Countries need a variety of solutions, including renewable energy and healthy forests, to reach net-zero greenhouse gas emissions. Photo by Aaron Minnick/honamphoto.com.Bạn đang xem: Greenhouse gas emissions là gì
Editor”s Note: This blog was updated on August 12, 2020 to include honamphoto.com”s recent paper on designing and communicating net-zero targets. You can read the paper here.
Đang xem: Greenhouse gas emissions là gì
The latest research is clear: To avoid the worst climate impacts, global greenhouse gas (GHG) emissions will need to drop by half by 2030 and reach net-zero around mid-century.
Recognizing this urgency, an unprecedented number of business and local government leaders are supporting strong national climate ambition through the U.N. High Level Climate Champions’ Race to Zero campaign. The global initiative sets minimum criteria for designing net-zero targets, asking regions, cities, businesses, investors and civil society to pledge to 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 come forward with net-zero targets. In addition, a growing number of countries have joined the Climate Ambition Alliance with aspirations to reach net-zero emissions.
Here we explore what a net-zero target means, explain the science behind net-zero, and discuss which countries have already made such commitments.
1. What Does It Mean to Reach Net-Zero Emissions?
We will achieve 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.
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First and foremost, human-caused emissions — like those from fossil-fueled vehicles and factories — should be reduced as close 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 and storage (DACS) technology. The concept of net-zero emissions is akin to “climate neutrality.”
2. When Does the World Need to Reach Net-Zero Emissions?
Under the Paris Agreement, countries agreed to 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 devastating heat waves and more intense storms — show the urgency of minimizing temperature increase to no more than 1.5 degrees C. The latest science suggests that to meet the Paris Agreement”s temperature goals, the world will need to reach net-zero emissions on the following timelines:
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 1.5 degrees C is considerably higher. The sooner emissions peak, and the lower they are at that point, the more realistic it is that we achieve net-zero in time. We would also need to 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 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 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 only CO2 or all major GHGs. A comprehensive net-zero emissions target would include all major GHGs, ensuring that non-CO2 gases are also reduced.
3. Do All Countries Need to Reach Net-Zero at the Same Time?
The timelines above are global averages. Because countries” economies and stages of development vary widely, there is no one-size-fits-all timeline for individual countries. There are, however, hard physical limits to 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 and China) should reach net-zero GHG emissions by 2050, or it will be hard for the math to work regardless of what other countries do. 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.
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4. How Many Countries Have Net-Zero Targets?
This list 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 and Intelligence Climate Unit maintains an updated list of net-zero announcements here. As of June 2020, 120 countries are committed to 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 into countries” commitments under the Paris Agreement.