scholarly journals A new method to diagnose the contribution of anthropogenic activities to temperature: temperature tagging

2013 ◽  
Vol 6 (2) ◽  
pp. 417-427 ◽  
Author(s):  
V. Grewe
Keyword(s):  
Greenhouse Gases ◽  
Surface Temperature ◽  
Greenhouse Effect ◽  
Climate Model ◽  
Co2 Concentration ◽  
Base Case ◽  
Atmospheric Absorption ◽  
The Difference ◽  
The Impact ◽  
Longwave Flux

Abstract. This study presents a new methodology, called temperature tagging. It keeps track of the contributions of individual processes to temperature within a climate model simulation. As a first step and as a test bed, a simple box climate model is regarded. The model consists of an atmosphere, which absorbs and emits radiation, and of a surface, which reflects, absorbs and emits radiation. The tagging methodology is used to investigate the impact of the atmosphere on surface temperature. Four processes are investigated in more detail and their contribution to the surface temperature quantified: (i) shortwave influx and shortwave atmospheric absorption ("sw"), (ii) longwave atmospheric absorption due to non-CO2 greenhouse gases ("nC"), (iii) due to a base case CO2 concentration ("bC"), and (iv) due to an enhanced CO2 concentration ("eC"). The differential equation for the temperature in the box climate model is decomposed into four equations for the tagged temperatures. This method is applied to investigate the contribution of longwave absorption to the surface temperature (greenhouse effect), which is calculated to be 68 K. This estimate contrasts an alternative calculation of the greenhouse effect of slightly more than 30 K based on the difference of the surface temperature with and without an atmosphere. The difference of the two estimates is due to a shortwave cooling effect and a reduced contribution of the shortwave to the total downward flux: the shortwave absorption of the atmosphere results in a reduced net shortwave flux at the surface of 192 W m−2, leading to a cooling of the surface by 14 K. Introducing an atmosphere results in a downward longwave flux at the surface due to atmospheric absorption of 189 W m−2, which roughly equals the net shortwave flux of 192 W m−2. This longwave flux is a result of both the radiation due to atmospheric temperatures and its longwave absorption. Hence the longwave absorption roughly accounts for 91 W m−2 out of a total of 381 W m−2 (roughly 25%) and therefore accounts for a temperature change of 68 K. In a second experiment, the CO2 concentration is doubled, which leads to an increase in surface temperature of 1.2 K, resulting from a temperature increase due to CO2 of 1.9 K, due to non-CO2 greenhouse gases of 0.6 K and a cooling of 1.3 K due to a reduced importance of the solar heating for the surface and atmospheric temperatures. These two experiments show the feasibility of temperature tagging and its potential as a diagnostic for climate simulations.

scholarly journals A new method to diagnose the contribution of anthropogenic activities to temperature: temperature tagging

2012 ◽  
Vol 5 (4) ◽  
pp. 3183-3215 ◽  
Author(s):  
V. Grewe
Keyword(s):  
Greenhouse Gases ◽  
Surface Temperature ◽  
Greenhouse Effect ◽  
Climate Model ◽  
Co2 Concentration ◽  
Base Case ◽  
Atmospheric Absorption ◽  
The Difference ◽  
The Impact ◽  
Longwave Flux

Abstract. This study presents a new methodology, called temperature tagging. It keeps track of the contributions of individual processes to temperature within a climate model simulation. As a first step and as a test bed a simple box climate model is regarded. The model consists of an atmosphere, which absorbs and emits radiation and of a surface, which reflects, absorbs and emits radiation. The tagging methodology is used to investigate the impact of the atmosphere on surface temperature. Four processes are investigated in more detail and their contribution to the surface temperature quantified: (i) shortwave influx and shortwave atmospheric absorption ("sw"), (ii) longwave atmospheric absorption due to non-CO2 greenhouse gases ("nC"), (iii) due to a base case CO2 concentration ("bC"), and (iv) due to an enhanced CO2 concentration ("eC"). The differential equation for the temperature in the box climate model is decomposed into four equations for the tagged temperatures. This method is applied to investigate the contribution of longwave absorption to the surface temperature (greenhouse effect), which is calculated to be 68 K. This estimate contrasts an alternative calculation of the greenhouse effect of slightly more than 30 K based on the difference of the surface temperature with and without an atmosphere. The difference of the two estimates is due to a shortwave cooling effect and a reduced contribution of the shortwave to the total downward flux: The shortwave absorption of the atmosphere results in a reduced net shortwave flux at the surface of 192 W m−2, leading to a cooling of the surface by 14 K. Introducing an atmosphere results in a downward longwave flux at the surface due to atmospheric absorption of 189 W m−2, which roughly equals the net shortwave flux of 192 W m−2. This longwave flux is a result of both, the radiation due to atmospheric temperatures and its longwave absorption. Hence the longwave absorption roughly accounts for 91 W m−2 out of a total of 381 W m−2 (roughly 25%) and therefore accounts for a temperature of 68 K. In a second experiment, the CO2 concentration is doubled, which leads to an increase in surface temperature of 1.2 K, resulting from an temperature increase due to CO2 of 1.9 K, due to non-CO2 greenhouse gases of 0.6 K and a cooling of 1.3 K due to a reduced importance of the solar heating for the surface and atmospheric temperatures. These two experiments show the feasibility of temperature tagging and its potential as a diagnostic for climate simulations.

scholarly journals Thermodynamics of climate change: generalized sensitivities

2010 ◽  
Vol 10 (2) ◽  
pp. 3699-3715 ◽  
Author(s):  
V. Lucarini ◽  
K. Fraedrich ◽  
F. Lunkeit
Keyword(s):  
Climate Change ◽  
Global Warming ◽  
Surface Temperature ◽  
Entropy Production ◽  
Theoretical Approach ◽  
Climate Model ◽  
Co2 Concentration ◽  
Energy Cycle ◽  
Lorenz Energy Cycle ◽  
The Impact

Abstract. Using a recent theoretical approach, we study how the impact of global warming of the thermodynamics of the climate system by performing experiments with a simplified yet Earth-like climate model. In addition to the globally averaged surface temperature, the intensity of the Lorenz energy cycle, the Carnot efficiency, the material entropy production and the degree of irreversibility of the system are linear with the logarithm of the CO2 concentration. These generalized sensitivities suggest that the climate becomes less efficient, more irreversible, and features higher entropy production as it becomes warmer.

scholarly journals The impact of climate model sea surface temperature biases on tropical cyclone simulations

2018 ◽  
Vol 53 (1-2) ◽  
pp. 173-192 ◽  
Author(s):  
Wei-Ching Hsu ◽  
Christina M. Patricola ◽  
Ping Chang
Keyword(s):  
Tropical Cyclone ◽  
Surface Temperature ◽  
Sea Surface Temperature ◽  
Climate Model ◽  
Sea Surface ◽  
The Impact

scholarly journals Acceleration of the Brewer–Dobson Circulation due to Increases in Greenhouse Gases

2008 ◽  
Vol 65 (8) ◽  
pp. 2731-2739 ◽  
Author(s):  
Rolando R. Garcia ◽  
William J. Randel
Keyword(s):  
Wave Propagation ◽  
Temperature Distribution ◽  
Greenhouse Gases ◽  
Gravity Waves ◽  
Greenhouse Effect ◽  
Lower Stratosphere ◽  
Climate Model ◽  
Community Climate Model ◽  
Mean Temperature ◽  
Westerly Winds

Abstract The acceleration of the Brewer–Dobson circulation under rising concentrations of greenhouse gases is investigated using the Whole Atmosphere Community Climate Model. The circulation strengthens as a result of increased wave driving in the subtropical lower stratosphere, which in turn occurs because of enhanced propagation and dissipation of waves in this region. Enhanced wave propagation is due to changes in tropospheric and lower-stratospheric zonal-mean winds, which become more westerly. Ultimately, these trends follow from changes in the zonal-mean temperature distribution caused by the greenhouse effect. The circulation in the middle and upper stratosphere also accelerates as a result of filtering of parameterized gravity waves by stronger subtropical westerly winds.

scholarly journals The CO<sub>2</sub> inhibition of terrestrial isoprene emission significantly affects future ozone projections

2008 ◽  
Vol 8 (6) ◽  
pp. 19891-19916 ◽  
Author(s):  
P. J. Young ◽  
A. Arneth ◽  
G. Schurgers ◽  
G. Zeng ◽  
J. A. Pyle
Keyword(s):  
Climate Model ◽  
Carbon Assimilation ◽  
Co2 Concentration ◽  
Atmospheric Co2 ◽  
Isoprene Emission ◽  
Atmospheric Co2 Concentration ◽  
Source Regions ◽  
Late 21St Century ◽  
Response To Temperature ◽  
The Impact

Abstract. Simulations of future tropospheric composition often include substantial increases in biogenic isoprene emissions arising from the Arrhenius-like leaf emission response and warmer surface temperatures, and from enhanced vegetation productivity in response to temperature and atmospheric CO2 concentration. However, a number of recent laboratory and field data have suggested a direct inhibition of leaf isoprene production by increasing atmospheric CO2 concentration, notwithstanding isoprene being produced from precursor molecules that include some of the primary products of carbon assimilation. The cellular mechanism that underlies the decoupling of leaf photosynthesis and isoprene production still awaits a full explanation but accounting for this observation in a dynamic vegetation model that contains a semi-mechanistic treatment of isoprene emissions has been shown to change future global isoprene emission estimates notably. Here we use these estimates in conjunction with a chemistry-climate model to compare the effects of isoprene simulations without and with a direct CO2-inhibition on late 21st century O3 and OH levels. The impact on surface O3 was significant. Including the CO2-inhibition of isoprene resulted in opposing responses in polluted (O3 decreases of up to 10 ppbv) vs. less polluted (O3 increases of up to 10 ppbv) source regions, due to isoprene nitrate and peroxy acetyl nitrate (PAN) chemistry. OH concentration increased with relatively lower future isoprene emissions, decreasing methane lifetime by ~7 months. Our simulations underline the large uncertainties in future chemistry and climate studies due to biogenic emission patterns and emphasize the problems of using globally averaged climate metrics to quantify the atmospheric impact of reactive, heterogeneously distributed substances.

Methane’s non-linear effect on climate in a three-dimensional Archean atmosphere

2021 ◽  
Author(s):  
Jake Eager ◽  
Nathan Mayne ◽  
Tim Lenton
Keyword(s):  
Surface Temperature ◽  
Climate Model ◽  
Methane Flux ◽  
Atmospheric Dynamics ◽  
Biogeochemical Model ◽  
Climate Conditions ◽  
Linear Effect ◽  
Methane Fluxes ◽  
The Impact ◽  
Methane Concentrations

&lt;p&gt;The interaction between reduced gases and the pre-oxygenic photosynthesising microbial population is key to determining the potential methane greenhouse that warmed the Archean. The potential biotic methane flux could have sustained methane concentrations between 100 to 35,000ppm [1]. Looking at the effect of these methane fluxes and concentrations in a 3D atmosphere are crucial to understanding these processes in more detail.&lt;/p&gt; &lt;p&gt;Here, I will present results from a state-of-the-art 3D climate model [2] along with a low dimensional biogeochemical model [3], exploring the potential biotic methane fluxes and subsequent concentrations. From this, we can examine the potential climate conditions during the Archean. We have extended a 1D exploration of methane&amp;#8217;s diminished greenhouse potential during the Archean [4] by looking at how methane concentrations affect cloud distribution, atmospheric dynamics and the surface temperature.&lt;/p&gt; &lt;p&gt;We find that global surface temperature peaks at pCH&lt;sub&gt;4&lt;/sub&gt; ~100 Pa, with this peak shifting at different CO&lt;sub&gt;2 &lt;/sub&gt;concentrations. Equator-to-pole temperature differences also has a peaked response, with the impact strongly dependant on the CO&lt;sub&gt;2 &lt;/sub&gt;concentration. These changes come about from the balance between the effect of methane and carbon dioxide on atmospheric dynamics. This is due to changes in the heating structure of the atmosphere, which also affects the cloud distribution.&lt;/p&gt; &lt;p&gt;[1] Kharecha, Kasting &amp; Siefert (2005) &lt;em&gt;Geobiology&lt;/em&gt; 3, 53-76.&lt;/p&gt; &lt;p&gt;[2] Mayne et al. (2014) &lt;em&gt;Geosci. Model Dev.&lt;/em&gt; 7, 3059&amp;#8211;3087.&lt;/p&gt; &lt;p&gt;[3] Lenton &amp; Daines (2017) &lt;em&gt;Ann. Rev. Mar. Sci.&lt;/em&gt; 9:1, 31-58.&lt;/p&gt; &lt;p&gt;[4] Byrne &amp; Goldblatt (2015) &lt;em&gt;Clim. Past&lt;/em&gt; 11, 559&amp;#8211;570.&lt;/p&gt;

scholarly journals If Anthropogenic CO2 Emissions Cease, Will Atmospheric CO2 Concentration Continue to Increase?

2013 ◽  
Vol 26 (23) ◽  
pp. 9563-9576 ◽  
Author(s):  
Andrew H. MacDougall ◽  
Michael Eby ◽  
Andrew J. Weaver
Keyword(s):  
Greenhouse Gases ◽  
Radiative Forcing ◽  
Climate Model ◽  
Carbon Sources ◽  
Co2 Concentration ◽  
Earth System ◽  
Terrestrial Source ◽  
The University ◽  
Aerosol Emissions ◽  
Over Time

If anthropogenic CO2 emissions were to suddenly cease, the evolution of the atmospheric CO2 concentration would depend on the magnitude and sign of natural carbon sources and sinks. Experiments using Earth system models indicate that the overall carbon sinks dominate, such that upon the cessation of anthropogenic emissions, atmospheric CO2 levels decrease over time. However, these models have typically neglected the permafrost carbon pool, which has the potential to introduce an additional terrestrial source of carbon to the atmosphere. Here, the authors use the University of Victoria Earth System Climate Model (UVic ESCM), which has recently been expanded to include permafrost carbon stocks and exchanges with the atmosphere. In a scenario of zeroed CO2 and sulfate aerosol emissions, whether the warming induced by specified constant concentrations of non-CO2 greenhouse gases could slow the CO2 decline following zero emissions or even reverse this trend and cause CO2 to increase over time is assessed. It is found that a radiative forcing from non-CO2 gases of approximately 0.6 W m−2 results in a near balance of CO2 emissions from the terrestrial biosphere and uptake of CO2 by the oceans, resulting in near-constant atmospheric CO2 concentrations for at least a century after emissions are eliminated. At higher values of non-CO2 radiative forcing, CO2 concentrations increase over time, regardless of when emissions cease during the twenty-first century. Given that the present-day radiative forcing from non-CO2 greenhouse gases is about 0.95 W m−2, the results suggest that if all CO2 and aerosols emissions were eliminated without also decreasing non-CO2 greenhouse gas emissions CO2 levels would increase over time, resulting in a small increase in climate warming associated with this positive permafrost–carbon feedback.

scholarly journals On the Accuracy of Deriving Climate Feedback Parameters from Correlations between Surface Temperature and Outgoing Radiation

2010 ◽  
Vol 23 (18) ◽  
pp. 4983-4988 ◽  
Author(s):  
D. M. Murphy ◽  
P. M. Forster
Keyword(s):  
Surface Temperature ◽  
Climate Model ◽  
Mixed Layer Depth ◽  
Box Model ◽  
Climate Feedback ◽  
Time Interval ◽  
Feedback Parameter ◽  
Outgoing Radiation ◽  
The Difference ◽  
Climate Studies

Abstract Changes in outgoing radiation are both a consequence and a cause of changes in the earth’s temperature. Spencer and Braswell recently showed that in a simple box model for the earth the regression of outgoing radiation against surface temperature gave a slope that differed from the model’s true feedback parameter. They went on to select input parameters for the box model based on observations, computed the difference for those conditions, and asserted that there is a significant bias for climate studies. This paper shows that Spencer and Braswell overestimated the difference. Differences between the regression slope and the true feedback parameter are significantly reduced when 1) a more realistic value for the ocean mixed layer depth is used, 2) a corrected standard deviation of outgoing radiation is used, and 3) the model temperature variability is computed over the same time interval as the observations. When all three changes are made, the difference between the slope and feedback parameter is less than one-tenth of that estimated by Spencer and Braswell. Absolute values of the difference for realistic cases are less than 0.05 W m−2 K−1, which is not significant for climate studies that employ regressions of outgoing radiation against temperature. Previously published results show that the difference is negligible in the Hadley Centre Slab Climate Model, version 3 (HadSM3).

scholarly journals Uncertainties in the global temperature change caused by carbon release from permafrost thawing

2012 ◽  
Vol 6 (5) ◽  
pp. 1063-1076 ◽  
Author(s):  
E. J. Burke ◽  
I. P. Hartley ◽  
C. D. Jones
Keyword(s):  
Soil Carbon ◽  
Climate Model ◽  
Co2 Concentration ◽  
High Concentration ◽  
Global Mean Temperature ◽  
Carbon Release ◽  
Thawing Permafrost ◽  
Hadley Centre ◽  
The Impact

Abstract. Under climate change thawing permafrost will cause old carbon which is currently frozen and inert to become vulnerable to decomposition and release into the climate system. This paper develops a simple framework for estimating the impact of this permafrost carbon release on the global mean temperature (P-GMT). The analysis is based on simulations made with the Hadley Centre climate model (HadGEM2-ES) for a range of representative CO2 concentration pathways. Results using the high concentration pathway (RCP 8.5) suggest that by 2100 the annual methane (CH4) emission rate is 2–59 Tg CH4 yr−1 and 50–270 Pg C has been released as CO2 with an associated P-GMT of 0.08–0.36 °C (all 5th–95th percentile ranges). P-GMT is considerably lower – between 0.02 and 0.11 °C – for the low concentration pathway (RCP2.6). The uncertainty in climate model scenario causes about 50% of the spread in P-GMT by the end of the 21st century. The distribution of soil carbon, in particular how it varies with depth, contributes to about half of the remaining spread, with quality of soil carbon and decomposition processes contributing a further quarter each. These latter uncertainties could be reduced through additional observations. Over the next 20–30 yr, whilst scenario uncertainty is small, improving our knowledge of the quality of soil carbon will contribute significantly to reducing the spread in the, albeit relatively small, P-GMT.

Quantifying the Summertime Response of the Austral Jet Stream and Hadley Cell to Stratospheric Ozone and Greenhouse Gases

2014 ◽  
Vol 27 (14) ◽  
pp. 5538-5559 ◽  
Author(s):  
Edwin P. Gerber ◽  
Seok-Woo Son
Keyword(s):  
Greenhouse Gases ◽  
Climate Sensitivity ◽  
Climate Model ◽  
Stratospheric Ozone ◽  
Coupled Model ◽  
Hadley Cell ◽  
Dynamical Response ◽  
Jet Stream ◽  
Temperature Trends ◽  
The Impact

Abstract The impact of anthropogenic forcing on the summertime austral circulation is assessed across three climate model datasets: the Chemistry–Climate Model Validation activity 2 and phases 3 and 5 of the Coupled Model Intercomparison Project. Changes in stratospheric ozone and greenhouse gases impact the Southern Hemisphere in this season, and a simple framework based on temperature trends in the lower polar stratosphere and upper tropical troposphere is developed to separate their effects. It suggests that shifts in the jet stream and Hadley cell are driven by changes in the upper-troposphere–lower-stratosphere temperature gradient. The mean response is comparable in the three datasets; ozone has chiefly caused the poleward shift observed in recent decades, while ozone and greenhouse gases largely offset each other in the future. The multimodel mean perspective, however, masks considerable spread in individual models’ circulation projections. Spread resulting from differences in temperature trends is separated from differences in the circulation response to a given temperature change; both contribute equally to uncertainty in future circulation trends. Spread in temperature trends is most associated with differences in polar stratospheric temperatures, and could be narrowed by reducing uncertainty in future ozone changes. Differences in tropical temperatures are also important, and arise from both uncertainty in future emissions and differences in models’ climate sensitivity. Differences in climate sensitivity, however, only matter significantly in a high emissions future. Even if temperature trends were known, however, differences in the dynamical response to temperature changes must be addressed to substantially narrow spread in circulation projections.

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