHG) emissions will need lớn drop by half by 2030 and reach net-zero around mid-century.

Recognizing this urgency, an unprecedented number of business và local government leaders are supporting svào national climate ambition through the U.N. High Level Climate Champions’ Race to Zero campaign. The global initiative sầu sets minimum criteria for designing net-zero targets, asking regions, cities, businesses, investors and civil society to pledge lớn reach net-zero emissions by 2050 and submit a plan in advance of the next U.N. Climate Summit in 2021. This comes on the heels of the U.N. Secretary General asking countries to lớn come forward with net-zero targets. In addition, a growing number of countries have sầu joined the Climate Ambition Alliance with aspirations to lớn reach net-zero emissions.

Here we explore what a net-zero target means, explain the science behind net-zero, and discuss which countries have sầu already made such commitments.

1. What Does It Mean to lớn Reach Net-Zero Emissions?

We will achieve sầu net-zero emissions when any remaining human-caused GHG emissions are balanced out by removing GHGs from the atmosphere in a process known as carbon removal.

First & foremost, human-caused emissions — like those from fossil-fueled vehicles & factories — should be reduced as cthua thảm to zero as possible. Any remaining GHGs would be balanced with an equivalent amount of carbon removal, for example by restoring forests or through direct air capture & storage (DACS) công nghệ. The concept of net-zero emissions is akin lớn "climate neutrality."


2. When Does the World Need khổng lồ Reach Net-Zero Emissions?

Under the Paris Agreement, countries agreed khổng lồ limit warming well below 2 degrees C (3.6 degrees F) and ideally 1.5 degrees C (2.7 degrees F). Climate impacts that are already unfolding around the world, even with only 1.1 degrees C (2 degrees F) of warming — from melting ice to lớn devastating heat waves và more intense storms — show the urgency of minimizing temperature increase lớn no more than 1.5 degrees C. The lakiểm tra science suggests that lớn meet the Paris Agreement"s temperature goals, the world will need khổng lồ reach net-zero emissions on the following timelines:

In 2 degrees C scenarquả táo, CO2 reaches net-zero on average by 2070 (in scenarquả táo with a greater than 66% likelihood of limiting warming to lớn 2 degrees C) lớn 2085 (50–66% likelihood). Total GHG emissions reach net-zero by the kết thúc of the century.

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The Special Report on Global Warming of 1.5˚C, from the Intergovernmental Panel on Climate Change (IPCC), finds that if the world reaches net-zero emissions one decade sooner, by 2040, the chance of limiting warming to lớn 1.5 degrees C is considerably higher. The sooner emissions peak, & the lower they are at that point, the more realistic it is that we achieve net-zero in time. We would also need khổng lồ rely less on carbon removal in the second half of the century.

Importantly, the time frame for reaching net-zero emissions differs significantly if one is referring to CO2 alone, or referring to lớn all major GHGs (including methane, nitrous oxide, and "F gases" such as hydrofluorocarbons, commonly known as HFCs). For non-CO2 emissions, the net-zero date is later because some of these emissions — such as methane from agricultural sources — are somewhat more difficult to lớn phase out. However, these potent but short-lived gases will drive sầu temperatures higher in the near-term, potentially pushing temperature change past the 1.5 degrees C threshold much earlier.

Because of this, it"s important for countries khổng lồ specify whether their net-zero targets cover only CO2 or all major GHGs. A comprehensive sầu net-zero emissions target would include all major GHGs, ensuring that non-CO2 gases are also reduced.

3. Do All Countries Need to lớn Reach Net-Zero at the Same Time?

The timelines above are global averages. Because countries" economies & stages of development vary widely, there is no one-size-fits-all timeline for individual countries. There are, however, hard physical limits khổng lồ the total emissions the atmosphere can support while limiting global temperature increase to the agreed goals of the Paris Agreement. At the very least, major emitters (such as the United States, the European Union và China) should reach net-zero GHG emissions by 2050, or it will be hard for the math to lớn work regardless of what other countries bởi vì. Ideally, major emitters will reach net-zero much earlier, given that the largest economies play an outsize role in determining the trajectory of global emissions.

4. How Many Countries Have Net-Zero Targets?

Twenty countries & regions adopted net-zero targets as of June 20đôi mươi — Austria, Bhurã, Costa Rica, Denmark, the European Union, Fiji, Finl&, France, Hungary, Iceland, nhật bản, the Marshall Islands, New Zealvà, Norway, Portugal, Singapore, Slovenia, Sweden, Switzerland & the United Kingdom.

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This các mục only includes countries that adopted a net-zero target in law or another policy document. This does not include targets in political speeches, such as China’s noteworthy announcement. The Energy và Intelligence Climate Unit maintains an updated danh mục of net-zero announcements here. As of June 2020, 1trăng tròn countries are committed lớn working on net-zero targets through the Climate Ambition Alliance, including all least-developed countries and a handful of high-emitting countries. However, only around 10% of global emissions are covered by some form of an adopted net-zero target. Some net-zero targets have been incorporated directly inlớn countries" commitments under the Paris Agreement.

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