A few months ago, forecasters declared: El Nino is here!
Just recently, the Climate Prediction Center said El Niño will strengthen during summer and into fall.
But will it really impact weather? CPC ENSO blog editor and meteorologist Tom DiLiberto says every weather event will be blamed on El Niño now, but its real effects in the summer are "minimal at best."
"El Niño does have substantial impact on rainfall patterns elsewhere globally during June through August," he says, acknowledging that it does impact seasonal hurricane activity. "However, it is hard to overcome the suspicion that El Niño is pulling all the atmospheric strings and creating an ever-increasing amount of extreme weather events compared to a year without an event."
In his recent post on El Niño's effects, DiLiberto answers a few questions on El Niño in the summer:
Is El Niño causing every weather event we see? ENSO (El Niño southern oscillation) is not the only influence on where or how much rain falls in any given region in a given year, he says.
"ENSO is only the cause of roughly 15-20% of the extreme precipitation," DiLiberto says. "The rest, 80-85%, is due to other factors on our planet. If extreme precipitation was a large pizza, ENSO would account for only two slices."
He says because ENSO doesn't control 100% of the precipitation extremes, no single El Niño or La Niña meets the ideal specifications of that pattern.
Are there a greater number of extreme precipitation events during El Niño years than a normal year? Research on observations since 1950 suggests only 20-30% of land areas across the globe are potentially affected during El Niño and La Niña, DiLiberto says, and extreme precipitation anomalies during El Niño and La Niña are actually comparable to those during Neutral conditions.
Ultimately, research suggests climate-related disasters do not increase during El Niño/La Niña years, he says.
"While there could be high profile impacts in certain regions during El Niño or La Niña, there are also inevitably going to be large precipitation anomalies somewhere across the globe even during years without an El Niño or La Niña," DiLiberto says.
How do we benefit from knowing where El Niño can influence these events? Though research shows only 20-30% of land areas show a repeatable pattern during ENSO events and ENSO explains only 15-20% of what is seen in extreme precipitation, forecasters really use that information, DiLiberto says.
"Unlike other atmospheric patterns that influence weather for weeks to seasons, ENSO is forecastable on a monthly to seasonal time scale," he says. "While never a guarantee, if ENSO occurs or is predicted several months in advance of its peak influence, then we can assume a tilt in the odds towards certain impacts."
According to averaged Heidke skill scores – which measure accuracy of forecasts – DiLiberto says forecasters' scores were higher during both El Niño and La Niña than they were for Neutral.
"This result is consistent with previous research that found seasonal rainfall forecasts are better during ENSO events and are often the best when ENSO events are stronger," he says. "While you cannot blame everything on El Niño or La Niña, El Niños and La Niñas still provide forecasters with a better idea for where changes in impacts (extreme or not) will occur."
Continued reading: Purdue climate tool lets you see impact of past El Niño events
Source: NOAA ENSO blog