Sahara Dust and Atlantic Ocean Temperatures

The Role of Aerosols in the Evolution of Tropical North Atlantic Ocean Temperature Anomalies

Observations and models show that northern tropical Atlantic surface temperatures are sensitive to regional changes in stratospheric volcanic and tropospheric mineral aerosols. However, it is unknown whether the temporal variability of these aerosols is a key factor in the evolution of ocean temperature anomalies. We used a simple physical model, incorporating 26 years of satellite data, to estimate the temperature response of the ocean mixed layer to changes in aerosol loadings. Our results suggest that the mixed layer’s response to regional variability in aerosols accounts for 69% of the recent upward trend, and 67% of the detrended and 5-year low pass–filtered variance, in northern tropical Atlantic Ocean temperatures.

Free Will

The Sources of Human Volition

Every day we make actions that seem to depend on our "free will" rather than on any obvious external stimulus. This capacity not only differentiates humans from other animals, but also gives us the clear sense of controlling our bodies and lives. It therefore forms a key element of our personal identity. However, such voluntary actions are a puzzle for modern neuroscience. Where do they come from? A study by Desmurget et al. (1) on page 811 of this issue reveals how the brain may produce our experience of initiating voluntary action.