1.1 Climate change at a large scale
At a large scale, climate change causes raise in temperatures,
also known as global warming. It also induces more drought and less rain events
(Eveno et al., 2016). Global warming can be defined as the average increase of
air temperature near the surface of Earth over the past one to two centuries
(E. Mann, Selin, 2022).
Climate change has so far caused the increase of the average
world yearly temperature over the last century, affecting the growing
conditions for grape producers.
Climate change at the viticultural scale can affect yield,
quality and economic viability (Jones et al., 2005). Due to global warming, the
phenological stages of grapevine will continue to be earlier in the second part
of the 21st century (Duchêne et al., 2010; Webb et al.,
2007).
Harvest date is a good indicator for climate change. Indeed, a
10-day variation in harvest reflects a 1°C variation of the temperature
received by grapevine over the growing season. Over the last 50 years, a 15 to
20 day difference was observed for harvest date in the French viticultural
regions (Daux et al., 2007).
Additionally, climate change can impact the geographical
repartition of grape varieties based on the evolution of climate indexes (Jones
and Webb, 2010). In order to maintain a certain quality and yield of grapes,
the easiest long-term solution is to change grape varieties.
Some studies based on different climate model simulations
suggest that our planet's average temperature could rise between 1.1 and
5.4°C by 2100, compared to our actual climate (Herring, 2021).
Consequently, this raise in temperatures is expected to only cause more yield
losses.
1.2 Climate change at the scale of the Bordeaux
vineyard
1.2.1 Global warming in Bordeaux constatation
In the Bordeaux region, according to
Météo-France (Lafon, 2021), the average temperatures have raised
by 1.2°C since the beginning of the century. Moreover, this tendency is
accompanied by an increase in heat wave events, as well as a reduction in cold
episodes. According to a comparison between different possible scenarios,
global warming will increase, and the annual average temperature in Aquitaine
will gain between 2 to 5 °C by the end of the century (Salles and Le
Treut, 2017).
According to the Aquitaine Artelia report, global warming will
keep increasing, and the annual average temperature in Aquitaine will gain
+2.2°C by the end of the century (Artelia, 2015).
During the last 20 years, the Médoc vineyard has faced
many canicular events happening during the summer. The frequency of those
events is growing and has consequences on the grapevine physiology, affecting
its photosynthesis process as well as its water resources.
The canicular events characteristics are evolving more rapidly
under the influence of climate change, becoming more frequent, longer, and more
intense since 2015 (Adélaïde and Chanel, 2021).
In the long-term, those temperatures are going to keep raising
until it won't be possible to keep cultivating the same grape varieties.
According to an article published by the Proceedings of the National Academy of
Sciences, close to 86% of the Bordeaux grape production is set up to be wiped
out by 2050 due to global warming (Hannah et al., 2013).
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