Interactions Between Boreal Forests and Climate Change

The increasing concentrations of CO2 and other greenhouse gases (Chapter 1) change the behaviour of radiation energy in the atmosphere. Several processes (Section 6.2) respond to this redistribution of radiation. The conservation equations of mass, energy and momentum described in Section 7.2 can be solved numerically to study the resulting effects on climate. Changes in climate occur both as a result of natural variability and as a response to anthropogenic forcing. Some part of the natural variability is forced, that is, caused by external factors such as solar variability and volcanic eruptions. Another part is unforced, associated with the nonlinear internal dynamics of the climate system such as interactions between the atmosphere and the oceans. Because of these natural mechanisms, climate has always varied, on time scales ranging from years to millions of years (Jansen et al., 2007), and it would continue to vary in the future regardless of what mankind is doing. Nevertheless, when we focus on this and the following centuries, the effects of natural variability will likely be secondary when compared with anthropogenic changes in the global climate (Meehl et al., 2007).