The main processes of land-climate interactions

In this lesson, you will learn about the main processes governing land-climate interactions, namely the energy, water and carbon cycles. You can visit the Climate Change Projects for additional information.

Land continuously interacts with the atmosphere by exchanges of mass and energy. The exchange of mass occurs through three cycles: the energy, water and carbon cycles. The nitrogen cycle is also part of the biochemical cycle of the Earth’s Climate.

As you have seen earlier, solar energy facilitates the exchange of water between land and atmosphere through the latent heat flux, the heat exerted to evaporate water from the surface. Solar radiation also enables the process of photosynthesis: a biochemical reaction in which water and carbon dioxide are combined to produce biomass in the form of carbohydrates. Land surface characteristics affect the three cycles (energy, water, and carbon). For example, land cover type determines the amount of reflected or absorbed solar energy. Land roughness influences turbulent exchanges of momentum, energy, water, and carbon exchange (IPCC).

In addition to its interaction with the atmosphere, the land also interacts with the ocean through processes such as the influx of freshwater, nutrients, carbon, and particles (IPCC). Figure (1) below shows how land interacts with the atmosphere and ocean.

Figure 1: Some of the fundamental land processes governing biophysical and biogeochemical effects and feedbacks to the climate, source IPCC report (Click to expand)

These interactions can well be investigated using satellite data records of essential climate variables (ECVs), for example, those produced by the Climate Change Initiative of the European Space Agency. An example of a land ECV relevant to the water cycle is soil moisture. The energy cycle may be studied using land surface temperature. Terrestrial carbon sinks and sources can be investigated by using land cover, fire and biomass ECVs.

So what is land?

The term “land” can be defined in various ways depending on the context, but in general, it refers to the Earth’s surface not permanently covered by water or ice. Land plays a critical role as a resource for agriculture, forestry, and land-use sector since it provides food, fibre, and fuel for approximately seven billion people. The importance of land in climate change mitigation plans is reflected in the activities of the Intergovernmental Panel on Climate Change (IPCC). According to the IPCC report, essential mitigation scenarios must consider land as the main emission source of greenhouse gases causing global warming. The anthropogenic (human-caused) enhancement of the greenhouse effect is mainly due to carbon dioxide emission from land-based activities (fossil fuel burning, deforestation, and land-use changes). Terrestrial ecosystems remove about 30% of the carbon dioxide emitted by human activities each year (Friedlingstein et al., 2020, Terre et al., 2021). However, processes like wildfire and deforestation disturb the functioning of land and affect all three cycles (energy, water and carbon).

Up Next

In the next article, you will develop a deeper understanding of how climate affects the ability of the land in producing vegetation: crops, plants, and forests.