scholarly journals Different Pathways to an Early Eocene Climate

2021 ◽  
Author(s):  
Matthew Henry ◽  
Geoffrey Vallis
Keyword(s):  
Heat Capacity ◽  
Surface Temperature ◽  
Land Surface ◽  
Co2 Concentration ◽  
Surface Heat ◽  
The Arctic ◽  
Early Eocene ◽  
Surface Temperature Change ◽  
High Co2 ◽  
Co2 Levels

The early Eocene was characterised by much higher temperatures and a smaller equator-to-pole surface temperature gradient than today. Comprehensive climate models have been reasonably successful in simulating many features of that climate in the annual average. However, good simulations of the seasonal variations, and in particular the much reduced Arctic land temperature seasonality and associated much warmer winters, have proven more difficult. Further, aside from an increased level of greenhouse gases, it remains unclear what the key processes are that give rise to an Eocene climate, and whether there is a unique combination of factors that leads to agreement with available proxies. Here we use a very flexible General Circulation Model to examine the sensitivity of the modelled climate to differences in CO2 concentration, land surface properties, ocean heat transport, and cloud extent and thickness. Even in the absence of ice or changes in cloudiness, increasing the CO2 concentration leads to a polar-amplified surface temperature change because of increased water vapour and the lack of convection at high latitudes. Additional low clouds over Arctic land generally decreases summer temperatures and, except at very high CO2 levels, increases winter temperatures, thus helping achieve an Eocene climate. An increase in the land surface heat capacity, plausible given large changes in vegetation and landscape, also decreases the Arctic land seasonality. In general, various different combinations of factors -- high CO2 levels, changes in low-level clouds, and an increase in land surface heat capacity -- can lead to a simulation consistent with current proxy data.

Seasonality of Polar Warming in Climates with Very High Carbon Dioxide.

2021 ◽  
Author(s):  
Matthew Henry ◽  
Geoffrey Vallis
Keyword(s):  
Heat Capacity ◽  
Surface Temperature ◽  
Temperature Change ◽  
High Latitude ◽  
Land Surface ◽  
Atmospheric Temperature ◽  
Surface Heat ◽  
The Arctic ◽  
Surface Temperature Change ◽  
Surface Enhanced

<p>Observations of warm past climates and projections of future climate change show that the Arctic warms more than the global mean, particularly during winter months. Past warm climates such as the early Eocene had above-freezing Arctic continental temperatures year-round. In this work, we show that an enhanced increase of Arctic continental winter temperatures with increased greenhouse gases is a robust consequence of the smaller surface heat capacity of land (compared to ocean), without recourse to other processes or feedbacks. We use a General Circulation Model (GCM) with no clouds or sea ice and a simple representation of land. The equator-to-pole surface temperature gradient falls with increasing CO2, but this is only a near-surface phenomenon and occurs with little change in total meridional heat transport. The high-latitude land has about twice as much warming in winter than in summer, whereas high-latitude ocean has very little seasonality in warming. A surface energy balance model shows how the combination of the smaller surface heat capacity of land and the nonlinearity of the temperature dependence of surface longwave emission gives rise to the seasonality of land surface temperature change. The atmospheric temperature change is surface-enhanced in winter as the atmosphere is near radiative-advective equilibrium, but more vertically homogeneous in summer as the Arctic land gets warm enough to trigger convection. While changes in clouds, sea ice and ocean heat transport undoubtedly play a role in high latitude warming, these results show that surface-enhanced atmospheric temperature change and enhanced land surface temperature change in winter can happen in their absence for very basic and robust reasons.</p>

scholarly journals Reduced High-Latitude Land Seasonality in Climates with Very High Carbon Dioxide

2021 ◽  
pp. 1-38
Author(s):  
Matthew Henry ◽  
Geoffrey K. Vallis
Keyword(s):  
Heat Capacity ◽  
Sea Ice ◽  
Surface Temperature ◽  
Temperature Dependence ◽  
Heat Transport ◽  
High Latitude ◽  
Land Surface ◽  
Surface Heat ◽  
The Arctic ◽  
Future Climate Change

AbstractObservations of warm past climates and projections of future climate change show that the Arctic warms more than the global mean, particularly during winter months. Previous work has attributed this reduced Arctic land seasonality to the effects of sea ice or clouds. In this paper, we show that the reduced Arctic land seasonality is a robust consequence of the relatively small surface heat capacity of land and the nonlinearity of the temperature dependence of surface longwave emission, without recourse to other processes or feedbacks. We use a General Circulation Model (GCM) with no clouds or sea ice and a simple representation of land. In the annual mean, the equator-to-pole surface temperature gradient falls with increasing CO2, but this is only a near-surface phenomenon and is not caused by the change in total meridional heat transport, which is virtually unaltered. The high-latitude land has about twice as much warming in winter than in summer, whereas high-latitude ocean has very little seasonality in warming. A surface energy balance model shows how the combination of the smaller surface heat capacity of land and the nonlinearity of the temperature dependence of surface longwave emission gives rise to the reduced seasonality of the land surface. The increase in evaporation over land also leads to winter amplification of warming over land, although amplification still occurs without it. While changes in clouds, sea ice, and ocean heat transport undoubtedly play a role in high-latitude warming, these results show that enhanced land surface temperature warming in winter can happen in their absence for robust reasons.

scholarly journals The Relationship between Land–Ocean Surface Temperature Contrast and Radiative Forcing

2011 ◽  
Vol 24 (13) ◽  
pp. 3239-3256 ◽  
Author(s):  
F. Hugo Lambert ◽  
Mark J. Webb ◽  
Manoj M. Joshi
Keyword(s):  
Surface Temperature ◽  
Heat Transport ◽  
Temperature Change ◽  
Land Surface ◽  
Radiative Forcing ◽  
Co2 Concentration ◽  
Ocean Surface ◽  
Heat Fluxes ◽  
Balance Model ◽  
Surface Temperature Change

Abstract Previous work has demonstrated that observed and modeled climates show a near-time-invariant ratio of mean land to mean ocean surface temperature change under transient and equilibrium global warming. This study confirms this in a range of atmospheric models coupled to perturbed sea surface temperatures (SSTs), slab (thermodynamics only) oceans, and a fully coupled ocean. Away from equilibrium, it is found that the atmospheric processes that maintain the ratio cause a land-to-ocean heat transport anomaly that can be approximated using a two-box energy balance model. When climate is forced by increasing atmospheric CO2 concentration, the heat transport anomaly moves heat from land to ocean, constraining the land to warm in step with the ocean surface, despite the small heat capacity of the land. The heat transport anomaly is strongly related to the top-of-atmosphere radiative flux imbalance, and hence it tends to a small value as equilibrium is approached. In contrast, when climate is forced by prescribing changes in SSTs, the heat transport anomaly replaces “missing” radiative forcing over land by moving heat from ocean to land, warming the land surface. The heat transport anomaly remains substantial in steady state. These results are consistent with earlier studies that found that both land and ocean surface temperature changes may be approximated as local responses to global mean radiative forcing. The modeled heat transport anomaly has large impacts on surface heat fluxes but small impacts on precipitation, circulation, and cloud radiative forcing compared with the impacts of surface temperature change. No substantial nonlinearities are found in these atmospheric variables when the effects of forcing and surface temperature change are added.

scholarly journals Monitoring Land Surface Temperature Change with Landsat Images during Dry Seasons in Bac Binh, Vietnam

2020 ◽  
Vol 12 (24) ◽  
pp. 4067
Author(s):  
Thanhtung Dang ◽  
Peng Yue ◽  
Felix Bachofer ◽  
Michael Wang ◽  
Mingda Zhang
Keyword(s):  
Climate Change ◽  
Land Cover ◽  
Surface Temperature ◽  
Land Surface Temperature ◽  
Land Surface ◽  
Dry Season ◽  
Landsat Images ◽  
Surface Temperature Change ◽  
Green Vegetation ◽  
Dry Seasons

Global warming-induced climate change evolved to be one of the most important research topics in Earth System Sciences, where remote sensing-based methods have shown great potential for detecting spatial temperature changes. This study utilized a time series of Landsat images to investigate the Land Surface Temperature (LST) of dry seasons between 1989 and 2019 in the Bac Binh district, Binh Thuan province, Vietnam. Our study aims to monitor LST change, and its relationship to land-cover change during the last 30 years. The results for the study area show that the share of Green Vegetation coverage has decreased rapidly for the dry season in recent years. The area covered by vegetation shrank between 1989 and 2019 by 29.44%. Our findings show that the LST increase and decrease trend is clearly related to the change of the main land-cover classes, namely Bare Land and Green Vegetation. For the same period, we find an average increase of absolute mean LST of 0.03 °C per year for over thirty years across all land-cover classes. For the dry season in 2005, the LST was extraordinarily high and the area with a LST exceeding 40 °C covered 64.10% of the total area. We expect that methodological approach and the findings can be applied to study change in LST, land-cover, and can contribute to climate change monitoring and forecasting of impacts in comparable regions.

scholarly journals Cymodocea nodosa response to simulated CO2-driven ocean acidification: a first insight from global transcriptome profiling

2015 ◽  
Author(s):  
Miriam Ruocco ◽  
Procaccini Gabriele ◽  
Francesco Musacchia ◽  
Remo Sanges ◽  
Irene Olivé ◽  
...  
Keyword(s):  
Ocean Acidification ◽  
Molecular Mechanisms ◽  
Transcriptome Assembly ◽  
Co2 Concentration ◽  
Marine Organisms ◽  
Photosynthetic Parameters ◽  
Cymodocea Nodosa ◽  
Field Station ◽  
High Co2 ◽  
Co2 Levels

Global climate changes are imposing multiple pressures to marine organisms. The rising atmospheric CO2 concentration is causing substantial changes in ocean physics, chemistry and biology. At least three synergic environmental stressors have been recognized as primary driven by CO2 emissions: ocean warming, oxygen loss and ocean acidification. The effects of CO2-driven ocean acidification on seagrass metabolism remain largely understudied. A few studies have been conducted near submarine volcanic vents, which mimic the future ocean acidification scenarios, allowing researchers to investigate the performance of marine organisms under long-term exposure to high-CO2 levels. Apart from these, some mesocosm-based experiments have investigated growth and physiological responses to high CO2. For this work, we built an outdoor mesocosm facility at the Centre of Marine Sciences’ field station in Algarve, Portugal, to experimentally manipulate CO2 levels and investigate the effects of high-CO2/low pH on seagrass metabolism and underlying molecular mechanisms. Cymodocea nodosa plants were collected in Cadiz Bay at the end of January 2014 and transported to the mesocosm facility. After a one week acclimation period, C. nodosa were either kept under normal (400 ppm) or elevated (1200 ppm) CO2 concentration for 12 days. Water physico-chemical parameters, irradiance, and chlorophyll-fluorescence-derived photosynthetic parameters were monitored on a daily basis. Here we present, for the first time in this species, results obtained using Illumina RNAseq technology and de-novo transcriptome assembly. Using C. nodosa RNAs extracted at the beginning and the end of the experiment, we assembled more than 70 thousands unique transcripts and were able to annotate more than 90% of them using the Annocript pipeline. Differential expression analysis revealed about 500 transcripts significantly differentially regulated between plants kept under control and high-CO2 conditions. Pathways showing largest changes in gene expression included isoprenoid and amino-acid biosynthesis, porphyrin-containing compound metabolism, amine and polyamine biosynthesis, lipid and carbohydrate metabolism. Transcriptome sequencing also significantly increases the molecular resources available for C. nodosa, almost completely absent before this study.

scholarly journals The Climate Impact of COVID19 Induced Contrail Changes

2021 ◽  
Author(s):  
Andrew Gettelman ◽  
Chieh-Chieh Chen ◽  
Charles G. Bardeen
Keyword(s):  
Surface Temperature ◽  
Land Surface ◽  
Radiative Forcing ◽  
Climate Impact ◽  
Climate Impacts ◽  
Infrared Heating ◽  
Boreal Summer ◽  
Surface Temperature Change ◽  
Effective Radiative Forcing ◽  
Standard Deviations

Abstract. The COVID19 pandemic caused significant economic disruption in 2020 and severely impacted air traffic. We use a state of the art Earth System Model and ensembles of tightly constrained simulations to evaluate the effect of the reductions in aviation traffic on contrail radiative forcing and climate in 2020. In the absence of any COVID19 pandemic caused reductions, the model simulates a contrail Effective Radiative Forcing (ERF) 62 ± 59 m Wm−2 (2 standard deviations). The contrail ERF has complex spatial and seasonal patterns that combine the offsetting effect of shortwave (solar) cooling and longwave (infrared) heating from contrails and contrail cirrus. Cooling is larger in June–August due to the preponderance of aviation in the N. Hemisphere, while warming occurs throughout the year. The spatial and seasonal forcing variations also map onto surface temperature variations. The net land surface temperature change due to contrails in a normal year is estimated at 0.13 ± 0.04 K (2 standard deviations) with some regions warming as much as 0.7 K. The effect of COVID19 reductions in flight traffic decreased contrails. The unique timing of such reductions, which were maximum in N. Hemisphere spring and summer when the largest contrail cooling occurs, means that cooling due to fewer contrails in boreal spring and fall was offset by warming due to fewer contrails in boreal summer to give no significant annual averaged ERF from contrail changes in 2020. Despite no net significant global ERF, because of the spatial and seasonal timing of contrail ERF, some land regions that would have cooled slightly (minimum −0.2 K) but significantly from contrail changes in 2020. The implications for future climate impacts of contrails are discussed.

scholarly journals Pattern and Trend of Land Surface Temperature Change on New Guinea Island

2020 ◽  
Vol 28 (4) ◽  
Author(s):  
Munawar ◽  
Tofan Agung Eka Prasetya ◽  
Rhysa McNeil ◽  
Rohana Jani
Keyword(s):  
Surface Temperature ◽  
Land Surface Temperature ◽  
Land Surface ◽  
New Guinea ◽  
Global Scale ◽  
Surface Temperature Change ◽  
Sea Levels ◽  
Moderate Resolution Imaging Spectroradiometer ◽  
Rising Sea Levels ◽  
The Many

Global warming will have an impact on nature in many ways, including rising sea levels and an increasing spread of infectious diseases. Land surface temperature is one of the many indicators that can be used to measure climate change on both a local and global scale. This study aims to analyze the change in land surface temperatures on New Guinea Island using a cubic spline method, autoregressive model, and multivariate regression. New Guinea Island was divided into 5 regions each consisting of 9 subregions. The data of each subregion was obtained from the National Aeronautics and Space Administration moderate resolution imaging spectroradiometer database from 2000 to 2019. The average change in temperature was +0.012°C per decade. However, the changes differed by region; significantly decreasing in the northwest at -0.107°C per decade (95% CI: -0.207, -0.007), significantly increasing in the south at 0.201°C per decade (95% CI: 0.069, 0.333), and remaining stable in the centralnorth, southeast and northeast.

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