NOAA researchers have built a "time machine" for weather that provides detailed snapshots of the global atmosphere from 1891 to 2008. The system's ability to "hindcast" past weather events is emerging as a powerful new tool for detecting and quantifying climate change.

For years, people have been pointing to El Niño as the culprit behind floods, droughts, famines, economic failures, and record-breaking global heat. Can a single climate phenomenon really cause all these events? Is the world just a step away from disaster when El Niño conditions develop?

The Southern Oscillation Index tracks differences in air pressure between the eastern and western sides of the tropical Pacific.

El Niño and La Niña conditions occur when abnormally warm or cool waters accumulate in tropical latitudes of the central and eastern Pacific Ocean. The Oceanic Nino Index is the tool NOAA scienitsts use to watch for these temperature changes. 

If we look only at rainfall changes, and not ocean temperatures, can we get a clearer picture of how climate change will influence ENSO? Guest blogger Mat Collins from University of Exeter explains what recent studies have to say.

ENSO diagnostic flowchart

The ENSO Diagnostic Discussion just came out. Sea surface temperatures are solidly above average in the equatorial Pacific... so what's behind forecasters' decision not to declare El Niño conditions?

An El Niño means lots of rain for California, correct? Well, some of the time, but not always.

After some very cold weather this month, folks are likely wondering if the early chill is a harbinger of things to come this winter. "Not necessarily," explains Mike Halpert of NOAA's Climate Prediction Center in this week's ENSO blog post.

How to interpret climate outlooks and make $$$$ millions.*

**OK, maybe an overstatement, but you'll at least understand probabilistic forecasts better.  

sea surface height anomaly from satellite data

What's behind the drop in probabilities this month? And why might forecasting this event be particularly tricky?

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