Climate change feedbacks

"Climate feedback" redirects here. For the fact-checking website, see Climate Feedback.

Climate change feedbacks are effects of global warming that amplify or diminish the effect of forces that initially cause the warming. Positive feedbacks enhance global warming while negative feedbacks weaken it.^[3]: 2233 Feedbacks are important in the understanding of climate change because they play an important part in determining the sensitivity of the climate to warming forces. Climate forcings and feedbacks together determine how much and how fast the climate changes. Large positive feedbacks can lead to tipping points—abrupt or irreversible changes in the climate system—depending upon the rate and magnitude of the climate change.^{[4][5][6][7][8]}

Examples of some effects of global warming that can amplify (positive feedbacks) or reduce (negative feedbacks) global warming^[1][2]

The main positive feedback is that warming increases the amount of atmospheric water vapor, which is a powerful greenhouse gas.^[9] Another positive feedback is the loss of reflective snow and ice cover. Positive carbon cycle feedbacks occur when organic matter burns or decays, releasing CO₂ back into the atmosphere. Loss of organic matter can happen through rainforest drying, forest fires, and desertification. Methane can also be released into the atmosphere by thawing permafrost.

The main cooling effect is called the Planck response, which comes from the Stefan–Boltzmann law. It states that the total energy radiated per unit surface area per unit time is directly proportional to the fourth power of the black body's temperature. The carbon cycle acts a negative feedback as it absorbs more than half of CO₂ emissions every year. Atmospheric CO₂ gets absorbed into rocks, absorbed into plants, and dissolved in the ocean (leading to ocean acidification).

Accounting for all feedbacks requires considering physical feedbacks, biological feedbacks and carbon cycle feedbacks. Different results can be produced depending on time frame and location. Carbon cycle feedbacks are negative as carbon uptake increases when atmospheric concentrations increase, but warming temperatures and saturation of carbon sinks will decrease that effect. Overall feedbacks are expected to trend in a positive direction over the near future, but the Planck response will become increasingly negative as the planet warms.^{[10]: 94–95} There is no threat of a runaway greenhouse effect from current climate change.

Definition and terminology

See also: Climate system, positive feedback, and negative feedback

In climate science, a feedback that amplifies an initial warming is called a positive feedback.^[1] On the other hand, a feedback that reduces an initial warming is called a negative feedback.^[1] Naming a feedback positive or negative does not imply that the feedback is good or bad.^[11]

A 2021 IPCC glossary defines a positive feedback as one in which an initial perturbation is enhanced, and a negative feedback as one in which the initial perturbation is weakened by the changes it causes.^[3]: 2222 The glossary explains that the initial perturbation may be externally forced, or may arise through the climate system's internal variability.^[3]: 2222

Here, external forcing refers to "a forcing agent outside the climate system causing a change in the climate system"^[3]: 2229 that may push the climate system in the direction of warming or cooling.^[12] External forcings may be human-caused (for example, greenhouse gas emissions or land use change) or natural (for example, volcanic eruptions).^[3]: 2229

Positive feedbacks through the carbon cycle

See also: Carbon cycle

The global warming projections contained in the IPCC's Fourth Assessment Report (AR4) include carbon cycle feedbacks.^[13] Authors of AR4, however, noted that scientific understanding of carbon cycle feedbacks was poor.^[14] Projections in AR4 were based on a range of greenhouse gas emissions scenarios, and suggested warming between the late 20th and late 21st century of 1.1 to 6.4 °C.^[13] This is the "likely" range (greater than 66% probability), based on the expert judgement of the IPCC's authors. Authors noted that the lower end of the "likely" range appeared to be better constrained than the upper end of the "likely" range, in part due to carbon cycle feedbacks.^[13] The American Meteorological Society has commented that more research is needed to model the effects of carbon cycle feedbacks in climate change projections.^[15]

There have been predictions, and some evidence, that global warming might cause loss of carbon from terrestrial ecosystems, leading to an increase of atmospheric CO₂ levels. Several climate models indicate that global warming through the 21st century could be accelerated by the response of the terrestrial carbon cycle to such warming.^[16] All 11 models in the C4MIP study found that a larger fraction of anthropogenic CO₂ will stay airborne if climate change is accounted for. By the end of the twenty-first century, this additional CO₂ varied between 20 and 200 ppm for the two extreme models, the majority of the models lying between 50 and 100 ppm. The higher CO₂ levels led to an additional climate warming ranging between 0.1° and 1.5 °C. However, there was still a large uncertainty on the magnitude of these sensitivities. Eight models attributed most of the changes to the land, while three attributed it to the ocean.^[17] The strongest feedbacks in these cases are due to increased respiration of carbon from soils throughout the high latitude boreal forests of the Northern Hemisphere. One model in particular (HadCM3) indicates a secondary carbon cycle feedback due to the loss of much of the Amazon Rainforest in response to significantly reduced precipitation over tropical South America.^[18] While models disagree on the strength of any terrestrial carbon cycle feedback, they each suggest any such feedback would accelerate global warming.

Observations show that soils in the U.K have been losing carbon at the rate of four million tonnes a year for the past 25 years^[19] according to a paper in Nature by Bellamy et al. in September 2005, who note that these results are unlikely to be explained by land use changes. Results such as this rely on a dense sampling network and thus are not available on a global scale. Extrapolating to all of the United Kingdom, they estimate annual losses of 13 million tons per year. This is as much as the annual reductions in carbon dioxide emissions achieved by the UK under the Kyoto Treaty (12.7 million tons of carbon per year).^[20]

It has also been suggested (by Chris Freeman) that the release of dissolved organic carbon (DOC) from peat bogs into water courses (from which it would in turn enter the atmosphere) constitutes a positive feedback for global warming. The carbon currently stored in peatlands (390–455 gigatonnes, one-third of the total land-based carbon store) is over half the amount of carbon already in the atmosphere.^[21] DOC levels in water courses are observably rising; Freeman's hypothesis is that, not elevated temperatures, but elevated levels of atmospheric CO₂ are responsible, through stimulation of primary productivity.^[22][23]

Tree deaths are believed to be increasing as a result of climate change, which is a positive feedback effect.^[24]

 

Methane climate feedbacks in natural ecosystems.

Wetlands and freshwater ecosystems are predicted to be the largest potential contributor to a global methane climate feedback.^[25] Long-term warming changes the balance in the methane-related microbial community within freshwater ecosystems so they produce more methane while proportionately less is oxidised to carbon dioxide.^[26]

Arctic methane release

 

Photo shows what appears to be permafrost thaw ponds in Hudson Bay, Canada, near Greenland. (2008) Global warming will increase permafrost and peatland thaw, which can result in collapse of plateau surfaces.^[27]

Main article: Arctic methane release

Warming is also the triggering variable for the release of carbon (potentially as methane) in the arctic.^[28] Methane released from thawing permafrost such as the frozen peat bogs in Siberia, and from methane clathrate on the sea floor, creates a positive feedback.^{[29][30][31][8]} In April 2019, Turetsky et al. reported permafrost was thawing quicker than predicted.^[32][31] Recently the understanding of the climate feedback from permafrost improved, but potential emissions from the subsea permafrost remain unknown and are - like many other soil carbon feedbacks^[33] - still absent from most climate models.^[34]

Thawing permafrost

See also: Permafrost thaw, Permafrost carbon cycle, and Arctic methane release

Western Siberia is the world's largest peat bog, a one million square kilometer region of permafrost peat bog that was formed 11,000 years ago at the end of the last ice age. The thawing of its permafrost is likely to lead to the release, over decades, of large quantities of methane. As much as 70,000 million tonnes of methane, an extremely effective greenhouse gas, might be released over the next few decades, creating an additional source of greenhouse gas emissions.^[35] Similar thawing has been observed in eastern Siberia.^[36] Lawrence et al. (2008) suggest that a rapid melting of Arctic sea ice may start a feedback loop that rapidly melts Arctic permafrost, triggering further warming.^[37][38] May 31, 2010. NASA published that globally "Greenhouse gases are escaping the permafrost and entering the atmosphere at an increasing rate - up to 50 billion tons each year of methane, for example - due to a global thawing trend. This is particularly troublesome because methane heats the atmosphere with 25 times the efficiency of carbon dioxide" (the equivalent of 1250 billion tons of CO₂ per year).^[39]

Researchers have also analysed how carbon released from permafrost might contribute to global warming.^[40] A study from 2011 projected changes in permafrost based on a medium greenhouse gas emissions scenario (SRES A1B). According to the study, by 2200, the permafrost feedback might contribute 190 (+/- 64) gigatons of carbon cumulatively to the atmosphere.

In 2019, a report called " Arctic report card " estimated the current greenhouse gas emissions from Arctic permafrost as almost equal to the emissions of Russia or Japan or less than 10% of the global emissions from fossil fuels.^[41]

The Sixth IPCC Assessment Report states that "projections from models of permafrost ecosystems suggest that future permafrost thaw will lead to some additional warming – enough to be important, but not enough to lead to a 'runaway warming' situation, where permafrost thaw leads to a dramatic, self-reinforcing acceleration of global warming."^[42]

Hydrates

Main article: Clathrate gun hypothesis

Methane clathrate, also called methane hydrate, is a form of water ice that contains a large amount of methane within its crystal structure. Extremely large deposits of methane clathrate have been found under sediments on the sea and ocean floors of Earth. The sudden release of large amounts of natural gas from methane clathrate deposits, in a climate tipping event, has been hypothesized as a cause of past and possibly future climate changes. The release of this trapped methane is a potential major outcome of a rise in temperature; it is thought that this might increase the global temperature by an additional 5° in itself, as methane is much more powerful as a greenhouse gas than carbon dioxide. The theory also predicts this will greatly affect available oxygen content of the atmosphere. This theory has been proposed to explain the most severe mass extinction event on earth known as the Permian–Triassic extinction event, and also the Paleocene-Eocene Thermal Maximum climate change event. In 2008, a research expedition for the American Geophysical Union detected levels of methane up to 100 times above normal in the Siberian Arctic, likely being released by methane clathrates being released by holes in a frozen 'lid' of seabed permafrost, around the outfall of the Lena River and the area between the Laptev Sea and East Siberian Sea.^[43][44][45]

In 2020, the first leak of methane from the sea floor in Antarctica was discovered. The scientists are not sure what caused it. The area where it was found had not warmed yet significantly. It is on the side of a volcano, but it seems that it is not from there. The methane-eating microbes consume much less methane than was supposed, and the researchers think this should be included in climate models. They also claim that there is much more to discover about the issue in Antarctica.^[46] A quarter of all marine methane is found in the region of Antarctica^[47]

Abrupt increases in atmospheric methane

Literature assessments by the Intergovernmental Panel on Climate Change (IPCC) and the US Climate Change Science Program (CCSP) have considered the possibility of future projected climate change leading to a rapid increase in atmospheric methane. The IPCC Third Assessment Report, published in 2001, looked at possible rapid increases in methane due either to reductions in the atmospheric chemical sink or from the release of buried methane reservoirs. In both cases, it was judged that such a release would be "exceptionally unlikely"^[48] (less than a 1% chance, based on expert judgement).^[49] The CCSP assessment, published in 2008, concluded that an abrupt release of methane into the atmosphere appeared "very unlikely"^[50] (less than 10% probability, based on expert judgement).^[51] The CCSP assessment, however, noted that climate change would "very likely" (greater than 90% probability, based on expert judgement) accelerate the pace of persistent emissions from both hydrate sources and wetlands.^[50]

On 10 June 2019 Louise M. Farquharson and her team reported that their 12-year study into Canadian permafrost had "Observed maximum thaw depths at our sites are already exceeding those projected to occur by 2090. Between 1990 and 2016, an increase of up to 4 °C has been observed in terrestrial permafrost and this trend is expected to continue as Arctic mean annual air temperatures increase at a rate twice that of lower latitudes."^[52] Determining the extent of new thermokarst development is difficult, but there is little doubt the problem is widespread. Farquharson and her team guess that about 231,000 square miles (600,000 square kilometers) of permafrost, or about 5.5% of the zone that is permafrost year-round, is vulnerable to rapid surface thawing.^[53]

Decomposition

Main article: Decomposition

Organic matter stored in permafrost generates heat as it decomposes in response to the permafrost thawing.^[54] The amount of carbon stored in the permafrost region is estimated to be around two times the amount of carbon that is in the Earth's atmosphere.^[55] As the tropics get wetter, as many climate models predict, soils are likely to experience greater rates of respiration and decomposition, limiting the carbon storage abilities of tropical soils.^[56]

Peat decomposition

Peat, occurring naturally in peat bogs, is a store of carbon significant on a global scale.^[57] When peat dries it decomposes, and may additionally burn.^[58] Water table adjustment due to global warming may cause significant excursions of carbon from peat bogs.^[59] This may be released as methane, which can exacerbate the feedback effect, due to its high global warming potential.

Rainforest drying

Rainforests, most notably tropical rainforests, are particularly vulnerable to global warming. There are a number of effects which may occur, but two are particularly concerning. Firstly, the drier vegetation may cause total collapse of the rainforest ecosystem.^[60][61] For example, the Amazon rainforest would tend to be replaced by caatinga ecosystems. Further, even tropical rainforests ecosystems which do not collapse entirely may lose significant proportions of their stored carbon as a result of drying, due to changes in vegetation.^[62][63]

Forest fires

See also: Wildfire § Climate change effects, and Effects of climate change on biomes

The IPCC Fourth Assessment Report predicts that many mid-latitude regions, such as Mediterranean Europe, will experience decreased rainfall and an increased risk of drought, which in turn would allow forest fires to occur on larger scale, and more regularly. This releases more stored carbon into the atmosphere than the carbon cycle can naturally re-absorb, as well as reducing the overall forest area on the planet, creating a positive feedback loop. Part of that feedback loop is more rapid growth of replacement forests and a northward migration of forests as northern latitudes become more suitable climates for sustaining forests. There is a question of whether the burning of renewable fuels such as forests should be counted as contributing to global warming.^[64][65][66] Cook & Vizy also found that forest fires were likely in the Amazon Rainforest, eventually resulting in a transition to Caatinga vegetation in the Eastern Amazon region.^{[citation needed]}

Desertification

Desertification is a consequence of global warming in some environments.^[67] Desert soils contain little humus, and support little vegetation. As a result, transition to desert ecosystems is typically associated with excursions of carbon.

Positive feedbacks through other mechanisms

See also: Soil carbon feedback

Water vapor feedback

Main article: Water vapor feedback

If the atmospheres are warmed, the saturation vapor pressure increases, and the amount of water vapor in the atmosphere will tend to increase. Since water vapor is a greenhouse gas, the increase in water vapor content makes the atmosphere warm further; this warming causes the atmosphere to hold still more water vapor (a positive feedback), and so on until other processes stop the feedback loop. The result is a much larger greenhouse effect than that due to CO₂ alone. Although this feedback process causes an increase in the absolute moisture content of the air, the relative humidity stays nearly constant or even decreases slightly because the air is warmer.^[68] Climate models incorporate this feedback. Water vapor feedback is strongly positive, with most evidence supporting a magnitude of 1.5 to 2.0 W/m²/K, sufficient to roughly double the warming that would otherwise occur.^[69] Water vapor feedback is considered a faster feedback mechanism.^[70]

Cloud feedback

Main article: Cloud feedback

Global warming is expected to change the distribution and type of clouds. Seen from below, clouds emit infrared radiation back to the surface, and so exert a warming effect; seen from above, clouds reflect sunlight and emit infrared radiation to space, and so exert a cooling effect. Whether the net effect is warming or cooling depends on details such as the type and altitude of the cloud. Low clouds are brighter and optically thicker, while high clouds are optically thin (transparent) in the visible and trap IR. Reduction of low clouds tends to increase incoming solar radiation and therefore have a positive feedback, while a reduction in high clouds (since they mostly just trap IR) would result in a negative feedback. These details were poorly observed before the advent of satellite data and are difficult to represent in climate models.^[68] Global climate models were showing a near-zero to moderately strong positive net cloud feedback, but the effective climate sensitivity has increased substantially in the latest generation of global climate models. Differences in the physical representation of clouds in models drive this enhanced climate sensitivity relative to the previous generation of models.^[71][72][73]

A 2019 simulation predicts that if greenhouse gases reach three times the current level of atmospheric carbon dioxide that stratocumulus clouds could abruptly disperse, contributing to additional global warming.^[74][7]

Ice–albedo feedback

Main articles: Arctic sea ice decline and Ice–albedo feedback

 

Aerial photograph showing a section of sea ice. The lighter blue areas are melt ponds and the darkest areas are open water; both have a lower albedo than the white sea ice. The melting ice contributes to ice–albedo feedback.

When ice melts, land or open water takes its place. Both land and open water are on average less reflective than ice and thus absorb more solar radiation. This causes more warming, which in turn causes more melting, and this cycle continues.^[75] During times of global cooling, additional ice increases the reflectivity, which reduces the absorption of solar radiation, resulting in more cooling through a continuing cycle.^[76] This is considered a faster feedback mechanism.^[70]

 

1870–2009 Northern hemisphere sea ice extent in million square kilometers. Blue shading indicates the pre-satellite era; data then is less reliable. In particular, the near-constant level extent in Autumn up to 1940 reflects lack of data rather than a real lack of variation.

Albedo change is also the main reason why IPCC predict polar temperatures in the northern hemisphere to rise up to twice as much as those of the rest of the world, in a process known as polar amplification. In September 2007, the Arctic sea ice area reached about half the size of the average summer minimum area between 1979 and 2000.^[77][78] Also in September 2007, Arctic sea ice retreated far enough for the Northwest Passage to become navigable to shipping for the first time in recorded history.^[79] The record losses of 2007 and 2008 may, however, be temporary.^[80] Mark Serreze of the US National Snow and Ice Data Center views 2030 as a "reasonable estimate" for when the summertime Arctic ice cap might be ice-free.^[81] The polar amplification of global warming is not predicted to occur in the southern hemisphere.^[82] The Antarctic sea ice reached its greatest extent on record since the beginning of observation in 1979,^[83] but the gain in ice in the south is exceeded by the loss in the north. The trend for global sea ice, northern hemisphere and southern hemisphere combined is clearly a decline.^[84]

Ice loss may have internal feedback processes, as melting of ice over land can cause eustatic sea level rise, potentially causing instability of ice shelves and inundating coastal ice masses, such as glacier tongues. Further, a potential feedback cycle exists due to earthquakes caused by isostatic rebound further destabilising ice shelves, glaciers and ice caps.

The ice–albedo in some sub-arctic forests is also changing, as stands of larch (which shed their needles in winter, allowing sunlight to reflect off the snow in spring and fall) are being replaced by spruce trees (which retain their dark needles all year).^[85]

Gas release by various sources

Main article: Greenhouse gas

Release of gases of biological origin may be affected by global warming, but research into such effects is at an early stage. Some of these gases, such as nitrous oxide released from peat or thawing permafrost, directly affect climate.^[86][87] Others, such as dimethyl sulfide released from oceans, have indirect effects.^[88]

A 2010 study suggested that if global methane emissions were to increase by a factor of 2.5 to 5.2 above (then) current emissions,^[89] the indirect contribution to radiative forcing would be about 250% and 400% respectively, of the forcing that can be directly attributed to methane. This amplification of methane warming is due to projected changes in atmospheric chemistry.

Negative feedbacks

Planck response

As the temperature of a black body increases, the emission of infrared radiation increases with the fourth power of its absolute temperature according to the Stefan–Boltzmann law. This increases the amount of outgoing radiation back into space as the Earth warms.^[90] It is a strong stabilizing response and has sometimes been called the "no-feedback response" because it is an intensive property of a thermodynamic system when considered to be purely a function of temperature.^[91] Although Earth has an effective emissivity less than unity, the ideal black body radiation emerges as a separable quantity when investigating perturbations to the planet's outgoing radiation.

The Planck "feedback" or Planck response is the comparable radiative response obtained from analysis of practical observations or global climate models (GCMs). Its expected strength has been most simply estimated from the derivative of the Stefan-Boltzmann equation as -4σT³ = -3.8 W/m²/K.^[90][91] Accounting from GCM applications has sometimes yielded a reduced strength, as caused by extensive properties of the stratosphere and similar residual artifacts subsequently identified as being absent from such models.^[91] Most extensive "grey body" properties of Earth that influence the outgoing radiation are usually postulated to be encompassed by the other GCM feedback components, and to be distributed in accordance with a particular forcing-feedback formulation of the climate system.^[92] Ideally the Planck response strength obtained from GCMs, indirect measurements, and black body estimates will further converge as analysis methods continue to mature.

This blackbody radiation or Planck response has been identified as "the most fundamental feedback in the climate system".^[93]: 19

Carbon cycle negative feedbacks

 

The impulse response following a 100 GtC injection of CO₂ into Earth's atmosphere.^[94] The majority of excess carbon is removed by ocean and land sinks in less than a few centuries, while a substantial portion persists.

Negative climate feedbacks from Earth's carbon cycle are thought to be relatively insensitive to temperature changes. For this reason they are sometimes considered separately or disregarded in studies which aim to quantify climate sensitivity.^[92] They are nevertheless significant feedbacks to anthropogenic CO₂ emissions over time, and have influence on climate inertia and within more general studies of dynamic (time-dependent) climate change.^[95]

Role of oceans

Following Le Chatelier's principle, the chemical equilibrium of the Earth's carbon cycle will shift in response to anthropogenic CO₂ emissions. The primary driver of this is the ocean, which absorbs anthropogenic CO₂ via the so-called solubility pump. At present this accounts for only about one third of the current emissions, but ultimately most (~75%) of the CO₂ emitted by human activities will dissolve in the ocean over a period of centuries: "A better approximation of the lifetime of fossil fuel CO₂ for public discussion might be 300 years, plus 25% that lasts forever".^[96] However, the rate at which the ocean will take it up in the future is less certain, and will be affected by stratification induced by warming and, potentially, changes in the ocean's thermohaline circulation.

Chemical weathering

Chemical weathering over the geological long term acts to remove CO₂ from the atmosphere. With current global warming, weathering is increasing, demonstrating significant feedbacks between climate and Earth surface.^[97] Biosequestration also captures and stores CO₂ by biological processes. The formation of shells by organisms in the ocean, over a very long time, removes CO₂ from the oceans.^[98] The complete conversion of CO₂ to limestone takes thousands to hundreds of thousands of years.^[99]

Primary production through photosynthesis

Net primary productivity changes in response to increased CO₂, as plants photosynthesis increased in response to increasing concentrations. However, this effect is swamped by other changes in the biosphere due to global warming.^[100]

Mechanisms with positive or negative feedback

Lapse rate

Main article: Lapse rate

The lapse rate is the rate at which an atmospheric variable, normally temperature in Earth's atmosphere, falls with altitude.^[101][102] It is therefore a quantification of temperature, related to radiation, as a function of altitude, and is not a separate phenomenon in this context. The lapse rate feedback is generally a negative feedback. However, it is in fact a positive feedback in polar regions where it strongly contributed to polar amplified warming, one of the biggest consequences of climate change.^[103] This is because in regions with strong inversions, such as the polar regions, the lapse rate feedback can be positive because the surface warms faster than higher altitudes, resulting in inefficient longwave cooling.^{[104][105][106]}

The atmosphere's temperature decreases with height in the troposphere. Since emission of infrared radiation varies with temperature, longwave radiation escaping to space from the relatively cold upper atmosphere is less than that emitted toward the ground from the lower atmosphere. Thus, the strength of the greenhouse effect depends on the atmosphere's rate of temperature decrease with height. Both theory and climate models indicate that global warming will reduce the rate of temperature decrease with height, producing a negative lapse rate feedback that weakens the greenhouse effect.^[104] Measurements of the rate of temperature change with height are very sensitive to small errors in observations, making it difficult to establish whether the models agree with observations.^{[93]: 25 [107]}

Mathematical formulation of global energy imbalance

Earth is a thermodynamic system for which long-term temperature changes follow the global energy imbalance (EEI stands for Earth's energy imbalance):

${\displaystyle EEI\equiv ASR-OLR}$ 

where ASR is the absorbed solar radiation and OLR is the outgoing longwave radiation at top of atmosphere. When EEI is positive the system is warming, when it is negative they system is cooling, and when it is approximately zero then there is neither warming or cooling. The ASR and OLR terms in this expression encompass many temperature-dependent properties and complex interactions that govern system behavior.^[108]

In order to diagnose that behavior around a relatively stable equilibrium state, one may consider a perturbation to EEI as indicated by the symbol Δ. Such a perturbation is induced by a radiative forcing (ΔF) which can be natural or man-made. Responses within the system to either return back towards the stable state, or to move further away from the stable state are called feedbacks λΔT:

${\displaystyle \Delta EEI=\Delta F+\lambda \Delta T}$ .

Collectively the feedbacks are approximated by the linearized parameter λ and the perturbed temperature ΔT because all components of λ (assumed to be first-order to act independently and additively) are also functions of temperature, albeit to varying extents, by definition for a thermodynamic system:

${\displaystyle \lambda =\sum _{i}\lambda _{i}=(\lambda _{wv}+\lambda _{c}+\lambda _{a}+\lambda _{cc}+\lambda _{p}+\lambda _{lr}+...)}$ .

Some feedback components having significant influence on EEI are: ${\displaystyle wv}$ = water vapor, ${\displaystyle c}$ = clouds, ${\displaystyle a}$ = surface albedo, ${\displaystyle cc}$ = carbon cycle, ${\displaystyle p}$ = Planck response, and ${\displaystyle lr}$ = lapse rate. All quantities are understood to be global averages, while T is usually translated to temperature at the surface because of its direct relevance to humans and much other life.^[92]

The negative Planck response, being an especially strong function of temperature, is sometimes factored out to give an expression in terms of the relative feedback gains g_i from other components:

${\displaystyle \lambda =\neg \lambda _{p}\times (1-\sum _{i}g_{i})}$ .

For example ${\displaystyle g_{wv}\approx 0.5}$  for the water vapor feedback.

Within the context of modern numerical climate modelling and analysis, the linearized formulation has limited use. One such use is to diagnose the relative strengths of different feedback mechanisms. An estimate of climate sensitivity to a forcing is then obtained for the case where the net feedback remains negative and the system reaches a new equilibrium state (ΔEEI=0) after some time has passed:^{[93]: 19–20}

${\displaystyle \Delta T={\frac {\Delta F}{\lambda _{p}\times (1-\sum _{i}g_{i})}}}$ .

Implications for climate policy

See also: Climate sensitivity

Uncertainty over climate change feedbacks has implications for climate policy. For instance, uncertainty over carbon cycle feedbacks may affect targets for reducing greenhouse gas emissions (climate change mitigation).^[109] Emissions targets are often based on a target stabilization level of atmospheric greenhouse gas concentrations, or on a target for limiting global warming to a particular magnitude. Both of these targets (concentrations or temperatures) require an understanding of future changes in the carbon cycle. If models incorrectly project future changes in the carbon cycle, then concentration or temperature targets could be missed. For example, if models underestimate the amount of carbon released into the atmosphere due to positive feedbacks (e.g., due to thawing permafrost), then they may also underestimate the extent of emissions reductions necessary to meet a concentration or temperature target.^{[citation needed]}

See also

• Climate variability and change
• Climate inertia
• Complex system
• Effects of climate change
• Parametrization (climate)
• Tipping points in the climate system

References

1. "The Study of Earth as an Integrated System". nasa.gov. NASA. 2016. from the original on November 2, 2016.
2. Fig. TS.17, Technical Summary, Sixth Assessment Report (AR6), Working Group I, IPCC, 2021, p. 96. from the original on July 21, 2022.
3. IPCC, 2021: Annex VII: Glossary [Matthews, J.B.R., V. Möller, R. van Diemen, J.S. Fuglestvedt, V. Masson-Delmotte, C.  Méndez, S. Semenov, A. Reisinger (eds.)]. In Climate Change 2021: The Physical Science Basis. Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change [Masson-Delmotte, V., P. Zhai, A. Pirani, S.L. Connors, C. Péan, S. Berger, N. Caud, Y. Chen, L. Goldfarb, M.I. Gomis, M. Huang, K. Leitzell, E. Lonnoy, J.B.R. Matthews, T.K. Maycock, T. Waterfield, O. Yelekçi, R. Yu, and B. Zhou (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, pp. 2215–2256, doi:10.1017/9781009157896.022.
4. IPCC (2021). "Summary for Policymakers" (PDF). The Physical Science Basis. Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change. p. 40. ISBN 978-92-9169-158-6.
5. IPCC. "Climate Change 2007: Synthesis Report. Contribution of Working Groups I, II and III to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. Pg 53" (PDF).
6. Lenton, Timothy M.; Rockström, Johan; Gaffney, Owen; Rahmstorf, Stefan; Richardson, Katherine; Steffen, Will; Schellnhuber, Hans Joachim (2019-11-27). "Climate tipping points — too risky to bet against". Nature. 575 (7784): 592–595. Bibcode:2019Natur.575..592L. doi:10.1038/d41586-019-03595-0. hdl:10871/40141. PMID 31776487.
7. Kemp, Luke; Xu, Chi; Depledge, Joanna; Ebi, Kristie L.; Gibbins, Goodwin; Kohler, Timothy A.; Rockström, Johan; Scheffer, Marten; Schellnhuber, Hans Joachim; Steffen, Will; Lenton, Timothy M. (2022-08-23). "Climate Endgame: Exploring catastrophic climate change scenarios". Proceedings of the National Academy of Sciences. 119 (34): e2108146119. Bibcode:2022PNAS..11908146K. doi:10.1073/pnas.2108146119. ISSN 0027-8424. PMC 9407216. PMID 35914185.
8. Armstrong McKay, David I.; Staal, Arie; Abrams, Jesse F.; Winkelmann, Ricarda; Sakschewski, Boris; Loriani, Sina; Fetzer, Ingo; Cornell, Sarah E.; Rockström, Johan; Lenton, Timothy M. (2022-09-09). "Exceeding 1.5°C global warming could trigger multiple climate tipping points". Science. 377 (6611): eabn7950. doi:10.1126/science.abn7950. hdl:10871/131584. ISSN 0036-8075. PMID 36074831. S2CID 252161375.
9. . ipcc.ch. Archived from the original on 2010-04-09. Retrieved 2010-04-23.
10. IPCC (2021). Masson-Delmotte, V.; Zhai, P.; Pirani, A.; Connors, S. L.; et al. (eds.). Climate Change 2021: The Physical Science Basis (PDF). Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge, United Kingdom and New York, NY, US: Cambridge University Press (In Press).
11. "Climate change and feedback loops" (PDF). National Oceanographic and Atmospheric Administration (NOAA). (PDF) from the original on 25 July 2023.
12. US NRC (2012), Climate Change: Evidence, Impacts, and Choices / How much are human activities heating Earth, US National Research Council (US NRC), p.9. Also available as PDF 2013-02-20 at the Wayback Machine
13. Meehl, G.A.; et al., , Sec 10.5.4.6 Synthesis of Projected Global Temperature at Year 2100, archived from the original on 2018-11-04, retrieved 2013-02-01, in: Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change [Solomon, S., D. Qin, M. Manning, Z. Chen, M. Marquis, K.B. Averyt, M. Tignor and H.L. Miller (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA.
14. Solomon; et al., , TS.6.4.3 Global Projections: Key uncertainties, archived from the original on 2018-11-03, retrieved 2013-02-01, in in: Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change [Solomon, S., D. Qin, M. Manning, Z. Chen, M. Marquis, K.B. Averyt, M. Tignor and H.L. Miller (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA.
15. AMS Council (20 August 2012), 2012 American Meteorological Society (AMS) Information Statement on Climate Change, Boston, MA, USA: AMS
16. Cox, Peter M.; Richard A. Betts; Chris D. Jones; Steven A. Spall; Ian J. Totterdell (November 9, 2000). "Acceleration of global warming due to carbon-cycle feedbacks in a coupled climate model". Nature. 408 (6809): 184–7. Bibcode:2000Natur.408..184C. doi:10.1038/35041539. PMID 11089968. S2CID 2689847.
17. Friedlingstein, P.; P. Cox; R. Betts; L. Bopp; W. von Bloh; V. Brovkin; P. Cadule; S. Doney; M. Eby; I. Fung; G. Bala; J. John; C. Jones; F. Joos; T. Kato; M. Kawamiya; W. Knorr; K. Lindsay; H.D. Matthews; T. Raddatz; P. Rayner; C. Reick; E. Roeckner; K.G. Schnitzler; R. Schnur; K. Strassmann; A.J. Weaver; C. Yoshikawa; N. Zeng (2006). "Climate–Carbon Cycle Feedback Analysis: Results from the C4MIP Model Intercomparison". Journal of Climate. 19 (14): 3337–53. Bibcode:2006JCli...19.3337F. doi:10.1175/JCLI3800.1. hdl:1912/4178. S2CID 1614769.
18. "5.5C temperature rise in next century". The Guardian. 2003-05-29. Retrieved 2008-01-02.
19. Tim Radford (2005-09-08). "Loss of soil carbon 'will speed global warming'". The Guardian. Retrieved 2008-01-02.
20. Schulze, E. Detlef; Annette Freibauer (September 8, 2005). "Environmental science: Carbon unlocked from soils". Nature. 437 (7056): 205–6. Bibcode:2005Natur.437..205S. doi:10.1038/437205a. PMID 16148922. S2CID 4345985.
21. Freeman, Chris; Ostle, Nick; Kang, Hojeong (2001). "An enzymic 'latch' on a global carbon store". Nature. 409 (6817): 149. Bibcode:2001Natur.409..149F. doi:10.1038/35051650. PMID 11196627. S2CID 3152551.
22. Freeman, Chris; et al. (2004). "Export of dissolved organic carbon from peatlands under elevated carbon dioxide levels". Nature. 430 (6996): 195–8. Bibcode:2004Natur.430..195F. doi:10.1038/nature02707. PMID 15241411. S2CID 4308328.
23. Connor, Steve (2004-07-08). "Peat bog gases 'accelerate global warming'". The Independent.
24. "Science: Global warming is killing U.S. trees, a dangerous carbon-cycle feedback". climateprogress.org.
25. Dean, Joshua F.; Middelburg, Jack J.; Röckmann, Thomas; Aerts, Rien; Blauw, Luke G.; Egger, Matthias; Jetten, Mike S. M.; de Jong, Anniek E. E.; Meisel, Ove H. (2018). "Methane Feedbacks to the Global Climate System in a Warmer World". Reviews of Geophysics. 56 (1): 207–250. Bibcode:2018RvGeo..56..207D. doi:10.1002/2017RG000559. hdl:1874/366386.
26. Zhu, Yizhu; Purdy, Kevin J.; Eyice, Özge; Shen, Lidong; Harpenslager, Sarah F.; Yvon-Durocher, Gabriel; Dumbrell, Alex J.; Trimmer, Mark (2020-06-29). "Disproportionate increase in freshwater methane emissions induced by experimental warming". Nature Climate Change. 10 (7): 685–690. Bibcode:2020NatCC..10..685Z. doi:10.1038/s41558-020-0824-y. ISSN 1758-6798. S2CID 220261158.
27. Dyke, Larry D.; Sladen, Wendy E. (2010). . Arctic. 63 (4): 1018. doi:10.14430/arctic3332. Archived from the original on 2014-08-10. Retrieved 2014-08-02.
28. Kvenvolden, K. A. (1988). "Methane Hydrates and Global Climate". Global Biogeochemical Cycles. 2 (3): 221–229. Bibcode:1988GBioC...2..221K. doi:10.1029/GB002i003p00221.
29. Zimov, A.; Schuur, A.; Chapin Fs, D. (Jun 2006). "Climate change. Permafrost and the global carbon budget". Science. 312 (5780): 1612–1613. doi:10.1126/science.1128908. ISSN 0036-8075. PMID 16778046. S2CID 129667039.
30. Archer, D (2007). "Methane hydrate stability and anthropogenic climate change". Biogeosciences Discussions. 4 (2): 993–1057. Bibcode:2007BGeo....4..521A. CiteSeerX 10.1.1.391.1275. doi:10.5194/bgd-4-993-2007.
31. "Scientists shocked by Arctic permafrost thawing 70 years sooner than predicted". The Guardian. Reuters. 2019-06-18. ISSN 0261-3077. Retrieved 2019-07-02.
32. Turetsky, Merritt R. (2019-04-30). "Permafrost collapse is accelerating carbon release". Nature. 569 (7754): 32–34. Bibcode:2019Natur.569...32T. doi:10.1038/d41586-019-01313-4. PMID 31040419.
33. Loisel, J.; Gallego-Sala, A. V.; Amesbury, M. J.; Magnan, G.; Anshari, G.; Beilman, D. W.; Benavides, J. C.; Blewett, J.; Camill, P.; Charman, D. J.; Chawchai, S. (2020-12-07). "Expert assessment of future vulnerability of the global peatland carbon sink". Nature Climate Change. 11: 70–77. doi:10.1038/s41558-020-00944-0. hdl:1826/16143. ISSN 1758-6798. S2CID 227515903.
34. Sayedi, Sayedeh Sara; Abbott, Benjamin W; Thornton, Brett F; Frederick, Jennifer M; Vonk, Jorien E; Overduin, Paul; Schädel, Christina; Schuur, Edward A G; Bourbonnais, Annie; Demidov, Nikita; Gavrilov, Anatoly (2020-12-01). "Subsea permafrost carbon stocks and climate change sensitivity estimated by expert assessment". Environmental Research Letters. 15 (12): B027-08. Bibcode:2020AGUFMB027...08S. doi:10.1088/1748-9326/abcc29. hdl:10852/83674. ISSN 1748-9326.
35. Fred Pearce (2005-08-11). "Climate warning as Siberia melts". New Scientist. Retrieved 2007-12-30.
36. Ian Sample (2005-08-11). . Guardian. Archived from the original on 2005-11-06. Retrieved 2007-12-30.
37. (Press release). UCAR. 10 June 2008. Archived from the original on 18 January 2010. Retrieved 2009-05-25.
38. Lawrence, D. M.; Slater, A. G.; Tomas, R. A.; Holland, M. M.; Deser, C. (2008). "Accelerated Arctic land warming and permafrost degradation during rapid sea ice loss". Geophysical Research Letters. 35 (11): L11506. Bibcode:2008GeoRL..3511506L. doi:10.1029/2008GL033985.
39. Cook-Anderson, Gretchen (2020-01-15). "Just 5 questions: What lies beneath". NASA Global Climate Change: Vital Signs of the Planet. Retrieved 2020-01-24.
40. KEVIN SCHAEFER; TINGJUN ZHANG; LORI BRUHWILER; ANDREW P. BARRETT (2011). "Amount and timing of permafrost carbon release in response to climate warming". Tellus Series B. 63 (2): 165–180. Bibcode:2011TellB..63..165S. doi:10.1111/j.1600-0889.2011.00527.x.
41. Freedman, Andrew (10 December 2019). "The Arctic may have crossed key threshold, emitting billions of tons of carbon into the air, in a long-dreaded climate feedback". The Washington Post. Retrieved 20 December 2019.
42. Canadell, J.G., P.M.S. Monteiro, M.H. Costa, L. Cotrim da Cunha, P.M. Cox, A.V. Eliseev, S. Henson, M. Ishii, S. Jaccard, C. Koven, A. Lohila, P.K. Patra, S. Piao, J. Rogelj, S. Syampungani, S. Zaehle, and K. Zickfeld, 2021: Chapter 5: Global Carbon and other Biogeochemical Cycles and Feedbacks. In Climate Change 2021: The Physical Science Basis. Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change [Masson-Delmotte, V., P. Zhai, A. Pirani, S.L. Connors, C. Péan, S. Berger, N. Caud, Y. Chen, L. Goldfarb, M.I. Gomis, M. Huang, K. Leitzell, E. Lonnoy, J.B.R. Matthews, T.K. Maycock, T. Waterfield, O. Yelekçi, R. Yu, and B. Zhou (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, pp. 673–816, doi:10.1017/9781009157896.007., Page: FAQ 5.2
43. Connor, Steve (September 23, 2008). "Exclusive: The methane time bomb". The Independent. Retrieved 2008-10-03.
44. Connor, Steve (September 25, 2008). "Hundreds of methane 'plumes' discovered". The Independent. Retrieved 2008-10-03.
45. N. Shakhova; I. Semiletov; A. Salyuk; D. Kosmach; N. Bel'cheva (2007). "Methane release on the Arctic East Siberian shelf" (PDF). Geophysical Research Abstracts. 9: 01071.
46. Carrington, Damian (22 July 2020). "First active leak of sea-bed methane discovered in Antarctica". The Guardian. Retrieved 24 July 2020.
47. Cockburn, Harry (23 July 2020). "Climate crisis: First active leaks of methane found on Antarctic seabed". The Independent. Retrieved 24 July 2020.
48. IPCC (2001d). "4.14". In R.T. Watson; the Core Writing Team (eds.). . Climate Change 2001: Synthesis Report. A Contribution of Working Groups I, II, and III to the Third Assessment Report of the Intergovernmental Panel on Climate Change. Print version: Cambridge University Press, Cambridge, U.K., and New York, N.Y., U.S.A.. This version: GRID-Arendal website. Archived from the original on 2011-06-04. Retrieved 2011-05-18.
49. IPCC (2001d). "Box 2-1: Confidence and likelihood statements". In R.T. Watson; the Core Writing Team (eds.). . Climate Change 2001: Synthesis Report. A Contribution of Working Groups I, II, and III to the Third Assessment Report of the Intergovernmental Panel on Climate Change. Print version: Cambridge University Press, Cambridge, U.K., and New York, N.Y., U.S.A.. This version: GRID-Arendal website. Archived from the original on 2011-06-04. Retrieved 2011-05-18.
50. Clark, P.U.; et al. (2008). . Abrupt Climate Change. A Report by the U.S. Climate Change Science Program and the Subcommittee on Global Change Research (PDF). U.S. Geological Survey, Reston, VA. p. 2. Archived from the original (PDF) on 2011-07-21. Retrieved 2011-05-18.
51. Clark, P.U.; et al. (2008). . Abrupt Climate Change. A Report by the U.S. Climate Change Science Program and the Subcommittee on Global Change Research (PDF). U.S. Geological Survey, Reston, VA. p. 12. Archived from the original (PDF) on 2011-07-21. Retrieved 2011-05-18.
52. Farquharson, Louise M.; Romanovsky, Vladimir E.; Cable, William L.; Walker, Donald A.; Kokelj, Steven V.; Nicolsky, Dmitry (2019). "Climate Change Drives Widespread and Rapid Thermokarst Development in Very Cold Permafrost in the Canadian High Arctic". Geophysical Research Letters. 46 (12): 6681–6689. Bibcode:2019GeoRL..46.6681F. doi:10.1029/2019GL082187.
53. Currin, Grant (June 14, 2019). "Arctic Permafrost Is Going Through a Rapid Meltdown — 70 Years Early". news.yahoo.com. Retrieved 2020-01-24.
54. Heimann, Martin; Markus Reichstein (2008-01-17). "Terrestrial ecosystem carbon dynamics and climate feedbacks". Nature. 451 (7176): 289–292. Bibcode:2008Natur.451..289H. doi:10.1038/nature06591. PMID 18202646.
55. Natali, Susan M.; Holdren, John P.; Rogers, Brendan M.; Treharne, Rachael; Duffy, Philip B.; Pomerance, Rafe; MacDonald, Erin (2021-05-25). "Permafrost carbon feedbacks threaten global climate goals". Proceedings of the National Academy of Sciences. 118 (21): e2100163118. Bibcode:2021PNAS..11800163N. doi:10.1073/pnas.2100163118. ISSN 0027-8424. PMC 8166174. PMID 34001617.
56. Hays, Brooks (2020-05-06). "Wetter climate to trigger global warming feedback loop in the tropics". UPI. Retrieved 2020-05-11.
57. "Peatlands and climate change". IUCN. 2017-11-06. Retrieved 2019-08-23.
58. Turetsky, Merritt R.; Benscoter, Brian; Page, Susan; Rein, Guillermo; van der Werf, Guido R.; Watts, Adam (2014-12-23). "Global vulnerability of peatlands to fire and carbon loss". Nature Geoscience. 8 (1): 11–14. doi:10.1038/ngeo2325. hdl:10044/1/21250. ISSN 1752-0894.
59. Ise, T.; Dunn, A. L.; Wofsy, S. C.; Moorcroft, P. R. (2008). "High sensitivity of peat decomposition to climate change through water-table feedback". Nature Geoscience. 1 (11): 763. Bibcode:2008NatGe...1..763I. doi:10.1038/ngeo331.
60. Cook, K. H.; Vizy, E. K. (2008). "Effects of Twenty-First-Century Climate Change on the Amazon Rain Forest". Journal of Climate. 21 (3): 542–821. Bibcode:2008JCli...21..542C. doi:10.1175/2007JCLI1838.1.
61. Nobre, Carlos; Lovejoy, Thomas E. (2018-02-01). "Amazon Tipping Point". Science Advances. 4 (2): eaat2340. Bibcode:2018SciA....4.2340L. doi:10.1126/sciadv.aat2340. ISSN 2375-2548. PMC 5821491. PMID 29492460.
62. Enquist, B. J.; Enquist, C. A. F. (2011). "Long-term change within a Neotropical forest: assessing differential functional and floristic responses to disturbance and drought". Global Change Biology. 17 (3): 1408. Bibcode:2011GCBio..17.1408E. doi:10.1111/j.1365-2486.2010.02326.x. S2CID 83489971.
63. Rammig, Anja; Wang-Erlandsson, Lan; Staal, Arie; Sampaio, Gilvan; Montade, Vincent; Hirota, Marina; Barbosa, Henrique M. J.; Schleussner, Carl-Friedrich; Zemp, Delphine Clara (2017-03-13). "Self-amplified Amazon forest loss due to vegetation-atmosphere feedbacks". Nature Communications. 8: 14681. Bibcode:2017NatCo...814681Z. doi:10.1038/ncomms14681. ISSN 2041-1723. PMC 5355804. PMID 28287104.
64. . David Suzuki Foundation. Archived from the original on 2007-12-08. Retrieved 2007-12-02.
65. . United States Environmental Protection Agency. 2000-01-07. Archived from the original on 2007-02-19. Retrieved 2007-12-02.
66. . Woods Hole Research Center. Archived from the original on 2007-10-25. Retrieved 2007-12-02.
67. Schlesinger, W. H.; Reynolds, J. F.; Cunningham, G. L.; Huenneke, L. F.; Jarrell, W. M.; Virginia, R. A.; Whitford, W. G. (1990). "Biological Feedbacks in Global Desertification". Science. 247 (4946): 1043–1048. Bibcode:1990Sci...247.1043S. doi:10.1126/science.247.4946.1043. PMID 17800060. S2CID 33033125.
68. Soden, B. J.; Held, I. M. (2006). "An Assessment of Climate Feedbacks in Coupled Ocean–Atmosphere Models". Journal of Climate. 19 (14): 3354. Bibcode:2006JCli...19.3354S. doi:10.1175/JCLI3799.1. Interestingly, the true feedback is consistently weaker than the constant relative humidity value, implying a small but robust reduction in relative humidity in all models on average clouds appear to provide a positive feedback in all models
69. (PDF). Archived from the original (PDF) on 2010-07-14. Retrieved 2010-09-02.
70. Hansen, J., "2008: Tipping point: Perspective of a climatologist." 2011-10-22 at the Wayback Machine, Wildlife Conservation Society/Island Press, 2008. Retrieved 2010.
71. Zelinka, Mark D.; Myers, Timothy A.; McCoy, Daniel T.; Po‐Chedley, Stephen; Caldwell, Peter M.; Ceppi, Paulo; Klein, Stephen A.; Taylor, Karl E. (2020). "Causes of Higher Climate Sensitivity in CMIP6 Models". Geophysical Research Letters. 47 (1): e2019GL085782. Bibcode:2020GeoRL..4785782Z. doi:10.1029/2019GL085782. hdl:10044/1/76038. ISSN 1944-8007.
72. Watts, Jonathan (2020-06-13). "Climate worst-case scenarios may not go far enough, cloud data shows". The Guardian. ISSN 0261-3077. Retrieved 2020-06-19.
73. Palmer, Tim (2020-05-26). "Short-term tests validate long-term estimates of climate change". Nature. 582 (7811): 185–186. Bibcode:2020Natur.582..185P. doi:10.1038/d41586-020-01484-5. PMID 32457461.
74. Pressel, Kyle G.; Kaul, Colleen M.; Schneider, Tapio (March 2019). "Possible climate transitions from breakup of stratocumulus decks under greenhouse warming" (PDF). Nature Geoscience. 12 (3): 163–167. Bibcode:2019NatGe..12..163S. doi:10.1038/s41561-019-0310-1. ISSN 1752-0908. S2CID 134307699. ^{[verification needed]}
75. Pistone, Kristina; Eisenman, Ian; Ramanathan, Veerabhadran (2019). "Radiative Heating of an Ice-Free Arctic Ocean". Geophysical Research Letters. 46 (13): 7474–7480. Bibcode:2019GeoRL..46.7474P. doi:10.1029/2019GL082914. ISSN 1944-8007. S2CID 197572148.
76. Stocker, T.F.; Clarke, G.K.C.; Le Treut, H.; Lindzen, R.S.; Meleshko, V.P.; Mugara, R.K.; Palmer, T.N.; Pierrehumbert, R.T.; Sellers, P.J.; Trenberth, K.E.; Willebrand, J. (2001). "Chapter 7: Physical Climate Processes and Feedbacks" (PDF). In Manabe, S.; Mason, P. (eds.). Climate Change 2001: The Scientific Basis. Contribution of Working Group I to the Third Assessment Report of the Intergovernmental Panel on Climate Change (Full free text). Cambridge, United Kingdom and New York, NY, USA: Cambridge University Press. pp. 445–448. ISBN 978-0-521-01495-3.
77. . University of Illinois at Urbana-Champaign Polar Research Group. Archived from the original on 2011-02-23. Retrieved 2008-01-02.
78. . National Snow and Ice Data Center. Archived from the original on 2007-12-23. Retrieved 2008-01-02..
79. "Arctic ice levels at record low opening Northwest Passage". Wikinews. September 16, 2007.
80. (PDF). The Met Office. 2008. p. 9. Archived from the original (PDF) on December 29, 2010. Retrieved August 29, 2008.
81. Adam, D. (2007-09-05). "Ice-free Arctic could be here in 23 years". The Guardian. Retrieved 2008-01-02.
82. Eric Steig; Gavin Schmidt (4 December 2004). "Antarctic cooling, global warming?". RealClimate. Retrieved 2008-01-20.
83. . Cryosphere Today. Archived from the original on 2008-01-13. Retrieved 2008-01-20.
84. . Cryosphere Today. Archived from the original on 2008-01-10. Retrieved 2008-01-20.
85. University of Virginia (March 25, 2011). "Russian boreal forests undergoing vegetation change, study shows". ScienceDaily.com. Retrieved March 9, 2018.
86. Repo, M. E.; Susiluoto, S.; Lind, S. E.; Jokinen, S.; Elsakov, V.; Biasi, C.; Virtanen, T.; Martikainen, P. J. (2009). "Large N2O emissions from cryoturbated peat soil in tundra". Nature Geoscience. 2 (3): 189. Bibcode:2009NatGe...2..189R. doi:10.1038/ngeo434.
87. Caitlin McDermott-Murphy (2019). "No laughing matter". The Harvard Gazette. Retrieved 22 July 2019.
88. Simó, R.; Dachs, J. (2002). "Global ocean emission of dimethylsulfide predicted from biogeophysical data". Global Biogeochemical Cycles. 16 (4): 1018. Bibcode:2002GBioC..16.1018S. doi:10.1029/2001GB001829. S2CID 129266687.
89. Isaksen, Ivar S. A.; Michael Gauss; Gunnar Myhre; Katey M. Walter; Anthony and Carolyn Ruppel (20 April 2011). (PDF). Global Biogeochemical Cycles. 25 (2): n/a. Bibcode:2011GBioC..25.2002I. doi:10.1029/2010GB003845. hdl:1912/4553. S2CID 17810925. Archived from the original (PDF) on 4 March 2016. Retrieved 1 February 2013.
90. Yang, Zong-Liang. "Chapter 2: The global energy balance" (PDF). University of Texas. Retrieved 2010-02-15.
91. Cronin, Timothy W.; Dutta, Ishir (17 July 2023). "How Well Do We Understand the Planck Feedback". Journal of Advances in Modeling Earth Systems. 15 (7): 1–19. doi:10.1029/2023MS003729.
92. Bony, Sandrine; Colman, Robert; Kattsov, Vladimir M.; Allan, Richard P.; Bretherton, Christopher S.; Dufresne, Jean-Louis; Hall, Alex; Hallegatte, Stephane; Holland, Marika M.; Ingram, William; Randall, David A.; Soden, Brian J.; Tseliousis, George; Webb, Mark J. (1 August 2006). "How Well Do We Understand and Evaluate Climate Change Feedback Processes?". Journal of Climate. 19 (15): 3445–3482. doi:10.1175/JCLI3819.1.See Appendices A and B for a more detailed review of this and similar formulations
93. National Research Council Panel on Climate Change Feedbacks (2003). Understanding Climate Change Feedbacks (Free PDF download). Washington D.C., United States: National Academies Press. doi:10.17226/10850. ISBN 978-0-309-09072-8.
94. Joos, F.; Roth, R.; Fuglestvedt, J.S.; Peters, G.P.; Enting, I.G.; et al. (8 March 2013). "Carbon dioxide and climate impulse response functions for the computation of greenhouse gas metrics: A multi-model analysis". Atmospheric Chemistry and Physics. 13 (5): 2793–2825   Material was copied from this source, which is available under a Creative Commons Attribution 3.0 Unported License. doi:10.5194/acpd-12-19799-2012. hdl:20.500.11850/58316.
95. Gregory, J.M.; Jones, C.D.; Cadule, P.; Friedlingstein, P. (2009). "Quantifying Carbon Cycle Feedbacks". Journal of Climate. 22 (19): 5232–5250. Bibcode:2009JCli...22.5232G. doi:10.1175/2009JCLI2949.1.
96. Archer, David (2005). "Fate of fossil fuel CO₂ in geologic time" (PDF). Journal of Geophysical Research. 110 (C9): C09S05. Bibcode:2005JGRC..110.9S05A. CiteSeerX 10.1.1.364.2117. doi:10.1029/2004JC002625.
97. Sigurdur R. Gislason; Eric H. Oelkers; Eydis S. Eiriksdottir; Marin I. Kardjilov; Gudrun Gisladottir; Bergur Sigfusson; Arni Snorrason; Sverrir Elefsen; Jorunn Hardardottir; Peter Torssander; Niels Oskarsson (2009). "Direct evidence of the feedback between climate and weathering". Earth and Planetary Science Letters. 277 (1–2): 213–222. Bibcode:2009E&PSL.277..213G. doi:10.1016/j.epsl.2008.10.018.
98. "The Carbon Cycle - Earth Science - Visionlearning". Visionlearning.
99. . princeton.edu. Archived from the original on 2010-07-04. Retrieved 2010-08-09.
100. Cramer, W.; Bondeau, A.; Woodward, F. I.; Prentice, I. C.; Betts, R. A.; Brovkin, V.; Cox, P. M.; Fisher, V.; Foley, J. A.; Friend, A. D.; Kucharik, C.; Lomas, M. R.; Ramankutty, N.; Sitch, S.; Smith, B.; White, A.; Young-Molling, C. (2001). "Global response of terrestrial ecosystem structure and function to CO₂ and climate change: results from six dynamic global vegetation models" (PDF). Global Change Biology. 7 (4): 357. Bibcode:2001GCBio...7..357C. doi:10.1046/j.1365-2486.2001.00383.x. S2CID 52214847.
101. Jacobson, Mark Zachary (2005). Fundamentals of Atmospheric Modeling (2nd ed.). Cambridge University Press. ISBN 978-0-521-83970-9.
102. Ahrens, C. Donald (2006). Meteorology Today (8th ed.). Brooks/Cole Publishing. ISBN 978-0-495-01162-0.
103. "Introduction to climate dynamics and climate modelling - Water vapour and lapse rate feedbacks". www.climate.be. Retrieved 2023-08-28.
104. Armour, Kyle C.; Bitz, Cecilia M.; Roe, Gerard H. (1 July 2013). "Time-Varying Climate Sensitivity from Regional Feedbacks". Journal of Climate. 26 (13): 4518–4534. Bibcode:2013JCli...26.4518A. doi:10.1175/jcli-d-12-00544.1. hdl:1721.1/87780. S2CID 2252857.
105. Goosse, Hugues; Kay, Jennifer E.; Armour, Kyle C.; Bodas-Salcedo, Alejandro; Chepfer, Helene; Docquier, David; Jonko, Alexandra; Kushner, Paul J.; Lecomte, Olivier; Massonnet, François; Park, Hyo-Seok; Pithan, Felix; Svensson, Gunilla; Vancoppenolle, Martin (15 May 2018). "Quantifying climate feedbacks in polar regions". Nature Communications. 9 (1): 1919. Bibcode:2018NatCo...9.1919G. doi:10.1038/s41467-018-04173-0. PMC 5953926. PMID 29765038.
106. Hahn, L. C.; Armour, K. C.; Battisti, D. S.; Donohoe, A.; Pauling, A. G.; Bitz, C. M. (28 August 2020). "Antarctic Elevation Drives Hemispheric Asymmetry in Polar Lapse Rate Climatology and Feedback". Geophysical Research Letters. 47 (16): e88965. Bibcode:2020GeoRL..4788965H. doi:10.1029/2020GL088965. S2CID 225410590.
107. A.E. Dessler; S.C. Sherwood (20 February 2009). (PDF). Science. 323 (5917): 1020–1021. doi:10.1126/science.1171264. PMID 19229026. S2CID 10362192. Archived from the original (PDF) on 2010-07-14. Retrieved 2010-09-02.
108. Hansen, James; Sato, Makiko; Kharecha, Pushker; von Schuckmann, Karina (January 2012). . NASA. Archived from the original on 2012-02-04.
109. Meehl, G.A., T.F. Stocker, W.D. Collins, P. Friedlingstein, A.T. Gaye, J.M. Gregory, A. Kitoh, R. Knutti, J.M. Murphy, A. Noda, S.C.B. Raper, I.G. Watterson, A.J. Weaver and Z.-C. Zhao, 2007: Chapter 10: Global Climate Projections. In: Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change [Solomon, S., D. Qin, M. Manning, Z. Chen, M. Marquis, K.B. Averyt, M. Tignor and H.L. Miller (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA. (Section 10.4.1 Carbon Cycle/Vegetation Feedbacks)

External links

• by NASA, Goddard Institute for Space Studies, October, 2010

•  Climate change portal