Hurricane Trends and Our Climate

Major storms are nature’s way to attempt to reduce temperature imbalances and restore equilibrium. Major winter storms move cold air south and warm air north. Hurricanes transport of excess heat from tropics to higher latitudes. There are more major winter storms when extreme cold comes south and hurricanes in warm years and eras when more heat builds on the tropics.

Hurricanes are giant heat engines - the average storm generates heat energy equivalent to all the electric energy produced in the US in an entire year. (Chris Landsea NOAA HRL). See how the hurricane threat diminished during the cold period from the 1960s to 1990s.

Hurricanes form over warm ocean water (primarily over 80F) during the summer into the fall. The activity varies year-to-year and over longer periods as natural equatorial ocean cycles like ENSO (El Nino or La Nina) and multi-decadal cycles in the northern Pacific (Pacific Decadal Oscillation or PDO) and Atlantic (Atlantic Multidecadal Oscillation or AMO) enhance or limit the ocean warming and affect the potential storm activity levels in one or more basins (West Pacific, East/Central Pacific or Atlantic).

There are more major hurricanes when the heat level in the ocean and the atmosphere in the tropics and subtropics is high. Cold periods are less stormy outside the tropics. See the drop in the 1960s to 1990s colder period.

Dr William Gray was a pioneer in hurricane forecasting. Gray and his associates at Colorado State University developed a very useful measure of global hurricane and major hurricane activity, the Accumulated Cyclone Energy (ACE Index). The ACE index takes into account the number, duration, and strength of all tropical storms and hurricanes in each ocean basin during the year.

The ACE Index 1851-2024 for the Atlantic Basin shows major year to year variance with active and quieter years and periods we can tie to natural variations in the ocean and atmosphere.

The trends are flat to down despite the active periods. See more here.

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Tornado Trends and Our Climate

Tornadoes occur on every continent but Antarctica, but the most activity is in North America because the conditions that trigger tornadoes are most common here. Here, western mountains and the high plains are often snow covered in winter into the spring keeping air masses cold there while as the sun returns north, temperatures warm in the south and moisture from the warm Gulf of Mexico is readily available. As storms move inland from off the cool eastern Pacific and come down from the mountains, the jet stream tightens and often buckles, draws moisture north and spins up tornadoes. Periods with strong contrasts in air masses and temperatures are associated with an increased threat of tornadoes.

In this backgrounder we will evaluate whether during periods of increased warmth are tornadoes more or less frequent. We will look at both the data provided by the Storm Prediction Center from 1950 to the present and the data since 1973 when tornadoes were first evaluated based on the Fujita tornado intensity scale in their immediate aftermath, making their rating more accurate. Tornado detection improved with the addition of Doppler radar (NEXRAD), the growth of the trained spotter networks, local and national media, storm chasers and the public armed with cell phone cameras and access to social media.  In this period, population growth and expansion outside urban areas have exposed more people and buildings to the tornadoes that once roared through open fields.

KEY TAKEAWAYS

* The claim that climate change is causing more and stronger tornadoes is invalidated by the relevant trend data.
* The 10 year running mean had dropped 66% since the peak in the cold mid 1960s.
* The U.S. has not seen an EF5 tornado in 11 years, the longest such streak since at least 1950. 

When tornados do occur, expansion of populated areas puts more property and lives at risk. Despite that fact, both inflation-adjusted and normalized tornado damage has decreased in the U.S. since 1950. Data clearly shows tornadoes are more frequent and stronger in colder years and periods (like the 1950s to 1970s).

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SEASONAL VARIANCE

The threat of tornadoes cycles across different regions of the U.S. from the Gulf coast from November to April, the Plains from May to early June, and the northern Plains and upper Midwest in June and July before most action shifts back to the southeast. Although there are clearly times of the year when tornadoes are most prominent, they can occur any time given the right weather conditions.

March. May, July and November Tornado Climatology
See https://youtu.be/z-oijdylBcQ for animation.

Tornadoes are failing to follow “global warming” based predictions.

The NOAA Storm Prediction Center (1)provided a history of tornadoes through 2021 that showed after an active period from the 1950s to the 1970s in EF3 level intensity tornadoes, the trend in these strong storms has been down. You do see spikes in some years most notably 2011.

SPC US Annual Count of EF3+ Tornadoes 1950-2022

Note the dozen year long lull followed a very active and deadly strong La Nina of 2010/11, which like the strong La Nina of 1973/74 produced record setting and very deadly outbreaks of tornadoes.

After the 2011 spike, the years 2012, 2013, 2014, 2015, 2016 all saw below average to near record low tornado counts in the U.S. since records began in 1954.  2017 rebounded only to the long-term mean while 2018 activity returned to well below the 25th percentile. 2019 bounced to the 75th percentile with a major outbreak centered on Easter Sunday. The following three years saw it drop well below average. In 2021 a long track tornado and major deadly December outbreak occurred but the annual count remained below the 25th percentile. 2022 started strong in March and early April but activity declined as dry and warmer conditions developed in the central states. It too ended well below the 25th percentile with only 24 reported deaths for the nation.

Data Reliability - Improved Detection

Coleman and Dixon (2014)2 and others found that prior to 1973, tornadoes were likely overrated due to the use of news clippings, sensational journalism, etc. But starting in 1973, tornadoes were evaluated based on the Fujita tornado intensity scale in their immediate aftermath, making their rating more accurate.  They found that indeed after NEXRAD radars went online nationwide in the early 1990s, the detection of all tornadoes, including weak ones became more likely. “This radar system alerts the NWS to areas with possible tornadoes (including weak tornadoes), even in unpopulated areas, that the NWS would have never found before the radar system. Also, since the early 1990s, with the Verification of the Origins of Rotation in Tornadoes Experiment (VORTEX; Rasmussen et al.)3 and the movie Twister, tornado chasing has become almost ubiquitous during days with tornado risk, especially in the Great Plains. This has also reduced the likelihood of unreported tornadoes.

See much more .

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Claim: Global Warming has increased U.S. Wildfires

REBUTTAL

In the U.S., wildfires are in the news every late summer and fall. The National Interagency Fire Center has recorded the number of fires and acreage affected since 1985. These data show that the trend in the number of fires is actually down while the trend in the acreage burned has increased.

In the past, lightning and campfires caused most forest fires; today most are the result of power lines igniting trees. The power lines have increased proportionately with the population, so it can be reasoned that most of the damage from large wildfires in California is partially a result of increased population not Global Warming. The increased danger is also greatly aggravated by poor government forest management choices.

“In the United States, wildfires are also due in part to a failure to thin forests or remove dead and diseased trees”. In 2014, forestry professor David B. South of Auburn University testified to the U.S. Senate Environment and Public Works Committee that “data suggest that extremely large megafires were four-times more common before 1940,” adding that “we cannot reasonably say that anthropogenic global warming causes extremely large wildfires.” As he explained, “To attribute this human-caused increase in fire risk to carbon dioxide emissions is simply unscientific.”

The NWS tracks the number of days where weather (not forest) conditions are conducive to wildfires such that they issue red-flag warnings. The number of red-flag days has not trended upward due to “Global Warming.”

90% of the fires are caused by humans though natural seasonal weather variations create conditions that are conducive to fires and the rapid spread of these fires west to increasingly populated areas. Human-caused fires result from campfires left unattended, the burning of debris, downed power lines, negligently discarded cigarettes, and intentional acts of arson.

Bjorn Lomborg overlapped National Interagency Fire Center (NIFC) annual US fire data with the Historical Statistics of the United States - Colonial Times to 1970. There we have statistics for area burnt since 1926 and up to 1970. Reassuringly, the data for 1960-1970 ‘completely overlap.’ This is the same data series. Professor Lomborg said. It shows recent forest fire activity is one-fifth the record since 1926 even with the recent increases in acreage burnt.

We can see prior to 1880, wildfires were more common. Sweetnam looked at long-term incidence of wildfires in North America and found they have declined the last century.