The system is so complex that, to date, our best computer models are only crude approximations --- and are not sophisticated enough to test hypotheses about the causes of climatic change.

该系统是如此复​​杂，以至于迄今为止，我们最好的计算机模型只是粗略的近似值——而且还不够复杂，无法检验关于气候变化原因的假设。