Warming Hiatus Research Articles

Dating hiatuses: a statistical model of the recent slowdown in global warming and the next one

Abstract. Much has been written about the so-called hiatus or pause in global warming, also known as the stasis period, the start of which is typically dated to 1998. HadCRUT4 global mean temperatures slightly decreased over the 1998–2013 period, although a simple statistical model predicts that they should have grown by 0.016 ∘C/yr, in proportion to the increases in the concentrations of well-mixed greenhouse gases (WMGHGs) and ozone. We employ a statistical approach to assess the contributions of model forcings and natural variability to the hiatus. Our point estimates suggest that none of the model forcings explain more than one-third of the missing heat, accounting for the upper bound of the confidence interval on the effect of tropospheric aerosols, which is the most prominent yet most uncertainly measured of the model forcings that could explain the missing heat. The El Niño–Southern Oscillation (ENSO) explains up to about one-third of the missing heat, and two-thirds and possibly up to 81 % is explained by the unusually high temperature of 1998. Looking forward, the simple model also fails to explain the large increases since then (0.087 ∘C/yr from 2013 to 2016). This period coincides with another El Niño, but the ENSO fails to satisfactorily account for the increase. Instead, we propose a semiparametric cointegrating statistical model that augments an energy balance model with a novel multi-basin measure of the oceans' multidecadal temperature cycles. The model partially explains the recent slowdown and explains all of the subsequent warming. The natural cycle suggests the possibility – depending in part on the rate of increase of WMGHG concentrations – of a much longer hiatus over the period from roughly 2023 to 2061, with potentially important implications for policy evaluation.

The 2000-2012 global warming hiatus more likely with a low climate sensitivity

The 2000-2012 global warming hiatus more likely with a low climate sensitivity

The 2000-2012 global warming hiatus more likely with a low climate sensitivity

The 2000-2012 global warming hiatus more likely with a low climate sensitivity

The 2000-2012 global warming hiatus more likely with a low climate sensitivity

The 2000-2012 global warming hiatus more likely with a low climate sensitivity

The 2000-2012 global warming hiatus more likely with a low climate sensitivity

The 2000-2012 global warming hiatus more likely with a low climate sensitivity

Late 20th Century Indian Ocean Heat Content Gain Masked by Wind Forcing

AbstractRapid increases in upper 700‐m Indian Ocean heat content (IOHC) since the 2000s have focused attention on its role during the recent global surface warming hiatus. Here, we use ocean model simulations to assess distinct multidecadal IOHC variations since the 1960s and explore the relative contributions from wind stress and buoyancy forcing regionally and with depth. Multidecadal wind forcing counteracted IOHC increases due to buoyancy forcing from the 1960s to the 1990s. Wind and buoyancy forcing contribute positively since the mid‐2000s, accounting for the drastic IOHC change. Distinct timing and structure of upper ocean temperature changes in the eastern and western Indian Ocean are linked to the pathway how multidecadal wind forcing associated with the Interdecadal Pacific Oscillation is transmitted and affects IOHC through local and remote winds. Progressive shoaling of the equatorial thermocline—of importance for low‐frequency variations in Indian Ocean Dipole occurrence—appears to be dominated by multidecadal variations in wind forcing.

Soil respiration spatial and temporal variability in China between 1961 and 2014

AbstractSoil respiration (Rs) plays an important role in terrestrial–atmospheric carbon exchange but remains one of the least studied components of the carbon cycle. How environmental changes influence Rs, and in turn, how Rs influences terrestrial carbon storage in China is unclear. Here, we estimated spatial patterns and temporal trends in Rs from 1961 to 2014 to determine the influence of the recent warming hiatus on the Rs temporal variability in China. We evaluated the relationship between Rs and a set of environmental factors and developed biome‐specific Rs models that were parameterized based on 2,862 Rs records and 18 continuous variables (e.g., air temperature, precipitation and leaf area index). Based on the biome‐specific Rs models and environmental information, we estimated the annual Rs as well as the change trend of Rs in China during the study period. The mean annual Rs from 1961 to 2014 was 3.50 (confidence interval ± 0.87) Pg·C·year−1. Rs in China increased at a rate of 0.008 Pg·C·year−2 between 1982 and 1998 (warming period), but was static between 1999 and 2014 (warming hiatus). This reduction in Rs increase rate may have an important role in enhancing terrestrial carbon sequestration. These findings confirm that temporal heterogeneity in Rs could be influenced by regional environmental changes, and further help in improving the understanding of soil carbon dynamics in China.Highlights No study in China has integrated multiple biotic and abiotic factors and analysed how soil respiration correlates with different factors across biomes. In this study, biome‐specific models, including biotic and abiotic factors, were developed to estimate soil respiration in China. Annual soil respiration in China was estimated to be 3.50 (confidence interval ± 0.87) Pg·C·year‐1. Annual soil respiration in China had greater deceleration compared to the global deceleration between 1999 and 2014.

Changes in extended boreal summer tropical cyclogenesis associated with large-scale flow patterns over the western North Pacific in response to the global warming hiatus

This study examines extended boreal summer (May–October) tropical cyclogenesis events (TCGEs) associated with large-scale flow patterns (LFPs) over the western North Pacific (WNP) between 1979–1997 and 1998–2012. WNP TCGEs are objectively identified to be associated with five LFPs [e.g., monsoon shear line (SL), monsoon confluence region (CR), monsoon gyre (GY), Pacific easterly wave (EW) and preexisting tropical cyclone (PTC)]. Results show that an apparent decrease in TCGEs from 1998–2012 was due to the significant decrease in TCGEs associated with the PTC pattern and to a somewhat lesser degree, TCGEs associated with the GY pattern. In contrast, TCGEs associated with the SL pattern show a small increase, which seems to contradict the weakened monsoon circulation since 1998 but corresponds well to cyclonic anomalies over the Philippines region. Decreased TCGEs associated with the GY pattern and increased TCGEs associated with the EW pattern are closely related to the strengthening of Pacific easterly waves in response to the Mega La Nina-like pattern that predominated during 1998–2012. Weakened easterly shear over the eastern WNP is not conducive to the development and propagation into the southeastern WNP of Rossby wave trains induced by preexisting TC energy dispersion. Consequently, there is a significant reduction of TCGEs associated with the PTC pattern and a weakening in the contribution of TCGEs associated with the PTC pattern to TCGEs associated with the EW pattern. An increased correlation between TCs associated with the SL/GY/EW patterns and central Pacific (CP)-type ENSO during 1998–2012 is observed. A stable and robust association between TCGEs associated with the CR pattern and tropical North Atlantic sea surface temperature is observed regardless of decadal climate regime shifts. However, there is no significant link between TCGEs associated with the PTC pattern and more CP ENSO events during 1998–2012, but there is a strong association between the Pacific meridional mode and TCGEs associated with the PTC pattern during 1979–1997. More observational analyses and numerical simulations are needed to further investigate the underlying physical mechanism.

Temporal variability of seasonal warming rates in China

AbstractCalculation of the warming rate is the key to addressing the current debate about the existence of a recent hiatus in global warming. Previous studies have calculated the warming rate based on either a long period or selected periods. We calculated the warming rate in the seasonal temperatures obtained from 2,479 weather stations across China. We identified all the trend change years and divided the period 1958–2017 into different sub‐periods based on these years. Our results showed that the warming rate is higher than 0.5°C per decade in numerous stations. The amount of seasonal warming over the past 60 years was highest in winter, followed by spring, then autumn and was lowest in summer. Northern China has shown stronger warming than southern China over the past 60 years. Our results quantified the short‐period rates and identified natural change points which allows a sound comparison across regions. As rapid warming has a strong influence on natural systems and human health, extra care should be taken in regions with a high rate of warming.

Status of glaciers and climate change of East Karakoram in early twenty-first century

This study aims to assess the glaciers change status in Shyok basin, East Karakoram in terms of area and mass balance, and to ascertain if glaciers in this part of Karakoram also display similar anomaly like central or western counterparts. The spatio-temporal monitoring of glaciers during the time frame of 24 years (1990/2000/2014) suggests major percentage of stable glaciers and insignificant retreat in the total glaciated area. The percentage of retreating glaciers has increased after year 2000. Area change analysis of glaciers having size >1 km2 (569 glaciers) suggests the number of fluctuated glaciers have substantially increased i.e. overall 56% glaciers remained stable, 35% retreated and 9% advanced during 1990–2014. The geodetic based findings using SRTM-C (2000) and Cartosat-1 (2010/2011/2014) stereo-imageries for 201 glaciers suggest the mass loss at the rate of −0.10 ± 0.07 m w.e. a−1. To better apprehend the status of glaciers changes in the region, climatic studies using in-situ observations as well as reanalysis dataset (ERA-I) were also undertaken of past 30 years. Therefore, this study is also a maiden attempt to ascertain if along with Karakoram anomaly, a climatic anomaly exists in the Eastern parts of Karakoram or not. A long term field collected snow-meteorological data of East Karakoram region suggests overall warming trend in annual temperature and no trend for snowfall during 1985–2015. The statistically significant increased rates of warming and decreased snowfall after year 2000 support the spatial variations in glaciers of East Karakoram and marginal mass loss. The observations of the marginal mass loss along with warming temperatures indicate that no Karakoram or climatic anomaly is existent over the East Karakoram region. Our study further refutes the prevalence of the elevation-dependent warming (EDW) over East Karakoram region vis-à-vis North-West Himalayan ranges. The impact of hiatus in global warming was also not observed over studied region.

Nonstationary El Ni\xf1o teleconnection on the post-summer upwelling off Vietnam

Summer upwelling has often been observed off Vietnam in the South China Sea (SCS). Occasional disappearance of the upwelling has attracted much attention because it modulates the regional climate and harms surrounding fisheries. Fluctuations of the East Asian monsoon associated with El Niño are considered responsible for the weakened or abolished upwelling. However, analyses of observations performed in the present study were equivocal in terms of the dominant influence of El Niño. Based on long-term sea surface temperature data, we demonstrated that weak upwelling off Vietnam occurs more frequently during periods of accelerated global warming compared to warming hiatus periods. Warming signals in the Indian Ocean vanished relatively quickly during the hiatus period. The accompanying easterly anomalies south of the anomalous anticyclone (AAC) in the northwestern Pacific were also weakened, reducing the impact of the El Niño teleconnection on the SCS summer monsoon and thus preserving the regular post-summer upwelling off Vietnam during warming hiatus periods.

Spatio-Temporal Variation of Drought within the Vegetation Growing Season in North Hemisphere (1982–2015)

Drought disasters jeopardize the production of vegetation and are expected to exert impacts on human well-being in the context of global climate change. However, spatiotemporal variations in drought characteristics (including the drought duration, intensity, and frequency), specifically for vegetation areas within a growing season, remain largely unknown. Here, we first constructed a normalized difference vegetation index to estimate the length of the growing season for each pixel (8 km) by four widely used phenology estimation methods; second, we analyzed the temporal and spatial patterns of climate factors and drought characteristics (in terms of the Standardized Precipitation Evapotranspiration Index (SPEI)), within a growing season over vegetation areas of the northern hemisphere before and after the critical time point of 1998, which was marked by the onset of a global warming hiatus. Finally, we extracted the highly drought-vulnerable areas of vegetation by examining the sensitivity of the gross primary production to the SPEI to explore the underlying effects of drought variation on vegetation. The results revealed, first, that significant (p < 0.05) increases in precipitation, temperature, and the SPEI (a wetting trend) occurred from 1982 to 2015. The growing season temperature increased even more statistically significant after 1998 than before. Second, the duration and frequency of droughts changed abruptly and decreased considerably from 1998 to 2015; and this wetting trend was located mainly in high-latitude areas. Third, at the biome level, the wetting areas occurred mainly in the tundra, boreal forest or taiga, and temperate coniferous forest biomes, whereas the highly drought-vulnerable areas were mainly located in the desert and xeric shrubland (43.5%) biomes. Our results highlight the fact that although the drought events within a growing season decreased significantly in the northern hemisphere from 1998 to 2015, the very existence of a mismatch between a reduction in drought areas and an increase in highly drought-vulnerable areas makes the impact of drought on vegetation nonnegligible. This work provides valuable information for designing coping measures to reduce the vegetative drought risk in the Northern Hemisphere.

Central Asian river streamflows have not continued to increase during the recent warming hiatus

The recent warming hiatus started around 1998; however, how Central Asian river streamflows have responded to this warming slowdown remains unclear. Based on the instrumental streamflow records of eight rivers in Central Asian, we showed that the Central Asian streamflow variation is due to the change in precipitation/drought resulting from sea surface temperature changes in the eastern tropical Pacific Ocean and that equatorial eastern Pacific surface cooling has been the main driver of the slowdown in streamflow increase in Central Asia over the past two decades. Temperature is also likely an important driver of streamflow variation on the Pamirs Plateau during the warm season; however, the linkage between temperature and streamflow is not stable due in part to the precipitation-induced cooling. Central Asian river streamflow is very sensitive to variations in climate factors, and the influences of climate change on streamflow should be considered continuously by water resource managers.

Responses of abrupt temperature changes/warming hiatuses to changes in their influencing factors: A case study of northern China

AbstractDetermining the response of abrupt temperature changes/warming hiatuses to changes in their influencing factors can provide a reference for investigating their mechanism. The present study, using the Mann–Kendall test, based on data (including average minimum temperature (Tmin), average temperature (Tave) and average maximum temperature (Tmax)) recorded at 357 meteorological stations in northern China and its surrounding regions as well as large‐spatial‐scale data (e.g. Atlantic multidecadal oscillation (AMO), global radiative forcing of CO2 (RFCO2) and radiative forcing of annual greenhouse gases (RFAGG)) for the period 1951–2016, the characteristics of abrupt temperature changes/warming hiatuses and their response to their influencing factors were qualitatively and quantitatively determined. The following results were obtained. Overall, from the late 1970s to the 1990s, as the RFAGG continuously increased, the Pacific decadal oscillation (PDO) remained in a positive phase, the AMO and total solar radiation (SR) continuously increased, the multivariate El Niño southern oscillation (ENSO) index (MEI) changed abruptly, the wind speed (WS), atmospheric pressure (AP) and relative humidity (RH) in each zone continuously decreased/increased, their trends changing subsequently, and abrupt changes in the three temperature metrics (i.e. the Tmin, Tave and Tmax) occurred in each zone during the period 1977–2004. Similarly, in the 1990s, particularly after 1998, as the increase in the AMO slowed, the PDO was in either a positive phase but exhibited a decreasing trend or a negative phase, the MEI and SR decreased, the WS, AP and RH decreased/increased, with subsequent changes in trends, and warming hiatuses occurred. The sensitivities of the responses of the Tmin to changes in the three types of influencing factors were the highest, followed by those of the Tave and Tmax. The effects of various influencing factors on the three kinds of temperature change and warming hiatus have strong spatial and temporal differences. As a result, there was a strong spatial difference in the year of the abrupt temperature change and the warming hiatus.

Spatial and temporal variability of the abrupt interannual temperature change and warming hiatus in China, 1951–2016

AbstractThe abrupt temperature change (ATC) and warming hiatus (WH) phenomena impact global resources and the environment. However, information on the spatial and temporal variability in the ATC and WH over large regions, long time scales and densely distributed stations is lacking. In the study, based on average minimum, average and average maximum temperatures data from 1951 to 2016 from 622 meteorological stations in China, the spatial and temporal variability in the timing of the ATC and WH events and the characteristics before and after these events were revealed by using the Mann–Kendall test. In most areas of China, an ATC occurred in the three temperature parameters, and the onset of the changes occurred later at lower latitudes. The ATC in the average minimum temperature occurred earlier than that in the average temperature, and the ATC in the average maximum temperature occurred the latest. After the ATC, a WH occurred at most of the stations that experienced an increase in temperature, whereas a cooling hiatus (CH) did not occur at stations that experienced a decrease in temperature. The regions with decreasing temperatures were concentrated in the hilly and plain areas of southern China and in subtropical and tropical monsoon climate zones. The WH of the average temperature occurred earlier than that of the average maximum temperature, which occurred earlier than that of the average minimum temperature. Overall, the WH began later from east to west and was mainly concentrated in approximately 1998 and 2007. Both the ATC and the WH in the Qinghai–Tibet Plateau area showed hysteresis. The ATC to WH period was between three and 27 years, and the earlier the ATC was, the longer was the period. Before the ATC, all three temperature parameters increased slightly. The average minimum temperature rose faster than the average temperature, and the average maximum temperature rose the slowest. Furthermore, the variation became more dramatic from southeast to northwest. After the ATC, the temperatures in most areas increased rapidly, and the rate of temperature increase increased with decreasing latitude. The average maximum temperature decreased in the area east of 100° E and south of 30° N. In this area, the rates of temperature increase for the average minimum and average temperatures were on a par with the rate of decrease in the absolute average maximum temperature, with the rates being three to five times greater than those before the ATC, but without dramatic variations. After the ATC, a CH did not occur at the stations where the temperature had decreased, whereas a WH occurred after a certain period of time at most of the stations where the temperature had increased. Moreover, such occurrences differed with latitude. A comparison of the temperature after the WH with that both before and after the ATC but before the WH revealed that the temperature did not vary dramatically. Eight to 10 years after the WH, the temperatures at a small number of stations in northern China rose again; however, due to the short length of the time series, it is impossible to determine whether the WH had truly ended. The results of the study enrich the findings of climate change research and provide a reference for addressing resource and environmental issues.

Multidecadal modulations of key metrics of global climate change

Widespread public and scientific interest in the recent global warming hiatus and related multidecadal climate variability stimulated a surge in our understanding of key metrics of global climate change. While seeking explanations for the nearly steady global mean temperature from late 1990s through the early 2010s, the scientific community also grappled with concomitant and seemingly inconsistent changes in other metrics. For example, over that period, Arctic sea ice experienced a rapid decline but Antarctic sea ice expanded slightly, summertime warm extremes continued to rise without evidence of a pause, and the expanding Hadley cell trend maintained its course. In this article, we review recent advances in understanding the multidecadal variability of these metrics of global climate change, focusing on how internal multidecadal variability may reconcile differences between projected and recently observed trends and apparent inconsistencies between recent trends in some metrics. We emphasize that the impacts of global scale, naturally occurring patterns on multidecadal timescales, most notably the Pacific and Atlantic Multidecadal Variability, tend to be more regionally heterogeneous than those of radiatively forced change, which weakens the relationship between local climate impacts and global mean temperature on multidecadal timescales. We conclude this review with a summary of current challenges and opportunities for progress.

Global warming hiatus contributed weakening of the Mascarene High in the Southern Indian Ocean

The Mascarene High (MH) is a semi-permanent subtropical high-pressure zone in the South Indian Ocean. Apart from its large influence on African and Australian weather patterns, it also helps in driving the inter-hemispheric circulation between the Indian Ocean in the south and subcontinental landmass in the north. Using observations and reanalysis products, this study for the first time investigates recent warming trend observed in the MH region during the Global Warming Hiatus (GWH) period (1998–2016). Significant positive trends are observed in sea surface temperature (SST), sea surface height (SSH) and oceanic heat content (OHC) during this period in the MH region. Mixed layer heat budget analysis reveals the dominant role of heat advection in the observed warming trend. During the GWH period, stronger zonal currents advect the warm waters from the Western Pacific (WP) towards the MH region via the Indonesian Throughflow (ITF). This warming in the MH reduces the sea level pressure therein and establishes a weak pressure gradient between the MH and the northern hemisphere landmass. This in-turn weakens the cross-equatorial winds in the western Indian Ocean.

The 2000-2012 global warming hiatus more likely with a low climate sensitivity

The 2000-2012 global warming hiatus more likely with a low climate sensitivity

Spatial Variability in Years of Abrupt Seasonal Temperature Changes and Warming (Cooling) Hiatuses in China from 1951–2018 and the Variation Trends before and after These Years

Abrupt temperature changes and warming (cooling) hiatuses have an impact on the ecological environment. Currently, research findings for the spatial variability in the years of abrupt temperature changes and warming (cooling) hiatuses covering a variety of climate zones, as well as the variation trends before and after these years, are lacking. In the present study, based on the seasonal (monthly) average minimum temperatures, average temperatures, and average maximum temperature data from 622 Chinese meteorological stations during 1951–2018, the spatial variability in the years of abrupt seasonal changes and warming (cooling) hiatuses for these three temperature types in China, as well as the variation trends before and after these years, were analyzed using the Mann-Kendall test. The results are as follows. For most stations in China, the abrupt changes in the three temperature types during each season began to occur over a wide range in the late 1980s and early 1990s, and abrupt changes did not occur at a few stations concentrated south of 30° N. After an abrupt change occurred, the average minimum temperatures and average temperatures both showed significant upward trends, while the average maximum temperatures showed significant downward trends in some regions of southern China. After five to 15 years of temperature increases (decreases) following the abrupt changes, warming (cooling) hiatuses occurred in some areas of China, with the hiatus years occurring between 1989 and 2013. These hiatuses mainly occurred in 1998 and 2007, and in terms of proximity, the stations without warming (cooling) hiatuses were concentrated south of 40° N. After nine to 17 years of warming (cooling) hiatuses, the hiatuses ended at some stations between 2013 and 2017, after which the temperatures again increased rapidly. The periods of warming (cooling) hiatuses were longer in northern China than in southern China. Currently, there are some stations where the hiatuses have not ended, suggesting that the hiatus period is apparently longer than 17 years. The years of abrupt change, no abrupt change, hiatus, no hiatus, end of hiatus, and no end of hiatus, as well as their variation trends before and after these years, have shown strong spatial variability. The results of this study have enriched the research findings on climate change.

Sea Surface Temperature Extremes of Different Intensity in the China Seas During the Global Warming Acceleration and Hiatus Periods

Based on the daily OISST V2 with 0.25o horizontal resolutions, the present study looks into the variations of sea surface temperature (SST) extremes in the China Seas for different segments of the period 1982-2013. The two segments include the warming acceleration period from 1982 to 1997 and the hiatus period from 1998 to 2013 when the global mean surface temperature (GMST) did not significantly increase as expected, or even decreased in some areas. First, we construct the regional average time series over the entire China Seas (15°-45°N, 105°-130°E) for these SST extremes. During the hiatus period, the regionally averaged 10th, 1th and 0.1th percentile of SSTs in each year decreased significantly by 0.40℃, 0.56℃ and 0.58℃ per decade, respectively. The regionally averaged 90th, 99th and 99.9th percentile of SSTs in each year decreased slightly or insignificantly. Our work confirm that the regional hiatus was primarily reflected by wintertime cold extremes. Spatially, the trends of cold extremes in different intensity were non-uniformly distributed. Cold extremes in the near-shore areas were much more sensitive to the global warming hiatus. Hot extremes exhibited non-significant trend in the China Seas during the hiatus period. In short, the variations of the SST extremes in the two periods were non-uniform spatially and asymmetric seasonally. It is unexpected that the hot and cold extremes of each year during 1998-2013 were still higher than those extremes during 1982-1997. It is obvious that compared with the warming acceleration period, hot extremes were far more likely to occur in the recent hiatus as a result of a 0.3℃ warmer shift in the mean temperature distribution. Moreover, hot extremes in the China Seas will be sustained or amplified with the end of warming hiatus and the continuous anthropogenic warming.