On interannual timescales the growth rate of atmospheric CO2 is largely controlled by the response of the land and ocean carbon sinks to climate variability. Yet, it is unknown to what extent this ...variability limits the predictability of atmospheric CO2 variations. Using perfect‐model Earth System Model simulations, we show that variations in atmospheric CO2 are potentially predictable for 3 years. We find a 2‐year predictability horizon for global oceanic CO2 flux with longer regional predictability of up to 7 years. The 2‐year predictability horizon of terrestrial CO2 flux originates in the tropics and midlatitudes. With the predictability of the isolated effects of land and ocean carbon sink on atmospheric CO2 of 5 and 12 years respectively, land dampens the overall predictability of atmospheric CO2 variations. Our research shows the potential of Earth System Model‐based predictions to forecast multiyear variations in atmospheric CO2.
Plain Language Summary
The amount of anthropogenic carbon emissions absorbed by land and ocean from the atmosphere varies annually due to their sensitivity to climate. Therefore, the atmospheric CO2 growth rate does not strictly follow the emissions signal. Whether decadal prediction systems can also predict variations of atmospheric CO2 has not been shown yet but is crucial to inform policy makers about the efficiency of the implementation of the Paris Agreement. Using numerical Earth System simulations in an idealized prediction framework, we show that global atmospheric CO2 is predictable up to 3 years in advance. The global ocean and land CO2 fluxes are predictable for 2 years. The isolated effects of the land and ocean carbon sink on atmospheric CO2 are predictable for 5 and 12 years, respectively. Therefore, the land carbon cycle limits atmospheric CO2 predictability. Our study demonstrates that simulation‐based multiyear forecasts have the potential to predict natural atmospheric CO2 variations.
Key Points
Global annual atmospheric CO2 variations are potentially predictable up to 3 years in advance
The global oceanic CO2 flux is predictable for 2 years with regional predictability up to a decade
The global land CO2 flux predictability of 2 years is dominated by the tropical forests
The growth rate of atmospheric CO2 on inter-annual time scales is largely controlled by the response of the land and ocean carbon sinks to climate variability. Therefore, the effect of CO2 emission ...reductions to achieve the Paris Agreement on atmospheric CO2 concentrations may be disguised by internal variability, and the attribution of a reduction in atmospheric CO2 growth rate to CO2 emission reductions induced by a policy change is unclear for the near term. We use 100 single-model simulations and interpret CO2 emission reductions starting in 2020 as a policy change from scenario Representative Concentration Pathway (RCP) 4.5 to 2.6 in a comprehensive causal theory framework. Five-year CO2 concentration trends grow stronger in 2021-2025 after CO2 emission reductions than over 2016-2020 in 30% of all realizations in RCP2.6 compared to 52% in RCP4.5 without CO2 emission reductions. This implies that CO2 emission reductions are sufficient by 42%, necessary by 31% and both necessary and sufficient by 22% to cause reduced atmospheric CO2 trends. In the near term, these probabilities are far from certain. Certainty implying sufficient or necessary causation is only reached after, respectively, ten and sixteen years. Assessments of the efficacy of CO2 emission reductions in the near term are incomplete without quantitatively considering internal variability.
•The uGIC is a surrogate marker of HFO activity, independent of discrete events.•HFOs and the uGIC identify cortical regions that overlap with the seizure onset zone.•HFOs and the uGIC have are ...strong positive predictors of post-surgical outcome.
To investigate the Graph Index Complexity (uGIC) as a marker of high frequency oscillatory (HFO) activity, the seizure onset zone (SOZ), and surgical outcome.
The SOZ, rates of HFOs at two thresholds (broad, strict), and uGIC were determined using EEG data from 41 patients. The correlation between HFOs and uGIC were calculated. HFOs and uGIC were compared within and outside the SOZ. Postsurgical outcome was compared to the colocalization of HFOs and resected SOZ.
There was significant correlation between uGIC and both broad (r = 0.69, p < 0.0005) and strict HFOs (r = 0.48, p < 0.0005). All were significantly greater within the SOZ overall, but only in 17/41 (strict, uGIC) or 18/41 (broad) patients. HFO markers were significantly greater within the SOZ for 8/15 patients with positive postsurgical outcomes, but not for any patients with negative outcomes (0/5).
The uGIC is a marker of HFO activity, while HFOs and uGIC are markers of the SOZ overall. Colocalization of HFOs and the SOZ has strong positive predictive value for postsurgical outcome, but poor negative predictive value.
The uGIC is an objective surrogate marker of HFO activity independent of identifying discrete HFO events.
Highlights • Epoched study design is an effective method of evaluating interrater reliability of visual assessment of high-frequency oscillations (HFOs). • HFO identification agreement between two ...visual reviewers is poor (mean Cohen’s Kappa = 0.403). • Translation of HFOs to clinical practice requires a framework to reconcile important findings of existing HFO studies.
This case report describes an atypical presentation of a relatively common opportunistic infection, without documented exposure to areas known at the time to be endemic, resulting in catastrophic ...complications. The patient presented with a two month progressive history of vomiting, diarrhea, productive cough, and shortness of breath, on the background of poorly-controlled HIV. There was a low index of suspicion for infection with histoplasmosis, particularly given the large differential diagnosis and the lack of travel or endemic precedence. The case was complicated by the development of disseminated intravascular coagulation (DIC) prior to identification of the pathogen. Ultimately, the patient’s goals of care transitioned to palliation, and treatments were discontinued. It is our hope that in the future, such outcomes might be prevented by considering disseminated histoplasmosis in systemically unwell patients with HIV, regardless of endemic exposure or specific presentation.
We examined the effect of a simple Delphi-method feedback on visual identification of high frequency oscillations (HFOs) in the ripple (80-250 Hz) band, and assessed the impact of this training ...intervention on the interrater reliability and generalizability of HFO evaluations.
We employed a morphology detector to identify potential HFOs at two thresholds and presented them to visual reviewers to assess the probability of each epoch containing an HFO. We recruited 19 board-certified epileptologists with various levels of experience to complete a series of HFO evaluations during three sessions. A Delphi-style intervention was used to provide feedback on the performance of each reviewer relative to their peers. A delayed-intervention paradigm was used, in which reviewers received feedback either before or after the second session. ANOVAs were used to assess the effect of the intervention on the reviewers' evaluations. Generalizability theory was used to assess the interrater reliability before and after the intervention.
The intervention, regardless of when it occurred, resulted in a significant reduction in the variability between reviewers in both groups (
= 0.037,
= 0.003). Prior to the delayed-intervention, the group receiving the early intervention showed a significant reduction in variability (
= 0.041), but the delayed-intervention group did not (
= 0.414). Following the intervention, the projected number of reviewers required to achieve strong generalizability decreased from 35 to 16.
This study shows a robust effect of a Delphi-style intervention on the interrater variability, reliability, and generalizability of HFO evaluations. The observed decreases in HFO marking discrepancies across 14 of the 15 reviewers are encouraging: they are necessarily associated with an increase in interrater reliability, and therefore with a corresponding decrease in the number of reviewers required to achieve strong generalizability. Indeed, the reliability of all reviewers following the intervention was similar to that of experienced reviewers prior to intervention. Therefore, a Delphi-style intervention could be implemented either to sufficiently train any reviewer, or to further refine the interrater reliability of experienced reviewers. In either case, a Delphi-style intervention would help facilitate the standardization of HFO evaluations and its implementation in clinical care.
We examined the interrater reliability and generalizability of high-frequency oscillation (HFO) visual evaluations in the ripple (80-250 Hz) band, and established a framework for the transition of ...HFO analysis to routine clinical care. We were interested in the interrater reliability or epoch generalizability to describe how similar the evaluations were between reviewers, and in the reviewer generalizability to represent the consistency of the internal threshold each individual reviewer.
We studied 41 adult epilepsy patients (mean age: 35.6 years) who underwent intracranial electroencephalography. A morphology detector was designed and used to detect candidate HFO events, lower-threshold events, and distractor events. These events were subsequently presented to six expert reviewers, who visually evaluated events for the presence of HFOs. Generalizability theory was used to characterize the epoch generalizability (interrater reliability) and reviewer generalizability (internal threshold consistency) of visual evaluations, as well as to project the numbers of epochs, reviewers, and datasets required to achieve strong generalizability (threshold of 0.8).
The reviewer generalizability was almost perfect (0.983), indicating there were sufficient evaluations to determine the internal threshold of each reviewer. However, the interrater reliability for 6 reviewers (0.588) and pairwise interrater reliability (0.322) were both poor, indicating that the agreement of 6 reviewers is insufficient to reliably establish the presence or absence of individual HFOs. Strong interrater reliability (≥0.8) was projected as requiring a minimum of 17 reviewers, while strong reviewer generalizability could be achieved with <30 epoch evaluations per reviewer.
This study reaffirms the poor reliability of using small numbers of reviewers to identify HFOs, and projects the number of reviewers required to overcome this limitation. It also provides a set of tools which may be used for training reviewers, tracking changes to interrater reliability, and for constructing a benchmark set of epochs that can serve as a generalizable gold standard, against which other HFO detection algorithms may be compared. This study represents an important step toward the reconciliation of important but discordant findings from HFO studies undertaken with different sets of HFOs, and ultimately toward transitioning HFO analysis into a meaningful part of the clinical epilepsy workup.
Abstract
The growth rate of atmospheric CO
2
on inter-annual time scales is largely controlled by the response of the land and ocean carbon sinks to climate variability. Therefore, the effect of CO
2
...emission reductions to achieve the Paris Agreement on atmospheric CO
2
concentrations may be disguised by internal variability, and the attribution of a reduction in atmospheric CO
2
growth rate to CO
2
emission reductions induced by a policy change is unclear for the near term. We use 100 single-model simulations and interpret CO
2
emission reductions starting in 2020 as a policy change from scenario Representative Concentration Pathway (RCP) 4.5 to 2.6 in a comprehensive causal theory framework. Five-year CO
2
concentration trends grow stronger in 2021–2025 after CO
2
emission reductions than over 2016–2020 in 30% of all realizations in RCP2.6 compared to 52% in RCP4.5 without CO
2
emission reductions. This implies that CO
2
emission reductions are sufficient by 42%, necessary by 31% and both necessary and sufficient by 22% to cause reduced atmospheric CO
2
trends. In the near term, these probabilities are far from certain. Certainty implying sufficient or necessary causation is only reached after, respectively, ten and sixteen years. Assessments of the efficacy of CO
2
emission reductions in the near term are incomplete without quantitatively considering internal variability.
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