What allows scientists to predict future climate change with some sense of accuracy?

They can look at previous data and compare it to current data of the climate, from there they can estimate climate change. Example: in 1977on july 23rd the temperature was 28°C. on july 23rd 2017 the temperature was 32°C. the temperature in 40 years the temperature changed by 4°C

To accurately predict future climate change, scientists use computer programs.

Explanation:

Scientists use computer programs that work on powerful supercomputers to predict what the weather will be like in the future, these programs are called climate models. The programs create a three-dimensional, global model based on the laws of physics about how the atmosphere, land and oceans behave. Experts first simulate the current climate to validate the model's effectiveness, then increase the amount of gas in the atmosphere and simulate the climate again. For this reason they can predict the weather with some precision time.