Judith Perlwitz

Cooperative Institute for Research in Environmental Sciences

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Martin P. Hoerling

University of Colorado Boulder

Jon Eischeid

University of Colorado Boulder

Xiao‐Wei Quan

Cooperative Institute for Research in Environmental Sciences

Andrew Hoell

NOAA Physical Sciences Laboratory

Steven Pawson

Goddard Space Flight Center

Tiffany A. Shaw

University of Chicago

Tao Zhang

University of Electronic Science and Technology of China

Amy H. Butler

NOAA Chemical Sciences Laboratory

David Rind

Goddard Institute for Space Studies

Donald Murray

Cooperative Institute for Research in Environmental Sciences

Cooperative Institutions

National Oceanic and Atmospheric Administration

Columbia University

NSF National Center for Atmospheric Research

University of Colorado Boulder

Cooperative Institute for Research in Environmental Sciences

Goddard Institute for Space Studies

NOAA Earth System Research Laboratory

Goddard Space Flight Center

NOAA Physical Sciences Laboratory

Max Planck Institute for Meteorology

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Effects of Greenhouse Gas Increase and Stratospheric Ozone Depletion on Stratospheric Mean Age of Air in 1960-2010

AGU Fall Meeting Abstracts (2017)

F. Li Paul A. Newman Steven Pawson Judith Perlwitz

The relative impacts of greenhouse gas (GHG) increase and stratospheric ozone depletion on stratospheric mean age of air in the 1960-2010 period are quantified using the Goddard Earth Observing System Chemistry-Climate Model. The experiment compares controlled simulations using a coupled atmosphere-ocean version of the Goddard Earth Observing System Chemistry-Climate Model, in which either GHGs or ozone depleting substances, or both factors evolve over time. The model results show that GHGs and ozone-depleting substances have about equal contributions to the simulated mean age decrease, but GHG increases account for about two thirds of the enhanced strength of the lower stratospheric residual circulation. It is also found that both the acceleration of the diabatic circulation and the decrease of the mean age difference between downwelling and upwelling regions are mainly caused by GHG forcing. The results show that ozone depletion causes an increase in the mean age of air in the Antarctic summer lower stratosphere through two processes: (1) a seasonal delay in the Antarctic polar vortex breakup that inhibits young midlatitude air from mixing with the older air inside the vortex, and (2) enhanced Antarctic downwelling that brings older air from middle and upper stratosphere into the lower stratosphere.

Downwelling

Ozone Depletion

Sudden stratospheric warming

Middle latitudes

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On the Time of Emergence of Tropical Width Change

Journal of Climate (2018)

Xiao‐Wei Quan Martin P. Hoerling Judith Perlwitz Henry F. Díaz

Abstract The tropical belt is expected to expand in response to global warming, although most of the observed tropical widening since 1980, especially in the Northern Hemisphere, is believed to have mainly originated from natural variability. The view is of a small global warming signal relative to natural variability. Here we focus on the question whether and, if so when, the anthropogenic signal of tropical widening will become detectable. Analysis of two large ensemble climate simulations reveals that the forced signal of tropical width is strongly constrained by the forced signal of global mean temperature. Under a representative concentration pathway 8.5 (RCP8.5) emissions scenario, the aggregate of the two models indicates a regression of about 0.5° lat °C −1 during 1980–2080. The models also reveal that interannual variability in tropical width, a measure of noise used herein, is insensitive to global warming. Reanalysis data are therefore used to constrain the interannual variability, whose magnitude is estimated to be 1.1° latitude. Defining the time of emergence (ToE) for tropical width change as the first year (post-1980) when the forced signal exceeds the magnitude of interannual variability, the multimodel simulations of CMIP5 are used to estimate ToE and its confidence interval. The aforementioned strong constraint between the signal of tropical width change and global mean temperature change motivates using CMIP5-simulated global mean temperature changes to infer ToE. Our best estimate for the probable year for ToE, under an RCP8.5 emissions scenario, is 2058 with 10th–90th percentile confidence of 2047–68. Various sources of uncertainty in estimating the ToE are discussed.

Global temperature

Representative Concentration Pathways

10.1175/jcli-d-18-0068.1

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Identifying human influences on atmospheric temperature

Proceedings of the National Academy of Sciences (2012)

Benjamin D. Santer Jeffrey F. Painter C. A. Mears Charles Doutriaux Peter Caldwell

We perform a multimodel detection and attribution study with climate model simulation output and satellite-based measurements of tropospheric and stratospheric temperature change. We use simulation output from 20 climate models participating in phase 5 of the Coupled Model Intercomparison Project. This multimodel archive provides estimates of the signal pattern in response to combined anthropogenic and natural external forcing (the fingerprint) and the noise of internally generated variability. Using these estimates, we calculate signal-to-noise (S/N) ratios to quantify the strength of the fingerprint in the observations relative to fingerprint strength in natural climate noise. For changes in lower stratospheric temperature between 1979 and 2011, S/N ratios vary from 26 to 36, depending on the choice of observational dataset. In the lower troposphere, the fingerprint strength in observations is smaller, but S/N ratios are still significant at the 1% level or better, and range from three to eight. We find no evidence that these ratios are spuriously inflated by model variability errors. After removing all global mean signals, model fingerprints remain identifiable in 70% of the tests involving tropospheric temperature changes. Despite such agreement in the large-scale features of model and observed geographical patterns of atmospheric temperature change, most models do not replicate the size of the observed changes. On average, the models analyzed underestimate the observed cooling of the lower stratosphere and overestimate the warming of the troposphere. Although the precise causes of such differences are unclear, model biases in lower stratospheric temperature trends are likely to be reduced by more realistic treatment of stratospheric ozone depletion and volcanic aerosol forcing.

Replicate

Forcing (mathematics)

10.1073/pnas.1210514109

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Citations (133)

Earth's Energy Imbalance: Confirmation and Implications

Science (2005)

James E. Hansen Larissa Nazarenko Reto Rüedy Makiko Sato J. K. Willis

Our climate model, driven mainly by increasing human-made greenhouse gases and aerosols, among other forcings, calculates that Earth is now absorbing 0.85 +/- 0.15 watts per square meter more energy from the Sun than it is emitting to space. This imbalance is confirmed by precise measurements of increasing ocean heat content over the past 10 years. Implications include (i) the expectation of additional global warming of about 0.6 degrees C without further change of atmospheric composition; (ii) the confirmation of the climate system's lag in responding to forcings, implying the need for anticipatory actions to avoid any specified level of climate change; and (iii) the likelihood of acceleration of ice sheet disintegration and sea level rise.

Climate commitment

Greenhouse effect

10.1126/science.1110252

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Citations (883)

The Making of an Extreme Event: Putting the Pieces Together

Bulletin of the American Meteorological Society (2013)

Randall M. Dole Martin P. Hoerling Arun Kumar Jon Eischeid Judith Perlwitz

We examine how physical factors spanning climate and weather contributed to record warmth over the central and eastern United States in March 2012, when daily temperature anomalies at many locations exceeded 20°C. Over this region, approximately 1°C warming in March temperatures has occurred since 1901. This long-term regional warming is an order of magnitude smaller than temperature anomalies observed during the event, indicating that most of the extreme warmth must be explained by other factors. Several lines of evidence strongly implicate natural variations as the primary cause for the extreme event. The 2012 temperature anomalies had a close analog in an exceptionally warm U.S. March occurring over 100 years earlier, providing observational evidence that an extreme event similar to March 2012 could be produced through natural variability alone. Coupled model forecasts and simulations forced by observed sea surface temperatures (SSTs) show that forcing from anomalous SSTs increased the probability of extreme warm temperatures in March 2012 above that anticipated from the long-term warming trend. In addition, forcing associated with a strong Madden–Julian oscillation further increased the probability for extreme U.S. warmth and provided important additional predictive information on the timing and spatial pattern of temperature anomalies. The results indicate that the superposition of a strong natural variation similar to March 1910 on longterm warming of the magnitude observed would be sufficient to account for the record warm March 2012 U.S. temperatures. We conclude that the extreme warmth over the central and eastern United States in March 2012 resulted primarily from natural climate and weather variability— a substantial fraction of which was predictable.

Forcing (mathematics)

10.1175/bams-d-12-00069.1

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What caused the recent “Warm Arctic, Cold Continents” trend pattern in winter temperatures?

Geophysical Research Letters (2016)

Lantao Sun Judith Perlwitz Martin P. Hoerling

Abstract The emergence of rapid Arctic warming in recent decades has coincided with unusually cold winters over Northern Hemisphere continents. It has been speculated that this “Warm Arctic, Cold Continents” trend pattern is due to sea ice loss. Here we use multiple models to examine whether such a pattern is indeed forced by sea ice loss specifically and by anthropogenic forcing in general. While we show much of Arctic amplification in surface warming to result from sea ice loss, we find that neither sea ice loss nor anthropogenic forcing overall yield trends toward colder continental temperatures. An alternate explanation of the cooling is that it represents a strong articulation of internal atmospheric variability, evidence for which is derived from model data, and physical considerations. Sea ice loss impact on weather variability over the high‐latitude continents is found, however, to be characterized by reduced daily temperature variability and fewer cold extremes.

Forcing (mathematics)

Arctic dipole anomaly

Arctic oscillation

10.1002/2016gl069024

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Citations (276)

A Flash of Insight: Learning Lessons from the 2017 Northern Great Plains Drought

Bulletin of the American Meteorological Society (2021)

Andrew Hoell Britt-Anne A. Parker Michael Downey Natalie Umphlett Kelsey Jencso

A familiar saying among agricultural producers of the U.S. northern Great Plains region comprising Montana, the Dakotas, and the adjacent Canadian Prairies is, "We're always in a drought.It just depends on how bad it is in a given year."2017 was a bad year.The 2017 northern Great Plains flash drought (a type of drought defined by its rapid onset or intensification) began in the spring, evolved rapidly through the summer, and became the most destructive drought in decades.The drought led to reduced agricultural production, wildfires, infrastructure damage, and financial, physical, and emotional hardship to those affected.Direct agricultural losses related to the drought exceeded $2.6 billion in the United States alone.This drought, and the devastation it caused motivated multiagency collaboration among academic, tribal, state, and federal partners to evaluate drought early warning systems, coordination efforts, communication, and management practices with the goal of improving resilience and accelerating the response to future droughts.

Flash flood

10.1175/bams-d-19-0272.a

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The Remarkably Strong Arctic Stratospheric Polar Vortex of Winter 2020: Links to Record‐Breaking Arctic Oscillation and Ozone Loss

Journal of Geophysical Research Atmospheres (2020)

Zachary D. Lawrence Judith Perlwitz Amy H. Butler G. L. Manney Paul A. Newman

Abstract The Northern Hemisphere (NH) polar winter stratosphere of 2019/2020 featured an exceptionally strong and cold stratospheric polar vortex. Wave activity from the troposphere during December–February was unusually low, which allowed the polar vortex to remain relatively undisturbed. Several transient wave pulses nonetheless served to help create a reflective configuration of the stratospheric circulation by disturbing the vortex in the upper stratosphere. Subsequently, multiple downward wave coupling events took place, which aided in dynamically cooling and strengthening the polar vortex. The persistent strength of the stratospheric polar vortex was accompanied by an unprecedentedly positive phase of the Arctic Oscillation in the troposphere during January–March, which was consistent with large portions of observed surface temperature and precipitation anomalies during the season. Similarly, conditions within the strong polar vortex were ripe for allowing substantial ozone loss: The undisturbed vortex was a strong transport barrier, and temperatures were low enough to form polar stratospheric clouds for over 4 months into late March. Total column ozone amounts in the NH polar cap decreased and were the lowest ever observed in the February–April period. The unique confluence of conditions and multiple broken records makes the 2019/2020 winter and early spring a particularly extreme example of two‐way coupling between the troposphere and stratosphere.

Sudden stratospheric warming

Arctic oscillation

Ozone Depletion

10.1029/2020jd033271

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Citations (248)

The Relative Importance of Solar and Anthropogenic Forcing of Climate Change between the Maunder Minimum and the Present

Journal of Climate (2004)

David Rind Drew Shindell Judith Perlwitz J. Lerner Patrick Lonergan

The climate during the Maunder Minimum is compared with current conditions in GCM simulations that include a full stratosphere and parameterized ozone response to solar spectral irradiance variability and trace gas changes. The Goddard Institute for Space Studies (GISS) Global Climate/Middle Atmosphere Model (GCMAM) coupled to a q-flux/mixed-layer model is used for the simulations, which begin in 1500 and extend to the present. Experiments were made to investigate the effect of total versus spectrally varying solar irradiance changes; spectrally varying solar irradiance changes on the stratospheric ozone/climate response with both preindustrial and present trace gases; and the impact on climate and stratospheric ozone of the preindustrial trace gases and aerosols by themselves. The results showed that 1) the Maunder Minimum cooling relative to today was primarily associated with reduced anthropogenic radiative forcing, although the solar reduction added 40% to the overall cooling. There is no obvious distinguishing surface climate pattern between the two forcings. 2) The global and tropical response was greater than 1°C, in a model with a sensitivity of 1.2°C (W m−2)−1. To reproduce recent low-end estimates would require a sensitivity one-fourth as large. 3) The global surface temperature change was similar when using the total and spectral irradiance prescriptions, although the tropical response was somewhat greater with the former, and the stratospheric response greater with the latter. 4) Most experiments produce a relative negative phase of the North Atlantic Oscillation/Arctic Oscillation (NAO/AO) during the Maunder Minimum, with both solar and anthropogenic forcing equally capable, associated with the tropical cooling and relative poleward Eliassen–Palm (EP) flux refraction. 5) A full stratosphere appeared to be necessary for the negative AO/NAO phase, as was the case with this model for global warming experiments, unless the cooling was very large, while the ozone response played a minor role and did not influence surface temperature significantly. 6) Stratospheric ozone was most affected by the difference between present-day and preindustrial atmospheric composition and chemistry, with increases in the upper and lower stratosphere during the Maunder Minimum. While the estimated UV reduction led to ozone decreases, this was generally less important than the anthropogenic effect except in the upper midstratosphere, as judged by two different ozone photochemistry schemes. 7) The effect of the reduced solar irradiance on stratospheric ozone and on climate was similar in Maunder Minimum and current atmospheric conditions.

Trace gas

Arctic oscillation

Forcing (mathematics)

10.1175/1520-0442(2004)017<0906:triosa>2.0.co;2

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Citations (104)

Contribution of sea ice loss to Arctic amplification

Geophysical Research Letters (2010)

Arun Kumar Judith Perlwitz Jon Eischeid Xiao‐Wei Quan Taiyi Xu

Atmospheric climate models are subjected to the observed sea ice conditions during 2007 to estimate the regionality, seasonality, and vertical pattern of temperature responses to recent Arctic sea ice loss. It is shown that anomalous sea ice conditions accounted for virtually all of the estimated Arctic amplification in surface ‐ based warming over the Arctic Ocean, and furthermore they accounted for a large fraction of Arctic amplification occurring over the high‐latitude land between 60°N and the Arctic Ocean. Sea ice loss did not appreciably contribute to observed 2007 land temperature warmth equatorward of 60°N. Likewise, the observed warming of the free atmosphere attributable to sea ice loss is confined to Arctic latitudes, and is vertically confined to the lowest 1000 m. The results further highlight a strong seasonality of the temperature response to the 2007 sea ice loss. A weak signal of Arctic amplification in surface based warming is found during boreal summer, whereas a dramatically stronger signal is shown to develop during early autumn that persisted through December even as sea ice coverage approached its climatological values in response to the polar night.

Arctic geoengineering

Arctic dipole anomaly

Ice-albedo feedback

Seasonality

10.1029/2010gl045022

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Citations (176)