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1. The Earth model
Significant advances have been made in climate prediction by taking into account the state of the
ocean. Ocean observations and models have helped refine simulations of its circulation system coupled
with that of the atmosphere for predicting the climate. A model is a simulation or a representation
simplified of a complex system like the climate.
Determination of the absolute altitude of the ocean surface using satellite altimetry yields continuous,
homogeneous measurements of the dynamic state of the ocean which constitute input data for the
ocean models. Such models provide essential information on the annual and inter-annual variations in
ocean circulation and sea levels. The average sea level measured is an indicator of climate change.
Campaign of oceanographic observations in the Pacific.
2. Early warning of El Niño
Models that couple together ocean and atmospheric events can successfully
predict most El Niño events between six and 18 months in advance. These
predictions are used by countries hit by this climatic anomaly so that
they can anticipate and reduce its effects on agriculture, fisheries, water
resources management and public health.
Every year Peru, a country severely affected by El Niño, issues seasonal rainfall
and temperature forecasts. These bulletins help farmers to adapt their crop
planting programmes and fishermen to prepare better for variations in fish
stocks.
3. Climate change – a challenge for research
In the face of warnings about intensification of the greenhouse effect, the international scientific community pulled together to
develop powerful calculation tools. Integrated models simulate climate trends over the whole of the globe for the next decades.
These simulations are based on different potential scenarios for trends in greenhouse gas concentration linked to human
activities.
The ocean absorbs a large fraction of the heat and CO2 emitted into the atmosphere as a result of the intensification of
the greenhouse effect. Part of this heat is transferred towards the depths of the ocean and raises a crucially important
question. Where and when will the ocean give up this heat? Carbon transfer between the surface and the sea floor
takes centuries and the ocean’s capacity to reabsorb this CO2 is unknown. Finding answers to these questions is a
major challenge for research on the oceans and the future climate of our planet.
Predictions for variations in average annual precipitation at the end of the XXIst Century
compared with the XXth Century
(Average scenario: stabilization of CO2 emission level 2020, after GIEC)
120 W
60 W
0
60 E
120
320 °
310 °
300 °
(in mm/day)