{"id":35062,"date":"2025-04-24T13:47:45","date_gmt":"2025-04-24T11:47:45","guid":{"rendered":"https:\/\/www.co2news.sk\/?p=35062"},"modified":"2025-04-24T13:50:19","modified_gmt":"2025-04-24T11:50:19","slug":"probability-of-triggering-climate-tipping-points","status":"publish","type":"post","link":"https:\/\/www.co2news.sk\/en\/2025\/04\/24\/probability-of-triggering-climate-tipping-points\/","title":{"rendered":"Probability of triggering climate tipping points"},"content":{"rendered":"

Study<\/span><\/a> deals with probabilities of triggering climate tipping points (TPs) \ud83e\udd75<\/span><\/strong> for five scenarios of shared socio-economic development (Shared Socioeconomic Pathways \u2013 SSPs) and examines how these probabilities change when additional carbon emissions are included that could arise from tipping points in the Earth's carbon cycle. A climate tipping point crossing at a certain level of global average surface temperature (the threshold temperature) would affect the Earth subsystem committed to sudden and largely irreversible changes<\/strong> with negative impacts on human well-being.<\/p>\n

The term \u201ctipping point\u201d is commonly used to describe a critical threshold in the forcing of a system at which a small additional forcing leads to significant and long-term changes in the system. Components of the Earth system that could exhibit tipping behavior are called \u201ctipping elements\u201d (TEs). They occur in the biosphere, cryosphere, and ocean or atmospheric circulation. Global mean surface temperature (GMST) relative to pre-industrial levels is used as a common metric to describe the forcing of TEs. Concerns about the possible proximity of climate tipping points are growing as estimates of threshold temperatures have been revised downwards, with some TEs at risk of \u201ctriggering\u201d (exceeding their threshold temperature) at GMST values as low as 1\u00b0C.<\/p>\n

The study follows a literature synthesis by Armstrong McKay et al. (2022) that identifies 16 TEs in the Earth system<\/strong> and provides estimates of their threshold temperatures, characteristic transition timescales, and their impact on global warming (Table 1 in the source). Armstrong McKay et al. (2022) distinguish between \u201cglobal core\u201d and \u201cregional impact\u201d TEs. Global core TEs must occur uniformly over a subcontinental scale (~1000 km), and when intact, contribute significantly to the overall operating regime of the Earth system. Regional impact TEs involve small tipping points that can be crossed almost synchronously on a subcontinental scale, and must either contribute significantly to human well-being or have great value in their own right as unique features of the Earth system.<\/p>\n

It is difficult to determine how safe a particular emission scenario is from the perspective of launching TEs, as several uncertainties need to be taken into account. These include uncertainty in climate sensitivity to anthropogenic emissions<\/strong>, uncertainties in threshold temperatures, timescales and impacts of climate tipping points, and even uncertainty about their existence. Additional uncertainty is introduced by potential interactions between climate tipping points<\/strong>, which tend to destabilize them. These interactions can be diverse in nature and often involve complex mechanisms. An example is TEs within the Earth's carbon cycle, which have the potential to release large amounts of greenhouse gases and thereby amplify global warming, which in turn increases the likelihood of triggering other TEs.<\/p>\n

The study calculates the triggering probabilities for 16 TEs identified by Armstrong McKay et al. (2022). Uncertainties in climate sensitivities and threshold temperatures are included using a Monte Carlo approach. The study also quantifies additional warming that could arise from TEs within the Earth's carbon cycle<\/strong>, and how this increases the probabilities of triggering other TEs.<\/p>\n

TEs with the potential to significantly affect the Earth's carbon cycle include abrupt permafrost thaw (PFAT, permafrost collapse (PFTP), Amazon rainforest dieback (AMAZ), and northern expansion and southern dieback of the boreal forest (BORF, TUND). Since northern expansion and southern dieback of the boreal forest balance each other out in terms of global warming, they were excluded from the analysis. Gradual permafrost thaw (PFGT) is not considered a tipping point and was therefore not included. The study focuses on PFAT, PFTP and AMAZ<\/strong>, referred to as \u201ccarbon tipping elements\u201d (carbon TEs).<\/p>\n

PFAT<\/strong> occurs regionally but almost synchronously in the permafrost region due to thermokarsts that can affect several meters of permafrost over a period of days to weeks. It is estimated that approximately 20 % of carbon emissions from PFAT are released as methane. PFAT is expected to enhance gradual thawing. Permafrost collapse (PFTP)<\/strong> may be caused by self-sustaining permafrost degradation due to heat released by microbial respiration of soil organic carbon, leading to further permafrost thawing and a positive feedback loop (so-called \u201ccompost bomb instability\u201d). Sudden Amazonian extinction (AMAZ)<\/strong> is hypothesized to be due to reduced moisture recycling and forest fire feedback triggered by initial tree loss due to global warming or deforestation.<\/p>\n

The study uses a reduced complexity model FaIR (Finite amplitude Impulse Response)<\/strong>, which is linked to the conceptual carbon tectonic element model (CTEM). CTEM can represent carbon emissions from AMAZ, PFAT and PFTP based on threshold temperature, timescale and impact estimates from Armstrong McKay et al. (2022). Each TE is represented by a cumulative carbon emission state that adds to the SSP carbon emissions. The CTEM model assumes immediate start<\/strong> The tipping point occurs when the global average surface temperature exceeds a threshold temperature. Carbon emissions from carbon TEs are added to the annual SSP emissions, and their sum is used to calculate temperature in the FaIR model, which then feeds back into the CTEM.<\/p>\n

Given the uncertainty regarding the effective time scales of TEs, the study provides three estimates of the probability of triggering<\/strong>:<\/p>\n

    \n
  1. Equilibrium triggering<\/strong>: TE will only be triggered if the stabilized temperature at the end of the model period (2400-2500) exceeds the threshold temperature. This is considered a conservative estimate and a lower bound.<\/li>\n
  2. Instantaneous triggering<\/strong>: TE will start immediately once the temperature exceeds the threshold temperature. This is considered the upper limit.<\/li>\n
  3. Instantaneous triggering + carbon TEs<\/strong>: Same as immediate start, but with additional warming caused by emissions from carbon TEs.<\/li>\n<\/ol>\n

    The results show that carbon emissions from carbon TEs increase from SSP1-1.9 to SSP5-8.5<\/strong>. Under SSP1-1.9 and SSP1-2.6, zero emissions from carbon TEs are still possible, while high emissions become much more likely under SSP2-4.5 and even more so under SSP3-7.0 and SSP5-8.5. Although the highest absolute carbon emissions from carbon TEs occur under the high-emission scenarios (SSP3-7.0 and SSP5-8.5), they remain small compared to anthropogenic emissions. At SSP2-4.5<\/strong> The 95th percentile of cumulative carbon emissions from carbon TEs reaches 35 % cumulative anthropogenic emissions<\/strong> in 2500, which is a high relative contribution compared to higher scenarios.<\/p>\n

    The additional warming caused by carbon TEs emissions (dT) varies between scenarios. Under SSP1-1.9 and SSP1-2.6, large temperature increases are possible but not common. Under SSP2-4.5 high impacts from carbon TEs become more common<\/strong>. The median additional warming reaches a maximum of 0.22 \u00b0C in 2300 under SSP2-4.5, compared to 0.08 \u00b0C under SSP1-2.6. Under the high-emissions scenarios (SSP3-7.0 and SSP5-8.5), additional warming becomes the baseline. The highest long-term temperature increase from carbon TEs becomes possible under SSP2-4.5<\/strong>, where the 95th percentile reaches 0.91 \u00b0C in 2500. Interestingly, this maximum is not observed in the scenarios with higher anthropogenic emissions, which is due to the smaller additional effect of GHGs at higher atmospheric concentrations. However, the highest short-term temperature increase (in 2100) is possible in the high emission scenarios SSP3-7.0 (0.93 \u00b0C) and SSP5-8.5 (1.11 \u00b0C). Average additional temperature increase from carbon TEs remains small<\/strong>, with the median always being at least an order of magnitude lower than the median of anthropogenic warming.<\/p>\n

    The probability of TEs triggering is highest under SSP5-8.5, with about 95 % on average for all TEs in all three estimation cases. Under SSP3-7.0, the probabilities are slightly lower. The differences between the three probability estimates are small under SSP5-8.5 and SSP3-7.0, because temperatures increase monotonically and the threshold temperatures of most TEs are exceeded even without the influence of carbon TEs.<\/p>\n

    Under SSP2-4.5<\/strong> the probability of triggering TEs is still high, with an equilibrium triggering probability of 62 % on average for all TEs<\/strong>. This probability varies among TEs. BARI, GRIS, PFAT, REEF and WAIS are run with more than 90 % probability in all three cases. AMOC, PFTP, TUND and AWSI remain below 50 % and EAIS even below 10 %. Among all SSPs, SSP2-4.5<\/strong> shows the highest increase in the probability of immediate triggering caused by additional warming from carbon TEs, with an increase of 3 percentage points<\/strong> on average for all TEs (Table 3). This increase remains small compared to the baseline instantaneous trigger probability of 64 %. Under SSP2-4.5, as with the higher scenarios, changing the assumption about the effective time scale of TEs does not significantly change the trigger probability estimates.<\/p>\n

    Under SSP1-2.6 and SSP1-1.9, the temperature increase does not become monotonic, but includes a peak in the 21st century, after which temperatures decrease and then stabilize. This causes the probability of immediate triggering is significantly higher than the probability of equilibrium triggering<\/strong>This difference represents the degree of uncertainty in the triggering probability resulting from the impossibility of constraining the effective time scale of TEs more precisely. Under both scenarios (SSP1-1.9 and SSP1-2.6) this uncertainty is an order of magnitude higher than the additional triggering probability due to carbon TEs.<\/p>\n

    Despite this uncertainty, transition from SSP2-4.5 to SSP1-2.6 significantly reduces the probability of triggering multiple TEs<\/strong>. Under SSP1-2.6, no TE exceeds a 90 % probability of triggering. PFAT, REEF, GRIS, WAIS and BARI all have probability estimates higher than 50 %. Under SSP1-1.9, the scenario with the most significant temperature overshoot and the highest uncertainty in the effective timescale assumptions, the probability of instantaneous triggering is more than twice as high as the equilibrium probability of triggering. Nevertheless, SSP1-1.9 is the scenario that minimizes the risk of triggering TEs. No TE has an equilibrium probability of triggering above 50 %, and for eight TEs the probabilities remain below 10 %.<\/p>\n

    Current policies<\/strong>, heading towards a trajectory comparable to SSP2-4.5, are highly dangerous<\/strong> in terms of triggering climate tipping points. Multiple TEs are likely to trigger under SSP2-4.5, with a 64 % probability of immediate triggering on average for all 16 TEs. Additional warming from carbon TEs increases this number by 3 percentage points, the highest increase in probability due to carbon TEs among all SSPs.<\/p>\n

    The triggering probabilities of climate TEs derived in this study are higher than estimates from previous studies, for example from the expert elicitation of Kriegler et al. (2009). This is explained recent evidence of the proximity of climate tipping points<\/strong>, leading to low estimates of the relevant threshold temperatures. For example, the probability of triggering AMOC, GRIS and WAIS under SSP2-4.5 in this study is significantly higher even at the most conservative estimate compared to the estimates from Kriegler et al. (2009) for the moderate warm corridor.<\/p>\n

    Although the study found an increase in the triggering probabilities due to additional carbon emissions from carbon TEs, this effect is not strong enough to trigger tipping point cascades and remains small compared to the scenario dependence of the triggering probabilities. The main physical interactions between TEs (apart from carbon emissions) are not taken into account in this study.<\/p>\n

    The study has some limitations and uncertainties. It was found that the FaIRv2.0.0 parameterization may not be sufficiently constrained for very high climate sensitivities, which could slightly overestimate the triggering probabilities. Estimates of impacts from carbon TEs remain speculative due to limited confidence in the existence of tipping points within the carbon TEs. The study excluded progressive permafrost thaw (PFGT), which is not assumed to be a tipping point but rather a non-threshold feedback to global warming, although significant additional carbon emissions are expected. The timing of the triggering of carbon TEs may be biased towards earlier times due to the assumption of instantaneous triggering in the CTEM model.<\/p>\n

    In conclusion, the study shows that additional carbon emissions from carbon TEs increase the risk of high-temperature trajectories, especially for SSPs with comparatively low anthropogenic emissions. However, on average, additional warming from carbon TEs remains small compared to anthropogenic warming. The probability of triggering climate TEs is therefore primarily determined by the emission scenario<\/strong> and not by whether carbon TEs are triggered. Uncertainty about the effective timescale of TEs makes it difficult to estimate the probability of triggering for scenarios involving overshoot.<\/p>\n

    If the risk of triggering TEs is to be reduced, it is necessary rapid action to reduce greenhouse gas emissions<\/strong>, because climate tipping points are already close and whether they will be exceeded will be decided in the coming decades. Spring<\/strong><\/em><\/p>\n

     <\/p>","protected":false},"excerpt":{"rendered":"

    The study looks at the probabilities of triggering climate tipping points (TPs) \ud83e\udd75 under five Shared Socioeconomic Pathways (SSPs) scenarios<\/p>","protected":false},"author":7,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[4],"tags":[],"class_list":["post-35062","post","type-post","status-publish","format-standard","hentry","category-klimaticka-zmena"],"acf":[],"_links":{"self":[{"href":"https:\/\/www.co2news.sk\/en\/wp-json\/wp\/v2\/posts\/35062","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.co2news.sk\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.co2news.sk\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.co2news.sk\/en\/wp-json\/wp\/v2\/users\/7"}],"replies":[{"embeddable":true,"href":"https:\/\/www.co2news.sk\/en\/wp-json\/wp\/v2\/comments?post=35062"}],"version-history":[{"count":0,"href":"https:\/\/www.co2news.sk\/en\/wp-json\/wp\/v2\/posts\/35062\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.co2news.sk\/en\/wp-json\/wp\/v2\/media?parent=35062"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.co2news.sk\/en\/wp-json\/wp\/v2\/categories?post=35062"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.co2news.sk\/en\/wp-json\/wp\/v2\/tags?post=35062"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}