  With climate change, we are expecting more frequent extreme weather events in
many regions worldwide. These events can trigger disruptive, deadly natural
hazards, which catch the attention of the media and raise awareness in citizens
and policymakers. Floods, wildfires, landslides are the object of a great deal
of research. Yet, they remain difficult to predict and handle. Climate change
also means warmer temperatures, especially on land. Glaciers melt, permafrost
thaws. Everywhere, the ground gets warmer down to increasing depths. At first
sight, not a big deal. What can a few extra degrees do? Microbes and fungi
becomes more active, chemical equilibria shift. Silent changes are left
unnoticed, even by scientists. In landslide studies, the stability of slopes is
a balance of weights, water pressures, and mechanical strengths. Above
freezing, temperature is left out, yet it should not be. The strength of clays,
which frequently are abundant in soils, is sensitive to temperature. With a
simple numerical exercise, we show to what extent temperature can condition and
even undermine the stability of clay-bearing slopes, across the seasons and
under global warming. A silent change that could make a non-extreme weather
event have much more severe consequences.
