The increase in temperature on Earth by the end of the 21st century is projected to be between 2.5 and 10.4 degrees Fahrenheit (1.4 and 5.8 degrees Celsius), depending on the level of greenhouse gas emissions and the effectiveness of mitigation efforts.
The Intergovernmental Panel on Climate Change (IPCC) has released several reports that provide projections for global temperature increase. According to the IPCC's Fifth Assessment Report (AR5), if greenhouse gas emissions continue to increase at their current rate, the global average temperature is likely to increase by 4.8 degrees Fahrenheit (2.6 degrees Celsius) or more by the end of the 21st century. However, if significant efforts are made to reduce emissions, the increase in temperature could be limited to 2.5 degrees Fahrenheit (1.4 degrees Celsius) or less.
It's worth noting that this is an estimate and there are many factors that can affect the temperature, such as natural variability, solar radiation, volcanic activity, and others. The actual temperature increase may be higher or lower than the projections depending on these factors and the effectiveness of global efforts to reduce emissions and mitigate the effects of climate change.