Climate Exchange

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ater

A near-surface atmospheric reanalysis was first performed, forced

by ERA-40 and ERA-Interim.

Suitable indices, already used in

other countries, have then been derived in order to characterize

the various types of droughts than can occur, based on the SIM

suite’s variables: precipitation, SWI and river flows. A new climatol-

ogy of droughts was established over France.

Such a climatology,

combined with the daily updated analysis, improved at the end of

each month and revisited at the end of each year, enables charac-

terization of the situation and paves the way to a large number of

tailored services. The Norbert Gerbier-Mumm prize, delivered in

2011 by the World Meteorological Organization, recognized the

interest of such an approach.

Work was next completed to address the impact of climate

change during the twenty-first century on water resources.

The

forcings used were in that case regional climate scenarios. Various

scenarios, climate models and downscaling techniques were used

to address some of the uncertainties inherent in high-resolution

climate projections. Results show a very strong increase in dry

conditions over France. The role of the rising temperatures is

prominent, driving a very strong increase in evaporation demand.

In most cases, this process is dominant in relation to changes

in precipitation. Severe soil drought conditions are expected to

prevail from the middle of the century, showing the

urgent need for adaptation measures.

This study is a first attempt from the research commu-

nity and the French meteorological service to address

the impact of climate change on water resources. The

models, the scenarios, and more generally all features

of this study could be refined, revisited and definitely

improved. This will of course be done in the near future,

with improvements of all components of the study.

Although weaknesses can still be found in the tools or

the methodology, the result of this work is a major one

for our society. The message is clear: France will almost

certainly experience severe droughts, and therefore

adaptation has to be prepared right now for sustainable

and reasonable water use, agreed by all stakeholders.

Perhaps a more complicated part of the work is now

to carry this message to citizens and decision-makers,

and to imagine suitable forms for delivering it. This is

a challenge that will drive climatologists to work with

even larger communities, with specialists in informa-

tion representation, sociologists, historians and more,

and to find ways to get the entire society moving!

Drought in Camargue, South France, August 2007