Fire and carbon cycling in boreal forests

From Wikipedia, the free encyclopedia
Fire and carbon cycling in boreal forests

High intensity crown fire is the typical fire regime in boreal forest regions

Terrestrial ecosystems found in the boreal (or taiga) regions of North America and Eurasia cover less than 17% of the earth's land surface, yet contain more than 30% of all carbon present in the terrestrial biome. In terms of carbon storage, the boreal region consists of three ecosystems: boreal forest, peatland, and tundra. Vast areas of the globe and are contributing greatly to atmospheric carbon release due to increased temperature and fire hazard. High northern latitudes will experience the most significant increase in warming on the planet as a result of increased atmospheric greenhouse gases thus placing in jeopardy the carbon sink in these areas. In addition to the release of carbon through the melting of permafrost, high intensity wildfires will become more common and thus contribute to the release of stored carbon. This means that the boreal forest and its fire regime is becoming an increasingly more significant factor in determining the global carbon budget.

Boreal forests are also important economic factors in Russia and Canada specifically, and the uncertainty of fire patterns in the future as a result of climate change is a major consideration in forest management plans. A decrease in allowed timber harvest could be a solution to long term uncertainty of fire cycles.

Carbon cycling in boreal forests

Although temperate and tropical forests in total cover twice as much land as boreal forest, boreal forest contains 20% more carbon than the other two combined. Boreal forests are susceptible to global warming because the ice/snow–albedo feedback is significantly influenced by surface temperature, so fire induced changes in surface albedo and infrared emissivity are more significant than in the tropics.

Boreal forest fires contribute greatly to greenhouse gas presence in the atmosphere. Large boreal fires produce enough energy to produce convective smoke columns that can break into the troposphere and occasionally penetrate across the tropopause. In addition, the cold temperature in boreal regions result in low levels of water vapor. This low level of water vapor combined with low solar radiation results in very low photochemical production of the OH radical, which is a chemical that controls the atmospheric lifetime of most tropospheric gases. Therefore, the greenhouse gas emission in boreal forest fires will have prolonged lifetimes over the forest.

Fire regime

The fire regimes of boreal forest in Canada and in Russia are distinct. In Russia, the climate is drier and the majority of fires are human caused. This means that there are more frequent fires of lower intensity than in Canada and that most carbon output as a result of fire is in Russia. Forestry practices in Russia involve the use of heavy machinery and large-scale clear-cuts, leading to the alteration of fuel complexes. This practice is reportedly causing areas to degrade into grass steppes, rather that regenerate as new forest. This may result in the shorting of fire return intervals. Industrial practices in Russia also create additional fire hazards (severe damages in the Russian Federation affect about 9 million ha). Radioactive contamination on an area of about 7 million ha creates a fire hazard because fire can redistribute radionuclides.

The majority of boreal forest fires in Canada are started by lighting. Subsequently, there are fewer fires on average in Canada but a much higher frequency of high intensity crown fire than Russia with a crown fire rate of 57% in Canada as opposed to 6% in Russia. Natural fire rotation across Canadian and Alaskan boreal forests is one to several centuries.

Peatland and tundra

Average surface air temperatures from 2011 to 2020 compared to the 1951–1980 average. Source: NASA

Fire indirectly plays a role in the exchange of carbon between terrestrial surface and the atmosphere by regulating soil and moisture regimes, including plant succession, photosynthesis, and soil microbial processes. Soil in boreal regions is a significant global carbon sink; boreal forest soil holds 200 Gt of carbon while boreal peatlands hold 400 Gt of carbon. Northernmost permafrost regions contain 10,355 ± 150 Pg of soil organic carbon (SOC) in the top 0-3 m and 21% of this carbon is in the soil organic layer (SOL) pool found in the top 30 cm of the ground layer.

The depth of the organic soil layer is one of the controls on permafrost, leading to a generalization of two domains in boreal forest: thick soil layer and thin soil layer. Thick organic soil insulates the subsoil from warmer summer temperatures and allows for permafrost to develop. Although permafrost keeps ground moist during winter, during summer months upper organic soil horizons will become desiccated. As average temperatures increase, Permafrost is melting at a faster rate and, correspondingly, the length of the fire season is increasing. When the fire-free interval (FFI) is decreased, the loss of the SOL may result in a domain change to a thin soil layer, leading to less carbon storage in the soil, greater fire vulnerability, and decreased permafrost. In black spruce forests, decreased FFI can ruin successional trajectories by opening the door for deciduous trees and shrubs to invade, which also further increases fire vulnerability.

Data regarding carbon storage in the permafrost region as well as fire activity in boreal forests is sparse, which is a significant barrier in determining an accurate carbon budget. An expert assessment indicates that the permafrost region will become a net carbon source by 2100.

A 5 - 10 degree C rise in forest floor temperature after a fire will significantly increase the rate of decomposition for years after the fire occurs, which temporarily turns the soil into a net carbon source (not sink) locally.

Fire enhances the biogenic emissions of NO and N20 from soil.

Carbon neutrality

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/Carbon_neutrality 

Carbon neutrality is a state of net zero carbon dioxide emissions. This can be achieved by balancing emissions of carbon dioxide by eliminating emissions from society (the transition to the "post-carbon economy") or carbon dioxide removal (such as through carbon offsetting). The term is used in the context of carbon dioxide-releasing processes associated with transport, energy production, agriculture, and industry.

Although the term "carbon neutral" is used, a carbon footprint also includes other greenhouse gases, measured in terms of their carbon dioxide equivalence. The term climate-neutral reflects the broader inclusiveness of other greenhouse gases in climate change, even if CO₂ is the most abundant.

The term net zero is increasingly used to describe a broader and more comprehensive commitment to decarbonization and climate action, moving beyond carbon neutrality by including more activities under the scope of indirect emissions, and often including a science-based target on emissions reduction, as opposed to relying solely on offsetting. Some climate scientists have stated that "the idea of net zero has licensed a recklessly cavalier 'burn now, pay later' approach which has seen carbon emissions continue to soar."

History

Plenary session of the COP21 adopting the Paris Agreement in 2015

In 2006, the New Oxford American Dictionary made the term carbon-neutral word of the year.

In December 2020, five years after the Paris Agreement, the Secretary-General of the United Nations António Guterres warned that the commitments made by countries in Paris were not sufficient and were not respected. He has urged all other countries to declare climate emergencies until carbon neutrality is reached.

In May 2021, the International Energy Agency (IEA) published Net Zero by 2050, a comprehensive study to demonstrate what changes would need to be done in order for the world to reach net zero carbon emissions by the year 2050. It compared the current state of affairs with projections matching the changes the report suggested in order to demonstrate a possible path towards the carbon neutrality goal.

Method

Carbon-neutral status can be achieved in two ways, although a combination of the two is most likely required:

Ending emissions

Ending carbon emissions can be done by moving towards energy sources and industry processes that produce no greenhouse gases, thereby transitioning to a zero-carbon economy. Shifting towards the use of renewable energy such as wind, geothermal, and solar power, zero-energy systems like passive daytime radiative cooling, as well as nuclear power, reduces greenhouse gas emissions. Although both renewable and non-renewable energy production produce carbon emissions in some form, renewable sources produce negligible to almost zero carbon emissions. Transitioning to a low-carbon economy would also mean making changes to current industrial and agricultural processes to reduce carbon emissions, for example, diet changes to livestock such as cattle can potentially reduce methane production by 40%. Carbon projects and emissions trading are often used to reduce carbon emissions, and carbon dioxide can even sometimes be prevented from entering the atmosphere entirely (such as by carbon scrubbing).

One way to implement carbon-neutral products is by making these products cheaper and more cost effective than carbon positive fuels. Various companies have pledged to become carbon neutral or negative by 2050, some of which include: Microsoft, Delta Air Lines, BP, IKEA, and BlackRock, although these distant pledges are typically not matched by real action and are often greenwashing - for instance with BP spending more on fossil fuels in 2022 than renewables despite its net zero pledge.

Carbon offsetting

Balancing remaining carbon dioxide emissions with carbon offsets is the process of reducing or avoiding greenhouse gas emissions or removing carbon dioxide from the atmosphere to make up for emissions elsewhere. If the total greenhouse gases emitted is equal to the total amount avoided or removed, then the two effects cancel each other out and the net emissions are 'neutral'.

Process

See also: 100% renewable energy

Carbon neutrality is usually achieved by combining the following steps, although these may vary depending whether the strategy is being implemented by individuals, companies, organizations, cities, regions, or countries:

Commitment

In the case of individuals, decision-making is likely to be straightforward, but for more complex institutions it usually requires political leadership and popular agreement that the effort is worth making.

Commitment from countries and the organizations within is critical to the forward movement of Carbon Neutrality. The Net Zero Challenge Report states that "commitments made by governments so far are far from sufficient." One way to obtain more commitment would be to set carbon-neutral goals but allow flexibility for the organizations and governments to decide how to achieve these goals. Large well-known companies like Apple are laying out roadmaps to help these commitments become a reality. Then lesser well-known companies like Kinaxis, a supply chain management company, met their net-zero goal in 2020 by fully committing to their carbon emission objectives.

Counting and analyzing

Counting and analyzing the emissions that need to be eliminated, and how it can be done, is an important step in the process of achieving carbon neutrality, as it establishes the priorities for where action needs to be taken and progress can begin being monitored. This can be achieved through a greenhouse gas inventory that aims to answer questions such as:

• Which operations, activities and units should be targeted?
• Which sources should be included (see section Direct and indirect emissions)?
• Who is responsible for which emissions?
• Which gases should be included?

For individuals, carbon calculators simplify compiling an inventory. Typically they measure electricity consumption in kWh, the amount and type of fuel used to heat water and warm the house, and how many kilometers an individual drives, flies and rides in different vehicles. Individuals may also set the limits of the system they are concerned with, for example, whether they want to balance out their personal greenhouse gas emissions, their household emissions, or their company's.

There are plenty of carbon calculators available online, which vary significantly in the parameters they measure. Some, for example, factor in only cars, aircraft and household energy use. Others cover household waste or leisure interests as well. In some circumstances, going beyond carbon neutral and becoming carbon negative (usually after a certain length of time taken to reach carbon breakeven) is an objective.

Cities and countries are challenging for carbon counting and analyzing. This is because the production of goods and services within their territory can be linked either to domestic consumption or exports. On the other hand, citizens also consume imported goods and services. To avoid double counting in the calculation of emissions, it should be specified where the emissions should be counted: at the point of production or consumption. This can be complicated given the long production chains in a globalized economy. In addition, embodied energy and the consequences of large-scale resource extraction needed for renewable energy systems and EV batteries are likely to present their own complications – local point-of-use emissions are likely to be greatly reduced, but life cycle emissions may still remain significant.

Reduction

One of the strongest arguments for reducing greenhouse gas emissions is that it will often save money. Examples of possible actions to reduce greenhouse gas emissions are:

• Limiting energy usage and emissions from transportation (walking, using bicycles or public transport, avoiding flying, using low-energy vehicles, carpooling), as well as from buildings, equipment, animals and processes.
• Obtaining electricity and other forms of energy from zero or low carbon energy sources.
• Electrification: using electrical energy, ideally from non-emitting sources, rather than combustion. For example, in transportation (e.g., electric vehicles and electric trains) and heating (e.g. heat pumps and electric heating).

Wind power, nuclear power, hydropower, solar power, and geothermal are the energy sources with the lowest life-cycle emissions, which includes deployment and operations.

Main article: Life-cycle greenhouse-gas emissions of energy sources

Offsetting

Carbon offsetting is the practice of removing greenhouse gases from the atmosphere equivalent to the emissions generated by other activities. This is often done by paying "projects that either emit fewer emissions at source, such as cleaner energy production, or remove them from the atmosphere, such as forestry schemes." This aims to neutralize a certain volume of greenhouse gas emissions by funding activities which are expected to cause an equivalent reduction elsewhere, for example, with paid-for ecosystem services, such as blue carbon. Offsetting schemes can also have significant co-benefits such as improving quality of life and reducing poverty.

Carbon offsetting has been critiqued on several fronts. One of the main concerns has been the potential for offsets to delay needed action on active emissions reductions. In 2007, for example, in a report from the Transnational Institute, Kevin Smith likens carbon offsets to medieval indulgences where people pay "offset companies to absolve them of their carbon sins." This, he contends, permits a "business as usual" attitude that stifles the required major changes. Offsets have also been widely criticised for playing a part in greenwashing, an argument which has even mobilised in a 2021 watchdog ruling against Shell.

Another critique of offsetting has been that loose regulation of claims by carbon offsetting schemes that, combined with the difficulties in calculating greenhouse gas sequestration and emissions reductions, can result in schemes that do not in reality adequately offset emissions. Moves have been made to create better regulation. The United Nations, for instance, has operated a certification process for carbon offsets since 2001 called the Clean Development Mechanism. This aims to stimulate "sustainable development and emission reductions, while giving industrialized countries some flexibility in how they meet their emission reduction limitation targets." However, the UK Government's Climate Change Committee has also noted that "Although standards both globally and in the UK are being improved, the risk remains that the emissions reduction or removal reported may have happened anyway or may not persist into the future."

Criticisms have also been levelled at the use of non-native and monocultural forest plantations as carbon offsets for its "limited—and at times negative—effects on native biodiversity" and other ecosystem services.

Evaluation and repeating

This phase includes evaluation of the results and compilation of a list of suggested improvements, with results documented and reported, so that experience gained of what does (and does not) work is shared with those who can put it to good use. Science and technology move on, regulations become tighter, the standards people demand go up. So the second cycle will go further than the first, and the process will continue, each successive phase building on and improving on what went before.

Being carbon neutral is increasingly seen as good corporate or state social responsibility and a growing list of corporations and states are announcing dates for when they intend to become fully neutral. Events such as the G8 Summit and organizations like the World Bank are also using offset schemes to become carbon neutral. Artists like The Rolling Stones and Pink Floyd have made albums or tours carbon neutral.

Direct and indirect emissions

To be considered carbon neutral, an organization must reduce its carbon footprint to zero. Determining what to include in the carbon footprint depends upon the organization and the standards they are following.

Generally, direct emissions sources must be reduced and offset completely, while indirect emissions from purchased electricity can be reduced with renewable energy purchases.

Direct emissions include all pollution from manufacturing, company owned vehicles and reimbursed travel, livestock and any other source that is directly controlled by the owner. Indirect emissions include all emissions that result from the use or purchase of a product. For instance, the direct emissions of an airline are all the jet fuel that is burned, while the indirect emissions include manufacture and disposal of airplanes, all the electricity used to operate the airline's office, and the daily emissions from employee travel to and from work. In another example, the power company has a direct emission of greenhouse gas, while the office that purchases it considers it an indirect emission.

Cities and countries represent a challenge with regard to emissions counting as production of goods and services within their territory can be related either to domestic consumption or exports. Conversely the citizens also consume imported goods and services. To avoid double counting in any emissions calculation it should be made clear where the emissions are to be counted: at the site of production or consumption. This may be complicated given long production chains in a globalized economy. Moreover, the embodied energy and consequences of large-scale raw material extraction required for renewable energy systems and electric vehicle batteries is likely to represent its own complications – local emissions at the site of utilization are likely to be very small but life-cycle emissions can still be significant.

Carbon is used as both a source of electricity and a feedstock in energy-intensive industries, making decarbonization impossible. If CO₂ emissions and sources are to be captured and stopped from entering the atmosphere, an alternate chemical solution must be formulated that achieves the desired output while not releasing CO₂ as a by-product.

Simplification of standards and definitions

Carbon neutral fuels are those that neither contribute to nor reduce the amount of carbon into the atmosphere. Before an agency can certify an organization or individual as carbon neutral, it is important to specify whether indirect emissions are included in the Carbon Footprint calculation. Most Voluntary Carbon neutral certifiers in the US, require both direct and indirect sources to be reduced and offset. As an example, for an organization to be certified carbon neutral, it must offset all direct and indirect emissions from travel by 1 lb CO₂ per passenger mile, and all non-electricity direct emissions 100%. Indirect electrical purchases must be equalized either with offsets, or renewable energy purchases. This standard differs slightly from the widely used World Resources Institute and may be easier to calculate and apply.

Much of the confusion in carbon neutral standards can be attributed to the number of voluntary carbon standards which are available. For organizations looking at which carbon offsets to purchase, knowing which standards are robust, credible and permanent is vital in choosing the right carbon offsets and projects to get involved in. Some of the main standards in the voluntary market include Verified Carbon Standard, Gold Standard and The American Carbon Registry. In addition companies can purchase Certified Emission Reductions (CERs) which result from mitigated carbon emissions from United Nations Framework Convention on Climate Change approved projects for voluntary purposes. The concept of shared resources also reduces the volume of carbon a particular organization has to offset, with all upstream and downstream emissions the responsibility of other organizations or individuals. If all organizations and individuals were involved then this would not result in any double accounting.

Regarding terminology in UK, in December 2011 the Advertising Standards Authority (in an ASA decision which was upheld by its Independent Reviewer, Sir Hayden Phillips) controversially ruled that no manufactured product can be marketed as "zero-carbon", because carbon was inevitably emitted during its manufacture. This decision was made in relation to a solar panel system whose embodied carbon was repaid during 1.2 years of use and it appears to mean that no buildings or manufactured products can legitimately be described as zero carbon in its jurisdiction.

Pledges

Being carbon neutral is increasingly seen as good corporate or state social responsibility, and a growing list of corporations, cities and states are announcing dates for when they intend to become fully neutral. Many countries have also announced dates by which they want to be carbon neutral, with many of them targeting the year 2050. However, setting an earlier date (i.e. 2025, 2030, or 2045) may be considered to send out a stronger signal internationally, and is recommended by the Climate Crisis Advisory Group. Also, delaying significant action to reduce greenhouse gas emissions is increasingly being considered to not be a financially sound idea.

Companies and organizations

The original Climate Neutral Network was an Oregon-based non-profit organization founded by Sue Hall and incorporated in 1999 to persuade companies that being climate neutral was potentially cost saving as well as environmentally sustainable. It developed both the Climate Neutral Certification and Climate Cool brand name with key stakeholders such as the United States Environmental Protection Agency, The Nature Conservancy, the Rocky Mountain Institute, Conservation International, and the World Resources Institute and succeeded in enrolling the 2002 Winter Olympics to compensate for its associated greenhouse gas emissions.

Few companies have actually attained Climate Neutral Certification, applying to a rigorous review process and establishing that they have achieved absolute net zero or better impact on the world's climate. Another reason that companies have difficulty in attaining the Climate Neutral Certification is due the lack clear guidelines on what it means to make a carbon neutral development. Shaklee Corporation became the first Climate Neutral certified company in April 2000. The company employs a variety of investments, and offset activities, including tree-planting, use of solar energy, methane capture in abandoned mines and its manufacturing processes. Climate Neutral Business Network states that it certified Dave Matthews Band's concert tour as Climate Neutral. The Christian Science Monitor criticized the use of NativeEnergy, a for-profit company that sells offset credits to businesses and celebrities like Dave Matthews.

Salt Spring Coffee became carbon neutral by lowering emissions through reducing long-range trucking and using bio-diesel fuel in delivery trucks, upgrading to energy efficient equipment and purchasing carbon offsets from its offset provider, Offsetters. The company claims to the first carbon neutral coffee sold in Canada. Salt Spring Coffee was recognized by the David Suzuki Foundation in their 2010 report Doing Business in a New Climate.

Some corporate examples of self-proclaimed carbon neutral and climate neutral initiatives include Dell, Google, HSBC, ING Group, PepsiCo, Sky Group, Tesco, Toronto-Dominion Bank, Asos and Bank of Montreal.

Under the leadership of Secretary-General Ban Ki-moon, the United Nations pledged to work towards climate neutrality in December 2007. The United Nations Environment Programme (UNEP) announced it was becoming climate neutral in 2008 and established a Climate Neutral Network to promote the idea in February 2008.

Events such as the G8 Summit and organizations like the World Bank are also using offset schemes to become carbon neutral. Artists like The Rolling Stones and Pink Floyd have made albums or tours carbon neutral, while Live Earth says that its seven concerts held on 7 July 2007 were the largest carbon neutral public event in history.

The Vancouver 2010 Olympic and Paralympic Winter Games were the first carbon neutral Games in history through a large partnership with the carbon offset provider, Offsetters.

Buildings, in 2019, made up 21% of global greenhouse gas emissions. The American Institute of Architects 2030 Commitment is a voluntary program for AIA member firms and other entities in the built environment that asks these organizations to pledge to design all their buildings to be carbon neutral by 2030.

In 2010, architectural firm HOK worked with energy and daylighting consultant The Weidt Group to design a 170,735-square-foot (15,861.8 m²) net zero carbon emissions Class A office building prototype in St. Louis, Missouri, U.S.

Goodvalley became a carbon neutral company as the first pork meat producer. It was possible by lowering greenhouse gases emission at every stage of production. In addition to reducing its primary carbon footprint, the company achieves carbon neutrality by producing green energy from its agricultural biogas plants. The sum of CO₂ emissions and reductions are calculated by NIRAS and since 2018, the calculation has labelled Goodvalley Group Corporate Carbon Neutral. The certification is done according to ISO-14064 and verified by TÜV Rheinland.

Since 2019, an increasing number of business organisations have committed to attaining carbon neutrality by, or before, 2050, such as Microsoft (2030), Amazon (2040), and L'Oreal (2050).

In 2020, BlackRock, the world's largest investment firm, announced that it would begin making decisions with climate change and sustainability in mind, and begin exiting assets that it believed represented a "high sustainablilty-related risk". Activists have accused the company of greenwashing, as it still has a considerable amount of money invested in coal companies. In CEO Larry Fink's 2021 annual letter, however, he further pushed for businesses to begin laying out explicit plans on how they will be carbon neutral by 2050.

Countries and nations

Countries and nations by intended year of climate neutrality

  Carbon neutral or negative

  2030

  2035

  2040

  2045

  2050

  2053

  2060

  2070

  Unknown or undeclared

Three countries have achieved or surpassed carbon neutrality:

•  Bhutan (carbon-negative)
•  Suriname (carbon negative since 2014, at least)
•  Panama probably carbon negative as of 2021, certification expected to arrive.

The 3 countries formed a small coalition at the 2021 United Nations Climate Change Conference and asked for help so that other countries will join it.

As of October 2021, numerous countries/nations have pledged carbon neutrality, including:

Canada

In June 2011, the Canadian province of British Columbia announced they had officially become the first provincial/state jurisdiction in North America to achieve carbon neutrality in public sector operations: Every school, hospital, university, Crown corporation, and government office measured, reported, and purchased carbon offsets on all of their 2010 greenhouse gas emissions as required under legislation. Local Governments across B.C. began to declare carbon neutrality, including the Regional District of Mount Waddington on Vancouver Island, whose indoor ice arena, the Chilton Regional Arena, is now carbon neutral and relies on solely on electricity from flooding their ice to mowing the grass. The province intended to accelerate the deployment of natural gas vehicles. Under the LiveSmart BC initiative, natural gas furnaces and water heaters receive cash back thereby promoting the burning of fossil fuel in the province. The province stated that an important part of new natural gas production will come from the Horn River basin where about 500 million tonnes of CO₂ will be released into the atmosphere.

On 24 September 2019, Prime Minister Justin Trudeau pledged to make Canada carbon neutral by 2050 if re-elected.^[140] On 21 October 2019, Trudeau was re-elected, and in December 2019, the Canadian government formally announced its goal for Canada to be carbon neutral by 2050. In its speech from the throne, which was delivered on 23 September 2020, the federal government pledged to legislate its goal of making Canada carbon neutral by 2050.

The city of Edmonton, Alberta, is currently developing a carbon neutral community called Blatchford, on the grounds of its former City Centre Airport.

China

By 2020, China has announced its goal of achieving carbon neutrality and has decided to complete this strategic plan by 2060.

Costa Rica

Costa Rica aims to be fully carbon neutral by at least 2050. In 2004, 46.7% of Costa Rica's primary energy came from renewable sources, while 94% of its electricity was generated from hydroelectric power, wind farms and geothermal energy in 2006. A 3.5% tax on gasoline in the country is used for payments to compensate landowners for growing trees and protecting forests and its government is making further plans for reducing emissions from transport, farming and industry. In 2019, Costa Rica was one of the first countries that crafted a national decarbonization plan.

European Union

Further information: European Green Deal

The EU has intermediate targets and in 2019 the bloc, with the exception of Poland, agreed to set a 2050 target for carbon neutrality.

The European Union has become the first area to embrace climate neutrality by 2050 through the European Green Deal, being committed to forming Green Alliances with partner nations and regions across the world.

On 29 September 2021, the EU Commission launched 100 Climate-Neutral and Smart Cities by 2030, one of the five EU missions. This EU mission aims to have 100+ carbon-neutral and smart cities by 2030 and also, inspire other cities towards the EU target of carbon neutrality by 2050.

On 28 April 2022, the EU Commission announced a list of 112 cities, which were selected from more than 370 cities, who have pledged to be part of the EU mission's goal of 100 Climate-Neutral and Smart Cities by 2030.

Denmark

Samsø island in Denmark, with a population of 4200, based on wind-generated electricity and biomass-based district heating currently generate extra wind power and export the electricity to compensate for petro-fueled vehicles. There are future hopes of using electric or biofuel vehicles.

France

On 27 June 2019, the French National Assembly voted into law the first article in a climate and energy package that sets goals for France to cut its greenhouse gas emissions and go carbon-neutral by 2050 in line with the 2015 Paris climate agreement. This was approved by the French Senate on 18 July 2019.

Iceland

Iceland is also moving towards climate neutrality. Iceland generates over 99% of its electricity from renewable sources, namely hydroelectricity (approximately 80%) and geothermal (approximately 20%). No other nation uses such a high proportion of renewable energy resources. Over 99% of electricity production and almost 80% of total energy production comes from hydropower and geothermal. In February 2008, Costa Rica, Iceland, New Zealand and Norway were the first four countries to join the Climate Neutral Network, an initiative led by the United Nations Environment Programme (UNEP) to catalyze global action towards low carbon economies and societies.

According to a 2019 study in the northern Icelandic municipality of Akureyri, low carbon transition will be effective by integrating disconnected carbon flows and establishing intermediary organisations. Reykjavík aims to be carbon neutral by 2040.

Japan

In October 2020, Japan announced its plans to reach carbon neutrality in real terms by 2050, this passed the National Diet and was codified in law on 26 May 2021.

Maldives

In March 2009, Mohamed Nasheed, then president of the Maldives, pledged to make his country carbon-neutral within a decade by moving to wind and solar power. After he left the office, successive administrations abandoned the plan.

New Zealand

On 7 November 2019, New Zealand passed a bill requiring the country to be net zero for all greenhouse gases by 2050 (with the exception of biogenic methane, with plans to reduce that by 24–47% below 2017 levels by 2050).

Norway

On 19 April 2007, Prime Minister Jens Stoltenberg announced to the Labour Party annual congress that Norway's greenhouse gas emissions would be cut by 10 percent more than its Kyoto commitment by 2012, and that the government had agreed to achieve emission cuts of 30% by 2020. He also proposed that Norway should become carbon neutral by 2050, and called upon other rich countries to do likewise. This carbon neutrality would be achieved partly by carbon offsetting, a proposal criticized by Greenpeace, who also called on Norway to take responsibility for the 500m tonnes of emissions caused by its exports of oil and gas. World Wildlife Fund Norway also believes that the purchase of carbon offsets is unacceptable, saying "it is a political stillbirth to believe that China will quietly accept that Norway will buy climate quotas abroad". The Norwegian environmental activist Bellona Foundation believes that Stoltenberg was forced to act due to pressure from anti-European Union members of the coalition government, and called the announcement "visions without content".

In January 2008, the Norwegian government went a step further and declared a goal of being carbon neutral by 2030. But the government has not been specific about any plans to reduce emissions at home; the plan is based on buying carbon offsets from other countries, and little has actually been done to reduce Norway's emissions, apart from a very successful policy for electric vehicles

Spain

In Spain, in 2014, the island of El Hierro became carbon neutral (for its power production). Also, the city of Logroño Montecorvo in La Rioja will be carbon neutral once completed.

In May 2021, Spain adopted the Climate Change and Energy Transition Law to achieve carbon neutrality by 2050. In October 2021, Prime Minister Pedro Sánchez released Spain 2050 report which sets 50 milestones towards Spain's goal to achieve carbon neutrality.

Sweden

Sweden aims to become carbon neutral by 2045. The Climate Act which enforces actions towards that goal was established in June 2017 and implemented in the beginning of 2018, making Sweden the first country with a legally-binding carbon neutrality target. The vision is that net greenhouse gas emissions should be zero. The overall objective is that the increase in global temperature should be limited to two degrees, and that the concentration of greenhouse gases in the atmosphere stabilizes at a maximum of 400 ppm.

In April 2022 an agreement between major parties in the Swedish Parliament was reached to include consumption and exports in its carbon neutrality target, which would make Sweden the first country in the world to include emissions from international trade in the pledges to mitigate climate change.

South Korea

South Korea aims to be carbon neutral by 2050, and enacted, on 31 August 2021, the enactment of the Carbon Neutral and Green Growth Basic Act, which stipulates the achievement of greenhouse gas reduction. This bill, also called the 'Climate Crisis Response Act', mandates, by 2030, a 35% greenhouse gas reduction in the country compared to 2018.

Vatican City

In July 2007, Vatican City announced a plan to become the first carbon-neutral state in the world, following the politics of the Pope to eliminate global warming. The goal would have been reached through a forest donated by a carbon offsetting company, which would have been located in the Bükk National Park, Hungary. Eventually no trees were planted under the project and the carbon offsets did not materialise.

In November 2008, the city state also installed and put into operation 2,400 solar panels on the roof of the Paul VI Centre audience hall.

United Kingdom

As recommended by the Committee on Climate Change (CCC) the government has legally committed to net zero greenhouse gas emissions by the United Kingdom by 2050 and the Energy and Climate Intelligence Unit (ECIU) has said it would be affordable. A range of techniques will be required including carbon sinks (greenhouse gas removal) in order to counterbalance emissions from agriculture and aviation. These carbon sinks might include reforestation, habitat restoration, soil carbon sequestration, bioenergy with carbon capture and storage and even direct air capture.

In 2020, the UK government has linked attainment of net zero targets as a potential mechanism for improved air quality as a co-benefit. The UK government estimated that eliminating fossil fuels for home heating and transportation could lead to a tripling of demand for electricity.

Scotland

Scotland has set a 2045 target. The islands of Orkney have significant wind and marine energy resources, and renewable energy has recently come into prominence. Although Orkney is connected to the mainland, it generates over 100% of its net power from renewables. This comes mainly from wind turbines situated right across Orkney

Thailand

Thailand aims to achieve carbon neutrality by 2050. As an initiative towards the carbon neutrality goal, Thailand's Ministry of Natural Resources and Environment launched its first Carbon Credit Exchange in 2022.

Taiwan

Taiwan has a 2050 target to achieve carbon neutrality. The Department of Forestry and Nature Conservation, Chinese Culture University and Forestry Economics Division, Taiwan Forestry Research Institute presented a study in August 2012 indicating that afforestation can offset the carbon footprint to implementing carbon neutrality. They analyzed the carbon reduction benefits of afforested air quality enhancement zones (AQEZs) established by the government in 1995.

Certification

Although there is currently no international certification scheme for carbon or climate neutrality, some countries have established national certification schemes. Examples include Norwegian Eco-Lighthouse Program and the Australian government's Climate Active certification. In the private sector, organizations such as ClimatePartner can, for a fee, allow companies from many sectors to offset their carbon emissions using techniques like reforestation. These companies can then claim climate neutral status and even use the title online. However, there is no international clarity around these certifications and their validity.

Certifications are also available from the CEB, BSI (PAS 2060) and The CarbonNeutral Company (CarbonNeutral).

Criticism

Tracing the history of certain illusions in climate policy from 1988 to 2021, climate scientists James Dyke, Robert Watson, and Wolfgang Knorr "[arrive] at the painful realisation that the idea of net zero has licensed a recklessly cavalier 'burn now, pay later' approach which has seen carbon emissions continue to soar... Current net zero policies will not keep warming to within 1.5 °C because they were never intended to. They were and still are driven by a need to protect business as usual, not the climate. If we want to keep people safe then large and sustained cuts to carbon emissions need to happen now. ...The time for wishful thinking is over."

In March 2021, Tzeporah Berman, chair of the Fossil Fuel Non-Proliferation Treaty Initiative, argued that the Treaty would be a more genuine and realistic way to achieve the goals of the Paris Agreement than the "Net zero" approach which, she claimed, is "delusional and based on bad science."

Eric Reguly, of the Globe and Mail states that, "The net-zero pledges are both welcome and dubious. Most are back-end loaded, meaning the majority of the cuts are to come well after 2030... Most of these targets also assume...steady technological advances and outright breakthroughs...Fossil fuel exports will not figure into the national accounting for the net-zero goal."

In his 16-page report, Dangerous Distractions, economist Marc Lee states that, "'Net zero' has the potential to be a dangerous distraction that reduces the political pressure to achieve actual emission reductions..." "A net zero target means less incentive to get to 'real zero' emissions from fossil fuels, an escape hatch that perpetuates business as usual and delays more meaningful climate action...Rather than gambling on carbon removal technologies of the future, Canada should plan for a managed wind down of fossil fuel production and invest public resources in bona fide solutions like renewables and a just transition from fossil fuels."

Permafrost carbon cycle

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/Permafrost_carbon_cycle

The permafrost carbon cycle or Arctic carbon cycle is a sub-cycle of the larger global carbon cycle. Permafrost is defined as subsurface material that remains below 0^o C (32^o F) for at least two consecutive years. Because permafrost soils remain frozen for long periods of time, they store large amounts of carbon and other nutrients within their frozen framework during that time. Permafrost represents a large carbon reservoir that is seldom considered when determining global terrestrial carbon reservoirs. Recent and ongoing scientific research however, is changing this view.

The permafrost carbon cycle deals with the transfer of carbon from permafrost soils to terrestrial vegetation and microbes, to the atmosphere, back to vegetation, and finally back to permafrost soils through burial and sedimentation due to cryogenic processes. Some of this carbon is transferred to the ocean and other portions of the globe through the global carbon cycle. The cycle includes the exchange of carbon dioxide and methane between terrestrial components and the atmosphere, as well as the transfer of carbon between land and water as methane, dissolved organic carbon, dissolved inorganic carbon, particulate inorganic carbon and particulate organic carbon.

Storage

Soils, in general, are the largest reservoirs of carbon in terrestrial ecosystems. This is also true for soils in the Arctic that are underlain by permafrost. In 2003, Tarnocai, et al. used the Northern and Mid Latitudes Soil Database to make a determination of carbon stocks in cryosols—soils containing permafrost within two meters of the soil surface. Permafrost affected soils cover nearly 9% of the earth's land area, yet store between 25 and 50% of the soil organic carbon. These estimates show that permafrost soils are an important carbon pool. These soils not only contain large amounts of carbon, but also sequester carbon through cryoturbation and cryogenic processes.

Processes

Carbon is not produced by permafrost. Organic carbon derived from terrestrial vegetation must be incorporated into the soil column and subsequently be incorporated into permafrost to be effectively stored. Because permafrost responds to climate changes slowly, carbon storage removes carbon from the atmosphere for long periods of time. Radiocarbon dating techniques reveal that carbon within permafrost is often thousands of years old. Carbon storage in permafrost is the result of two primary processes.

• The first process that captures carbon and stores it is syngenetic permafrost growth. This process is the result of a constant active layer where thickness and energy exchange between permafrost, active layer, biosphere, and atmosphere, resulting in the vertical increase of the soil surface elevation. This aggradation of soil is the result of aeolian or fluvial sedimentation and/or peat formation. Peat accumulation rates are as high as 0.5mm/yr while sedimentation may cause a rise of 0.7mm/yr. Thick silt deposits resulting from abundant loess deposition during the last glacial maximum form thick carbon-rich soils known as yedoma. As this process occurs, the organic and mineral soil that is deposited is incorporated into the permafrost as the permafrost surface rises.
• The second process responsible for storing carbon is cryoturbation, the mixing of soil due to freeze-thaw cycles. Cryoturbation moves carbon from the surface to depths within the soil profile. Frost heaving is the most common form of cryoturbation. Eventually, carbon that originates at the surface moves deep enough into the active layer to be incorporated into permafrost. When cryoturbation and the deposition of sediments act together carbon storage rates increase.

Current estimates

It is estimated that the total soil organic carbon (SOC) stock in northern circumpolar permafrost region equals around 1,460-1,600 Pg. (1 Pg = 1 Gt = 10¹⁵g) With the Tibetan Plateau carbon content included, the total carbon pools in the permafrost of the Northern Hemisphere is likely to be around 1832 Gt. This estimation of the amount of carbon stored in permafrost soils is more than double the amount currently in the atmosphere.

Soil column in the permafrost soils is generally broken into three horizons, 0–30 cm, 0–100 cm, and 1–300 cm. The uppermost horizon (0–30 cm) contains approximately 200 Pg of organic carbon. The 0–100 cm horizon contains an estimated 500 Pg of organic carbon, and the 0–300 cm horizon contains an estimated 1024 Pg of organic carbon. These estimates more than doubled the previously known carbon pools in permafrost soils. Additional carbon stocks exist in yedoma (400 Pg), carbon rich loess deposits found throughout Siberia and isolated regions of North America, and deltaic deposits (240 Pg) throughout the Arctic. These deposits are generally deeper than the 3 m investigated in traditional studies. Many concerns arise because of the large amount of carbon stored in permafrost soils. Until recently, the amount of carbon present in permafrost was not taken into account in climate models and global carbon budgets.

Carbon release from the permafrost

Carbon is continually cycling between soils, vegetation, and the atmosphere. As climate change increases mean annual air temperatures throughout the Arctic, it extends permafrost thaw and deepens the active layer, exposing old carbon that has been in storage for decades to millennia to biogenic processes which facilitate its entrance into the atmosphere. In general, the volume of permafrost in the upper 3 m of ground is expected to decrease by about 25% per 1 °C of global warming. According to the IPCC Sixth Assessment Report, there is high confidence that global warming over the last few decades has led to widespread increases in permafrost temperature. Observed warming was up to 3 °C in parts of Northern Alaska (early 1980s to mid-2000s) and up to 2 °C in parts of the Russian European North (1970-2020), and active layer thickness has increased in the European and Russian Arctic across the 21st century and at high elevation areas in Europe and Asia since the 1990s. In Yukon, the zone of continuous permafrost might have moved 100 kilometres (62 mi) poleward since 1899, but accurate records only go back 30 years. Based on high agreement across model projections, fundamental process understanding, and paleoclimate evidence, it is virtually certain that permafrost extent and volume will continue to shrink as global climate warms.

Carbon emissions from permafrost thaw contribute to the same warming which facilitates the thaw, making it a positive climate change feedback. The warming also intensifies Arctic water cycle, and the increased amounts of warmer rain are another factor which increases permafrost thaw depths. The amount of carbon that will be released from warming conditions depends on depth of thaw, carbon content within the thawed soil, physical changes to the environment and microbial and vegetation activity in the soil. Microbial respiration is the primary process through which old permafrost carbon is re-activated and enters the atmosphere. The rate of microbial decomposition within organic soils, including thawed permafrost, depends on environmental controls, such as soil temperature, moisture availability, nutrient availability, and oxygen availability. In particular, sufficient concentrations of iron oxides in some permafrost soils can inhibit microbial respiration and prevent carbon mobilization: however, this protection only lasts until carbon is separated from the iron oxides by Fe-reducing bacteria, which is only a matter of time under the typical conditions. Depending on the soil type, Iron(III) oxide can boost oxidation of methane to carbon dioxide in the soil, but it can also amplify methane production by acetotrophs: these soil processes are not yet fully understood.

Altogether, the likelihood of the entire carbon pool mobilizing and entering the atmosphere is low despite the large volumes stored in the soil. Although temperatures will increase, this does not imply complete loss of permafrost and mobilization of the entire carbon pool. Much of the ground underlain by permafrost will remain frozen even if warming temperatures increase the thaw depth or increase thermokarsting and permafrost degradation. Moreover, other elements such as iron and aluminum can adsorb some of the mobilized soil carbon before it reaches the atmosphere, and they are particularly prominent in the mineral sand layers which often overlay permafrost. On the other hand, once the permafrost area thaws, it will not go back to being permafrost for centuries even if the temperature increase reversed, making it one of the best-known examples of tipping points in the climate system.

A 1993 study suggested that while the tundra was a carbon sink until the end of 1970s, it had already transitioned to a net carbon source by the time the study concluded. The 2019 Arctic Report Card estimated that Arctic permafrost releases between 0.3 and 0.6 Pg C per year. That same year, a study settled on the 0.6 Pg C figure, as the net difference between the annual emissions of 1,66 Pg C during the winter season (October–April), and the model-estimated vegetation carbon uptake of 1 Pg C during the growing season. It estimated that under RCP 8.5, a scenario of continually accelerating greenhouse gas emissions, winter CO₂ emissions from the norther permafrost domain would increase 41% by 2100. Under the "intermediate" scenario RCP 4.5, where greenhouse gas emissions peak and plateau within the next two decades, before gradually declining for the rest of the century (a rate of mitigation deeply insufficient to meet the Paris Agreement goals) permafrost carbon emissions would increase by 17%. In 2022, this was challenged by a study which used a record of atmospheric observations between 1980 to 2017, and found that permafrost regions have been gaining carbon on net, as process-based models underestimated net CO₂ uptake in the permafrost regions and overestimated it in the forested regions, where increased respiration in response to warming offsets more of the gains than was previously understood.

Notably, estimates of carbon release alone do not fully represent the impact of permafrost thaw on climate change. This is because carbon can either be released as carbon dioxide (CO₂) or methane (CH₄). Aerobic respiration releases carbon dioxide, while anaerobic respiration releases methane. This is a substantial difference, as while biogenic methane lasts less than 12 years in the atmosphere, its global warming potential is around 80 times larger than that of CO₂ over a 20-year period and between 28 and 40 times larger over a 100-year period.

Carbon dioxide emissions

Most of the permafrost soil are oxic and provide a suitable environment for aerobic microbial respiration. As such, carbon dioxide emissions account for the overwhelming majority of permafrost emissions and of the Arctic emissions in general. There's some debate over whether the observed emissions from permafrost soils primarily constitute microbial respiration of ancient carbon, or simply greater respiration of modern-day carbon (i.e. leaf litter), due to warmer soils intensifying microbial metabolism. Studies published in the early 2020s indicate that while soil microbiota still primarily consumes and respires modern carbon when plants grow during the spring and summer, these microorganisms then sustain themselves on ancient carbon during the winter, releasing it into the atmosphere.

On the other hand, former permafrost areas consistently see increased vegetation growth, or primary production, as plants can set down deeper roots in the thawed soil and grow larger and uptake more carbon. This is generally the main counteracting feedback on permafrost carbon emissions. However, in areas with streams and other waterways, more of their leaf litter enters those waterways, increasing their dissolved organic carbon content. Leaching of soil organic carbon from permafrost soils is also accelerated by warming climate and by erosion along river and stream banks freeing the carbon from the previously frozen soil. Moreover, thawed areas become more vulnerable to wildfires, which alter landscape and release large quantities of stored organic carbon through combustion. As these fires burn, they remove organic matter from the surface. Removal of the protective organic mat that insulates the soil exposes the underlying soil and permafrost to increased solar radiation, which in turn increases the soil temperature, active layer thickness, and changes soil moisture. Changes in the soil moisture and saturation alter the ratio of oxic to anoxic decomposition within the soil.

A hypothesis promoted by Sergey Zimov is that the reduction of herds of large herbivores has increased the ratio of energy emission and energy absorption tundra (energy balance) in a manner that increases the tendency for net thawing of permafrost. He is testing this hypothesis in an experiment at Pleistocene Park, a nature reserve in northeastern Siberia. On the other hand, warming allows the beavers to extend their habitat further north, where their dams impair boat travel, impact access to food, affect water quality, and endanger downstream fish populations. Pools formed by the dams store heat, thus changing local hydrology and causing localized permafrost thaw.

Methane emissions

See also: Arctic methane emissions

Global warming in the Arctic accelerates methane release from both existing stores and methanogenesis in rotting biomass. Methanogenesis requires thoroughly anaerobic environments, which slows down the mobilization of old carbon. A 2015 Nature review estimated that the cumulative emissions from thawed anaerobic permafrost sites were 75-85% lower than the cumulative emissions from aerobic sites, and that even there, methane emissions amounted to only 3% to 7% of CO₂ emitted in situ. While they represented between 25% to 45% of the CO₂'s potential impact on climate over a 100-year timescale, the review concluded that aerobic permafrost thaw still had a greater warming impact overall. In 2018, however, another study in Nature Climate Change performed seven-year incubation experiments and found that methane production became equivalent to CO₂ production once a methanogenic microbial community became established at the anaerobic site. This finding had substantially raised the overall warming impact represented by anaerobic thaw sites.

Since methanogenesis requires anaerobic environments, it is frequently associated with Arctic lakes, where the emergence of bubbles of methane can be observed. Lakes produced by the thaw of particularly ice-rich permafrost are known as thermokarst lakes. Not all of the methane produced in the sediment of a lake reaches the atmosphere, as it can get oxidized in the water column or even within the sediment itself: However, 2022 observations indicate that at least half of the methane produced within thermokarst lakes reaches the atmosphere. Another process which frequently results in substantial methane emissions is the erosion of permafrost-stabilized hillsides and their ultimate collapse. Altogether, these two processes - hillside collapse (also known as retrogressive thaw slump, or RTS) and thermokarst lake formation - are collectively described as abrupt thaw, as they can rapidly expose substantial volumes of soil to microbial respiration in a matter of days, as opposed to the gradual, cm by cm, thaw of formerly frozen soil which dominates across most permafrost environments. This rapidity was illustrated in 2019, when three permafrost sites which would have been safe from thawing under the "intermediate" Representative Concentration Pathway 4.5 for 70 more years had undergone abrupt thaw. Another example occurred in the wake of a 2020 Siberian heatwave, which was found to have increased RTS numbers 17-fold across the northern Taymyr Peninsula - from 82 to 1404, while the resultant soil carbon mobilization increased 28-fold, to an average of 11 grams of carbon per square meter per year across the peninsula (with a range between 5 and 38 grams).

Until recently, Permafrost carbon feedback (PCF) modeling had mainly focused on gradual permafrost thaw, due to the difficulty of modelling abrupt thaw, and because of the flawed assumptions about the rates of methane production. Nevertheless, a study from 2018, by using field observations, radiocarbon dating, and remote sensing to account for thermokarst lakes, determined that abrupt thaw will more than double permafrost carbon emissions by 2100. And a second study from 2020, showed that under the scenario of continually accelerating emissions (RCP 8.5), abrupt thaw carbon emissions across 2.5 million km² are projected to provide the same feedback as gradual thaw of near-surface permafrost across the whole 18 million km² it occupies. Thus, abrupt thaw adds between 60 and 100 gigatonnes of carbon by 2300, increasing carbon emissions by ~125–190% when compared to gradual thaw alone.

However, there is still scientific debate about the rate and the trajectory of methane production in the thawed permafrost environments. For instance, a 2017 paper suggested that even in the thawing peatlands with frequent thermokarst lakes, less than 10% of methane emissions can be attributed to the old, thawed carbon, and the rest is anaerobic decomposition of modern carbon. A follow-up study in 2018 had even suggested that increased uptake of carbon due to rapid peat formation in the thermokarst wetlands would compensate for the increased methane release. Another 2018 paper suggested that permafrost emissions are limited following thermokarst thaw, but are substantially greater in the aftermath of wildfires. In 2022, a paper demonstrated that peatland methane emissions from permafrost thaw are initially quite high (82 milligrams of methane per square meter per day), but decline by nearly three times as the permafrost bog matures, suggesting a reduction in methane emissions in several decades to a century following abrupt thaw.

Subsea permafrost

Subsea permafrost occurs beneath the seabed and exists in the continental shelves of the polar regions. Thus, it can be defined as "the unglaciated continental shelf areas exposed during the Last Glacial Maximum (LGM, ~26 500 BP) that are currently inundated". Large stocks of organic matter (OM) and methane (CH₄) are accumulated below and within the subsea permafrost deposits.This source of methane is different from methane clathrates, but contributes to the overall outcome and feedbacks in the Earth's climate system.

The size of today's subsea permafrost has been estimated at around 2 million km² (~1/5 of the terrestrial permafrost domain size), which constitutes a 30-50% reduction since the LGM. Containing around 560 GtC in OM and 45 GtC in CH₄, with a current release of 18 and 38 MtC per year respectively, which is due to the warming and thawing that the subsea permafrost domain has been experiencing since after the LGM (~14000 years ago). In fact, because the subsea permafrost systems responds at millennial timescales to climate warming, the current carbon fluxes it is emitting to the water are in response to climatic changes occurring after the LGM. Therefore, human-driven climate change effects on subsea permafrost will only be seen hundreds or thousands of years from today. According to predictions under a business-as-usual emissions scenario RCP 8.5, by 2100, 43 GtC could be released from the subsea permafrost domain, and 190 GtC by the year 2300. Whereas for the low emissions scenario RCP 2.6, 30% less emissions are estimated. This constitutes a significant anthropogenic-driven acceleration of carbon release in the upcoming centuries.

Cumulative

In 2011, preliminary computer analyses suggested that permafrost emissions could be equivalent to around 15% of anthropogenic emissions.

A 2018 perspectives article discussing tipping points in the climate system activated around 2 degrees Celsius of global warming suggested that at this threshold, permafrost thaw would add a further 0.09 °C to global temperatures by 2100, with a range between 0.04 °C and 0.16 °C In 2021, another study estimated that in a future where zero emissions were reached following a emission of a further 1000 Pg C into the atmosphere (a scenario where temperatures ordinarily stay stable after the last emission, or start to decline slowly) permafrost carbon would add 0.06 °C (with a range between 0.02 °C and 0.14 °C) 50 years after the last anthropogenic emission, 0.09 °C (with a range between 0.04 °C to 0.21 °C) 100 years later and 0.27 °C (ranging between 0.12 to 0.49 °C) 500 years later. However, neither study was able to take abrupt thaw into account.

In 2020, a study of the northern permafrost peatlands (a smaller subset of the entire permafrost area, covering 3.7 million km² out of the estimated 18 million km²) would amount to ∼1% of anthropogenic radiative forcing by 2100, and that this proportion remains the same in all warming scenarios considered, from 1.5 °C to 6 °C. It had further suggested that after 200 more years, those peatlands would have absorbed more carbon than what they had emitted into the atmosphere.

The IPCC Sixth Assessment Report estimates that carbon dioxide and methane released from permafrost could amount to the equivalent of 14–175 billion tonnes of carbon dioxide per 1 ºC of warming. For comparison, by 2019 the anthropogenic emission of all carbon dioxide into the atmosphere stood around 40 billion tonnes.

A 2021 assessment of the economic impact of climate tipping points estimated that permafrost carbon emissions would increase the social cost of carbon by about 8.4%  However, the methods of that assessment have attracted controversy: when researchers like Steve Keen and Timothy Lenton had accused it of underestimating the overall impact of tipping points and of higher levels of warming in general, the authors have conceded some of their points.

In 2021, a group of prominent permafrost researchers like Merritt Turetsky had presented their collective estimate of permafrost emissions, including the abrupt thaw processes, as part of an effort to advocate for a 50% reduction in anthropogenic emissions by 2030 as a necessary milestone to help reach net zero by 2050. Their figures for combined permafrost emissions by 2100 amounted to 150–200 billion tonnes of carbon dioxide equivalent under 1.5 degrees of warming, 220–300 billion tonnes under 2 degrees and 400–500 billion tonnes if the warming was allowed to exceed 4 degrees. They compared those figures to the extrapolated present-day emissions of Canada, the European Union and the United States or China, respectively. The 400–500 billion tonnes figure would also be equivalent to the today's remaining budget for staying within a 1.5 degrees target. One of the scientists involved in that effort, Susan M. Natali of Woods Hole Research Centre, had also led the publication of a complementary estimate in a PNAS paper that year, which suggested that when the amplification of permafrost emissions by abrupt thaw and wildfires is combined with the foreseeable range of near-future anthropogenic emissions, avoiding the exceedance (or "overshoot") of 1.5 degrees warming is already implausible, and the efforts to attain it may have to rely on negative emissions to force the temperature back down.

An updated 2022 assessment of climate tipping points concluded that abrupt permafrost thaw would add 50% to gradual thaw rates, and would add 14 billion tons of carbon dioxide equivalent emissions by 2100 and 35 by 2300 per every degree of warming. This would have a warming impact of 0.04 °C per every full degree of warming by 2100, and 0.11 °C per every full degree of warming by 2300. It also suggested that at between 3 and 6 degrees of warming (with the most likely figure around 4 degrees) a large-scale collapse of permafrost areas could become irreversible, adding between 175 and 350 billion tons of CO₂ equivalent emissions, or 0.2–0.4 degrees, over about 50 years (with a range between 10 and 300 years).