Blame global warming for wild weather? NASA says, “Blame La Nada”


Here’s what NASA said:

What’s to Blame for Wild Weather? “La Nada”

Such sheets of fire, such bursts of horrid thunder,
Such groans of roaring wind and rain, I never
Remember to have heard; man’s nature cannot carry
The affliction nor the fear
… from Shakespeare’s Tragedy of King Lear

June 21, 2011: Record snowfall, killer tornadoes, devastating floods: There’s no doubt about it. Since Dec. 2010, the weather in the USA has been positively wild. But why?

Some recent news reports have attributed the phenomenon to an extreme “La Niña,” a band of cold water stretching across the Pacific Ocean with global repercussions for climate and weather. But NASA climatologist Bill Patzert names a different suspect: “La Nada.”

“La Niña was strong in December,” he says. “But back in January it pulled a disappearing act and left us with nothing – La Nada – to constrain the jet stream. Like an unruly teenager, the jet stream took advantage of the newfound freedom–and the results were disastrous.”

Wild Weather (La Nina, 558px)

The blue and purple band in this satellite image of the Pacific Ocean traces the cool waters of the La Niña phenomenon in December 2010. (from Ocean Surface Topography Mission (OSTM)/Jason-2 satellite, Credit: NASA JPL)

La Niña and El Niño are opposite extremes of a great Pacific oscillation. Every 2 to 7 years, surface waters across the equatorial Pacific warm up (El Niño) and then they cool down again (La Niña). Each condition has its own distinct effects on weather.

The winter of 2010 began with La Niña conditions taking hold. A “normal” La Niña would have pushed the jet stream northward, pushing cold arctic air (one of the ingredients of severe weather) away from the lower US. But this La Niña petered out quickly, and no El Niño rose up to replace it. The jet stream was free to misbehave.

“By mid-January 2011, La Niña weakened rapidly and by mid-February it was ‘adios La Niña,’ allowing the jet stream to meander wildly around the US. Consequently the weather pattern became dominated by strong outbreaks of frigid polar air, producing blizzards across the West, Upper Midwest, and northeast US.”1

The situation lingered into spring — and things got ugly. Russell Schneider, Director of the NOAA-NWS Storm Prediction Center, explains:

“First, very strong winds out of the south carrying warm, moist air from the Gulf of Mexico met cold jet stream winds racing in from the west. Stacking these two air masses on top of each other created the degree of instability that fuels intense thunderstorms.”

Extreme contrasts in wind speeds and directions of the upper and lower atmosphere transformed ordinary thunderstorms into long-lived rotating supercells capable of producing violent tornadoes.2

Wild Weather (La Nada, 558px)

This satellite image, taken in April 2011, reveals La Niña's rapid exit from the equator near the US coast. The cool (false-color blue) water was gone by early spring. (from Ocean Surface Topography Mission (OSTM)/Jason-2 satellite, Credit: NASA JPL)

In Patzert’s words, “The jet stream — on steroids — acted as an atmospheric mix master, causing tornadoes to explode across Dixie and Tornado Alleys, and even into Massachusetts.”

All this because of a flaky La Niña?

“La Niña and El Niño affect the atmosphere’s energy balance because they determine the location of warm water in the Pacific, and that in turn determines where huge clusters of tropical thunderstorms form,” explains Schneider. “These storms are the main energy source from the tropics influencing the large scale pattern of the jet stream that flows through the US.”

In agreement with Patzert, he notes that the very strong and active jet stream across the lower US in April “may have been related to the weakening La Niña conditions observed over the tropical Pacific.”

And of course there’s this million dollar question: “Does any research point to climate change as a cause of this wild weather?”

“Global warming is certainly happening,” asserts Patzert, “but we can’t discount global warming or blame it for the 2011 tornado season. We just don’t know … Yet.”3

What will happen next? And please don’t say, “La Nada.”

Author: Dauna Coulter | Editor: Dr. Tony Phillips | Credit: Science@NASA

End Notes

(1) Other atmospheric factors also contributed to the inflow of frigid polar air, says Patzert. One of the most significant was a weakening in the whirlpool motion of the air around the North Pole. As a result of this weakening, more cold air flowed away from the pole and down toward the states. Climatologists call this an “arctic oscillation.”

(2) Imagine a paddle wheel oriented like a Ferris wheel and placed in winds that that are much stronger at the top than at the bottom. The wheel will spin in the direction of the strong winds above. This spring, these strong, turning winds led to ongoing rotation of the supercells themselves. So we ended up with intense rotation and updraft close to Earth’s surface — conditions ripe for strong tornadoes.

(3) On May 26, 2011, Patzert posted a comment about this topic on Andrew Revkin’s The New York Times’ DOT EARTH Blog, “Demography, Design, Atom Bombs and Tornado Deaths.” See comment 6 at this URL.

Looks to me as if the people at NASA are saying we should go slow, and not rush to blame our weather woes on climate change. Climate change “skeptics” should be so skeptical.

About these ads

2 Responses to Blame global warming for wild weather? NASA says, “Blame La Nada”

  1. [...] Climate What is causing our crazy weather? Answer: a very naughty jet-stream, which isn’t being contained by La nina or El nino (La nada?… [...]

    Like

  2. Pangolin says:

    While any specific weather event is not attributable to climate change the cumulative pattern of weather disruptions, extreme weather events and disasters shows a clear signal of change.

    One Cheerio isn’t a breakfast but the whole bowl with a banana and milk clearly are. You can dismiss any one event but you can’t dismiss them all one by one.

    Climate Change is here and it is a killer. It is also only going to get worse.

    Like

Play nice in the Bathtub -- splash no soap in anyone's eyes.

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

Follow

Get every new post delivered to your Inbox.

Join 2,333 other followers

%d bloggers like this: