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Asymmetric and Non-Monotonic Respons...

Mitevski, Ivan.

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Asymmetric and Non-Monotonic Response of the Climate System to Idealized CO2 Forcing.

Record Type:	Electronic resources : Monograph/item
Title/Author:	Asymmetric and Non-Monotonic Response of the Climate System to Idealized CO2 Forcing./
Author:	Mitevski, Ivan.
Published:	Ann Arbor : ProQuest Dissertations & Theses, : 2023,
Description:	159 p.
Notes:	Source: Dissertations Abstracts International, Volume: 85-02, Section: B.
Contained By:	Dissertations Abstracts International85-02B.
Subject:	Atmospheric sciences. -
Online resource:	https://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=30636411
ISBN:	9798380134729

Asymmetric and Non-Monotonic Response of the Climate System to Idealized CO2 Forcing.
Mitevski, Ivan.

Asymmetric and Non-Monotonic Response of the Climate System to Idealized CO2 Forcing. - Ann Arbor : ProQuest Dissertations & Theses, 2023 - 159 p.

Source: Dissertations Abstracts International, Volume: 85-02, Section: B.

Thesis (Ph.D.)--Columbia University, 2023.

This item must not be sold to any third party vendors.

In this thesis, I explore the climate system's response to symmetric abrupt and transient CO2 forcing across a range of concentrations, from 1/8x to 8xCO2, relative to pre-industrial levels. I use two CMIP6 class models: the CESM Large Ensemble (CESM-LE) model configuration and the NASA Goddard Institute for Space Studies Model E2.1-G (GISS-E2.1-G). I use a hierarchy of (1) fully coupled atmosphere-ocean-sea-ice-land, (2) slab ocean, and (3) prescribed sea surface temperature simulations to analyze and support the findings.First, I find an asymmetric response in global mean surface air temperature (∆Ts) and effective climate sensitivity (EffCS) between colder and warmer experiments. The ∆Ts response at 8xCO2 is more than a third larger than the corresponding cooling at 1/8xCO2. I attribute this assymetry primarily due to the non-logarithmic CO2 forcing, not to changes in the radiative feedbacks.Second, I identify a non-monotonic response of EffCS in the warmer scenarios, with a minimum occurring at 4xCO2 (3xCO2) in CESM-LE (GISS-E2.1-G). This minimum in the warming simulations is associated with a non-monotonicity in the radiative feedback. Similar non-monotonic responses in Northern Hemisphere sea-ice, precipitation, the latitude of zero precipitation-minus-evaporation, and the strength of the Hadley cell are also identified. Comparing the climate response over the same CO2 range between fully coupled and slab-ocean versions of the same models, I demonstrate that the climate system's non-monotonic response is linked to changes in ocean dynamics, associated with a collapse of the Atlantic Meridional Overturning Circulation (AMOC).Third, to establish the significance of North Atlantic cooling in driving the non-monotonic changes in the radiative feedback, I conducted additional atmosphere-only (AMIP) simulations using the same models but with prescribed sea surface temperatures (SSTs) restricted to different regions. Through these simulations, I uncovered that the minimum EffCS value, characterized by notably negative radiative feedbacks, primarily originates from relative cooling of the sea surface temperature (SST) in the tropical and subtropical North Atlantic. This cooling of SSTs contributes to an increase in low-level cloud content in the eastern region of the North Atlantic, subsequently leading to a pronounced negative (stabilizing) feedback response.Furthermore, I investigated the state dependence of the effective radiative forcing (ERF) from 1/16x to 16xCO2. I found that ERF increases with CO2 concentration due to the increase in Instantaneous Radiative Forcing (IRF). Specifically, the IRF increases at higher CO2 values primarily due to stronger stratospheric cooling induced by CO2 forcing. On the other hand, the radiative adjustments counteract the IRF increase, causing the ERF to rise at a slower pace compared to the corresponding increase in IRF induced by higher CO2 concentrations.Lastly, I studied the winter storm tracks in the Southern Hemisphere, focusing on experiments up to 8xCO2. Through this analysis, I identified a non-linear response in the low latitude storm tracks. It is projected that the storm tracks will experience an intensification by the end of the century. However, my findings reveal that this intensification does not scale linearly with CO2 forcing. In fact, the storm tracks shift poleward, including a reduction of the storm tracks at low-mid latitudes and intensification at mid-high latitudes.

ISBN: 9798380134729Subjects--Topical Terms:

3168354
Atmospheric sciences.
Subjects--Index Terms:

CO2 dependence

Asymmetric and Non-Monotonic Response of the Climate System to Idealized CO2 Forcing.
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245 1 0 $a Asymmetric and Non-Monotonic Response of the Climate System to Idealized CO2 Forcing.
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300 $a 159 p.
500 $a Source: Dissertations Abstracts International, Volume: 85-02, Section: B.
500 $a Advisor: Polvani, Lorenzo M;Orbe, Clara.
502 $a Thesis (Ph.D.)--Columbia University, 2023.
506 $a This item must not be sold to any third party vendors.
520 $a In this thesis, I explore the climate system's response to symmetric abrupt and transient CO2 forcing across a range of concentrations, from 1/8x to 8xCO2, relative to pre-industrial levels. I use two CMIP6 class models: the CESM Large Ensemble (CESM-LE) model configuration and the NASA Goddard Institute for Space Studies Model E2.1-G (GISS-E2.1-G). I use a hierarchy of (1) fully coupled atmosphere-ocean-sea-ice-land, (2) slab ocean, and (3) prescribed sea surface temperature simulations to analyze and support the findings.First, I find an asymmetric response in global mean surface air temperature (∆Ts) and effective climate sensitivity (EffCS) between colder and warmer experiments. The ∆Ts response at 8xCO2 is more than a third larger than the corresponding cooling at 1/8xCO2. I attribute this assymetry primarily due to the non-logarithmic CO2 forcing, not to changes in the radiative feedbacks.Second, I identify a non-monotonic response of EffCS in the warmer scenarios, with a minimum occurring at 4xCO2 (3xCO2) in CESM-LE (GISS-E2.1-G). This minimum in the warming simulations is associated with a non-monotonicity in the radiative feedback. Similar non-monotonic responses in Northern Hemisphere sea-ice, precipitation, the latitude of zero precipitation-minus-evaporation, and the strength of the Hadley cell are also identified. Comparing the climate response over the same CO2 range between fully coupled and slab-ocean versions of the same models, I demonstrate that the climate system's non-monotonic response is linked to changes in ocean dynamics, associated with a collapse of the Atlantic Meridional Overturning Circulation (AMOC).Third, to establish the significance of North Atlantic cooling in driving the non-monotonic changes in the radiative feedback, I conducted additional atmosphere-only (AMIP) simulations using the same models but with prescribed sea surface temperatures (SSTs) restricted to different regions. Through these simulations, I uncovered that the minimum EffCS value, characterized by notably negative radiative feedbacks, primarily originates from relative cooling of the sea surface temperature (SST) in the tropical and subtropical North Atlantic. This cooling of SSTs contributes to an increase in low-level cloud content in the eastern region of the North Atlantic, subsequently leading to a pronounced negative (stabilizing) feedback response.Furthermore, I investigated the state dependence of the effective radiative forcing (ERF) from 1/16x to 16xCO2. I found that ERF increases with CO2 concentration due to the increase in Instantaneous Radiative Forcing (IRF). Specifically, the IRF increases at higher CO2 values primarily due to stronger stratospheric cooling induced by CO2 forcing. On the other hand, the radiative adjustments counteract the IRF increase, causing the ERF to rise at a slower pace compared to the corresponding increase in IRF induced by higher CO2 concentrations.Lastly, I studied the winter storm tracks in the Southern Hemisphere, focusing on experiments up to 8xCO2. Through this analysis, I identified a non-linear response in the low latitude storm tracks. It is projected that the storm tracks will experience an intensification by the end of the century. However, my findings reveal that this intensification does not scale linearly with CO2 forcing. In fact, the storm tracks shift poleward, including a reduction of the storm tracks at low-mid latitudes and intensification at mid-high latitudes.
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650 4 $a Chemistry. $3 516420
650 4 $a Climate change. $2 bicssc $3 2079509
653 $a CO2 dependence
653 $a ECS
653 $a Pattern effect
653 $a Radiative feedbacks
653 $a Radiative forcing
653 $a Storm track
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690 $a 0404
690 $a 0485
710 2 $a Columbia University. $b Applied Mathematics. $3 3179529
773 0 $t Dissertations Abstracts International $g 85-02B.
790 $a 0054
791 $a Ph.D.
792 $a 2023
793 $a English
856 4 0 $u https://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=30636411