Climate Sense

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Climate watch – purpose and requirements

Omar Baddour, World Meteorological Organization, Chief Data Management Applications Division;

and Pierre Bessemoulin, Météo France, President, World Meteorological Organization Commission for Climatology

atural climate variability operates on multiple

scales at all times and can affect global and regional

atmospheric and oceanic circulations. Many of these

variations are recurrent and are usually recognized as well

known climatic patterns – warming/cooling of Sea Surface

Temperatures in the tropical oceans such as the El Niño

Southern Oscillation (ENSO), the North Atlantic Oscillation

(NAO), the Madden-Julian oscillation and the strengthening/

weakening of the upper level jets – and are often characterized

in terms of climate indices (for example, ENSO or NAO index).

They correlate significantly with departures from the mean

state of climate parameters at monthly, seasonal and interan-

nual timescales, as well as with the possible onset at some

regional levels of extreme climate and weather

events leading to direct and indirect impacts on

lives, goods, properties and the well-being of soci-

eties. Droughts, heat waves, cold waves, flooding,

extreme wind storms, landslides, bush and forest

fires, and coastal erosions are just a few of the

impacts that can be triggered by one or several of

such anomalies. In the context of global warming

these extremes are expected to become more

frequent, more severe and of a greater geographi-

cal extent than previously recorded.

Some of the

observed increases in climate extremes already fit

in with such projections.

bserving

, P

redicting

and

rojecting

limate

onditions

Climate watches help people and the authorities to prepare for extreme weather conditions and mitigate the damage caused

Image: NOAA