  Particularly in the presence of a hydrothermal system, many volcanoes output
large quantities of heat through the transport of water from deep within the
edifice to the surface. Thus, heat flux is a prime tool for evaluating volcanic
activity and unrest. We review the volcanic unrest at La Soufri\`ere de
Guadeloupe (French West Indies) using an airborne thermal camera survey, and
in-situ measurements of temperature and flow rate through temperature probes,
Pitot-tube and MultiGAS measurements. We deduce mass and heat fluxes for the
fumarolic, ground and thermal spring outputs and follow these over a period
spanning 2000--2020. Our results are compared with published data and we
performed a retrospective analysis of the temporal variations in heat flux over
this period using the literature data.
  We find that the heat emitted by the volcano is 36.5 +/- 7.9 MW, of which the
fumarolic heat flux is dominant at 28.3 +/- 6.8 MW. Given a total heated area
of 26780 m2, this equates to a heat flux density of 627 +/- 94 W/m2, which is
amongst the highest established for worldwide volcanoes with hydrothermal
systems, particularly for dome volcanoes. A major change at La Soufri\`ere de
Guadeloupe, however, is the development of a widespread region of ground
heating at the summit where heat output has increased from 0.2 +/- 0.1 MW in
2010 to 5.7 +/- 0.9 MW in 2020. This change is concurrent with accelerating
unrest at the volcano, and the emergence of two new high-flux fumaroles in
recent years. Our findings highlight the importance of continued and enhanced
surveillance and research strategies at La Soufri\`ere de Guadeloupe, the
results of which can be used to better understand hydrothermal volcanism the
world over.
