## 1 Introduction
The paper extends the STIRPAT model and sets three scenarios, namely, rapid, steady, and green developments, based on China's and Shanghai's development plans and relevant policies. The paper predicts the carbon-peaking implementation pathways for Shanghai from 2020 to 2040 in these three scenarios;  
2. Based on the penetration level of the renewable energy, three typical RIES system configurations are constructed, including fossil, hybrid, and clean. The integration of energy storage devices is introduced to facilitate the absorption of wind and solar energies, addressing the issue of unstable power output from renewable energy sources;  
3. Using the predicted carbon-peaking implementation pathways for Shanghai from 2020 to 2040 as a carbon emission constraint, a multi-objective optimization model is established, including system costs, carbon emissions, and primary energy consumption. This model is used to analyze the carbon emission behavior of the three typical RIES system configurations. In different development scenarios within the carbon-peaking implementation pathways, the paper explores the carbon emission behaviors of RIES systems under the constraint of carbon peaking. It also analyzes the impacts of the carbon-peaking implementation pathway constraint, system configuration, and operational mode on the carbon emissions of individual RIES systems. Additionally, an analysis of marginal abatement costs is conducted;  
4. To investigate the role of market mechanisms in promoting carbon emission reduction in the RIES, four carbon emission reduction policy scenarios are established based on carbon-trading and green-certificate-trading mechanisms: a no-policy-impact scenario, a scenario with the sole influence of the green-certificate-trading mechanism, a scenario with the sole influence of the carbon-trading mechanism, and a scenario with the combined influence of the green-certificate- and carbon-trading mechanisms. The multi-objective optimization analysis considers the system costs of the RIES and carbon penalty costs to examine the cross-RIES carbon emission behavior, including carbon emission, carbon intensity, and marginal abatement costs. Additionally, sensitivity analysis is conducted to assess the impacts of key parameters, such as carbon-trading prices, green-certificate-trading prices, and renewable energy quotas, on the systemic carbon emission behavior;  
5. An improved version of NSGA-III is proposed for multi-objective optimization in analyzing carbon emission behavior by incorporating simulated binary crossover (SBX) and normal distribution crossover (NDX). Despite extensive research demonstrating the effectiveness of low-carbon technologies and market mechanisms in reducing carbon emissions in regional integrated energy systems (RIESs), existing literature lacks targeted studies from the perspective of carbon peaking. There is a dearth of analysis on the carbon emission behavior of RIESs constrained by the goal for achieving carbon peaking, a critical aspect for planning and constructing RIESs while meeting the requirements of carbon-peaking implementation. This research aims to address this gap and fill the existing knowledge void. The research in this paper is organized into six chapters. Section 1 provides an overview of the current research status both domestically and internationally. Section 2 outlines the research framework and the main contributions of this paper. Section 3 delves into the prediction of the carbon-peaking implementation pathway in Shanghai using the STIRPAT model. Section 4 establishes three typical configurations of regional integrated energy systems (RIESs) and their optimization models. Section 5 explores the carbon emission behaviors of the three typical RIES configurations under the constraint of the carbon-peaking pathway. It also examines the carbon emission behavior across RIESs in four carbon reduction policy scenarios that utilize green certificates and carbon-trading mechanisms.