And the sad part - the usual suspects still try to pin the blame for the tragedy in Moore, OK on CAGW.

The Oklahoma tornado provides a good example of the unpredictable death toll that disasters can inflict. Before it flattened Plaza Towers Elementary, the tornado also tore through Briarwood Elementary and — though the roof collapsed — everyone at Briarwood appears to have survived. Both schools lacked tornado safe rooms, and at both, students initially were sent to the halls before some teachers squeezed them into seemingly safer places such as closets and bathrooms.
Interestingly, an MSM article showed up which actually covers the state of the science: that there is no link detected thus far whatsoever between tornados and CAGW:

On Monday a massive and devastating tornado struck Moore, Okla., bringing death and destruction to the community south of Oklahoma City.
The Moore tornado killed more than 50 people. (AP)

Almost immediately, on the weather blog where I was chronicling the twister’s deadly path, the topic of climate change came up. Specifically, CenTexDem wrote:

Just one more reason to stop burning coal and other carbon fuels which are the primary generators of global warming driving these devastating super storms.

As that blog is devoted to weather, and this one to science, I promised to raise the issue here. And so I am doing so.


The question of a climate-tornado link has been simmering for years, but came to a boil in 2011 during the end of the busiest 12-month period on record for tornadoes in U.S. history.

At the time NOAA’s Earth System Research Laboratory, under the direction of Martin Hoerling, assessed whether the warming climate had affected the 2011 severe weather season in general, and specifically tornado activity.

They reported

Neither the time series of thermodynamic nor dynamic variables suggests the presence of a discernible trend for April conditions during the last 30 years; any small trend that may exist would be statistically insignificant relative to the intensity of yearly fluctuations. A change in the mean climate properties that are believed to be particularly relevant to major destructive tornado events has thus not been detected for April, at least during the last 30 years. So far, we have not been able to link any of the major causes of the tornado outbreak to global warming. Barring a detection of change, a claim of attribution (to human impacts) is thus problematic, although it does not exclude that a future change in such environmental conditions may occur as anthropogenic greenhouse gas forcing increases.

Translation: There is no evidence at this time to link present tornado activity to climate change. The time series to which the assessment referred to is shown below.

A 1979-2010 time series of April total column precipitable water (PW, top and second panel, kg/m2) and CAPE (third panel, J/kg), and the magnitude of the vector wind shear in surface-500 mb layer (bottom, m/s). (NOAA)

The basic gist of this graphic is that none of the primary variables associated with tornado formation, including ”convective available potential energy” or “CAPE,” have showed a trend during April for the previous 30 years.

The Intergovernmental Panel on Climate Change has also addressed the issue of severe weather in a warming world, and it’s conclusion about tornado activity in a warming world is similar (see page 11 of this report):

There is low confidence in projections of small spatial-scale phenomena such as tornadoes and hail because competing physical processes may affect future trends and because current climate models do not simulate such phenomena.

The bottom line from the Hoerling and IPCC analyses is that it’s conceivable that a warming climate could affect tornado activity, but that there’s simply no evidence it is doing so yet.


Ironically, just a few weeks ago we were talking about a significant drought of tornadoes.

During the 12-month period from May 2012-April 2013 there were just 197 tornadoes rated EF1 or stronger, which represented a record low for U.S. tornadoes in a 12-month period, said NOAA tornado expert Harold Brooks.
Running 12-month total of EF1+ tornadoes starting in January 1954 and ending in April 2013. (NOAA)

The fact that the United States swung from a record high in 2010-11 (see graphic above) to record low in 2012-13 caught the attention of meteorologist Patrick Marsh of NOAA’s Storm Prediction Center.

He calculated that the record 12-month tornado maximum of 1,050 EF-1 and stronger tornadoes from June 2010-May 2011 was a 1-in-62,500 year event, and the record 12-month low of 197 EF-1 and stronger tornadoes that occurred from May 2012-April 2013 was a 1-in-3000 to 1-in-4000 year event.

In summary, Marsh wrote: “Anyway you look at it, the recent tornado ‘surplus’ and the current tornado ‘drought’ is extremely rare. The fact that we had both of them in the span of a few years is even more so!”

Could this be related to climate change? Perhaps climate change is causing more extremes, both and high low. “The extraordinary contrast underscores the crazy fluctuations we’ve seen in Northern Hemisphere jet stream patterns during the past three years. Call it ‘Weather Whiplash’ of the tornado variety,” says Jeff Masters.

Nevertheless, when it comes to tornadoes and a warmer world, science really cannot say at this time. The basic fact of the Moore, Okla., tornado is that the town is smack dab in the middle of the Central Plains, where there are frequent collisions of warm, moist air from the south and cold air from further north, and there are no land features to block the flow of air between these two disparate air masses.

So there are lots of tornadoes.