Step-by-step explanation:
The human activity that would have the most significant effect on the temperature of the earth is the large-scale burning of fossil fuels, such as coal, oil, and natural gas. This process releases vast amounts of greenhouse gases like carbon dioxide (CO2) and methane (CH4) into the atmosphere, which trap heat and cause the greenhouse effect. As a consequence, global temperatures rise, leading to climate change and its associated effects on ecosystems, weather patterns, and sea levels. Additionally, deforestation and industrial processes contribute to greenhouse gas emissions and also have a significant impact on global temperatures.