Chapter 2 Understanding nighttime methane signals at ATTO 21 Chapter 3 The CO 2 record at the Amazon Tall Tower Observatory: a new opportunity to study processes on seasonal and inter-annual scales 57 Chapter 4 Net carbon exchange in tropical South America 97 Chapter 5 Discussion and outlook 137 References 151 About the author 183 During 1999 and 2006 the atmospheric growth rate of CH 4 was stable (Dlugokencky E. et al., 2011), followed by a renewed growth, steeper than that of the years before 1999 (Nisbet et al., 2016). These contrasting dynamics have led to large interest in understanding what caused the stagnation and what is causing the actual steep growth.