Citola Blog
Solar Winds, Carbon Sinks
In a previous blog we described an intriguing recent study which reported a correlation between cosmic-ray intensity and tree-growth rate. Before we consider the implications of this study in climate change science and forestry, we’d like to take a look at what exactly “cosmic rays” are.
Cosmic rays are the name given to energetic particles which stream through space before hitting the Earth’s atmosphere. The “ray” part of the name is actually a misnomer (they’re particles, not rays) dating back to when they were first detected in the early 20th century and less fully understood. The vast majority of cosmic rays are protons, with a small proportion being made up of helium nuclei and electrons.
The level of cosmic rays that reach Earth is affected by two factors: the Earth’s magnetic field, and solar winds. The former is responsible for cosmic-ray intensity varying at different latitudes and longitudes. The latter is responsible for the differing levels of cosmic-ray intensity over time. It is this variation over time which is correlated with tree growth in Sigrid Dengel's research. Solar winds vary on an eleven-year cycle; high levels of solar activity impede cosmic rays on their journey to Earth. Hence solar activity and cosmic ray intensity are inversely related.
As mentioned in our initial blog on this topic, Dengel and her colleagues offer two explanations for the correlation they found between tree growth rate and cosmic rays. One is that the cosmic rays have some direct effect on tree growth. How this direct effect would actually function hasn’t been agreed upon. There has been research which demonstrates cosmic rays playing a role in the creation of organic molecules in space, although just how these kinds of reactions would effect Earth is unknown.
The second explanation for the correlation involves another variable – cloud cover. In 1997 Svensmark and Friis-Christensen demonstrated a correlation between cosmic ray intensity and cloud cover, hypothesising that the cosmic rays ionise molecules in the atmosphere around which clouds form, hence higher levels of cosmic rays result in more cloud cover. Cloud cover results in the diffusion of light and diffused light more easily penetrates through forests resulting in greater photosynthesis and increased growth.
In our next blog we’ll consider how these explanations and the findings themselves sit within our understanding of climate change…
Post new comment