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3  Reciprocity between land cover and climate

               On a planetary scale, anthropogenic forcing has led to a persistent imbalance in the global mean top-of-
               atmosphere radiation budget (Forster et al., 2021). Perturbations in the radiation budget alters the global
               mean temperature, rainfall patterns and climate extremes (Pörtner et al., 2022). The burning of fossil fuels
               and subsequent rising CO2 levels as the main cause of climate change has become conventional wisdom
               among scientists and policy makers, and has led to a carbon focus for climate mitigation strategies all over
               the globe. However, the exclusive focus on greenhouse gas (GHG) emissions as the only cause of climate
               change  has  distracted  us  from  another  major  climate-impacting  development  that  has  occurred
               synchronously, namely land use change. Over the past 10,000 years, but particularly the past 3000 years, we
               have altered vast areas of terrestrial surfaces by clearing forests and expanding agriculture  (Ellis, 2021),
               enough to degrade up to 40% of Earth’s surface, according to the UNCCD (UNCCD, 2022). This has greatly
               altered the capacity of the land surface to infiltrate/retain rainfall, protect soils from solar radiation/erosion
               and  contribute  to  the  water/energy  cycles  via  evapotranspiration  and  cloud  formation  (Anthes,  1984;
               Lawrence et al., 2022; Seneviratne et al., 2010). Whilst recognizing CO2 emissions should be cut back, devising
               all climate change solutions within the carbon math paradigm will likely fall short in the long term. The state
               of the climate is not only a function of GHG, but also of water and radiant energy. These are biologically-
               mediated, interrelated cycles, and deploying only carbon-sequestering technology or reduction strategies
               will not restore the natural climate-regulating capacity of the biosphere.

               3.1  The climate regulating role of the biosphere

               The biosphere includes all life on Earth. The different components of the biosphere have co-evolved with the
               land, atmosphere and oceans and together govern the state of the climate through regulating the carbon,
               water and radiant energy cycles (Gettelman & Rood, 2016). This includes a climate in which life on Earth
               (including humans) has evolved and continue to depend on for their existence. The physical and ecological
               processes of the biosphere are driven by the energy from the Sun. Incident solar energy that reaches Earth’s
               atmosphere (insolation) will either reflect back to space (depending on clouds, aerosols or atmospheric
               composition), be absorbed by the atmosphere or penetrate through and reach Earth’s surface directly. After
               which this radiation is reflected or absorbed depending on albedo, which is determined by the colour/texture
               of  the  land  surface  (Spellman,  2017).  Upon  absorption  at  the  surface,  solar  energy  undergoes  a
               transformation  in  which  biosphere  largely  governs  the  flux  of  energy  between  the  surface  and  the
               atmosphere (Gerten et al., 2004). In particular, the biosphere plays an important role in the partitioning of
               latent and sensible heat (the Bowen ratio), which determines the amount of evapotranspiration and the
               temperature at the surface (Moon et al., 2020).
               Evapotranspiration refers to the process by which water moves from Earth’s surface to the atmosphere
               through  soil evaporation and  plant transpiration. Globally  this process consumes more than  half of the
               incoming  radiant  energy  (Trenberth  et  al.,  2009).  Vegetation  is  the  primary  factor  affecting
               evapotranspiration, as 59% of global evapotranspiration comes from terrestrial plant transpiration (Wang-
               Erlandsson et al., 2014). These exchanges and interactions between the biosphere and atmosphere regulate
               the hydrological cycle, govern the heat dynamics of the Earth and together produce the climate patterns we
               know today (te Wierik et al., 2021).

               Land-atmospheric  interactions  in  the  form  of  water  and  energy  exchanges  occur  at  the  atmospheric
               boundary layer (ABL), which marks the interface between these two spheres and largely influence global
               weather  and  climate  patterns  (Santanello  et  al.,  2018).  Changes  in  land  surface  affect  its  roughness
               properties, which, in turn, govern the degree of albedo and evapotranspiration coming from it (Perugini et
               al., 2017). Changes in evapotranspiration mediate the energy and water balance of the atmosphere and can
               influence local and regional climate and temperature (Wang-Erlandsson et al., 2022). For example, changes

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