Relative Importance of Internal Climate Variability versus Anthropogenic Climate Change in Global Climate Change

Abstract To better understand the role of internal climate variability (ICV) in change impact studies, this study quantifies importance ICV [defined as intermember a single model initial-condition large ensemble (SMILE)] relation to anthropogenic (ACC; defined multimodel mean) global and regional using criterion time emergence (ToE). The uncertainty estimated ToE is specifically investigated by three SMILEs estimate ICV. results show that 1921–40 baseline period, annual mean precipitation ACC expected emerge within century over extratropical regions well along equatorial band. However, ToEs are unlikely occur, even end century, intratropical outside In contrast, temperature has already emerged from for most globe. Similar spatial patterns observed at seasonal scale, while weaker boreal summer (June–August) additional winter (December–February) translate later some regions. addition, related choice SMILE mostly less than 20 years temperature. it can be 90 Overall, indicate significant source estimation based on only one should interpreted with caution.