Publications by Raymond Pierrehumbert

Ice-shelf damming in the glacial Arctic Ocean: dynamical regimes of a basin-covering kilometre-thick ice shelf

CRYOSPHERE 11 (2017) 1745-1765

J Nilsson, M Jakobsson, C Borstad, N Kirchner, G Bjork, RT Pierrehumbert, C Stranne

Observational evidence against strongly stabilizing tropical cloud feedbacks


IN Williams, RT Pierrehumbert

Linking the Climate and Thermal Phase Curve of 55 Cancri e

Astrophysical Journal 849 (2017)

M Hammond, RT Pierrehumbert

© 2017. The American Astronomical Society. All rights reserved. The thermal phase curve of 55 Cancri e is the first measurement of the temperature distribution of a tidally locked super-Earth, but raises a number of puzzling questions about the planet's climate. The phase curve has a high amplitude and peak offset, suggesting that it has a significant eastward hot-spot shift as well as a large day-night temperature contrast. We use a general circulation model to model potential climates, and investigate the relation between bulk atmospheric composition and the magnitude of these seemingly contradictory features. We confirm theoretical models of tidally locked circulation are consistent with our numerical model of 55 Cnc e, and rule out certain atmospheric compositions based on their thermodynamic properties. Our best-fitting atmosphere has a significant hot-spot shift and day-night contrast, although these are not as large as the observed phase curve. We discuss possible physical processes that could explain the observations, and show that night-side cloud formation from species such as SiO from a day-side magma ocean could potentially increase the phase curve amplitude and explain the observations. We conclude that the observations could be explained by an optically thick atmosphere with a low mean molecular weight, a surface pressure of several bars, and a strong eastward circulation, with night-side cloud formation a possible explanation for the difference between our model and the observations.

Reconstructing Climate from Glaciers

Annual Review of Earth and Planetary Sciences 45 (2017) 649-680

AN Mackintosh, BM Anderson, RT Pierrehumbert

Copyright © 2017 by Annual Reviews. All rights reserved. Glaciers offer the potential to reconstruct past climate over timescales from decades to millennia. They are found on nearly every continent, and at the Last Glacial Maximum, glaciers were larger in all regions on Earth. The physics of glacier-climate interaction are relatively well understood, and glacier models can be used to reconstruct past climate from geological evidence of past glacier extent. This can lead to significant insights regarding past, present, and future climate. For example, glacier modeling has demonstrated that the near-ubiquitous global pattern of glacier retreat during the last few centuries resulted from a global-scale climate warming of ∼1°C, consistent with instrumental data and climate proxy records. Climate reconstructions from glaciers have also demonstrated that the tropics were colder at the Last Glacial Maximum than was originally inferred from sea surface temperature reconstructions. Future efforts to reconstruct climate from glaciers may provide new constraints on climate sensitivity to CO2 forcing, polar amplification of climate change, and more.

Consequences of twenty-first-century policy for multi-millennial climate and sea-level change

NATURE CLIMATE CHANGE 6 (2016) 360-369

PU Clark, JD Shakun, SA Marcott, AC Mix, M Eby, S Kulp, A Levermann, GA Milne, PL Pfister, BD Santer, DP Schrag, S Solomon, TF Stocker, BH Strauss, AJ Weaver, R Winkelmann, D Archer, E Bard, A Goldner, K Lambeck, RT Pierrehumbert, G-K Plattner

How to decarbonize? Look to Sweden

Bulletin of the Atomic Scientists 72 (2016) 105-111

R Pierrehumbert



F Ding, RT Pierrehumbert

Dynamics of atmospheres with a non-dilute condensible component.

Proceedings. Mathematical, physical, and engineering sciences 472 (2016) 20160107-

RT Pierrehumbert, F Ding

The diversity of characteristics for the host of recently discovered exoplanets opens up a great deal of fertile new territory for geophysical fluid dynamics, particularly when the fluid flow is coupled to novel thermodynamics, radiative transfer or chemistry. In this paper, we survey one of these new areas-the climate dynamics of atmospheres with a non-dilute condensible component, defined as the situation in which a condensible component of the atmosphere makes up a substantial fraction of the atmospheric mass within some layer. Non-dilute dynamics can occur for a wide range of condensibles, generically applying near both the inner and the outer edges of the conventional habitable zone and in connection with runaway greenhouse phenomena. It also applies in a wide variety of other planetary circumstances. We first present a number of analytical results developing some key features of non-dilute atmospheres, and then show how some of these features are manifest in simulations with a general circulation model adapted to handle non-dilute atmospheres. We find that non-dilute atmospheres have weak horizontal temperature gradients even for rapidly rotating planets, and that their circulations are largely barotropic. The relative humidity of the condensible component tends towards 100% as the atmosphere becomes more non-dilute, which has important implications for runaway greenhouse thresholds. Non-dilute atmospheres exhibit a number of interesting organized convection features, for which there is not yet any adequate theoretical understanding.

New use of global warming potentials to compare cumulative and short-lived climate pollutants


MR Allen, JS Fuglestvedt, KP Shine, A Reisinger, RT Pierrehumbert, PM Forster

Comparison of "warm and wet" and "cold and icy" scenarios for early Mars in a 3-D climate model

Journal of Geophysical Research E: Planets (2015)

RD Wordsworth, RD Wordsworth, L Kerber, RT Pierrehumbert, F Forget, JW Head

©2015. American Geophysical Union. All Rights Reserved.. We use a 3-D general circulation model to compare the primitive Martian hydrological cycle in "warm and wet" and "cold and icy" scenarios. In the warm and wet scenario, an anomalously high solar flux or intense greenhouse warming artificially added to the climate model are required to maintain warm conditions and an ice-free northern ocean. Precipitation shows strong surface variations, with high rates around Hellas basin and west of Tharsis but low rates around Margaritifer Sinus (where the observed valley network drainage density is nonetheless high). In the cold and icy scenario, snow migration is a function of both obliquity and surface pressure, and limited episodic melting is possible through combinations of seasonal, volcanic, and impact forcing. At surface pressures above those required to avoid atmospheric collapse (∼0.5bar) and moderate to high obliquity, snow is transported to the equatorial highland regions where the concentration of valley networks is highest. Snow accumulation in the Aeolis quadrangle is high, indicating an ice-free northern ocean is not required to supply water to Gale crater. At lower surface pressures and obliquities, both H<inf>2</inf>O and CO<inf>2</inf> are trapped as ice at the poles and the equatorial regions become extremely dry. The valley network distribution is positively correlated with snow accumulation produced by the cold and icy simulation at 41.8<sup>{ring operator}</sup> obliquity but uncorrelated with precipitation produced by the warm and wet simulation. Because our simulations make specific predictions for precipitation patterns under different climate scenarios, they motivate future targeted geological studies.

Feedback temperature dependence determines the risk of high warming

Geophysical Research Letters (2015)

J Bloch-Johnson, RT Pierrehumbert, DS Abbot

©2015. American Geophysical Union. The long-term warming from an anthropogenic increase in atmospheric CO<inf>2</inf> is often assumed to be proportional to the forcing associated with that increase. This paper examines this linear approximation using a zero-dimensional energy balance model with a temperature-dependent feedback, with parameter values drawn from physical arguments and general circulation models. For a positive feedback temperature dependence, warming increases Earth's sensitivity, while greater sensitivity makes Earth warm more. These effects can feed on each other, greatly amplifying warming. As a result, for reasonable values of feedback temperature dependence and preindustrial feedback, Earth can jump to a warmer state under only one or two CO<inf>2</inf> doublings. The linear approximation breaks down in the long tail of high climate sensitivity commonly seen in observational studies. Understanding feedback temperature dependence is therefore essential for inferring the risk of high warming from modern observations. Studies that assume linearity likely underestimate the risk of high warming.

Climate Intervention: Reflecting Sunlight to Cool Earth

National Academies Press, 2015

Committee on Geoengineering Climate, RT Pierrehumbert

Weather modification, which could also be called “weather intervention,” is the intentional alteration of the composition, behavior, or dynamics of the atmosphere occurring over a specified area and time period to accomplish a particular goal&nbsp;...

Climate Intervention Carbon Dioxide Removal and Reliable Sequestration

National Academies Press, 2015

Committee on Geoengineering Climate, RT Pierrehumbert

Carbon Dioxide Removal and Reliable Sequestration Committee on Geoengineering Climate: Technical Evaluation and Discussion of Impacts, Board on Atmospheric Sciences and Climate, Ocean Studies Board, Division on Earth and Life&nbsp;...

Climate impact of beef: an analysis considering multiple time scales and production methods without use of global warming potentials


RT Pierrehumbert, G Eshel

Constraints on southern hemisphere tropical climate change during the Little Ice Age and Younger Dryas based on glacier modeling of the Quelccaya Ice Cap, Peru


AGO Malone, RT Pierrehumbert, TV Lowell, MA Kelly, JS Stroup

A simple carbon cycle representation for economic and policy analyses

Climatic Change 126 (2014) 319-335

MJ Glotter, RT Pierrehumbert, JW Elliott, NJ Matteson, EJ Moyer

© 2014, Springer Science+Business Media Dordrecht. Integrated Assessment Models (IAMs) that couple the climate system and the economy require a representation of ocean CO 2 uptake to translate human-produced emissions to atmospheric concentrations and in turn to climate change. The simple linear carbon cycle representations in most IAMs are not however physical at long timescales, since ocean carbonate chemistry makes CO 2 uptake highly nonlinear. No linearized representation can capture the ocean’s dual-mode behavior, with initial rapid uptake and then slow equilibration over ∽10,000 years. In a business-as-usual scenario followed by cessation of emissions, the carbon cycle in the 2007 version of the most widely used IAM, DICE (Dynamic Integrated model of Climate and the Economy), produces errors of ∽2 ∘ C by the year 2300 and ∽6 ∘ C by the year 3500. We suggest here a simple alternative representation that captures the relevant physics and show that it reproduces carbon uptake in several more complex models to within the inter-model spread. The scheme involves little additional complexity over the DICE model, making it a useful tool for economic and policy analyses.

Short-lived climate pollution

Annual Review of Earth and Planetary Sciences 42 (2014) 341-379

RT Pierrehumbert

Although carbon dioxide emissions are by far the most important mediator of anthropogenic climate disruption, a number of shorter-lived substances with atmospheric lifetimes of under a few decades also contribute significantly to the radiative forcing that drives climate change. In recent years, the argument that early and aggressive mitigation of the emission of these substances or their precursors forms an essential part of any climate protection strategy has gained a considerable following. There is often an implication that such control can in some way make up for the current inaction on carbon dioxide emissions. The prime targets for mitigation, known collectively as short-lived climate pollution (SLCP), are methane, hydrofluo-rocarbons, black carbon, and ozone. A re-examination of the issues shows that the benefits of early SLCP mitigation have been greatly exaggerated, largely because of inadequacies in the methodologies used to compare the climate effects of short-lived substances with those of CO2, which causes nearly irreversible climate change persisting millennia after emissions cease. Eventual mitigation of SLCP can make a useful contribution to climate protection, but there is little to be gained by implementing SLCP mitigation before stringent carbon dioxide controls are in place and have caused annual emissions to approach zero. Any earlier implementation of SLCP mitigation that substitutes to any significant extent for carbon dioxide mitigation will lead to a climate irreversibly warmer than will a strategy with delayed SLCP mitigation. SLCP mitigation does not buy time for implementation of stringent controls on CO2 emissions. © 2014 by Annual Reviews. All rights reserved.

Water loss from terrestrial planets with CO<inf>2</inf>-rich atmospheres

Astrophysical Journal 778 (2013)

RD Wordsworth, RT Pierrehumbert

Water photolysis and hydrogen loss from the upper atmospheres of terrestrial planets is of fundamental importance to climate evolution but remains poorly understood in general. Here we present a range of calculations we performed to study the dependence of water loss rates from terrestrial planets on a range of atmospheric and external parameters. We show that CO 2 can only cause significant water loss by increasing surface temperatures over a narrow range of conditions, with cooling of the middle and upper atmosphere acting as a bottleneck on escape in other circumstances. Around G-stars, efficient loss only occurs on planets with intermediate CO 2 atmospheric partial pressures (0.1-1 bar) that receive a net flux close to the critical runaway greenhouse limit. Because G-star total luminosity increases with time but X-ray and ultraviolet/ultravoilet luminosity decreases, this places strong limits on water loss for planets like Earth. In contrast, for a CO 2 -rich early Venus, diffusion limits on water loss are only important if clouds caused strong cooling, implying that scenarios where the planet never had surface liquid water are indeed plausible. Around M-stars, water loss is primarily a function of orbital distance, with planets that absorb less flux than ∼270 W m -2 (global mean) unlikely to lose more than one Earth ocean of H 2 O over their lifetimes unless they lose all their atmospheric N 2 /CO 2 early on. Because of the variability of H 2 O delivery during accretion, our results suggest that many "Earth-like" exoplanets in the habitable zone may have ocean-covered surfaces, stable CO 2 /H 2 O-rich atmospheres, and high mean surface temperatures. © 2013. The American Astronomical Society. All rights reserved..

Hot climates, high sensitivity.

Proceedings of the National Academy of Sciences of the United States of America 110 (2013) 14118-14119

RT Pierrehumbert

Cumulative Carbon and Just Allocation of the Global Carbon Commons

Chicago Journal of International Law 13 (2013) 12

RT Pierrehumbert