Final answer:
If humans replace much of today's fossil fuel combustion with new and more efficient technologies, global surface temperatures by the year 2100 are expected to increase within the range of 1-2°C, assuming aggressive reduction efforts and global cooperation in reducing greenhouse gas emissions.
Step-by-step explanation:
The question asks about the expected increase in global surface temperatures by the year 2100 if humans significantly reduce the use of fossil fuels by replacing them with new and more efficient technologies. Considering that climate models predict a rise of 0.3-4.8 degrees Celsius without specifying the extent of technological advancements and fossil fuel replacement, it is challenging to pinpoint an exact temperature increase. However, mathematical models suggest that with a super-aggressive effort to wean off fossil fuels by 2050, we might expect a temperature rise of approximately 2°C. This implies that if such efforts are implemented, we might expect an increase within the range of 1-2°C, assuming the strategies for reducing greenhouse gas emissions are effective and global cooperation is achieved.
The greenhouse effect works by trapping heat in the Earth's atmosphere through the absorption of infrared radiation by greenhouse gases such as carbon dioxide (CO2). If humans manage to reduce these emissions by transitioning to more efficient energy technologies, the potential warming could be limited. Most climate experts agree that limiting future global warming to less than 2.0 degrees Celsius is crucial to avoid catastrophic impacts and allow for adaptation by natural and human systems.