Publications


Exoplanetary Monte Carlo radiative transfer with correlated-k - I. Benchmarking transit and emission observables

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY 487 (2019) 2082-2096

GKH Lee, J Taylor, SL Grimm, J-L Baudino, R Garland, PGJ Irwin, K Wood


Forced summer stationary waves: the opposing effects of direct radiative forcing and sea surface warming

Climate Dynamics (2019)

HS Baker, T Woollings, C Mbengue, MR Allen, CH O’Reilly, H Shiogama, S Sparrow

© 2019, The Author(s). We investigate the opposing effects of direct radiative forcing and sea surface warming on the atmospheric circulation using a hierarchy of models. In large ensembles of three general circulation models, direct CO 2 forcing produces a wavenumber 5 stationary wave over the Northern Hemisphere in summer. Sea surface warming produces a similar wave, but with the opposite sign. The waves are also present in the Coupled Model Intercomparison Project phase 5 ensemble with opposite signs due to direct CO 2 and sea surface warming. Analyses of tropical precipitation changes and equivalent potential temperature changes and the results from a simple barotropic model show that the wave is forced from the tropics. Key forcing locations are the Western Atlantic, Eastern Atlantic and in the Indian Ocean just off the east coast of Africa. The stationary wave has a significant impact on regional temperature anomalies in the Northern Hemisphere summer, explaining some of the direct effect that CO 2 concentration has on temperature extremes. Ultimately, the climate sensitivity and future changes in the land–sea temperature contrast will dictate the balance between the opposing effects on regional changes in mean and extreme temperature and precipitation under climate change.


There is no Plan B for dealing with the climate crisis

BULLETIN OF THE ATOMIC SCIENTISTS (2019)

R Pierrehumbert


Southern Hemisphere atmospheric blocking in CMIP5 and future changes in the Australia‐New Zealand sector

Geophysical Research Letters American Geophysical Union (AGU) (2019) 2019GL083264

M Patterson, T Bracegirdle, T Woollings


The Eddy-Driven Jet and Storm-Track Responses to Boundary Layer Drag: Insights from an Idealized Dry GCM Study

JOURNAL OF THE ATMOSPHERIC SCIENCES 76 (2019) 1055-1076

CO Mbengue, T Woollings


Atmospheric Circulation of Tide-Locked Exoplanets

ANNUAL REVIEW OF FLUID MECHANICS, VOL 51 51 (2019) 275-303

RT Pierrehumbert, M Hammond


ATMOSPHERIC VARIABILITY DRIVEN BY RADIATIVE CLOUD FEEDBACK IN BROWN DWARFS AND DIRECTLY IMAGED EXTRASOLAR GIANT PLANETS

The Astrophysical Journal American Astronomical Society (2019)

XIANYU TAN, A Showman


The importance of stratospheric initial conditions for winter North Atlantic Oscillation predictability and implications for the signal-to-noise paradox

QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY 145 (2019) 131-146

CH O'Reilly, A Weisheimer, T Woollings, LJ Gray, D MacLeod


How confident are predictability estimates of the winter North Atlantic Oscillation?

QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY 145 (2019) 140-159

A Weisheimer, D Decremer, D MacLeod, C O'Reilly, TN Stockdale, S Johnson, TN Palmer


The Linear Sensitivity of the North Atlantic Oscillation and Eddy-Driven Jet to SSTs

JOURNAL OF CLIMATE 32 (2019) 6491-6511

HS Baker, T Woollings, CE Forest, MR Allen


Seasonal Predictability of the Winter North Atlantic Oscillation From a Jet Stream Perspective

Geophysical Research Letters (2019)

T Parker, T Woollings, A Weisheimer, C O'Reilly, L Baker, L Shaffrey

©2019. The Authors. The winter North Atlantic Oscillation (NAO) has varied on interannual and decadal timescales over the last century, associated with variations in the speed and latitude of the eddy-driven jet stream. This paper uses hindcasts from two operational seasonal forecast systems (the European Centre for Medium-range Weather Forecasts's seasonal forecast system, and the U.K. Met Office global seasonal forecast system) and a century-long atmosphere-only experiment (using the European Centre for Medium-range Weather Forecasts's Integrated Forecasting System model) to relate seasonal prediction skill in the NAO to these aspects of jet variability. This shows that the NAO skill realized so far arises from interannual variations in the jet, largely associated with its latitude rather than speed. There likely remains further potential for predictability on longer, decadal timescales. In the small sample of models analyzed here, improved representation of the structure of jet variability does not translate to enhanced seasonal forecast skill.


The roles of static stability and tropical-extratropical interactions in the summer interannual variability of the North Atlantic sector

CLIMATE DYNAMICS 52 (2019) 1299-1315

CO Mbengue, T Woollings, HF Dacre, KI Hodges


Applying Machine Learning to Improve Simulations of a Chaotic Dynamical System Using Empirical Error Correction.

Journal of advances in modeling earth systems 11 (2019) 1402-1417

PAG Watson

Dynamical weather and climate prediction models underpin many studies of the Earth system and hold the promise of being able to make robust projections of future climate change based on physical laws. However, simulations from these models still show many differences compared with observations. Machine learning has been applied to solve certain prediction problems with great success, and recently, it has been proposed that this could replace the role of physically-derived dynamical weather and climate models to give better quality simulations. Here, instead, a framework using machine learning together with physically-derived models is tested, in which it is learnt how to correct the errors of the latter from time step to time step. This maintains the physical understanding built into the models, while allowing performance improvements, and also requires much simpler algorithms and less training data. This is tested in the context of simulating the chaotic Lorenz '96 system, and it is shown that the approach yields models that are stable and that give both improved skill in initialized predictions and better long-term climate statistics. Improvements in long-term statistics are smaller than for single time step tendencies, however, indicating that it would be valuable to develop methods that target improvements on longer time scales. Future strategies for the development of this approach and possible applications to making progress on important scientific problems are discussed.


Climate impacts of cultured meat and beef cattle.

Frontiers in sustainable food systems 3 (2019)

J Lynch, R Pierrehumbert

Improved greenhouse gas (GHG) emission efficiency of production has been proposed as one of the biggest potential advantages of cultured meat over conventional livestock production systems. Comparisons with beef are typically highlighted, as it is a highly emissions intensive food product. In this study we present a more rigorous comparison of the potential climate impacts of cultured meat and cattle production than has previously been made. Warming impacts are evaluated using a simple climate model that simulates the different behaviours of carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O), rather than relying on carbon dioxide equivalent (CO2e) metrics. We compare the temperature impact of beef cattle and cultured meat production at all times to 1000 years in the future, using four synthetic meat GHG footprints currently available in the literature and three different beef production systems studied in an earlier climate modelling paper. Cattle systems are associated with the production of all three GHGs above, including significant emissions of CH4, while cultured meat emissions are almost entirely CO2 from energy generation. Under continuous high global consumption, cultured meat results in less warming than cattle initially, but this gap narrows in the long term and in some cases cattle production causes far less warming, as CH4 emissions do not accumulate, unlike CO2. We then model a decline in meat consumption to more sustainable levels following high consumption, and show that although cattle systems generally result in greater peak warming than cultured meat, the warming effect declines and stabilises under the new emission rates of cattle systems, while the CO2 based warming from cultured meat persists and accumulates even under reduced consumption, again overtaking cattle production in some scenarios. We conclude that cultured meat is not prima facie climatically superior to cattle production; its relative impact instead depends on the availability of decarbonised energy generation and the specific production systems that are realised.


Seasonal Sensitivity of the Hadley Cell and Cross-Hemispheric Responses to Diabatic Heating in an Idealized GCM

GEOPHYSICAL RESEARCH LETTERS 45 (2018) 2533-2541

HS Baker, C Mbengue, T Woollings


Exonephology: transmission spectra from a 3D simulated cloudy atmosphere of HD 209458b

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY 481 (2018) 194-205

S Lines, J Manners, NJ Mayne, J Goyal, AL Carter, IA Boutle, GKH Lee, C Helling, B Drummond, DM Acreman, DK Sing


The Signature of Oceanic Processes in Decadal Extratropical SST Anomalies

GEOPHYSICAL RESEARCH LETTERS 45 (2018) 7719-7730

CH O'Reilly, L Zanna


Higher CO2 concentrations increase extreme event risk in a 1.5 degrees C world

NATURE CLIMATE CHANGE 8 (2018) 604-+

HS Baker, RJ Millar, DJ Karoly, U Beyerle, BP Guillod, D Mitchell, H Shiogama, S Sparrow, T Woollings, MR Allen


Skilful Seasonal Predictions of Summer European Rainfall

GEOPHYSICAL RESEARCH LETTERS 45 (2018) 3246-3254

N Dunstone, D Smith, A Scaife, L Hermanson, D Fereday, C O'Reilly, A Stirling, R Eade, M Gordon, C Maclachlan, T Woollings, K Sheen, S Belcher


Flow dependent ensemble spread in seasonal forecasts of the boreal winter extratropics

ATMOSPHERIC SCIENCE LETTERS 19 (2018) UNSP e815

D MacLeod, C O'Reilly, T Palmer, A Weisheimer

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