"Potential effects on climate in the 21st century include the creation of drought-prone regions in North America and central Asia as part of a shifting of climate zones, erosion of the West Antarctic ice sheet with a consequent worldwide rise in sea level, and opening of the fabled Northwest Passage.”
Projecting changes in climate due to changes in atmospheric composition or other factors is easier than predicting the weather. It is impossible to predict the age at which any particular man will die, but we can say with high confidence what the average age of death for men is.
Similarly, a climate prediction might say that average summer rainfall over London is predicted to be 50% less by the 2080s.
It will not predict that it will be raining in London on the morning of 23rd August 2089. Another way to predict the outcomes of climate change is to examine the geological record of ancient events.
Atmospheric CO2 is now around 400 parts per million (ppm).