Postmortem of the Global Warming Hiatus

A special issue of Climate (ISSN 2225-1154).

Deadline for manuscript submissions: closed (30 November 2018) | Viewed by 58138

Special Issue Editor


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Guest Editor
NCAR, 3090 Center Green Dr., Boulder, CO 80301, USA
Interests: climate variability; climate dynamics; global climate models; climate observations; decadal ocean variability; sea level change; Earth system modeling; water cycles; energy budget

Special Issue Information

Dear Colleagues,

The recent so-called “hiatus” in global warming drew considerable attention from the both the scientific community and general public, and several hundred peer-reviewed manuscripts were published to further our understanding of it. Here, a collection of various retrospective assessments of the event are presented that address its phenomenology, early indications and key insights regarding its origins and evolution, and the current state of our understanding given the challenges involved in monitoring transient variability in Earth’s climate. The collection illustrates the synergistic use of models and observations in understanding the evolving climate state and its implications for the future.

Dr. John T. Fasullo
Guest Editor

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Keywords

  • climate variability
  • climate dynamics
  • global climate models
  • climate observations
  • decadal ocean variability

Published Papers (5 papers)

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Research

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19 pages, 6919 KiB  
Article
Decadal Ocean Heat Redistribution Since the Late 1990s and Its Association with Key Climate Modes
by Lijing Cheng, Gongjie Wang, John P. Abraham and Gang Huang
Climate 2018, 6(4), 91; https://doi.org/10.3390/cli6040091 - 19 Nov 2018
Cited by 19 | Viewed by 9379
Abstract
Ocean heat content (OHC) is the major component of the earth’s energy imbalance. Its decadal scale variability has been heavily debated in the research interest of the so-called “surface warming slowdown” (SWS) that occurred during the 1998–2013 period. Here, we first clarify that [...] Read more.
Ocean heat content (OHC) is the major component of the earth’s energy imbalance. Its decadal scale variability has been heavily debated in the research interest of the so-called “surface warming slowdown” (SWS) that occurred during the 1998–2013 period. Here, we first clarify that OHC has accelerated since the late 1990s. This finding refutes the concept of a slowdown of the human-induced global warming. This study also addresses the question of how heat is redistributed within the global ocean and provides some explanation of the underlying physical phenomena. Previous efforts to answer this question end with contradictory conclusions; we show that the systematic errors in some OHC datasets are partly responsible for these contradictions. Using an improved OHC product, the three-dimensional OHC changes during the SWS period are depicted, related to a reference period of 1982–1997. Several “hot spots” and “cold spots” are identified, showing a significant decadal-scale redistribution of ocean heat, which is distinct from the long-term ocean-warming pattern. To provide clues for the potential drivers of the OHC changes during the SWS period, we examine the OHC changes related to the key climate modes by regressing the Pacific Decadal Oscillation (PDO), El Niño-Southern Oscillation (ENSO), and Atlantic Multi-decadal Oscillation (AMO) indices onto the de-trended gridded OHC anomalies. We find that no single mode can fully explain the OHC change patterns during the SWS period, suggesting that there is not a single “pacemaker” for the recent SWS. Our observation-based analyses provide a basis for further understanding the mechanisms of the decadal ocean heat uptake and evaluating the climate models. Full article
(This article belongs to the Special Issue Postmortem of the Global Warming Hiatus)
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18 pages, 1557 KiB  
Article
The Hiatus in Global Warming and Interactions between the El Niño and the Pacific Decadal Oscillation: Comparing Observations and Modeling Results
by Knut L. Seip and Hui Wang
Climate 2018, 6(3), 72; https://doi.org/10.3390/cli6030072 - 04 Sep 2018
Cited by 3 | Viewed by 10408
Abstract
Ocean oscillations interact across large regions and these interactions may explain cycles in global temperature anomaly, including hiatus periods. Here, we examine ocean interaction measures and compare results from model simulations to observations for El Niño and the Pacific decadal oscillation (PDO). We [...] Read more.
Ocean oscillations interact across large regions and these interactions may explain cycles in global temperature anomaly, including hiatus periods. Here, we examine ocean interaction measures and compare results from model simulations to observations for El Niño and the Pacific decadal oscillation (PDO). We use the global climate model of the Met Office Hadley Centre. A relatively novel method for identifying running leading-agging LL-relations show that the observed El Niño generally leads the observed PDO and this pattern is strengthened in the simulations. However, LL-pattern in both observations and models shows that there are three periods, around 1910–1920, around 1960 and around 2000 where El Niño lags PDO, or the leading signature is weak. These periods correspond to hiatus periods in global warming. The power spectral density analysis, (PSD), identifies various ocean cycle lengths in El Niño and PDO, but the LL-algorithm picks out common cycles of 7–8 and 24 years that shows leading-lagging relations between them. Full article
(This article belongs to the Special Issue Postmortem of the Global Warming Hiatus)
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14 pages, 779 KiB  
Article
The Life and Death of the Recent Global Surface Warming Hiatus Parsimoniously Explained
by Kristoffer Rypdal
Climate 2018, 6(3), 64; https://doi.org/10.3390/cli6030064 - 21 Jul 2018
Cited by 7 | Viewed by 5282
Abstract
The main features of the instrumental global mean surface temperature (GMST) are reasonably well described by a simple linear response model driven by anthropogenic, volcanic and solar forcing. This model acts as a linear long-memory filter of the forcing signal. The physical interpretation [...] Read more.
The main features of the instrumental global mean surface temperature (GMST) are reasonably well described by a simple linear response model driven by anthropogenic, volcanic and solar forcing. This model acts as a linear long-memory filter of the forcing signal. The physical interpretation of this filtering is the delayed response due to the thermal inertia of the ocean. This description is considerably more accurate if El Niño Southern Oscillation (ENSO) and the Atlantic Multidecadal Oscillation (AMO) are regarded as additional forcings of the global temperature and hence subject to the same filtering as the other forcing components. By considering these as predictors in a linear regression scheme, more than 92% of the variance in the instrumental GMST over the period 1870–2017 is explained by this model, in particular, all features of the 1998–2015 hiatus, including its death. While the more prominent pauses during 1870–1915 and 1940–1970 can be attributed to clustering in time of strong volcanic eruptions, the recent hiatus is an unremarkable phenomenon that is attributed to ENSO with a small contribution from solar activity. Full article
(This article belongs to the Special Issue Postmortem of the Global Warming Hiatus)
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18 pages, 5046 KiB  
Article
Changes in Earth’s Energy Budget during and after the “Pause” in Global Warming: An Observational Perspective
by Norman G. Loeb, Tyler J. Thorsen, Joel R. Norris, Hailan Wang and Wenying Su
Climate 2018, 6(3), 62; https://doi.org/10.3390/cli6030062 - 11 Jul 2018
Cited by 64 | Viewed by 24209
Abstract
This study examines changes in Earth’s energy budget during and after the global warming “pause” (or “hiatus”) using observations from the Clouds and the Earth’s Radiant Energy System. We find a marked 0.83 ± 0.41 Wm−2 reduction in global mean reflected shortwave [...] Read more.
This study examines changes in Earth’s energy budget during and after the global warming “pause” (or “hiatus”) using observations from the Clouds and the Earth’s Radiant Energy System. We find a marked 0.83 ± 0.41 Wm−2 reduction in global mean reflected shortwave (SW) top-of-atmosphere (TOA) flux during the three years following the hiatus that results in an increase in net energy into the climate system. A partial radiative perturbation analysis reveals that decreases in low cloud cover are the primary driver of the decrease in SW TOA flux. The regional distribution of the SW TOA flux changes associated with the decreases in low cloud cover closely matches that of sea-surface temperature warming, which shows a pattern typical of the positive phase of the Pacific Decadal Oscillation. Large reductions in clear-sky SW TOA flux are also found over much of the Pacific and Atlantic Oceans in the northern hemisphere. These are associated with a reduction in aerosol optical depth consistent with stricter pollution controls in China and North America. A simple energy budget framework is used to show that TOA radiation (particularly in the SW) likely played a dominant role in driving the marked increase in temperature tendency during the post-hiatus period. Full article
(This article belongs to the Special Issue Postmortem of the Global Warming Hiatus)
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Review

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19 pages, 4070 KiB  
Review
Understanding the Recent Global Surface Warming Slowdown: A Review
by Ka-Kit Tung and Xianyao Chen
Climate 2018, 6(4), 82; https://doi.org/10.3390/cli6040082 - 24 Oct 2018
Cited by 22 | Viewed by 7370
Abstract
The Intergovernmental Panel on Climate Change (IPCC) noted a recent 15-year period (1998–2012) when the rate of surface global warming was a factor of 4 smaller than the mean of the state-of-art climate model projections and than that observed in the previous three [...] Read more.
The Intergovernmental Panel on Climate Change (IPCC) noted a recent 15-year period (1998–2012) when the rate of surface global warming was a factor of 4 smaller than the mean of the state-of-art climate model projections and than that observed in the previous three decades. When updated to include 2014 by Karl et al. using the new version of NOAA data, the observed warming trend is higher, but is still half or less, depending on dataset used, that of previous decades and the multi-model mean projections. This period is called a surface warming slowdown. Intense community efforts devoted to understanding this puzzling phenomenon—puzzling because atmospheric greenhouse gas accumulation has not abated while surface warming slowed—have yielded insights on our climate system, and this may be an opportune time to take stock of what we have learned. Proposed explanations differ on whether it is forced by counteracting agents (such as volcanic and pollution aerosols and stratospheric water vapor) or is an internal variability, and if the latter, on which ocean basin is responsible (Pacific, Indian, or Atlantic Ocean). Here we critically review the observational records, their analyses and interpretations, and offer interpretations of model simulations, with emphasis on sorting through the rather confusing signals at the ocean’s surface, and reconciling them with the subsurface signals. Full article
(This article belongs to the Special Issue Postmortem of the Global Warming Hiatus)
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