The MPI‐ESM1.2 is the latest version of the Max Planck Institute Earth System Model and is the baseline for the Coupled Model Intercomparison Project Phase 6 and current seasonal and decadal climate ...predictions. This paper evaluates a coupled higher‐resolution version (MPI‐ESM1.2‐HR) in comparison with its lower‐resolved version (MPI‐ESM1.2‐LR). We focus on basic oceanic and atmospheric mean states and selected modes of variability, the El Niño/Southern Oscillation and the North Atlantic Oscillation. The increase in atmospheric resolution in MPI‐ESM1.2‐HR reduces the biases of upper‐level zonal wind and atmospheric jet stream position in the northern extratropics. This results in a decrease of the storm track bias over the northern North Atlantic, for both winter and summer season. The blocking frequency over the European region is improved in summer, and North Atlantic Oscillation and related storm track variations improve in winter. Stable Atlantic meridional overturning circulations are found with magnitudes of ~16 Sv for MPI‐ESM1.2‐HR and ~20 Sv for MPI‐ESM1.2‐LR at 26°N. A strong sea surface temperature bias of ~5°C along with a too zonal North Atlantic current is present in both versions. The sea surface temperature bias in the eastern tropical Atlantic is reduced by ~1°C due to higher‐resolved orography in MPI‐ESM‐HR, and the region of the cold‐tongue bias is reduced in the tropical Pacific. MPI‐ESM1.2‐HR has a well‐balanced radiation budget and its climate sensitivity is explicitly tuned to 3 K. Although the obtained reductions in long‐standing biases are modest, the improvements in atmospheric dynamics make this model well suited for prediction and impact studies.
Key Points
A higher‐resolution version of MPI‐ESM1.2 is presented, which has a well‐balanced radiation budget and stable ocean circulation
The higher atmospheric resolution improves North Atlantic storm tracks, blocking frequency, and NAO representation
The higher computational costs remain manageable and enable studies of seasonal to decadal predictions and climate impacts
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
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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.
The possibility of a rapid collapse in the strength of the Atlantic meridional overturning circulation (AMOC), with associated impacts on climate, has long been recognized. The suggested basis for ...this risk is the existence of two stable regimes of the AMOC (‘on’ and ‘off’), and such bistable behaviour has been identified in a range of simplified climate models. However, up to now, no state‐of‐the‐art atmosphere‐ocean coupled global climate model (AOGCM) has exhibited such behaviour, leading to the interpretation that the AMOC is more stable than simpler models indicate. Here we demonstrate AMOC bistability in the response to freshwater perturbations in the FAMOUS AOGCM ‐ the most complex AOGCM to exhibit such behaviour to date. The results also support recent suggestions that the direction of the net freshwater transport at the southern boundary of the Atlantic by the AMOC may be a useful physical indicator of the existence of bistability. We also present new estimates for this net freshwater transport by the AMOC from a range of ocean reanalyses which suggest that the Atlantic AMOC is currently in a bistable regime, although with large uncertainties. More accurate observational constraints, and an improved physical understanding of this quantity, could help narrow uncertainty in the future evolution of the AMOC and to assess the risk of a rapid AMOC collapse.
Key Points
Demonstrated hysteresis of the AMOC in an AOGCM
A potential indicator of bistability is demonstrated
Tentative results suggest the real ocean is in a bistable regime
We introduce an improved initialization to the decadal predictions performed for the Mittelfristige Klimaprognosen (MiKlip) project based on the Max‐Planck‐Institute Earth System Model and ...furthermore test the effect of increased ocean and atmosphere model resolutions. The new initialization includes both a more sophisticated oceanic initialization and additionally an atmospheric initialization. We compare the performance of retrospective decadal forecasts over the past 50 years with that of the previous system. The new oceanic initialization considerably improves the performance in terms of surface air temperature over the tropical oceans on the 2–5 years time scale, which also helps to improve the predictive skill of global mean surface air temperature on this time scale. The higher model resolution improves the predictive skill of surface air temperature over the tropical Pacific even further. Through the newly introduced atmospheric initialization, the quasi‐biennial oscillation exhibits predictive skill of up to 4 years when a sufficiently high vertical atmospheric resolution is used.
Key Points
The new initialization improves temperature predictions in the tropics
A higher model resolution leads to further improvements in the tropical Pacific
The quasi‐biennial oscillation exhibits prediction skill of up to 4 years
A seasonal forecast system is presented, based on the global coupled climate model MPI-ESM as used for CMIP5 simulations. We describe the initialisation of the system and analyse its predictive skill ...for surface temperature. The presented system is initialised in the atmospheric, oceanic, and sea ice component of the model from reanalysis/observations with full field nudging in all three components. For the initialisation of the ensemble, bred vectors with a vertically varying norm are implemented in the ocean component to generate initial perturbations. In a set of ensemble hindcast simulations, starting each May and November between 1982 and 2010, we analyse the predictive skill. Bias-corrected ensemble forecasts for each start date reproduce the observed surface temperature anomalies at 2–4 months lead time, particularly in the tropics. Niño3.4 sea surface temperature anomalies show a small root-mean-square error and predictive skill up to 6 months. Away from the tropics, predictive skill is mostly limited to the ocean, and to regions which are strongly influenced by ENSO teleconnections. In summary, the presented seasonal prediction system based on a coupled climate model shows predictive skill for surface temperature at seasonal time scales comparable to other seasonal prediction systems using different underlying models and initialisation strategies. As the same model underlying our seasonal prediction system—with a different initialisation—is presently also used for decadal predictions, this is an important step towards seamless seasonal-to-decadal climate predictions.
In a 6-month, placebo-controlled trial, oral fingolimod (FTY720) 1.25 or 5.0 mg, once daily, significantly reduced MRI inflammatory activity and annualized relapse rate compared with placebo in ...patients with relapsing multiple sclerosis (MS). The objectives were to monitor the 36-month, interim efficacy and safety results of the ongoing extension of this study. In the extension (months 7—36), placebo-treated patients were re-randomized to either dose of fingolimod; fingolimod-treated patients continued at the same dose. During months 15—24, all patients receiving fingolimod 5.0 mg switched to 1.25 mg. Of the 250 patients who entered the extension study, 173 (69%) continued to month 36. Most patients were free from gadolinium-enhanced lesions (88—89%) or new T2 lesions (70—78%) at month 36. Patients receiving continuous fingolimod treatment had sustained low annualized relapse rates of 0.20—0.21, and 68—73% remained relapse-free at month 36. Over 36 months, nasopharyngitis (34%), headache (30%), fatigue (19%) and influenza (18%) were the most commonly reported adverse events. Pulmonary function remained stable and blood pressure was stable after an initial increase (3—5 mmHg) during the first 6 months of fingolimod treatment; serious adverse events included infections and skin cancer. The low MRI and clinical disease activity at 6 months were maintained at 36 months with fingolimod, which was generally well tolerated by most patients. The efficacy and safety of oral fingolimod are being further evaluated in a large phase III MS study programme.
An ensemble of yearly initialized decadal predictions is performed with the Max Planck Institute Earth System Model to examine the forecast skill for the period from 1901 to 2010. Compared to the ...more recent period (1960 to present day), the extended period leads to an enlargement of regions with significant anomaly correlation coefficients (ACC) for predicted surface temperatures. This arises from an increased contribution of the trend, which is also found in the uninitialized runs. Additionally, in the North Atlantic decadal variability plays a larger role over the extended period, with detrended time series showing higher ACC for the extended compared to the short period. Furthermore, in contrast to the uninitialized simulations, the initialized predictions capture the North Atlantic warming events during the 1920s and 1990s, together with some of the surface climate impacts including warm European summer temperatures and a northward shift of Atlantic tropical rainfall.
Key Points
First decadal climate predictions made starting from 1901
Inclusion of few more cycles of decadal variability for skill estimation
First prediction of the 1920s North Atlantic climate transition and impact
To report the results of a 24-month extension of a phase II trial assessing the efficacy, safety, and tolerability of the once-daily oral sphingosine-1-phosphate receptor modulator, fingolimod ...(FTY720), in relapsing multiple sclerosis (MS).
In the randomized, double-blind, placebo-controlled core study, 281 patients received placebo or FTY720, 1.25 or 5.0 mg/day, for 6 months. During the subsequent dose-blinded extension, patients assigned to placebo were re-randomized to either dose of FTY720; those originally assigned to FTY720 continued at the same dose. Patients receiving FTY720 5.0 mg were switched to 1.25 mg during the month 15 to month 24 study visits.
Of 281 patients randomized in the core study, 250 (89%) entered the extension phase, and 189 (75.6%) received treatment for 24 months. During the core study, FTY720 significantly reduced gadolinium-enhanced (Gd(+)) lesions and annualized relapse rate (ARR) compared with placebo, with no differences between doses. During the extension phase, patients who switched from placebo to FTY720 showed clear reductions in ARR and lesion counts compared with the placebo phase; ARR and lesion counts remained low in patients who continued FTY720 treatment. After 24 months, 79 to 91% of patients were free from Gd(+) lesions and up to 77% of patients remained relapse free. FTY720 was well tolerated; no new safety concerns emerged during months 7 to 24 compared with the 6-month core study.
Once-daily oral treatment with FTY720, 1.25 or 5.0 mg, for up to 2 years, was well tolerated and was associated with low relapse rates and lesion activity.
This review paper discusses the physical basis and the potential for decadal climate predictability over the Atlantic and its adjacent land areas. Many observational and modeling studies describe ...pronounced decadal and multidecadal variability in the Atlantic Ocean. However, it still needs to be quantified to which extent the variations in the ocean drive variations in the atmosphere and over land. In particular, although a clear impact of the Tropics on the midlatitudes has been demonstrated, it is unclear if and how the extratropical atmosphere responds to midlatitudinal sea surface temperature anomalies.
Although the mechanisms behind the decadal to multidecadal variability in the Atlantic sector are still controversial, there is some consensus that some of the longer-term multidecadal variability is driven by variations in the thermohaline circulation. The variations in the North Atlantic thermohaline circulation appear to be predictable one to two decades ahead, as shown by a number of perfect model predictability experiments. The next few decades will be dominated by these multidecadal variations, although the effects of anthropogenic climate change are likely to introduce trends. Some impact of the variations of the thermohaline circulation on the atmosphere has been demonstrated in some studies so that useful decadal predictions with economic benefit may be possible.
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