Together with his counterparts in 10 other national academies of sciences, CAS President Lu Yongxiang recently signed a statement, stressing that the scientific understanding of climate change is now sufficiently clear and urging world leaders, including those meeting at the G8 summit next month, to do the following:    - Acknowledge that the threat of climate change is clear and increasing.    - Launch an international study to explore scientifically-informed targets for atmospheric greenhouse gas concentrations, and their associated emissions scenarios, that will enable nations to avoid impacts deemed unacceptable.    - Identify cost-effective steps that can be taken now to contribute to substantial and long-term reduction in net global greenhouse gas emissions. Recognize that delayed action will increase the risk of adverse environmental effects and will likely incur a greater cost.    - Work with developing nations to build a scientific and technological capacity best suited to their circumstances, enabling them to develop innovative solutions to mitigate and adapt to the adverse effects of climate change, while explicitly recognizing their legitimate development rights.    - Show leadership in developing and deploying clean energy technologies and approaches to energy efficiency, and share this knowledge with all other nations.    - Mobilize the science and technology community to enhance research and development efforts, which can better inform climate change decisions.    The statement is signed by Academia Brasiliera de Ciëncias, Brazil; Royal Society of Canada, Canada; Chinese Academy of Sciences, China; Acadëmie des Sciences, France; Deutsche Akademie der Naturforscher, Germany; Indian National Science Academy, India; Accademia Nazionale dei Lincei, Italy; Science Council of Japan, Japan; Russian Academy of Sciences, Russia; Royal Society, UK; and the National Academy of Sciences, US.