Transient Climate Simulations with the HadGEM1 Climate Model: Causes of Past Warming and Future Climate Change

Stott, Peter; Jones, Gareth S.; Lowe, Jason; Thorne, Peter; Durman, C. F.; Johns, T. C.; Thelen, Jean-Claude

doi:10.1175/jcli3731.1

Cited by 112 publications

(120 citation statements)

References 51 publications

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“…Volcanic eruptions in ACCESS-ESM1 are prescribed based on monthly global-mean stratospheric volcanic aerosol optical depth (Sato et al, 2002), which is then averaged over four equal-area latitude zones, similar to the way it is done in the Hadley Centre Global Environmental Model (HadGEM) (Stott et al, 2006;Jones et al, 2011). Globally significant volcanoes within the historical period are Krakatoa (1883), Santa Maria (1903), Agung (1963), El Chichón (1982 and Pinatubo (1991).…”

Section: Simulationsmentioning

confidence: 99%

The carbon cycle in the Australian Community Climate and Earth System Simulator (ACCESS-ESM1) – Part 2: Historical simulations

et al. 2017

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Abstract. Over the last decade many climate models have evolved into Earth system models (ESMs), which are able to simulate both physical and biogeochemical processes through the inclusion of additional components such as the carbon cycle. The Australian Community Climate and Earth System Simulator (ACCESS) has been recently extended to include land and ocean carbon cycle components in its ACCESS-ESM1 version. A detailed description of ACCESS-ESM1 components including results from pre-industrial simulations is provided in Part 1. Here, we focus on the evaluation of ACCESS-ESM1 over the historical period in terms of its capability to reproduce climate and carbon-related variables. Comparisons are performed with observations, if available, but also with other ESMs to highlight common weaknesses. We find that climate variables controlling the exchange of carbon are well reproduced. However, the aerosol forcing in ACCESS-ESM1 is somewhat larger than in other models, which leads to an overly strong cooling response in the land from about 1960 onwards. The land carbon cycle is evaluated for two scenarios: running with a prescribed leaf area index (LAI) and running with a prognostic LAI. We overestimate the seasonal mean (1.7 vs. 1.4) and peak amplitude (2.0 vs. 1.8) of the prognostic LAI at the global scale, which is common amongst CMIP5 ESMs. However, the prognostic LAI is our preferred choice, because it allows for the vegetation feedback through the coupling between LAI and the leaf carbon pool. Our globally integrated land-atmosphere flux over the historical period is 98 PgC for prescribed LAI and 137 PgC for prognostic LAI, which is in line with estimates of land use emissions (ACCESS-ESM1 does not include land use change).The integrated ocean-atmosphere flux is 83 PgC, which is in agreement with a recent estimate of 82 PgC from the Global Carbon Project for the period 1959-2005. The seasonal cycle of simulated atmospheric CO 2 is close to the observed seasonal cycle (up to 1 ppm difference for the station at Mace Head and up to 2 ppm for the station at Mauna Loa), but shows a larger amplitude (up to 6 ppm) in the high northern latitudes. Overall, ACCESS-ESM1 performs well over the historical period, making it a useful tool to explore the change in land and oceanic carbon uptake in the future.

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Section: Simulationsmentioning

confidence: 99%

The carbon cycle in the Australian Community Climate and Earth System Simulator (ACCESS-ESM1) – Part 2: Historical simulations

et al. 2017

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“…A significant cooling dominated by aerosols, is a robust feature of a wide range of detection analyses. A key factor in identifying the aerosol fingerprint, and therefore the amount of aerosol cooling is the change through time of the hemispheric temperature contrast, which is affected by the different evolution of aerosol forcing in the two hemispheres as well as the greater thermal inertia of the larger ocean area in the Southern Hemisphere (Santer et al, 1995(Santer et al, , 1996Hegerl et al, 2001;Stott et al, 2006). Regional and seasonal aspects of the temperature response may help to distinguish the response to greenhouse gas increases from the response to aerosols (e.g., Ramanathan et al, 2005;Nagashima et al, 2006).…”

Section: Episodes Of Global Warming and Cooling?mentioning

confidence: 99%

Quantifying and specifying the solar influence on terrestrial surface temperature

Jager

Duhau

Geel

2010

Journal of Atmospheric and Solar-Terrestrial Physics

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This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues.Other uses, including reproduction and distribution, or selling or licensing copies, or posting to personal, institutional or third party websites are prohibited. b s t r a c tThis investigation is a follow-up of a paper in which we showed that both major magnetic components of the solar dynamo, viz. the toroidal and the poloidal ones, are correlated with average terrestrial surface temperatures. Here, we quantify, improve and specify that result and search for their causes. We studied seven recent temperature files. They were smoothed in order to eliminate the Schwabe-type (11 years) variations. While the total temperature gradient over the period of investigation (1610-1970) is 0.087 1C/century; a gradient of 0.077 1C/century is correlated with the equatorial (toroidal) magnetic field component. Half of it is explained by the increase of the Total Solar Irradiance over the period of investigation, while the other half is due to feedback by evaporated water vapour. A yet unexplained gradient of À 0.040 1C/century is correlated with the polar (poloidal) magnetic field. The residual temperature increase over that period, not correlated with solar variability, is 0.051 1C/century. It is ascribed to climatologic forcings and internal modes of variation.We used these results to study present terrestrial surface warming. By subtracting the above-mentioned components from the observed temperatures we found a residual excess of 0.311 in 1999, this being the triangularly weighted residual over the period 1990-2008. We show that solar forcing of the ground temperature associated with significant feedback is a regularly occurring feature, by describing some well observed events during the Holocene.

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“…D elineating the relative role of anthropogenic forcing, natural forcing, and long-term natural variability in 20th century climate change presents a significant challenge to our understanding of the climate system (1)(2)(3)(4)(5)(6)(7). Observations suggest the warming of the 20th century global mean surface temperature has not been monotonic, even when smoothed by a 10-20 year low-pass filter.…”

mentioning

confidence: 99%

Long-term natural variability and 20th century climate change

Swanson

Sugihara

Tsonis

2009

Proc. Natl. Acad. Sci. U.S.A.

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Global mean temperature at the Earth's surface responds both to externally imposed forcings, such as those arising from anthropogenic greenhouse gases, as well as to natural modes of variability internal to the climate system. Variability associated with these latter processes, generally referred to as natural long-term climate variability, arises primarily from changes in oceanic circulation. Here we present a technique that objectively identifies the component of inter-decadal global mean surface temperature attributable to natural long-term climate variability. Removal of that hidden variability from the actual observed global mean surface temperature record delineates the externally forced climate signal, which is monotonic, accelerating warming during the 20th century.climate modeling ͉ ocean variability D elineating the relative role of anthropogenic forcing, natural forcing, and long-term natural variability in 20th century climate change presents a significant challenge to our understanding of the climate system (1-7). Observations suggest the warming of the 20th century global mean surface temperature has not been monotonic, even when smoothed by a 10-20 year low-pass filter. Temperatures reached a relative maximum around 1940, cooled until the mid 1970s, and have warmed from that point to the present. Radiative forcings due to solar variations, volcanoes, and aerosols have often been invoked as explanations for this non-monotonic variation (4). However, it is possible that long-term natural variability, rooted in changes in the ocean circulation, underlies much of this variability over multiple decades (8)(9)(10)(11)(12). Quantifying whether there is a large role for long-term natural variability in the climate system is important, as such variability could exacerbate or ameliorate the impact of climate change in the near future. Further, large magnitude variability may require revisiting the types and magnitudes of imposed forcings thought to be responsible for the observed 20th century climate trajectory (12). More ominously, a climate with large magnitude natural long-term variability in general is a climate very sensitive to imposed forcings, raising concerns about extreme impacts due to future climate change (13).Due to its large heat capacity, the ocean is the likely source of natural long-term climate variability on interdecadal time scales. The oceans can impact global mean surface temperature in several ways; directly, through surface fluxes of heat, or indirectly, by altering the atmospheric circulation and impacting the distribution of clouds and water vapor. However, our understanding of how the ocean impacts the global mean surface temperature is strongly limited by available observations, which historically have consisted primarily of sea surface temperature (SST) measurements.The desire to optimally use these SST observations suggests a two-stage approach to objectively quantify the role of internal variability in the 20th century climate trajectory. The first step requires linking SST a...

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Transient Climate Simulations with the HadGEM1 Climate Model: Causes of Past Warming and Future Climate Change

Cited by 112 publications

References 51 publications

The carbon cycle in the Australian Community Climate and Earth System Simulator (ACCESS-ESM1) – Part 2: Historical simulations

The carbon cycle in the Australian Community Climate and Earth System Simulator (ACCESS-ESM1) – Part 2: Historical simulations

Quantifying and specifying the solar influence on terrestrial surface temperature

Long-term natural variability and 20th century climate change

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