Global-scale drought caused atmospheric CO2 increase



Identifying the mechanisms driving interannual fluctuations of atmospheric carbon dioxide is necessary for predicting future CO2 concentrations and climate change [Prentice et al., 2001]. A possible clue comes from a well-established positive correlation between atmospheric CO2 growth rates and the El Niño-Southern Oscillation phenomenon [Keeling et al., 1989; Bousquet et al., 2000]. Most tropical droughts are also linked to El Niño [Lyon, 2004], suggesting carbon losses from drought as a major cause for interannual CO2 variations.

A lag correlation between 7-month running means (see Figure 1) of monthly atmospheric CO2 concentrations [Cooperative Atmospheric Data Integration Project, 2004] and Niño 3 sea surface temperatures (available at for the period 1979–2003 peaks at a lag of four months with a correlation of 0.49, and a significance level above 99.9% (assuming 42 independent measurements).