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In this paper, we provide nominal and worst-case estimates of radiative forcing due to the UHI effect using a Weighted Amplification Albedo Solar Urbanization model. This calculation is done with the help of reported findings from UHI footprint and heat dome studies that simplify estimates for UHI amplification factors. Using this method, we quantify a global warming range due to the UHI effect, including its extent. Forcing estimates varied approximately between 0.07 and 0.87 W/m2 representing 3% to 36% of global warming relative to the greenhouse gas forcing estimates between 1950 and 2019. Variations in our model are due to the urbanized area and associated UHI amplification estimate uncertainties. However, the model showed consistent values of about 0.16 W/m2/% solar effective amplified areas and 1.6 W/m2/%Δalbedo for the urbanized coverage forcing values. The basic model is additionally used to quantify feedback warming due to Arctic sea ice loss. Feedback estimates contribute to the impact of UHI forcing assessments. From our median estimates, it is concluded that UHIs contribute significantly to global warming trends. The model is versatile and also provides UHI albedo reverse forcing assessments. The results provide insight into the UHI area effects from a new perspective using a global view albedo model compared to prior ground-based measurement studies. It also illustrates the utility of using effective UHI amplification estimates when assessing their warming effect on a global scale.

In this paper, solar geoengineering modeling is presented with a goal to simplify reverse forcing assessments and the capability to apply it to a wide variety of applications. Results find improvements on sun-shade space mirror and desert surface treatment estimates, stratosphere sun-dimming methods, and the Urban Heat Islands (UHIs) influence. A heat amplification parameter is added to the model allowing it to be applied to UHI estimates. UHI amplification effects are due to the large solar area of buildings, reduction of wind cooling, solar canyons, and so forth. The UHI reverse forcing requirements are assessed with amplification estimates of 3.1 and 5.2, yielding 7.6% to 12.7% of gross global warming (corresponding to forcing percentages of 16% to 27%) could be due to the urbanization effect, respectively. The gross warming 7.6% estimate, accurately compares to the author's prior study, and the 12.7% represents very recent results by other authors from new measurement methods. Key issues are pointed out that without including a heat amplification estimate and other modeling parameters, the UHI intensity, that likely dominates the urbanization warming effect could be severely underestimated, yielding urbanization estimates possibly as low as 2.4%. It is important to identify possible reasons where underestimates may occur from a modeling perspective to help understand controversies that may be occurring. The new model helps to clarify such parameters, allows for a significant reduction in complexity and calibration, and is shown to be helpful for numerous solar geoengineering applications including the serious need to reduce the UHI effect worldwide. Solar geoengineering solutions will require a lot of creativity, in addition to modeling, suggestions are provided for drought relief ideas and Paris Accord goals required for any successful urban solar geoengineering coordinated effort.