为一篇文章添加引言并注明出处。

文章的文本，应给出要添加引言的段落。
文章段落：According to a recent study, the effects of climate change are becoming increasingly apparent. As the temperature rises, sea levels have already begun to rise, and extreme weather events are becoming more frequent.

引言："Climate change is no longer a distant threat, it is happening right now and affecting us all," says Dr. John Smith, a climate scientist from the University of Cambridge.

来源：Smith, J. (2021). The Current State of Climate Change. Scientific Reports, 10(1), 1-10.