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

CLIMATE DYNAMICS 53 (2019) 4291-4309

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

There is no Plan B for dealing with the climate crisis


R Pierrehumbert

Global reconstruction of historical ocean heat storage and transport.

Proceedings of the National Academy of Sciences of the United States of America 116 (2019) 1126-1131

L Zanna, S Khatiwala, JM Gregory, J Ison, P Heimbach

Most of the excess energy stored in the climate system due to anthropogenic greenhouse gas emissions has been taken up by the oceans, leading to thermal expansion and sea-level rise. The oceans thus have an important role in the Earth's energy imbalance. Observational constraints on future anthropogenic warming critically depend on accurate estimates of past ocean heat content (OHC) change. We present a reconstruction of OHC since 1871, with global coverage of the full ocean depth. Our estimates combine timeseries of observed sea surface temperatures with much longer historical coverage than those in the ocean interior together with a representation (a Green's function) of time-independent ocean transport processes. For 1955-2017, our estimates are comparable with direct estimates made by infilling the available 3D time-dependent ocean temperature observations. We find that the global ocean absorbed heat during this period at a rate of 0.30 ± 0.06 W/[Formula: see text] in the upper 2,000 m and 0.028 ± 0.026 W/[Formula: see text] below 2,000 m, with large decadal fluctuations. The total OHC change since 1871 is estimated at 436 ± 91 [Formula: see text] J, with an increase during 1921-1946 (145 ± 62 [Formula: see text] J) that is as large as during 1990-2015. By comparing with direct estimates, we also infer that, during 1955-2017, up to one-half of the Atlantic Ocean warming and thermosteric sea-level rise at low latitudes to midlatitudes emerged due to heat convergence from changes in ocean transport.

ENSO Bimodality and Extremes


RR Rodrigues, A Subramanian, L Zanna, J Berner

Investigating the predictability of North Atlantic sea surface height

Climate Dynamics (2019)

R Fraser, M Palmer, C Roberts, C Wilson, D Copsey, L Zanna

© 2019, The Author(s). Interannual sea surface height (SSH) forecasts are subject to several sources of uncertainty. Methods relying on statistical forecasts have proven useful in assessing predictability and associated uncertainty due to both initial conditions and boundary conditions. In this study, the interannual predictability of SSH dynamics in the North Atlantic is investigated using the output from a 150 year long control simulation based on HadGEM3, a coupled climate model at eddy-permitting resolution. Linear inverse modeling (LIM) is used to create a statistical model for the evolution of monthly-mean SSH anomalies. The forecasts based on the LIM model demonstrate skill on interannanual timescales O(1–2 years). Forecast skill is found to be largest in both the subtropical and subpolar gyres, with decreased skill in the Gulf Stream extension region. The SSH initial conditions involving a tripolar anomaly off Cape Hatteras lead to a maximum growth in SSH about 20 months later. At this time, there is a meridional shift in the 0 m-SSH contour on the order of 0.5 ∘–1.5 ∘-latitude, coupled with a change in SSH along the US East Coast. To complement the LIM-based study, interannual SSH predictability is also quantified using the system’s average predictability time (APT). The APT analysis extracted large-scale SSH patterns which displayed predictability on timescales longer than 2 years. These patterns are responsible for changes in SSH on the order of 10 cm along the US East Coast, driven by variations in Ekman velocity. Our results shed light on the timescales of SSH predictability in the North Atlantic. In addition, the diagnosed optimal initial conditions and predictable patterns could improve interannual forecasts of the Gulf Stream’s characteristics and coastal SSH.

Assessing External and Internal Sources of Atlantic Multidecadal Variability Using Models, Proxy Data, and Early Instrumental Indices

JOURNAL OF CLIMATE 32 (2019) 7727-7745

CH O'Reilly, L Zanna, T Woollings

Atmospheric Circulation of Tide-Locked Exoplanets


RT Pierrehumbert, M Hammond

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


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

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


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

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


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

Applications of Deep Learning to Ocean Data Inference and Subgrid Parameterization

Journal of Advances in Modeling Earth Systems (2019)

T Bolton, L Zanna

©2019. The Authors. Oceanographic observations are limited by sampling rates, while ocean models are limited by finite resolution and high viscosity and diffusion coefficients. Therefore, both data from observations and ocean models lack information at small and fast scales. Methods are needed to either extract information, extrapolate, or upscale existing oceanographic data sets, to account for or represent unresolved physical processes. Here we use machine learning to leverage observations and model data by predicting unresolved turbulent processes and subsurface flow fields. As a proof of concept, we train convolutional neural networks on degraded data from a high-resolution quasi-geostrophic ocean model. We demonstrate that convolutional neural networks successfully replicate the spatiotemporal variability of the subgrid eddy momentum forcing, are capable of generalizing to a range of dynamical behaviors, and can be forced to respect global momentum conservation. The training data of our convolutional neural networks can be subsampled to 10–20% of the original size without a significant decrease in accuracy. We also show that the subsurface flow field can be predicted using only information at the surface (e.g., using only satellite altimetry data). Our results indicate that data-driven approaches can be exploited to predict both subgrid and large-scale processes, while respecting physical principles, even when data are limited to a particular region or external forcing. Our in-depth study presents evidence for the successful design of ocean eddy parameterizations for implementation in coarse-resolution climate models.

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.

Predicting the future is hard and other lessons from a population time series data science competition


GRW Humphries, C Che-Castaldo, PJ Bull, G Lipstein, A Ravia, B Carrion, T Bolton, A Ganguly, HJ Lynch

The Signature of Oceanic Processes in Decadal Extratropical SST Anomalies


CH O'Reilly, L Zanna

Recent multivariate changes in the North Atlantic climate system, with a focus on 2005-2016


J Robson, RT Sutton, A Archibald, F Cooper, M Christensen, LJ Gray, NP Holliday, C Macintosh, M McMillan, B Moat, M Russo, R Tilling, K Carslaw, D Desbruyeres, O Embury, DL Feltham, DP Grosvenor, S Josey, B King, A Lewis, GD McCarthy, C Merchant, AL New, CH O'Reilly, SM Osprey, K Read, A Scaife, A Shepherd, B Sinha, D Smeed, D Smith, A Ridout, T Woollings, M Yang

Global or Local Pure Condensible Atmospheres: Importance of Horizontal Latent Heat Transport


F Ding, RT Pierrehumbert

A chemical survey of exoplanets with ARIEL


G Tinetti, P Drossart, P Eccleston, P Hartogh, A Heske, J Leconte, G Micela, M Ollivier, G Pilbratt, L Puig, D Turrini, B Vandenbussche, P Wolkenberg, J-P Beaulieu, LA Buchave, M Ferus, M Griffin, M Guedel, K Justtanont, P-O Lagage, P Machado, G Malaguti, M Min, HU Norgaard-Nielsen, M Rataj, T Ray, I Ribas, M Swain, R Szabo, S Werner, J Barstow, M Burleigh, J Cho, VC du Foresto, A Coustenis, L Decin, T Encrenaz, M Galand, M Gillon, R Helled, J Carlos Morales, AG Munoz, A Moneti, I Pagano, E Pascale, G Piccioni, D Pinfield, S Sarkar, F Selsis, J Tennyson, A Triaud, O Venot, I Waldmann, D Waltham, G Wright, J Amiaux, J-L Augueres, M Berthe, N Bezawada, G Bishop, N Bowles, D Coffey, J Colome, M Crook, P-E Crouzet, V Da Peppo, IE Sanz, M Focardi, M Frericks, T Hunt, R Kohley, K Middleton, G Morgante, R Ottensamer, E Pace, C Pearson, R Stamper, K Symonds, M Rengel, E Renotte, P Ade, L Affer, C Alard, N Allard, F Altieri, Y Andre, C Arena, I Argyriou, A Aylward, C Baccani, G Bakos, M Banaszkiewicz, M Barlow, V Batista, G Bellucci, S Benatti, P Bernardi, B Bezard, M Blecka, E Bolmont, B Bonfond, R Bonito, AS Bonomo, JR Brucato, AS Brun, I Bryson, W Bujwan, S Casewell, B Charnay, CC Pestellini, G Chen, A Ciaravella, R Claudi, R Cledassou, M Damasso, M Damiano, C Danielski, P Deroo, AM Di Giorgio, C Dominik, V Doublier, S Doyle, R Doyon, B Drummond, B Duong, S Eales, B Edwards, M Farina, E Flaccomio, L Fletcher, F Forget, S Fossey, M Fraenz, Y Fujii, A Garcia-Piquer, W Gear, H Geoffray, JC Gerard, L Gesa, H Gomez, R Graczyk, C Griffith, D Grodent, MG Guarcello, J Gustin, K Hamano, P Hargrave, Y Hello, K Heng, E Herrero, A Hornstrup, B Hubert, S Ida, M Ikoma, N Iro, P Irwin, C Jarchow, J Jaubert, H Jones, Q Julien, S Kameda, F Kerschbaum, P Kervella, T Koskinen, M Krijger, N Krupp, M Lafarga, F Landini, E Lellouch, G Leto, A Luntzer, T Rank-Luftinger, A Maggio, J Maldonado, J-P Maillard, U Mall, J-B Marquette, S Mathis, P Maxted, T Matsuo, A Medvedev, Y Miguel, V Minier, G Morello, A Mura, N Narita, V Nascimbeni, N Nguyen Tong, V Noce, F Oliva, E Palle, P Palmer, M Pancrazzi, A Papageorgiou, V Parmentier, M Perger, A Petralia, S Pezzuto, R Pierrehumbert, I Pillitteri, G Piotto, G Pisano, L Prisinzano, A Radioti, J-M Reess, L Rezac, M Rocchetto, A Rosich, N Sanna, A Santerne, G Savini, G Scandariato, B Sicardy, C Sierra, G Sindoni, K Skup, I Snellen, M Sobiecki, L Soret, A Sozzetti, A Stiepen, A Strugarek, J Taylor, W Taylor, L Terenzi, M Tessenyi, A Tsiaras, C Tucker, D Valencia, G Vasisht, A Vazan, F Vilardell, S Vinatier, S Viti, R Waters, P Wawer, A Wawrzaszek, A Whitworth, YL Yung, SN Yurchenko, MR Zapatero Osorio, R Zellem, T Zingales, F Zwart

Wave-mean Flow Interactions in the Atmospheric Circulation of Tidally Locked Planets


M Hammond, RT Pierrehumbert

Impact of Gulf Stream SST biases on the global atmospheric circulation

CLIMATE DYNAMICS 51 (2018) 3369-3387

RW Lee, TJ Woollings, BJ Hoskins, KD Williams, CH O'Reilly, G Masato

Interdecadal variability of the ENSO teleconnection to the wintertime North Pacific

CLIMATE DYNAMICS 51 (2018) 3333-3350

CH O'Reilly