The runaway greenhouse on subNeptune waterworlds

ArXiv 2212.02644 (2022)

The strong role of external forcing in seasonal forecasts of European summer temperature

Environmental Research Letters IOP Publishing 17:10 (2022) 104033

Authors:

Matthew Patterson, Antje Weisheimer, Daniel J Befort, Christopher O'Reilly

Abstract:

Since the 1980s, external forcings from increasing greenhouse gases and declining aerosols have had a large effect on European summer temperatures. These forcings may therefore provide an important source of forecast skill, even for timescales as short as a season ahead. However, the relative importance of external forcings for seasonal forecasts has thus far received little attention, particularly on a regional scale. In this study, we investigate forcing-induced skill by comparing the near-surface temperature skill of a multi-model ensemble of seasonal predictions from the Copernicus Climate Change Service archive to that of an uninitialised ensemble of Coupled Model Intercomparison Project phase 6 projections for European summers (June–July–August) spanning the years 1993–2016. As expected, predictive skill over southern Europe is larger for initialised seasonal predictions compared to uninitialised climate projections. However, for northern Europe, we find that predictive skill is generally small in current seasonal models and surprisingly even smaller compared to uninitialised climate projections. These results imply that further research is necessary to understand the role of external forcing on seasonal temperature variations over Europe.

Explaining and predicting earth system change: a world climate research programme call to action

Bulletin of the American Meteorological Society American Meteorological Society (2022)

Authors:

Kirsten L Findell, Rowan Sutton, Nico Caltabiano, Anca Brookshaw, Patrick Heimbach, Masahide Kimoto, Scott Osprey, Doug Smith, James S Risbey, Zhuo Wang, Lijing Cheng, Leandro Diaz, Markus G Donat, Michael Ek, June-Yi Lee, Shoshiro Minobe, Matilde Rusticucci, Frederic Vitart, Lin Wang

Abstract:

The World Climate Research Programme (WCRP) envisions a world “that uses sound, relevant, and timely climate science to ensure a more resilient present and sustainable future for humankind.” This bold vision requires the climate science community to provide actionable scientific information that meets the evolving needs of societies all over the world. To realize its vision, WCRP has created five Lighthouse Activities to generate international commitment and support to tackle some of the most pressing challenges in climate science today. The overarching goal of the Lighthouse Activity on Explaining and Predicting Earth System Change is to develop an integrated capability to understand, attribute, and predict annual to decadal changes in the Earth system, including capabilities for early warning of potential high impact changes and events. This article provides an overview of both the scientific challenges that must be addressed, and the research and other activities required to achieve this goal. The work is organized in three thematic areas: (i) monitoring and modeling Earth system change; (ii) integrated attribution, prediction and projection; and (iii) assessment of current and future hazards. Also discussed are the benefits that the new capability will deliver. These include improved capabilities for early warning of impactful changes in the Earth system, more reliable assessments of meteorological hazard risks, and quantitative attribution statements to support the Global Annual to Decadal Climate Update and State of the Climate reports issued by the World Meteorological Organization.

Attribution of multi-annual to decadal changes in the climate system: The Large Ensemble Single Forcing Model Intercomparison Project (LESFMIP)

Frontiers in Climate Frontiers Media 4 (2022) 955414

Authors:

Doug Smith, Nathan Gillett, Isla Simpson, Panos Athanasiadis, Johanna Baehr, Ingo Bethke, Tarkan Bilge, Olivier Boucher, Kirsten Findell, Guillaume Gastineau, Silvio Gauldi, Leon Hermanson, Juliette Mignot, Wolfgang Mueller, Scott Osprey, Odd Helge Ottera, Geeta Persad, Adam Scaife, Gavin Schmidt, Hideo Shiogama, Rowan Sutton, Didier Swingedouw, Shuting Yang, Tianjun Zhou, Tilo Ziehn

Abstract:

Multi-annual to decadal changes in climate are accompanied by changes in extreme events that cause major impacts on society and severe challenges for adaptation. Early warnings of such changes are now potentially possible through operational decadal predictions. However, improved understanding of the causes of regional changes in climate on these timescales is needed both to attribute recent events and to gain further confidence in forecasts. Here we document the Large Ensemble Single Forcing Model Intercomparison Project that will address this need through coordinated model experiments enabling the impacts of different external drivers to be isolated. We highlight the need to account for model errors and propose an attribution approach that exploits differences between models to diagnose the real-world situation and overcomes potential errors in atmospheric circulation changes. The experiments and analysis proposed here will provide substantial improvements to our ability to understand near-term changes in climate and will support the World Climate Research Program Lighthouse Activity on Explaining and Predicting Earth System Change.

K2 and Spitzer phase curves of the rocky ultra-short-period planet K2-141 b hint at a tenuous rock vapor atmosphere

Astronomy and Astrophysics EDP Sciences 664 (2022) A79

Authors:

S Zieba, M Zilinskas, L Kreidberg, Tg Nguyen, Y Miguel, Nb Cowan, R Pierrehumbert, L Carone, L Dang, M Hammond, T Louden, R Lupu, L Malavolta, Kb Stevenson

Abstract:

K2-141 b is a transiting, small (1.5 R⊕) ultra-short-period (USP) planet discovered by the Kepler space telescope orbiting a K-dwarf host star every 6.7 h. The planet's high surface temperature of more than 2000 K makes it an excellent target for thermal emission observations. Here we present 65 h of continuous photometric observations of K2-141 b collected with Spitzer's Infrared Array Camera (IRAC) Channel 2 at 4.5 μm spanning ten full orbits of the planet. We measured an infrared eclipse depth of ppm and a peak to trough amplitude variation of ppm. The best fit model to the Spitzer data shows no significant thermal hotspot offset, in contrast to the previously observed offset for the well-studied USP planet 55 Cnc e. We also jointly analyzed the new Spitzer observations with the photometry collected by Kepler during two separate K2 campaigns. We modeled the planetary emission with a range of toy models that include a reflective and a thermal contribution. With a two-temperature model, we measured a dayside temperature of Tp,d = 2049 362-359 K and a night-side temperature that is consistent with zero (Tp,n < 1712 K at 2σ). Models with a steep dayside temperature gradient provide a better fit to the data than a uniform dayside temperature (ΔBIC = 22.2). We also found evidence for a nonzero geometric albedo Ag = 0.2820.070-0.078. We also compared the data to a physically motivated, pseudo-2D rock vapor model and a 1D turbulent boundary layer model. Both models fit the data well. Notably, we found that the optical eclipse depth can be explained by thermal emission from a hot inversion layer, rather than reflected light. A thermal inversion may also be responsible for the deep optical eclipse observed for another USP, Kepler-10 b. Finally, we significantly improved the ephemerides for K2-141 b and c, which will facilitate further follow-up observations of this interesting system with state-of-the-art observatories such as James Webb Space Telescope.