Observations
suggest the global reflectivity of Earth changed during recent decades. Although there is some ambiguity surrounding
these findings, it is clear that, should there be changes in clouds or
scattering aerosols, a change in the total solar radiation received at the
surface and the fraction of diffuse light could result. Intriguingly, the d18O of CO2
time series measured at Mauna Loa shows variability
during the 1990s that does not match secular trends in CO2
concentration or d13C. While a decrease in total solar radiation
alone would reduce biospheric productivity, an increase in diffuse light can
increase productivity, as has been argued for the period following the eruption
of Pinatubo. Moreover, since the changes in radiation affect the surface latent
energy exchange, the isotopic composition of terrestrial water with which CO2
interacts (specifically leaf and soil water) will be modified and can thus
drive a change in isotopic fluxes.
Author: N. Buenning, D. Noone, C. Still, W. Riley, et al (buenning at colorado dot edu)
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