Abstract: Common Era climate change research is one of the key ways to resolve the attribution of climate warming in the 20th century. In recent years, it has made considerable progress. This paper reviews the research history, introduces the representative reconstruction results and summarizes some new scientific understanding of Common Era climate change research in some aspects:temperature reconstructions of the past 2 000 years in Northern Hemisphere (NH) and China, external forcing variabilities and their effects on temperature. The main scientific knowledges are summarized as follows:(1) Variation in the extratropical NH summer temperature is in phase at timescales from decadal to centennial during the last millennium; (2) At a centennial timescale, solar variability may play an important role in the NH temperature variation, but large volcanic eruptions are primary drivers of interannual-to-decadal temperature variability, and consecutive large volcanic eruptions may cause century-scale regime shifts of the climatic mean state; (3) Greenhouse gases is one of the leading factors of climate warming since industrial revolution, but interdecadal temperature fluctuations are also affected by internal variability of the climate system.In the future, the main research focuses of Common Era climate change will be to quantify the impact of various drivers on climate change and reveal the mechanism of climate change by combining the simulation and reconstruction results.

Key words: temperature reconstruction, external forcing, Northern Hemisphere, China