Extreme Events and Climate Variability

Issues: Scientists are telling us that global warming means more extreme weather. Every year we seem to experience weather extremes. What is the origin of extreme events?

A Major Issue for All Countries Is Global Warming and Its Regional Impacts

Seasonal Climate Impacts Depend on the Simultaneous Influences of: Natural Climate Variability El Nino/La Nina Pacific Decadal Oscillation (PDO) Arctic Oscillation (weak impact in Tropics) Climate Change Atmospheric Noise Extreme Events are Mostly Related to Circulation Changes, i.e. to Variability

The El Nino/Southern Oscillation (ENSO) is a major factor in global climate variability.

The Pacific Decadal Oscillation (PDO) Typical wintertime Sea Surface Temperature (colors), Sea Level Pressure (contours) and surface windstress (arrows) anomaly patterns during warm and cool phases of PDO

Societal Impacts from 1997/98 El Nino

Major Weather-Related Natural Disasters (1999 La Nina)

Impacts of December 1999 Floods in Venezuela

Typical winter Weather Anomalies and Atmosphere Circulation Changes During El Nino & La Nina

Contributions to Surface Temperature Trend from

SUMMARY Extremes result from: - major climate anomalies (e.g. especially El Nino and La Nina in Tropics) - unusual atmospheric circulation patterns (mostly related to climate variability) - factors acting together for air temperature (e.g. ENSO, PDO, AO, global warming) The impacts of the warming trend on circulation changes, i.e. also extremes, is still a research issue