Climate models are seen by many to be unverifiable. However, near-term climate predictions up to 10 years into the future carried out recently with these models can be rigorously verified against ...observations. Near-term climate prediction is a new information tool for the climate adaptation and service communities, which often make decisions on near-term time scales, and for which the most basic information is unfortunately very scarce. The Fifth Coupled Model Intercomparison Project set of co-ordinated climate-model experiments includes a set of near-term predictions in which several modelling groups participated and whose forecast quality we illustrate here. We show that climate forecast systems have skill in predicting the Earth's temperature at regional scales over the past 50 years and illustrate the trustworthiness of their predictions. Most of the skill can be attributed to changes in atmospheric composition, but also partly to the initialization of the predictions.
The tropical Pacific cooling from the early 1990s to 2013 has contributed to the slowdown of globally averaged sea surface temperatures (SSTs). The origin of this regional cooling trend still remains ...elusive. Here we demonstrate that the remote impact of Atlantic SST anomalies, as well as local atmosphere‐ocean interactions, contributed to the eastern Pacific cooling during this period. By assimilating observed three‐dimensional Atlantic temperature and salinity anomalies into a coupled general circulation model, we are able to qualitatively reproduce the observed Pacific decadal trends of SST and sea level pressure (SLP), albeit with reduced amplitude. Although a major part of the Pacific SLP trend can be explained by equatorial Pacific SST forcing only, the origin of this low‐frequency variability can be traced back further to the remote impacts of equatorial Atlantic and South Atlantic SST trends. Atlantic SST impacts on the atmospheric circulation can also be detected for the Northeastern Pacific, thus providing a linkage between Atlantic climate and Western North American drought conditions.
Key Points
Atlantic SST anomalies contribute to generation of Pacific decadal variability
Equatorial and South Atlantic SST trends reorganize global Walker Circulation
Phase of Interdecadal Pacific Oscillation influenced by SST anomalies in other ocean basins
Robust skill of decadal climate predictions Smith, D. M.; Eade, R.; Scaife, A. A. ...
NPJ climate and atmospheric science,
05/2019, Letnik:
2, Številka:
1
Journal Article, Publication
Recenzirano
Odprti dostop
Abstract
There is a growing need for skilful predictions of climate up to a decade ahead. Decadal climate predictions show high skill for surface temperature, but confidence in forecasts of ...precipitation and atmospheric circulation is much lower. Recent advances in seasonal and annual prediction show that the signal-to-noise ratio can be too small in climate models, requiring a very large ensemble to extract the predictable signal. Here, we reassess decadal prediction skill using a much larger ensemble than previously available, and reveal significant skill for precipitation over land and atmospheric circulation, in addition to surface temperature. We further propose a more powerful approach than used previously to evaluate the benefit of initialisation with observations, improving our understanding of the sources of skill. Our results show that decadal climate is more predictable than previously thought and will aid society to prepare for, and adapt to, ongoing climate variability and change.
Quantifying signals and uncertainties in climate models is essential for the detection, attribution, prediction and projection of climate change
. Although inter-model agreement is high for ...large-scale temperature signals, dynamical changes in atmospheric circulation are very uncertain
. This leads to low confidence in regional projections, especially for precipitation, over the coming decades
. The chaotic nature of the climate system
may also mean that signal uncertainties are largely irreducible. However, climate projections are difficult to verify until further observations become available. Here we assess retrospective climate model predictions of the past six decades and show that decadal variations in North Atlantic winter climate are highly predictable, despite a lack of agreement between individual model simulations and the poor predictive ability of raw model outputs. Crucially, current models underestimate the predictable signal (the predictable fraction of the total variability) of the North Atlantic Oscillation (the leading mode of variability in North Atlantic atmospheric circulation) by an order of magnitude. Consequently, compared to perfect models, 100 times as many ensemble members are needed in current models to extract this signal, and its effects on the climate are underestimated relative to other factors. To address these limitations, we implement a two-stage post-processing technique. We first adjust the variance of the ensemble-mean North Atlantic Oscillation forecast to match the observed variance of the predictable signal. We then select and use only the ensemble members with a North Atlantic Oscillation sufficiently close to the variance-adjusted ensemble-mean forecast North Atlantic Oscillation. This approach greatly improves decadal predictions of winter climate for Europe and eastern North America. Predictions of Atlantic multidecadal variability are also improved, suggesting that the North Atlantic Oscillation is not driven solely by Atlantic multidecadal variability. Our results highlight the need to understand why the signal-to-noise ratio is too small in current climate models
, and the extent to which correcting this model error would reduce uncertainties in regional climate change projections on timescales beyond a decade.
A linkage between climate change in the Atlantic and the Pacific oceans during the 1990s is investigated using three versions of the coupled climate model MIROC and CMIP5 multi‐model ensemble. From ...the early 1990s to the early 2000s, the observed sea surface temperature (SST) shows warming in the North Atlantic and a La Niña‐like pattern in the Pacific. Associated with the SST pattern, the observations indicate a strengthened Walker circulation in the tropical Pacific and enhanced precipitation in the tropical Atlantic. These SST and precipitation patterns are simulated well by hindcast experiments with external forcing and an initialized ocean anomaly state but are poorly simulated by uninitialized simulation with external forcing only. In particular, the observed La Niña‐like SST pattern becomes prominent in ensemble members with large amplitudes of Atlantic Multidecadal Oscillation (AMO) index during 1996–1998. Our results suggest that ocean initialization in both the Pacific and the Atlantic plays an important role in predicting the Pacific stepwise climate change during the 1990s, which contributes to the accurate estimation of global temperature change in the coming decade. Forecasting typhoon frequency or marine fisheries production in the coming decade may be possible by improving the predictive skill of stepwise climate change.
Key Points
Pacific decadal climate change is predictable with a help of North Atlantic
Decadal ENSO variability is predictable beyond 1 year
Initialization contributes to the accurate temperature change
The Paris Agreement calls for efforts to limit anthropogenic global warming to less than 1.5 °C above preindustrial levels. However, natural internal variability may exacerbate anthropogenic warming ...to produce temporary excursions above 1.5 °C. Such excursions would not necessarily exceed the Paris Agreement, but would provide a warning that the threshold is being approached. Here we develop a new capability to predict the probability that global temperature will exceed 1.5 °C above preindustrial levels in the coming 5 years. For the period 2017 to 2021 we predict a 38% and 10% chance, respectively, of monthly or yearly temperatures exceeding 1.5 °C, with virtually no chance of the 5‐year mean being above the threshold. Our forecasts will be updated annually to provide policy makers with advanced warning of the evolving probability and duration of future warming events.
Plain Language Summary
The Paris Agreement calls for efforts to limit human‐induced global warming to less than 1.5 °C above preindustrial levels. Observations of global mean temperature contain both human‐induced temperature change and superimposed natural variability. Natural variability may temporarily add to the underlying human‐induced warming, leading to observed temperatures that are higher than 1.5 °C for short‐term periods. This would not necessarily exceed the Paris agreement, which is usually interpreted to refer to long‐term averages, but would give an important indication that the threshold is being approached. If exceedance occurs, policy makers will require guidance regarding how long temperatures will remain above the threshold. Here we develop a new capability to predict the likelihood that global temperature will exceed 1.5 °C above preindustrial levels in the coming 5 years. We use decadal climate predictions that are regularly produced by several international climate prediction centers. Importantly, these predictions take into account the observed present day conditions since this is essential to predict the evolution of natural variability. For the period 2017 to 2021 we predict a 38% and 10% chance, respectively, of monthly or yearly temperatures exceeding 1.5 °C, with virtually no chance of the 5‐year mean being above the threshold. We will update our forecasts every year to provide policy makers with advanced warning of the evolving probability and duration of future warming events.
Key Points
Early temporary excursions above 1.5 °C would provide a warning that one of the Paris Agreement thresholds is being approached
Initialized climate predictions indicate a 38% (10%) chance of at least 1 month (year) exceeding 1.5 °C in the 5 year period 2017‐2021
Five‐year mean temperatures above 1.5 °C are extremely unlikely in this period
Toll-like receptor (TLR) 4/MD-2 dimerization is thought to be required for the initiation of signaling during innate immune responses. In this study, we examined the molecular mechanisms underlying ...receptor dimerization in the context of accessory molecules, i.e. CD14 and lipopolysaccharide-binding protein (LBP), to determine whether dimerization is required for the initiation of signaling in response to LPS stimulation. We found that LPS-induced TLR4/MD-2 dimerization occurred only in membrane-associated CD14 (mCD14)-expressing cells. Furthermore, dimerization required LBP, but not soluble CD14 (sCD14), as an essential serum component. LPS-induced signaling as assessed by IκB-α degradation, however, occurred in mCD14-negative cells in the presence of serum and sCD14. Signaling also occurred in mCD14-positive cells in the absence of serum. Time course studies on mCD14-positive cells have demonstrated that LPS stimulation induces rapid activation of nuclear factor-kappaB and p38 in the presence of LBP (TLR4/MD-2 receptor dimerization) as compared with stimulation without LBP (receptor non-dimerization). This early activation was blocked by inhibitory anti-CD14 mAb. These studies suggest that LPS-induced TLR4/MD-2 receptor dimerization is not essential for signaling but prompts rapid signaling during innate immune responses.
We have conducted a multi-model intercomparison of cloud-water in five state-of-the-art AGCMs run for control and doubled carbon dioxide climates. The most notable feature of the differences between ...the control and doubled carbon dioxide climates is in the distribution of cloud-water in the mixed-phase temperature band. The difference is greatest at mid and high latitudes. We found that the amount of cloud ice in the mixed phase layer in the control climate largely determines how much the cloud-water distribution changes for the doubled carbon dioxide climate. Therefore evaluation of the cloud ice distribution by comparison with data is important for future climate sensitivity studies. Cloud ice and cloud liquid both decrease in the layer below the melting layer, but only cloud liquid increases in the mixed-phase layer. Although the decrease in cloud-water below the melting layer occurs at all latitudes, the increase in cloud liquid in the mixed-phase layer is restricted to those latitudes where there is a large amount of cloud ice in the mixed-phase layer. If the cloud ice in the mixed-phase layer is concentrated at high latitudes, doubling of carbon dioxide might shift the center of cloud water distribution poleward which could decrease solar reflection because solar insolation is less at higher latitude. The magnitude of this poleward shift of cloud water appears to be larger for the higher climate sensitivity models, and it is consistent with the associated changes in cloud albedo forcing. For the control climate there is a clear relationship between the differences in cloud-water and relative humidity between the different models, for both magnitude and distribution. On the other hand the ratio of cloud ice to cloud-water follows the threshold temperature which is determined in each model. Improved measurements of relative humidity could be used to constrain the modeled representation of cloud water. At the same time, comparative analysis in global cloud resolving model simulations is necessary for further understanding of the relationships suggested in this paper.
Although the rotation of lower extremities has gained increasing recognition as a risk factor for anterior cruciate ligament (ACL) injury. This study clarified the influence of lower extremity ...rotation on the knee during single-leg landing. Design and Setting: We recruited 30 students to perform single-leg landing from a height of 30 cm with their lower extremities in neutral, and externally and internally rotated. The knee abduction, flexion angles, and abduction angular velocity were measured. Furthermore, the abduction angle was analyzed at knee flexion angles of 15°, 20°, 25°, and 30° and compared among the three conditions using a repeated measures analysis of variance with Bonferroni post hoc tests.
The maximum abduction angle was significantly greater when internally rotated than in the neutral. The maximum abduction angular velocity was significantly greater in the internally rotated compared to in the neutral. Finally, the abduction angle at a knee flexion angle of 30° was significantly greater when internally rotated compared to in the neutral.
Rotation of the lower extremities affects knee kinematics, and landing on a knee that is internally rotated may increase the risk of ACL injury.
•We studied the impact of lower extremity rotation on the knee in single-leg landing.•The maximum valgus angle and angular velocity were greater when internally rotated than in the neutral.•Rotation of the lower extremities affects knee kinematics.•Landing on an internally rotated knee may increase risk of ACL injury.
Decadal modulation of El Niño/Southern Oscillation (ENSO) amplitude is reproduced by a long‐term simulation with an atmosphere‐ocean general circulation model. A frequency of the modulation is in ...phase with Pacific decadal variability (PDV). A detailed analysis of the budget of sea surface temperature (SST) shows that effect of a change in anomalous zonal advection of mean temperature correlated to ENSO development has a dominant role in low‐frequency modulation of ENSO. That is because an equatorial zonal SST gradient changes periodically in the PDV cycle as a change in the background mean state for ENSO. Such characteristics are consistent with an observed climate shift and changes in ENSO characteristics that occurred in mid‐1970s.
PDF
