365 Days of Climate Awareness 137 – 2002 State of the World Climate

2002 World Climate Data

• Atmospheric CO₂ concentration: 372.59 ppm, +2.02 ppm from 2001
• Surface air temperature anomaly: +0.56°C/1.01°F, 16^th all-time 1880-2021
• Precipitation below 1961-1990 global average
• ENSO: neutral at year's beginning, El Niño by September

Global Conditions

• Above-average temperatures: Northern Hemisphere +0.63°C/1.13°F over 20^th century average; ocean surface +0.42°C/0.76°F over 20^th century average; Paraguay; Bolivia; Russia;
• Drought: Australia (esp. eastern); Indian monsoon (-19%); north coast of China; Mexico; parts of Central America; southern Brazil; eastern Africa; western Russia; northeast China; central Asia; Australia (as El Niño emerged)
• Extreme rain: southeast Asia; Japan; central and southern China; Taiwan; Philippines; eastern and northern Brazil; Argentina; Urugay; central and eastern Russia
  
  
  
  Larger version

Climate science features at times endless sequences of chicken-and-egg questions. Where do we stop in looking for causes for El Niño and La Niña events, when the sea surface temperatures which mark them are both effects and causes in a worldwide network of activity in the ocean and atmosphere? The point is not to throw our hands up in futility but rather go on analyzing what is happening, and what its antecedents and consequences are.

ENSO is one of the clearest examples we have on the planet of a large phenomenon which impacts the whole climate system, and is both caused by and generates chains of events on different timescales. Each interaction of these several different chains of events is unique. ENSO is an important indicator for global weather patterns and we are continuing to learn not only more specific detail about how it operates but also its role in historical trends.

In a year like 2002, with neutral ENSO giving way to El Niño conditions, a number of signs appear in the ocean and atmosphere months before the relaxation of the easterly trade winds and the eastward flow of warm surface water. The ocean and atmosphere in the Pacific tropics mirror each other, as warm water and air gather in the equatorial region. The tropical thermocline, denoted by the 20°C isotherm in the ocean, deepens from 100 to 200 m or more, signaling buildup of warm water at the surface. Meanwhile a dome of warm air builds over the zone of deepening warm ocean water. These are reliable predictors of an approaching El Niño.

Tomorrow: teleconnections.

Be brave, and be well.