Greenhouse gas emissions là gì

September 17, 2019 By Kelly Levin, Taryn Fransen, Clea Schumer và Chantal Davis Cover Image by: Aaron Minnick/

Editor"s Note: This article was updated in May 2021 khổng lồ include’s lachạy thử research & information about new national net-zero targets.

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

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Recognizing this urgency, a rapidly growing number of national government, local government & business leaders are making commitments lớn reach net-zero emissions within their jurisdictions or businesses. To date, over fifty countries have communicated such “net-zero targets,” including the world’s largest emitters (Đài Loan Trung Quốc and the United States). On top of that, hundreds more regions, cities and businesses have set targets of their own.

These numbers are climbing quickly, particularly because the U.N. Secretary General asked countries to lớn come forward with net-zero targets. The U.N. High Level Climate Champions’ Race khổng lồ Zero chiến dịch also calls on regions, cities, businesses, investors & civil society to lớn submit plans to reach net-zero emissions by 2050 in advance of the United Nations climate negotiations (COPhường 26) in Glasgow in November 2021.

But what does a net-zero target mean, what’s the science behind net-zero and which countries have already made such commitments? Here are nine common questions and answers about net zero:

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

Net-zero emissions will be achieved when all GHG emissions released by humans are counterbalanced by removing GHGs from the atmosphere in a process known as carbon removal.

First and foremost, human-caused emissions (such as those from fossil-fueled vehicles and factories) should be reduced as cchiến bại lớn zero as possible. Any remaining GHGs should then be balanced with an equivalent amount of carbon removal, which can happen through things like restoring forests or using direct air capture and storage (DACS) công nghệ. Reaching net-zero emissions is akin to achieving "climate neutrality."


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 by 2040, the chance of limiting warming lớn 1.5 degrees C is considerably higher. The sooner emissions peak, & the lower they are at that point, the more realistic achieving net zero becomes. This would also create less reliance on carbon removal in the second half of the century.

This does not suggest that all countries need to reach net-zero emissions at the same time. The chances of limiting warming to 1.5 degrees C, however, depkết thúc significantly on how soon the highest emitters reach net-zero emissions. Equity-related considerations — including responsibility for past emissions, eunique in per-capita emissions and capathành phố to act — also suggest earlier dates for wealthier, higher-emitting countries.

Importantly, the time frame for reaching net-zero emissions is different for CO2 alone versus for CO2 plus other GHGs lượt thích methane, nitrous oxide & fluorinated gases. For non-CO2 emissions, the net zero date is later because models suggest that some of these emissions — such as methane from agricultural sources — are more difficult lớn phase out. However, these potent but short-lived gases will drive 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 to specify whether their net-zero targets cover CO2 only or all GHGs. A comprehensive net-zero emissions target would include all GHGs, ensuring that non-CO2 gases are also reduced.

3. What Needs lớn Happen to lớn Achieve Net-Zero Emissions?

Policy, công nghệ & behavior need to shift across the board. For example, in pathways khổng lồ 1.5 degrees C, renewables are projected khổng lồ supply 70-85% of electriđô thị by 2050. Energy efficiency and fuel-switching measures are critical for transportation. Improving the efficiency of food production, changing dietary choices, halting deforestation, restoring degraded lands and reducing food loss & waste also have sầu significant potential lớn reduce emissions.


In some cases, emissions are actually getting worse. Despite tremendous acceleration in renewable energy, adoption will need khổng lồ increase by a factor of five sầu to lớn reach 2030 và 2050 goals. Current rates of renovation for both residential & commercial buildings, for instance, fall between 1% và 2% per year on average, whereas they need khổng lồ reach 2.5-3.5% per year by 2030. And the world needs to drastically slow deforestation và increase tree cover gain five sầu times faster by 2030.

5. How Many Countries Have Net-Zero Targets?

Global momentum for web10_setting net-zero targets is growing quickly, with key economies like Đài Loan Trung Quốc, the United States and the European Union articulating such commitments. Bhutan was the first country to lớn mix a net-zero target in năm ngoái. Now over 50 countries, representing more than half of global emissions, have sầu set a net-zero target.

Climate Watch’s Net-Zero Tracker shows how these targets were set, such as through nationally determined contributions (NDCs), long-term low GHG emissions development strategies (LTS), domestic laws,policies or high-cấp độ political pledges from heads of state or other cabinet members.

6. Why và How Should Countries Align Their 2030 Emissions-Reduction Targets with a Net-Zero Emissions Goal?

When beginning a journey lớn reach net-zero emissions by mid-century, countries must pursue near-term action with their long-term objectives in mind. This will help avoid locking in carbon-intensive sầu, non-resilient infrastructure & technologies. Countries can also cut near- và long-term costs by investing in green infrastructure that will not need to be phased out later, designing consistent policies & sending strong signals to the private sector khổng lồ invest in climate action.

Under the Paris Agreement, countries agreed khổng lồ submit climate plans every five years, known as nationally determined contributions, or NDCs. NDCs are an important tool khổng lồ align near- và long-term goals. When informed by a country’s long-term vision, these documents can help governments implement the types of policies, signals, targets and other enhancement strategies necessary in the nearer term to realize an ambitious mid-century objective sầu.

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Many countries with net-zero targets are beginning to incorporate them directly into their near-term NDCs. These targets are also being expressed in many countries across other law and policy documents. The most advantageous action, ultimately, will be for countries to express their net-zero commitments in as many source documents as possible, including NDCs. This will make the target as durable and binding as possible, allowing for synergistic planning.

7. Does the Paris Agreement Commit Countries to Achieving Net-Zero Emissions?

In short, yes. However, while the Paris Agreement establishes a global goal that implies reaching net-zero emissions, it was left unresolved when individual countries should reach that goal.

The Paris Agreement sets a long-term goal of achieving "a balance between anthropogenic emissions by sources & removals by sinks of greenhouse gases in the second half of this century, on the basis of equity, và in the context of sustainable development and efforts khổng lồ eradicate poverty." This concept of balancing emissions và removals is akin khổng lồ reaching net-zero emissions.

The Paris Agreement also commits governments lớn putting forward plans khổng lồ sharply reduce emissions và ramp up efforts to reach net-zero emissions. The Paris Agreement’s invitation lớn countries to submit long-term, low-emissions development strategies by COP 26 is one opportunity for countries to lớn set net-zero targets và chart how they alặng to lớn make such transitions.

Ultimately, commitments to create bold short- & long-term targets that align with a net-zero emissions future skết thúc important signals to all levels of government, the private sector và the public that leaders are betting on a safe and prosperous future.

8. Are Net-Zero Targets a Form of Greenwashing?

No, but they can be if used as an excuse to lớn not take bold climate action in the near-term.

Although net-zero targets continue lớn gain traction with governments và companies, skeptical voices have sầu emerged, from academic journals khổng lồ chiến dịch groups lớn Greta Thunberg’s speech in Davos. Critiques of net-zero targets include:

a. The “net” aspect of net-zero targets could dampen efforts to rapidly cut emissions.

Critics are concerned that this could foster an overreliance on carbon dioxide removal, allowing decision-makers to use net-zero targets khổng lồ avoid emission reductions in the near-term. Decision-makers can address this concern by web10_setting absolute reduction targets (targets that bởi vì not rely on removals) alongside their longer-term net reduction targets.

b. Some countries’ net-zero targets rely on purchasing emissions reductions, delaying reductions within their own boundaries.

Some countries are web10_setting net-zero targets that rely on investing in or paying for emissions reductions from other countries khổng lồ use toward their own targets. There’s concern that government leaders might use this strategy lớn avoid reducing their own emissions in the long-term. Decision-makers can address this concern by web10_setting deep emission reduction targets that explicitly avoid or limit using offsets lớn achieve their goals.

c. The time horizon for net-zero targets — typically 2050 — feels distant.

Today’s infrastructure can last for decades và have sầu a major impact on mid-century targets. Decision-makers must take this inkhổng lồ tài khoản by establishing near- and mid-term milestones for their path khổng lồ net-zero emissions, including by web10_setting ambitious 2030 emission reduction targets as part of their NDCs. NDCs are subject khổng lồ transparency and accountability mechanisms under the Paris Agreement that can foster implementation in the near term, which is critical for a long-term net-zero goal lớn be credible.

In short, net-zero commitments must be robust lớn be effective sầu & advance climate action. Countries must take concrete steps lớn mix robust targets.