Decarbonizing the built environment to mitigate climate change and carbon emissions is a global target with various pathways and action plans in different countries. This study aimed to develop an understanding of the real impact of glazing used in building envelopes on operational carbon emissions in different climates, categorized into warm-hot (Zones 0-3), temperate or mixed climate (Zone4), and cool-cold (Zones 5-8), by answering the main research question, “What is the impact of different glazing systems as a form of building envelopes on the operational carbon emissions of a high-rise office building across multiple climates?” The high-rise office building was modelled with four alternatives of glazing systems of different thermal transmittance (U-factor) in Open Studio/ Energy Plus to simulate the annual operational energy used and calculate the operational carbon (OC) accordingly across multiple scenarios of window-to-wall ratio (WWR). As a result, the operational carbon (OC) was analyzed concerning the glazing systems type, WWR, and the U-factor of each system. The results emphasize that operational carbon relates directly to the U-factor and WWR of different glazing systems. As the WWR or the U-factor reduced, so did the operational carbon due to the decrease in the office building's Energy Use Intensity (EUI) in different climate zones (ASHRAE, 2020). Operational carbon is directly related to the energy use intensity (EUI) that can be reduced by 42% from (380.5 kWh/m2) to (219.6 kWh/m2) on average by reducing the amount of glazing from 90% to 25% of the walls and changing the glazing system to a lower U-factor. An average reduction of 29% to 50% in carbon emissions of the high-rise office building can be achieved if the WWR changes from 90% to 25% and a U-factor decrease from 0.47 W/m²K to 0.19 W/m²K, based on a natural gas heating system with a carbon emissions factor of (0.2 KgCO₂e/MWh) as per the IPCC Database on Carbon dioxide emissions factor (Data source: IPCC - Emission Factor Database (2023)) and an electrical-powered cooling system with an average carbon factor of (0.31 KgCO₂e/MWh) calculated for the cities representing the climate zones for this study referring to electricity carbon emissions calculated in the Carbon Calculator https://www.carbonfootprint.com/calculator.aspx. The Operational carbon reduction percentage varies based on the climate zone; the lowest is 22% for cool-cold climates (Zones 5-8) when reducing the WWR from 90% to 25% at 0.19 W/m²K U-factor. The highest is 60% for mixed climates (Zone-4) when reducing the WWR from 90% to 25% at 0.47 W/m²K U-factor. The operational carbon reduction in warm-hot climates (zones 0-3) is 48% when reducing the WWR from 90% to 25% at 0.19 W/m²K U-factor and 44% at 0.47 W/m²K U-factor. However, more cutbacks in operational carbon are expected if the electricity carbon factor gradually decreases in the next 30 years to zero afterward when the electricity is assumed to become clean in 30 years.