Do All Projections Agree?
Although the various climate models agree in most important respects, they do show differences. Why?
1. Natural Variability
It is difficult or even impossible to predict variations in natural causes, such as the Sun or volcanoes. And it is difficult to predict the complex interactions of other natural factors, such as the oceans, atmosphere, and ecosystems.
2. Human Choices
Future CO2 emissions will depend on future population growth, technology developments, and global policy choices. This is not a factor in the two models shown previously because both were driven by the same scenario.
3. Scientific Uncertainty
Climate models are not perfect reflections of the natural climate system. For example, a major source of the differences between the NCAR and GFDL climate projections shown here is the way each simulates the behavior of clouds.
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