Utilizing the reduced-complexity model Hector, a regional scale analysis was conducted quantifyin... more Utilizing the reduced-complexity model Hector, a regional scale analysis was conducted quantifying the possible effects climate change may have on dimethyl sulfide (DMS) emissions within the oceans. The investigation began with a review of the sulfur cycle in modern Earth system models. We then expanded the biogeochemical representation within Hector to include a natural ocean component while accounting for acidification and planktonic community shifts. The report presents results from both a latitudinal and a global perspective. This new approach highlights disparate outcomes which have been inadequately characterized via planetary averages in past publications. Our findings suggest that natural sulfur emissions (ESN) may exert a forcing up to 4 times that of the CO 2 marine feedback, 0.62 and 0.15 Wm −2 , respectively, and reverse the radiative forcing sign in low latitudes. Additionally, sensitivity tests were conducted to demonstrate the need for further examination of the DMS loop. Ultimately, the present work attempts to include dynamic ESN within reduced-complexity simulations of the sulfur cycle, illustrating its impact on the global radiative budget.
Earth System Models (ESMs) are excellent tools for quantifying many aspects of future climate dyn... more Earth System Models (ESMs) are excellent tools for quantifying many aspects of future climate dynamics but are too computationally expensive to produce large collections of scenarios for downstream users of ESM data. In particular, many researchers focused on the impacts of climate change require large collections of ESM runs to rigorously study the impacts to both human and natural systems of low-frequency high-importance events, such as multi-year droughts. Climate model emulators provide an effective mechanism for filling this gap, reproducing many aspects of ESMs rapidly but with lower precision. The fldgen v1.0 R package quickly generates thousands of realizations of gridded temperature fields by randomizing the residuals of pattern scaling temperature output from any single ESM, retaining the spatial and temporal variance and covariance structures of the input data at a low computational cost. The fldgen v2.0 R package described here extends this capability to produce joint realizations of multiple variables, with a focus on temperature and precipitation in an open source software package available for community use (https://github.com/ jgcri/fldgen). This substantially improves the fldgen package by removing the requirement that the ESM variables be normally distributed, and will enable researchers to quickly generate covarying temperature and precipitation data that are synthetic but faithful to the characteristics of the original ESM.
The approximate proportional relationship between cumulative carbon emissions and instantaneous g... more The approximate proportional relationship between cumulative carbon emissions and instantaneous global temperature rise (the carbon budget approximation) has proven to be a useful concept to translate policy-relevant temperature objectives into CO 2 emissions pathways. However, when non-CO 2 forcing is changing along with CO 2 forcing, error in the approximation increases. Using the GCAM model to produce an ensemble of ~3,000 scenarios, we show that linked changes in CO 2 forcing, aerosol forcing, and non-CO 2 greenhouse gas forcing lead to an increase in total non-CO 2 forcing over the 21 st century across mitigation scenarios. This increase causes the relationship between instantaneous temperature and cumulative CO 2 emissions to become more complex than the proportional approximation often assumed, particularly for low temperature objectives such as 1.5 °C. The same linked changes in emissions also contribute to a near-term increase in aerosol forcing that effectively places a limit on how low peak temperature could be constrained through greenhouse gas mitigation alone. In particular, we find that 23% of scenarios that include CCS, but only 1% of scenarios that do not include CCS, achieve a temperature objective of 1.5 °C without temperature overshoot. The stated aim of the Paris Agreement is to keep the global temperature increase in this century "well below" 2 °C (compared to preindustrial levels) and to "pursue efforts" to limit the temperature increase to 1.5 °C. 1 In understanding such objectives, the concept of a carbon budget linking temperature increases to cumulative CO 2 emissions has proven useful, because it enables policy objectives (stated in terms of temperature increases) to be related to potential policy actions (stated in terms of CO 2 emissions reductions) (
Tropical forests have been a permanent feature of the Amazon basin for at least 55 million years,... more Tropical forests have been a permanent feature of the Amazon basin for at least 55 million years, yet climate change and land use threaten the forest's future over the next century. Understory forest fires, common under current climate in frontier forests, may accelerate Amazon forest losses from climate-driven dieback and deforestation. Far from land use frontiers, scarce fire ignitions and high moisture levels preclude significant burning, yet projected climate and land use changes may increase fire activity in these remote regions. Here, we used a fire model specifically parameterized for Amazon understory fires to examine the interactions between anthropogenic activities and climate under current and projected conditions. In a scenario of low mitigation efforts with substantial land use expansion and climate change – the representative concentration pathway (RCP) 8.5 – projected understory fires increase in frequency and duration, burning 4–28 times more fo...
Pattern scaling is used to efficiently emulate general circulation models and explore uncertainty... more Pattern scaling is used to efficiently emulate general circulation models and explore uncertainty in climate projections under multiple forcing scenarios. Pattern scaling methods assume that local climate changes scale with a global mean temperature increase, allowing for spatial patterns to be generated for multiple models for any future emission scenario. For uncertainty quantification and probabilistic statistical analysis, a library of patterns with descriptive statistics for each file would be beneficial, but such a library does not presently exist. Of the possible techniques used to generate patterns, the two most prominent are the delta and least squares regression methods. We explore the differences and statistical significance between patterns generated by each method and assess performance of the generated patterns across methods and scenarios. Differences in patterns across seasons between methods and epochs were largest in high latitudes (60–90° N/S). Bias and mean error...
Pyhector is a Python interface for the simple climate model Hector (Hartin et al. 2015) developed... more Pyhector is a Python interface for the simple climate model Hector (Hartin et al. 2015) developed in C++. Simple climate models like Hector can, for instance, be used in the analysis of scenarios within integrated assessment models like GCAM 1 , in the emulation of complex climate models, and in uncertainty analyses.
Subantarctic Mode Water (SAMW) and Antarctic Intermediate Water (AAIW) are large volume mid-depth... more Subantarctic Mode Water (SAMW) and Antarctic Intermediate Water (AAIW) are large volume mid-depth (400-1200 m) water masses, which transport heat, freshwater and CO2 into the Southern Hemisphere subtropical gyres and to the equatorial thermoclines. This study investigates variations in SAMW and AAIW properties and circulation in the southeast Pacific between the present and Last Glacial Maximum (LGM). Observations from the
... Reed, 2005). Ninety minerals were studied with an SEM/EDX Zeiss Supra 50VP with EDS. All anal... more ... Reed, 2005). Ninety minerals were studied with an SEM/EDX Zeiss Supra 50VP with EDS. All analyses were conducted at 20 kV; tilt 0.00; AmpT 35.0; Det Type SUTW, Sapphire Res 130.92 for 60 s (Table 2; Appendix B). Table ...
The new Community Climate System Model, version 4 (CCSM4), provides a powerful tool to understand... more The new Community Climate System Model, version 4 (CCSM4), provides a powerful tool to understand and predict the earth's climate system. Several aspects of the Southern Ocean in the CCSM4 are explored, including the surface climatology and interannual variability, simulation of key climate water masses (Antarctic Bottom Water, Subantarctic Mode Water, and Antarctic Intermediate Water), the transport and structure of the Antarctic Circumpolar Current, and interbasin exchange via the Agulhas and Tasman leakages and at the Brazil-Malvinas Confluence. It is found that the CCSM4 has varying degrees of accuracy in the simulation of the climate of the Southern Ocean when compared with observations. This study has identified aspects of the model that warrant further analysis that will result in a more comprehensive understanding of oceanatmosphere-ice dynamics and interactions that control the earth's climate and its variability.
Geophysical Research Letters fs01.tif ( ): CFC-12 concentration within the mixed layer (moles km ... more Geophysical Research Letters fs01.tif ( ): CFC-12 concentration within the mixed layer (moles km -3 ) for SAMW for a) observations; and b) CCSM4. The dashed line is the SAF and the solid line the PF, taken from Orsi et al. [1995]. The black contours in a) represent the 26.8 and 27.06 kg m -3 isopycnals and in b) represent the 26.8 and 27.0 kg m -3 isopycnals. Note, this data is only within the mixed layer within SAMW (26.8 -27.06 kg m -3 ) and does not reflect the entire sea surface concentration.
Utilizing the reduced-complexity model Hector, a regional scale analysis was conducted quantifyin... more Utilizing the reduced-complexity model Hector, a regional scale analysis was conducted quantifying the possible effects climate change may have on dimethyl sulfide (DMS) emissions within the oceans. The investigation began with a review of the sulfur cycle in modern Earth system models. We then expanded the biogeochemical representation within Hector to include a natural ocean component while accounting for acidification and planktonic community shifts. The report presents results from both a latitudinal and a global perspective. This new approach highlights disparate outcomes which have been inadequately characterized via planetary averages in past publications. Our findings suggest that natural sulfur emissions (ESN) may exert a forcing up to 4 times that of the CO 2 marine feedback, 0.62 and 0.15 Wm −2 , respectively, and reverse the radiative forcing sign in low latitudes. Additionally, sensitivity tests were conducted to demonstrate the need for further examination of the DMS loop. Ultimately, the present work attempts to include dynamic ESN within reduced-complexity simulations of the sulfur cycle, illustrating its impact on the global radiative budget.
Earth System Models (ESMs) are excellent tools for quantifying many aspects of future climate dyn... more Earth System Models (ESMs) are excellent tools for quantifying many aspects of future climate dynamics but are too computationally expensive to produce large collections of scenarios for downstream users of ESM data. In particular, many researchers focused on the impacts of climate change require large collections of ESM runs to rigorously study the impacts to both human and natural systems of low-frequency high-importance events, such as multi-year droughts. Climate model emulators provide an effective mechanism for filling this gap, reproducing many aspects of ESMs rapidly but with lower precision. The fldgen v1.0 R package quickly generates thousands of realizations of gridded temperature fields by randomizing the residuals of pattern scaling temperature output from any single ESM, retaining the spatial and temporal variance and covariance structures of the input data at a low computational cost. The fldgen v2.0 R package described here extends this capability to produce joint realizations of multiple variables, with a focus on temperature and precipitation in an open source software package available for community use (https://github.com/ jgcri/fldgen). This substantially improves the fldgen package by removing the requirement that the ESM variables be normally distributed, and will enable researchers to quickly generate covarying temperature and precipitation data that are synthetic but faithful to the characteristics of the original ESM.
The approximate proportional relationship between cumulative carbon emissions and instantaneous g... more The approximate proportional relationship between cumulative carbon emissions and instantaneous global temperature rise (the carbon budget approximation) has proven to be a useful concept to translate policy-relevant temperature objectives into CO 2 emissions pathways. However, when non-CO 2 forcing is changing along with CO 2 forcing, error in the approximation increases. Using the GCAM model to produce an ensemble of ~3,000 scenarios, we show that linked changes in CO 2 forcing, aerosol forcing, and non-CO 2 greenhouse gas forcing lead to an increase in total non-CO 2 forcing over the 21 st century across mitigation scenarios. This increase causes the relationship between instantaneous temperature and cumulative CO 2 emissions to become more complex than the proportional approximation often assumed, particularly for low temperature objectives such as 1.5 °C. The same linked changes in emissions also contribute to a near-term increase in aerosol forcing that effectively places a limit on how low peak temperature could be constrained through greenhouse gas mitigation alone. In particular, we find that 23% of scenarios that include CCS, but only 1% of scenarios that do not include CCS, achieve a temperature objective of 1.5 °C without temperature overshoot. The stated aim of the Paris Agreement is to keep the global temperature increase in this century "well below" 2 °C (compared to preindustrial levels) and to "pursue efforts" to limit the temperature increase to 1.5 °C. 1 In understanding such objectives, the concept of a carbon budget linking temperature increases to cumulative CO 2 emissions has proven useful, because it enables policy objectives (stated in terms of temperature increases) to be related to potential policy actions (stated in terms of CO 2 emissions reductions) (
Tropical forests have been a permanent feature of the Amazon basin for at least 55 million years,... more Tropical forests have been a permanent feature of the Amazon basin for at least 55 million years, yet climate change and land use threaten the forest's future over the next century. Understory forest fires, common under current climate in frontier forests, may accelerate Amazon forest losses from climate-driven dieback and deforestation. Far from land use frontiers, scarce fire ignitions and high moisture levels preclude significant burning, yet projected climate and land use changes may increase fire activity in these remote regions. Here, we used a fire model specifically parameterized for Amazon understory fires to examine the interactions between anthropogenic activities and climate under current and projected conditions. In a scenario of low mitigation efforts with substantial land use expansion and climate change – the representative concentration pathway (RCP) 8.5 – projected understory fires increase in frequency and duration, burning 4–28 times more fo...
Pattern scaling is used to efficiently emulate general circulation models and explore uncertainty... more Pattern scaling is used to efficiently emulate general circulation models and explore uncertainty in climate projections under multiple forcing scenarios. Pattern scaling methods assume that local climate changes scale with a global mean temperature increase, allowing for spatial patterns to be generated for multiple models for any future emission scenario. For uncertainty quantification and probabilistic statistical analysis, a library of patterns with descriptive statistics for each file would be beneficial, but such a library does not presently exist. Of the possible techniques used to generate patterns, the two most prominent are the delta and least squares regression methods. We explore the differences and statistical significance between patterns generated by each method and assess performance of the generated patterns across methods and scenarios. Differences in patterns across seasons between methods and epochs were largest in high latitudes (60–90° N/S). Bias and mean error...
Pyhector is a Python interface for the simple climate model Hector (Hartin et al. 2015) developed... more Pyhector is a Python interface for the simple climate model Hector (Hartin et al. 2015) developed in C++. Simple climate models like Hector can, for instance, be used in the analysis of scenarios within integrated assessment models like GCAM 1 , in the emulation of complex climate models, and in uncertainty analyses.
Subantarctic Mode Water (SAMW) and Antarctic Intermediate Water (AAIW) are large volume mid-depth... more Subantarctic Mode Water (SAMW) and Antarctic Intermediate Water (AAIW) are large volume mid-depth (400-1200 m) water masses, which transport heat, freshwater and CO2 into the Southern Hemisphere subtropical gyres and to the equatorial thermoclines. This study investigates variations in SAMW and AAIW properties and circulation in the southeast Pacific between the present and Last Glacial Maximum (LGM). Observations from the
... Reed, 2005). Ninety minerals were studied with an SEM/EDX Zeiss Supra 50VP with EDS. All anal... more ... Reed, 2005). Ninety minerals were studied with an SEM/EDX Zeiss Supra 50VP with EDS. All analyses were conducted at 20 kV; tilt 0.00; AmpT 35.0; Det Type SUTW, Sapphire Res 130.92 for 60 s (Table 2; Appendix B). Table ...
The new Community Climate System Model, version 4 (CCSM4), provides a powerful tool to understand... more The new Community Climate System Model, version 4 (CCSM4), provides a powerful tool to understand and predict the earth's climate system. Several aspects of the Southern Ocean in the CCSM4 are explored, including the surface climatology and interannual variability, simulation of key climate water masses (Antarctic Bottom Water, Subantarctic Mode Water, and Antarctic Intermediate Water), the transport and structure of the Antarctic Circumpolar Current, and interbasin exchange via the Agulhas and Tasman leakages and at the Brazil-Malvinas Confluence. It is found that the CCSM4 has varying degrees of accuracy in the simulation of the climate of the Southern Ocean when compared with observations. This study has identified aspects of the model that warrant further analysis that will result in a more comprehensive understanding of oceanatmosphere-ice dynamics and interactions that control the earth's climate and its variability.
Geophysical Research Letters fs01.tif ( ): CFC-12 concentration within the mixed layer (moles km ... more Geophysical Research Letters fs01.tif ( ): CFC-12 concentration within the mixed layer (moles km -3 ) for SAMW for a) observations; and b) CCSM4. The dashed line is the SAF and the solid line the PF, taken from Orsi et al. [1995]. The black contours in a) represent the 26.8 and 27.06 kg m -3 isopycnals and in b) represent the 26.8 and 27.0 kg m -3 isopycnals. Note, this data is only within the mixed layer within SAMW (26.8 -27.06 kg m -3 ) and does not reflect the entire sea surface concentration.
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Papers by Corinne Hartin