Differences in Radiative Forcing, Not Sensitivity, Explain Differences in Summertime Land Temperature Variance Change Between CMIP5 and CMIP6

Chan, Duo; Rigden, A. J.; Proctor, J.; Chan, Pak Wah; Huybers, Peter

doi:10.1029/2021ef002402

Cited by 3 publications

(4 citation statements)

References 49 publications

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“…Previous studies have found that there was a warming hiatus from 1998 to 2012, whereas other studies suggest a warming hiatus occurred from 2000 to 2014 (Fyfe et al., 2016; Karl et al., 2015; Knight et al., 2009). Hypothesized reasons for warming‐trend slowdown include changes in radiative forcing processes (Guan et al., 2015), and the models were more sensitive to radiative forcing due to suppressed surface evapotranspiration in CMIP6 models, which could cause the uncertainty of model simulation results of past and future air temperature change (Chan et al., 2022; Fyfe et al., 2021). However, warming trends were significant from 1980 to 2014 with 0.349°C/decade.…”

Section: Discussionmentioning

confidence: 99%

Continued Warming of the Permafrost Regions Over the Northern Hemisphere Under Future Climate Change

Zhao

et al. 2022

Earth's Future

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Surface air temperatures can directly affect the thermal state of permafrost in the permafrost region of the Northern Hemisphere (PRONH). It is necessary to understand the trends in air temperatures and consider actual CMIP future scenario output instead of a linear temperature increase over different permafrost regions. In this study, air temperatures from 23 models of the sixth coupled‐model intercomparison project (CMIP6) are evaluated against observational data from the PRONH. It is shown that most of the models reasonably represent the dominant characteristics of air temperature variations. Under three different future scenarios, air temperature and warming trends are examined using an optimal model ensemble. Results show that mean annual air temperature (MAAT) is higher in sporadic‐permafrost and isolated‐permafrost regions than in continuous‐permafrost regions. MAAT warming rates were 0.10°C/decade and 0.35°C/decade from 1900 to 2014 and from 1980 to 2014, respectively, and were 0.09°C/decade, 0.38°C/decade, and 0.95°C/decade from 2015 to 2100 under the low‐ to high‐emission scenarios. Air temperature varies considerably between the high‐altitude, transitional, and high‐latitude permafrost regions (HLR), and warming trends are the greatest in HLR under future scenarios. Moreover, warming trends in different permafrost classes vary little from the historical values from 1900 to 2014, and with a gradual increase from isolated‐permafrost regions to continuous‐permafrost regions under future scenarios. The results suggested that air temperatures in the PRONH warmed approximately 1.6 times faster than global air temperatures from 1980 to 2014 and under the three future scenarios.

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Section: Discussionmentioning

confidence: 99%

Continued Warming of the Permafrost Regions Over the Northern Hemisphere Under Future Climate Change

Zhao

et al. 2022

Earth's Future

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“…So far, this model is identical to the one presented in [19], but one final alteration is required to (8). Figure 4 shows that when the surface soil is depleted, the latent heat flux does not approach zero.…”

Section: Derivation Of Smacm Model Equationsmentioning

confidence: 99%

“…This owes to the fact that deep, root-level soil moisture is present, and contributes to the latent heat flux. We therefore add an additional soil moisture fraction to (8) to capture this e↵ect, denoted as m 0 , resulting in the final temperature evolution equation,…”

Section: Derivation Of Smacm Model Equationsmentioning

confidence: 99%

“…Statistical approaches to attribution depend on fitting the limited number of observations to a generalized probability distribution with many free parameters, which makes it di cult to assign a likelihood to even well-characterized events such as the 2021 Pacific Northwest Heat Wave [7]. At the same time, climate models show no consistent pattern between mean warming and changes in temperature distributions [8], and are biased in their representation of temperature variability [9]. These limitations of both the empirical record and numerical models highlight a growing need for a general theory of present-day heat waves, especially outside the tropics [10,11].…”

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confidence: 99%

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Soil moisture modulation of midlatitude heat waves

Bauer¹,

Zeppetello²,

Proistosescu³

2023

Preprint

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Heat waves are broadly expected to increase in severity and frequency under climate change. Case studies highlight a number of physical mechanisms that play a role in present-day heat waves, which typically occur during a coalescence of anomalous atmospheric and land surface conditions. However, a unified model of heat wave physics is lacking, primarily owing to difficulty in disentangling the forcing versus feedback roles of soil moisture and atmospheric variability. Here, we provide observational evidence that soil moisture modulation of heat waves is a generic feature of midlatitude continental climates, and develop a theoretical framework to understand this modulation. Using separation of timescales we derive a diagnostic equation for the nonlinear response of temperature to soil moisture variations, and a dynamical Hasselmann-like model for the soil moisture variations themselves. We find that soil moisture fluctuations control the frequency and intensity of temperature extremes by slowly altering the background state on which rapid atmospheric variability acts, rather than by altering atmospheric variability itself. We also find the slow soil moisture variations are well-approximated as being primarily driven by stochastic precipitation variability. Our framework provides a first-principles understanding of soil moisture’s role in midlatitude temperature extremes.

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Heatwave–blocking relation change likely dominates over decrease in blocking frequency under global warming

2022

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Extra-tropical continental summer heatwaves often occur under persistent anticyclones or blocking. Here we partition heatwave changes into contributions from blocking changes, heatwave–blocking relation change and mean temperature increase, under global warming in climate models. We employ an optimized blocking index that best correlates with heatwaves (Pearson correlation of 0.7) and find heatwave-driving blocking decreases but the change in heatwave–blocking relation likely dominates. Over Europe, with a historical heatwave frequency of 2.5%, less blocking will cause 0.6% fewer heatwaves, steepened heatwave–blocking relation will cause 1.4% more heatwaves, and the mean temperature increase will cause 60% more heatwaves. Over Greenland, flattened heatwave–blocking relation will dominate over the insignificant decrease in blocking. The future increase in heatwave frequency is not caused by changes in blocking frequency, but by factors such as thermodynamics, that enhance the capacity of blocking to drive heatwaves.

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Differences in Radiative Forcing, Not Sensitivity, Explain Differences in Summertime Land Temperature Variance Change Between CMIP5 and CMIP6

Cited by 3 publications

References 49 publications

Continued Warming of the Permafrost Regions Over the Northern Hemisphere Under Future Climate Change

Continued Warming of the Permafrost Regions Over the Northern Hemisphere Under Future Climate Change

Soil moisture modulation of midlatitude heat waves

Heatwave–blocking relation change likely dominates over decrease in blocking frequency under global warming

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