Are Current Hot and Cold Extremes Climate Change or Natural Variability?

While sizzling temperatures in Europe have captured the attention of the mainstream media, recent prolonged bouts of cold in the Southern Hemisphere have gone almost unnoticed. Can these simultaneous weather extremes be ascribed to climate change, or is natural variability playing a major role?

It’s difficult to answer the question because a single year is a short time in the climate record. Formally, climate is the average of weather, or short-term changes in atmospheric conditions, over a 30-year period. But it is possible to compare the current heat and cold in different parts of the globe with their historical trends.

The recent heat wave in western and southern Europe is only one of several that have afflicted the continent recently. The July scorcher this year, labeled unprecedented by the media, was in fact less severe than back-to-back European heat waves in the summer of 2019.

In the second 2019 wave, which also occurred in July, the mercury in Paris reached a new record high of 42.6 degrees Celsius (108.7 degrees Fahrenheit), besting the previous record of 40.4 degrees Celsius (104.7 degrees Fahrenheit) set back in July 1947. A month earlier, during the first heat wave, temperatures in southern France hit a blistering 46.0 degrees Celsius (114.8 degrees Fahrenheit). Both readings exceed the highest temperatures reported in France during the July 2022 heat wave.

Yet back in 1930, the temperature purportedly soared to a staggering 50 degrees Celsius (122 degrees Fahrenheit) in the Loire valley during an earlier French heat wave, according to Australian and New Zealand newspapers. The same newspapers reported that in 1870, the ther­mometer had reached an even higher, unspecified level in that region. Europe’s official all-time high-temperature record is 48.0 degrees Celsius (118.4 degrees Fahrenheit) set in 1977.

Although the UK, Portugal and Spain have also suffered from searing heat this year, Europe experienced an unseasonably chilly spring. On April 4, France experienced its coldest April night since records began in 1947, with no less than 80 new low-temperature records being established across the nation. Fruit growers all across western Europe resorted to drastic measures to save their crops, including the use of pellet stoves for heating and spraying the fruit with water to create an insulating layer of ice.

South of the Equator, Australia and South America have seen some of their coldest weather in a century. Australia’s misery began with frigid Antarctic air enveloping the continent in May, bringing with it the heaviest early-season mountain snow in more than 50 years. In June, Brisbane in normally temperate Queensland had its coldest start to winter since 1904. And Alice Springs, which usually enjoys a balmy winter in the center of the country, has just endured 12 consecutive mornings of sub-freezing temperatures, surpassing the previous longest streak set in 1976.

South America too is experiencing icy conditions this year, after an historically cold winter in 2021 which decimated crops. The same Antarctic cold front that froze Australia in May brought bone-numbing cold to northern Argentina, Paraguay and southern Brazil; Brazil’s capital Brasilia logged its lowest temperature in recorded history. Later in the month the cold expanded north into Bolivia and Peru.

Based on history alone then, there’s nothing particularly unusual about the 2022 heat wave in Europe or the shivery winter down under, which included the coldest temperatures on record at the South Pole. Although both events have been attributed to climate change by activists and some climate scientists, natural explanations have also been put forward.

A recent study links the recent uptick in European heat waves to changes in the northern polar and subtropical jet streams. The study authors state that an increasingly persistent double jet stream pattern and its associated heat dome can explain "almost all of the accelerated trend" in heat waves across western Europe. Existence of a stable double-jet pattern is related to the blocking phenomenon, an example of which is shown in the figure below.

Blocking refers to a jet stream buckling that produces alternating, stationary highs and lows in pressure. Normally, highs and lows move on quickly, but the locking in place of a jet stream for several days or weeks can produce a heat dome. The authors say double jets and blocking are closely connected, but further research is needed to ascertain whether the observed increase in European double jets is part of internal natural variability of the climate system, or a response to climate change.

Likewise, it has been suggested that the frigid Southern Hemisphere winter may have a purely natural explanation, namely cooling caused by the January eruption of an undersea volcano in the South Pacific kingdom of Tonga. Although I previously showed how the massive submarine blast could not have contributed to global warming, it’s well known that such eruptions pour vast quantities of ash into the upper atmosphere, where it lingers and causes subsequent cooling by reflecting sunlight.

Next: Evidence for More Frequent and Longer Heat Waves Is Questionable

No Evidence That Hurricanes Are Becoming More Likely or Stronger

Despite the claims of activists and the mainstream media that climate change is making major hurricanes – such as U.S. Hurricane Harvey in 2017 or Hurricane Katrina in 2005 – more frequent and stronger, several recent studies have found no evidence for either of these assertions.

In fact, a 2022 study reveals that tropical cyclones in general, which include hurricanes, typhoons and tropical storms, are letting up as the globe warms. Over the period from 1900 to 2012, the study authors found that the annual number of tropical cyclones declined by about 13% compared with the period between 1850 and 1900, when such powerful storms were actually on the rise.

This is illustrated in the figure below, showing the tropical cyclone trend calculated by the researchers, using a combination of actual sea-level observations and climate model experiments. The solid blue line is the annual number of tropical cyclones globally, and the red line is a five-year running mean. 

The tropical cyclone trend is almost the opposite of the temperature trend: the average global temperature went down from 1880 to 1910, and increased by approximately 1.0 degrees Celsius (1.8 degrees Fahrenheit) between 1910 and 2012. After 1950, the rate of cyclone decline accelerated to about 23% compared to the 1850-1900 baseline, as global warming increased during the second half of the 20th century. Although the study authors noted a variation from one ocean basin to another, all basins demonstrated the same downward trend.

The authors remark how their findings are consistent with the predictions of climate models, in spite of the popular belief that a warming climate will spawn more, not fewer, hurricanes and typhoons, as more water evaporates into the atmosphere from the oceans and provides extra fuel. At the same time, however, tropical cyclone formation is inhibited by wind shear, which also increases as sea surface temperatures rise.    

Some climate scientists share the view of the IPCC (Intergovernmental Panel on Climate Change)’s Sixth Assessment Report that, while tropical cyclones overall may be diminishing as the climate changes, the strongest storms are becoming more common, especially in the North Atlantic. The next figure depicts the frequency of all major North Atlantic hurricanes back to 1851. Major hurricanes in Categories 3, 4 or 5 have a top wind speed of 178 km per hour (111 mph) or higher.

You can see that hurricane activity in this basin has escalated over the last 20 years, especially in 2005 and 2020. But, despite the upsurge, the data also show that the frequency of major North Atlantic hurricanes in recent decades is merely comparable to that in the 1950s and 1960s – a period when the earth was cooling rather than warming.

A team of hurricane experts concluded in a 2021 study that, at least in the Atlantic, the recent apparent increase in major hur­ricanes results from improvements in observational capabilities since 1970 and is unlikely to be a true climate trend. And, even though it appears that major Atlantic hurricanes were less frequent before about 1940, the lower numbers simply reflect the rela­tive lack of measurements in early years of the record. Aircraft re­connaissance flights to gather data on hurricanes only began in 1944, while satellite coverage dates only from the 1960s.

The team of experts found that once they corrected the data for under­counts in the pre-satellite era, there were no significant recent increases in the frequency of either major or all North Atlantic hurricanes. They suggested that the reduction in major hurricanes between the 1970s and the 1990s, clearly visible in the figure above, could have been the result of natural climate variability or possibly aerosol-induced weakening.

Natural climate cycles thought to contribute to Atlantic hurricanes include the AMO (Atlantic Multi-Decadal Oscillation) and La Niña, the cool phase of ENSO (the El Niño – Southern Oscillation). The AMO, which has a cycle time of approximately 65 years and alternates between warm and cool phases, governs many extremes, such as cyclonic storms in the Atlantic basin and major floods in eastern North America and western Europe. In the U.S., La Niñas influence major landfalling hurricanes.

Just as there’s no good evidence that global warming is increasing the strength of hurricanes, the same is true for their typhoon cous­ins in the northwestern Pacific. Although long-term data on major typhoons is not available, the frequency of all typhoon categories combined appears to be un­changed since 1951, according to the Japan Meteorological Agency. Yet a new study demonstrates a decline in both total and major typhoons for the 32-year period from 1990 to 2021, reinforcing the recent decrease in global tropical cyclones discussed above.

Next: Are Current Hot and Cold Extremes Climate Change or Natural Variability?