Weather Events and Climate Change: Separating Fact from Fiction – Part 2



Part 1 here.

In May, I testified before the Senate Budget Committee and summarized what the Intergovernmental Panel on Climate Change (IPCC) said about trends in drought. My testimony included the figure below showing a decrease in the areal extent of extreme drought conditions in the United States.

I also included another figure that showed an increase in extreme drought conditions across the United States.

Completing the set, I also included the figure below, showing no trend in U.S. extreme drought conditions.

So which is it? Is extreme drought in the U.S. increasing, decreasing, or not changing over climate time scales?

The question has multiple answers, all of which are correct — increasing, decreasing, and not changing. We can arrive at these different trends by selecting different starting dates for our analysis, in this case 1933, 1981, and 1895.

The multiple correct answers coexist because the areal extent of extreme drought in the U.S. varies a great deal from year to year and decade to decade. Some years having no extreme drought and in some years 40% or more of the U.S. experiences extreme drought. Even if the statistics of extreme drought were not changing (i.e., no change in the climatology of extreme drought) we should still expect on climate time scales to observe trends in metrics of extreme drought.

In other words, not all climate trends are climate change trends.

Climate — a statistical description of the climate system — varies on all time scales. The IPCC defines climate variability:

Deviations of climate variables from a given mean state (including the occurrence of extremes, etc.) at all spatial and temporal scales beyond that of individual weather events. Variability may be intrinsic, due to fluctuations of processes internal to the climate system (internal variability), or extrinsic, due to variations in natural or anthropogenic external forcing (forced variability).

For many people, climate variability will be most obvious and familiar in the annual seasonal cycle. The IPCC discusses eight primary modes of variability, including the El Niño Southern Oscillation (ENSO).1

Over longer time periods climate variability creates obstacles to the detection of change in the statistics of extreme weather. The IPCC recognizes the challenge for detection posed by variability in its definition of the detection of change (emphasis added):

An identified change is detected in observations if its likelihood of occurrence by chance due to internal variability alone is determined to be small, for example, <10%.

It is exceedingly common in the media and even in the peer reviewed literature to highlight a trend in a particular climate metric and then conclude that the existence of the trend suffices to conclude that the trend was caused by “climate change.”2 Let’s look at an example.

But did they?

In 2020, the New York Times covered a paper in PNAS by declaring definitively that “climate change is making hurricanes stronger.” Even if we were to correct the headline — “Emissions of Greenhouse Gases are Making Hurricanes Stronger” — that is not what the paper claims nor did it even attempt such an analysis.3

The research paper that the NYT was reporting on acknowledges the importance of various modes of climate variability on tropical cyclones and the authors explain that they have not attempted “formal detection” of changes in tropical cyclone metrics and nor do they make any effort to identify any human influences on tropical cyclones (emphases added):

Ultimately, there are many factors that contribute to the characteristics and observed changes in TC intensity, and this work makes no attempt to formally disentangle all of these factors. In particular, the significant trends identified in this empirical study do not constitute a traditional formal detection, and cannot precisely quantify the contribution from anthropogenic factors.

A formal approach to detecting a change in metrics of tropical cyclones would have to place any observed trends into the context of climate variability and show that such trends are unlikely to result from known modes of variability — as in the drought example above.

The IPCC AR6 is very clear on the detection of trends indicating change in tropical cyclone metrics:

There is low confidence in most reported long-term (multi-decadal to centennial) trends in TC frequency- or intensity-based metrics due to changes in the technology used to collect the best-track data. This should not be interpreted as implying that no physical (real) trends exist, but rather as indicating that either the quality or the temporal length of the data is not adequate to provide robust trend detection statements, particularly in the presence of multi-decadal variability.

You know what is inconvenient? The hurricane is spinning the wrong way.

What accounts for the enormous gap between what the IPCC concludes and what much of the legacy media says about tropical cyclones, and extreme events more generally?

Among climate activists there has long been a “desire” to connect climate change with extreme events in order to promote climate politics— I get it, extreme events are impactful, tragic, photogenic, and occur every day.

However, reality has so far failed to play along.

Read more

5 1 vote
Article Rating
Notify of
Inline Feedbacks
View all comments

comment image

Here in Etna Ca in Scott Valley and Siskiyou County and I to have seen those Chem Trials most of them going North and South

I don’t know about how weather relates to “climate change,” (which takes thousands of years to trend) but greg always waxes apoplectic about “Microplastics,” so this is right up his alley:
A new study published in Nature Communications has uncovered a concerning link between lithium-ion batteries, commonly used in electric vehicles, and the spread of harmful per-and polyfluoroalkyl substances (PFAS), also known as “forever chemicals.”
 These chemicals, which are used to enhance battery performance and reduce flammability, were found in high concentrations in environmental samples near EV battery manufacturing plants in the United States, Belgium, and France.
PFAS have earned the moniker “forever chemicals” due to their persistence in the environment and their potential to accumulate in living organisms. 
The study’s findings highlight a complex challenge in the fight against climate change.
While supporters argue that electric vehicles are crucial for reducing carbon dioxide emissions, the potential increase in PFAS pollution presents a new environmental hurdle.

Gee, ya think?
What could go wrong?

Last edited 10 days ago by Nan G

So when’s Gore the Bore going to return his ill gotten Nobel Prize and Oscar?