A strange thing has been happening to the historic temperature dataset.  NOAA/NCDC have been frequently revising the temperatures, and not just for recent data, but for temperatures going all the way back to 1880.  The folks at C3Headlines have been keeping track of temperature data sets for several years.  They noticed that NOAA has been revising the dataset almost monthly, and noted that there were six revisions in December and three so far in January.  The revisions have a particular pattern.  Temperatures from dates before 1940 are being gradually made cooler, while temperatures since 1951 are being made warmer.  The effect is to make recent warming seem more alarming.  Other agencies that keep temperature data sets rarely make revisions.  See the story from C3Headlines here.

The National Oceanic and Atmospheric Administration (NOAA) has just published the “new normal” temperature for the U.S. Every ten years NOAA calculates the average high and low temperatures for a 30-year period and this is used as the “normal” temperature baseline.

The new normal temperature will be about 0.5 F warmer than the old normal temperature because the period 1998-2008 was warmer than mid-20^th Century norms. See graph below.

Notice than the 1920s and 1930s were as warm as 1998-2008. This was followed by a cooler period from 1940 to about 1978. The warm period of 1998 to 2008 is attributed to a super El Niño in 1998. It appears that the average temperatures have cooled since 2009. It remains to be seen whether this cooling will persist as some predict based on total solar irradiance and sunspot observations (see articles below).

The “normal” temperature baselines have some value to farmers in judging when to plant crops. Energy utilities also use these baselines to help predict energy demand. The “normal” temperature is just a mathematical construct. By choosing longer or shorter periods, the “normal” temperature would be different.

For more extensive discussion of the “new normal” see here and here.

See also:

Astronomers predict a major drop in solar activity, that means a cold spell

Declining Sunspots my trigger deep cooling period

Geophysicist predicts new “Little Ice Age” by 2050

NASA Says Earth Is Entering A Cooling Period

NASA Lowers Estimate of Carbon Dioxide Warming Effect

In the wake of the devastating tornadoes in the southeastern U.S., the global warming industry was quick to blame it on climate change and offered it as proof of their unfounded theories.

An article in the Huffington Post is typical of the hype: “Violent tornadoes throughout the southeastern U.S. must be a front-page reminder that no matter how successful climate deniers are in confusing the public or delaying action on climate change in Congress or globally, the science is clear: Our climate is worsening.”

But back on Planet Earth, reality prevailed. Dr. Roy Spencer , a scientist at UAH and NASA, writes,

If there is one weather phenomenon global warming theory does NOT predict more of, it would be severe thunderstorms and tornadoes.

Tornadic thunderstorms do not require tropical-type warmth. In fact, tornadoes are almost unheard of in the tropics, despite frequent thunderstorm activity.

Instead, tornadoes require strong wind shear (wind speed and direction changing rapidly with height in the lower atmosphere), the kind which develops when cold and warm air masses ‘collide.’ Of course, other elements must be present, such as an unstable airmass and sufficient low-level humidity, but wind shear is the key. Strong warm advection (warm air riding up and over the cooler air mass, which is also what causes the strong wind shear) in advance of a low pressure area riding along the boundary between the two air masses is where these storms form.

But contrasting air mass temperatures is the key. Active tornado seasons in the U.S. are almost always due to unusually COOL air persisting over the Midwest and Ohio Valley longer than it normally does as we transition into spring.

A paper published in 2005 predicted the possibility of more tornadoes, given the right conditions: “Colder than normal temperatures in the western US/Canada along with warmer than normal temperatures in the southern United States during La Niña events would act to strengthen the interactions between warm and cold air in the mid-west. There would be an increase in the number of days favorable for tornadic development. This would act to increase the number of violent tornadoes that occur during the late spring-early summer. Large multiple tornado outbreaks are more likely for the same reason.” (Atmospheric Science Paper No. 755, Colorado State University).

“US meteorologists warned Thursday it would be a mistake to blame climate change for a seeming increase in tornadoes in the wake of deadly storms that have ripped through the US south.” (Physorg.com)

“A top official at the National Oceanic and Atmospheric Administration (NOAA) rejected claims by environmental activists that the outbreak of tornadoes ravaging the American South is related to climate change brought on by global warming…There really is no scientific consensus or connection between global warming and tornadic activity….Jumping from a large-scale event like global warming to relatively small-scale events like tornadoes is a huge leap across a variety of scales.” (Fox News)

“The case linking tornadoes to global warming is even sketchier, and the science is far from settled. A 2007 NASA study predicted that the number of tornadoes would increase with global warming. A 2009 study by University of Georgia found the opposite. The number of recorded tornadoes has risen in the last 20 years, but the rise coincides with greater use of Doppler radar and other advanced means of detecting tornadic activity, creating an acute issue of data artifice.” (Washington Times)

The author of the 2009 paper cited above, Thomas Mote, director of University of Georgia Atmospheric Sciences program, “I know it is ironic saying this after last night when we had the most extensive outbreaks in 40 years, but there is some reason to believe we will see drier, more stable conditions in the southern U.S. as a consequence of climate change.” In other words, global warming should result in fewer tornadoes, and that has been the case. The graphic below from NOAA shows the incidence of strong tornadoes since 1950.