Global Warming and Extreme Weather

By Andy May

In this post, the sixth of seven, we will discuss the connection between climate change and extreme weather. In previous posts, we’ve discussed whether humans are harming the environment, whether our population is growing too fast, the cost of global warming, are species extinctions increasing, and climate related mortality.

In the IPCC WGII AR5 Technical Summary, page 52, they list the following risks of climate change, among others:

“Virtually certain that, in most places, there will be more hot and fewer cold temperature extremes as global mean temperatures increase, for events defined as extremes on both daily and seasonal time scales.”

Global warming and the frequency and severity of natural disasters

The cost of natural disasters, including hurricanes, has been increasing with time. Most of the reason is more people live on the coast or in areas prone to natural disasters (forests, flood plains, mountain sides, next to levees, etc.) and they build very expensive buildings in these places. The IPCC acknowledges this, but in a slightly devious way, IPCC WGII AR5 Technical Summary, page 49:

“Economic losses due to extreme weather events have increased globally, mostly due to increase in wealth and exposure, with a possible influence of climate change (low confidence in attribution to climate change).”

This statement is technically correct. There is “low confidence” in a possible influence on extreme weather by climate change. But, it is worded cleverly, so that one can easily read into it that man-made climate change has some influence on extreme weather, and many have.

Dr. Roger Pielke Jr. does not believe reducing fossil fuel use will influence extreme weather, although he does believe fossil fuel use should be curtailed for other reasons (an opinion I do not share).

“Adaptation and mitigation are not trade-offs but complements that address different issues on very different timescales of costs and benefits. If a policy goal is to reduce the future impacts of climate on society, then energy [fossil fuel] policies are insufficient, and indeed largely irrelevant, to achieving that goal. There are other sensible reasons for efforts to accelerate decarbonization; protecting us from disasters is not one of them, and arguments and advocacy to the contrary are not in concert with research in this area. Governments and businesses are already heavily invested in climate policy and thus should focus resources on decisions likely to be effective with respect to policy goals. In the context of extreme events, such decisions might focus increasingly on land use, insurance, engineering, warnings and forecasts, risk assessments, and so on.” Pielke Jr., Roger. The Climate Fix: What Scientists and Politicians Won’t Tell You About Global Warming (p. 189).

Thus, the focus on planetary CO2 reduction to mitigate planetary extreme weather is pointless, focus on local risks, properly price disaster insurance, discourage people from building in high risk areas, build protective infrastructure and so on. Be aware of the risks in your own community, and deal with them locally. He follows with this:

“… poor countries, lack a basic resilience in the face of climate extremes, there is much work to be done to improve adaptive capacities. Such policies make sense independent of human-caused climate change, but they will also make these communities more robust in the face of human-caused climate change.” Pielke Jr., Roger. The Climate Fix: What Scientists and Politicians Won’t Tell You About Global Warming (p. 190).

In other words, climate disasters are much worse in poor communities. Indeed, all disasters are. Poor communities are much less adaptable than wealthy, developed communities. Wealthy countries are also healthier and have cleaner environments (See figure 2 in post 1). Fossil fuel use is what makes developed countries wealthy, taking it away will make them poorer and more vulnerable to natural disasters.

There is another reason the world will not give up on fossil fuels until something comes along that is both cheaper and better. The cost of energy is a fundamental component of standard of living. Pielke, Jr. describes the “iron law of climate policy.” This unbreakable law is that all countries expect economic growth. People in wealthier countries will pay some amount for environmental goals, they want clean air and water. But, they will not sacrifice their prosperity for it and they will not accept a declining economy.

I find Pielke Jr.’s book The Climate Fix a little frustrating. He often says, in various ways:

“Make no mistake: carbon dioxide matters a great deal.” Pielke Jr., Roger. The Climate Fix: What Scientists and Politicians Won’t Tell You About Global Warming (p. 18).

The book destroys the connection between CO2 and climate extremes, the iconic “2°C limit” on warming as well as any positive effect of reducing CO2 emissions. He also shows that there is no evidence that a “tipping point” temperature exists. At least in this book, he never really explains why CO2 emissions need to be reduced or why current global warming is a bad thing. My question is why? We don’t need to stop using fossil fuels to have clean air, as we have found in the U.S. and Europe, we can have both. In fact, properly used fossil fuels are safer than burning wood in a fireplace or stove. This quote is telling:

“John Beddington, science adviser to the UK government, said … in early 2010: ‘It’s unchallengeable that CO2 traps heat and warms the Earth and that burning fossil fuels shoves billions of tonnes of CO2 into the atmosphere. But where you can get challenges is on the speed of change. When you get into large-scale climate modeling there are quite substantial uncertainties. On the rate of change and the local effects, there are uncertainties both in terms of empirical evidence and the climate models themselves.’ Even with uncertainties about the future, there is ample evidence, broadly accepted, that humans are influencing the global earth system. Such influences carry with them a risk of undesirable outcomes.” Pielke Jr., Roger. The Climate Fix: What Scientists and Politicians Won’t Tell You About Global Warming (p. 32).

He seems to be saying, humans are putting billions of tons of CO2 in the air, we have no idea what the effect is going to be, but since man is doing it; it must be bad, and we need to stop it. We hear this sort of argument all the time. We know the planet has been warming since the Little Ice Age, the coldest period in the Holocene, could this be a natural reversion to the mean? This is not the first book or article I’ve read on climate science where the body of the presented evidence is at odds with the conclusions.

Another telling quote from the book:

“The literature on this topic is so vast that one could easily cherry-pick a few studies suggesting that the impacts [of CO2] may be benign or, in contrast, that those impacts may be catastrophic. Science cannot presently adjudicate between these possibilities, or even give reliable odds on particular outcomes, …. Many, if not most, scientists believe that the impacts will be on balance negative and significant.” Pielke Jr., Roger. The Climate Fix: What Scientists and Politicians Won’t Tell You About Global Warming (p. 61).

We don’t know whether CO2 is good or bad, nor can we measure the impact, but the “gut feeling” of most scientists is it will be bad. Really? I make my living as an investor these days, I learned a long time ago that investing “from the gut” is a sure way to lose money. Is it a good company or sector? A fair price? What is the dividend? What is the expected total return? You need facts to invest wisely. Think of investing in reducing CO2 emissions like you would any smart investment. Compare the investment to alternatives. Our point is, there are an array of solutions out there for extreme weather events and for climate change, we need to know which one has the best rate-of-return. Which one does the best job at the cheapest cost?

Global warming will increase the frequency and severity of hurricanes

There is a recent climate model-based study (Emanuel, 2017) that attempts to quantify the probability of a Hurricane Harvey type of rain event, in the Houston area, in the period 1981-2000 by analyzing retrospective meteorological forecast data from the U.S. National Center for Atmospheric Research, NASA, and the European Center for Medium Range Weather Forecasts (ECMWF). He then uses the IPCC RCP8.5 scenario results from six global climate models for the same area to predict a Hurricane Harvey probability for the period 2081-2100. Finally, he assumes that the change in probability is linear during the 21st century. He calculates that a Hurricane Harvey event is a 1 in 100-year event in 2000 and a 1 in 5.5-year event in 2100. This makes the probability of the event, in 2017, 1 in 16 years. His conclusions are based entirely on computer models and the RCP8.5 scenario, although actual data may have made some difference in the weather forecast re-analyses. This is only valid if the model is accurate and, as we have seen the models have not been validated, thus it is a speculative exercise.

Roger Pielke Jr. has pointed us to a paper (Ritchie and Dowlatabadi, 2017) that believes the RCP8.5 scenario is implausible:

“Accounting for this bias [toward the use of coal] indicates RCP8.5 and other ‘business-as-usual scenarios’ consistent with high CO2 forcing from vast future coal combustion are exceptionally unlikely. Therefore, SSP5-RCP8.5 should not be a priority for future scientific research or a benchmark for policy studies.”

Thus, Emanuel’s calculation of the odds of Harvey occurring in 1981-2000 may be correct, but his projection from that period of time into the future is very unlikely to be correct.

Risser and Wehner, 2017, Geophysical Research Letters, is a statistical study that attempts to model ENSO (La Niña and El Niño) effects on climate and human effects on historical Houston area climate precipitation data from the Global Historical Climatology Network or GHCN. The stations used are shown in figure 1. The NOAA Advanced Hydrologic Prediction Service (AHPS) estimates, based on radar and rain gauge data are on the right of figure 1. The study finds that human-induced climate change likely increased the chances of the observed Harvey precipitation by a factor of 3.5. They claim that man-made climate change increased the Harvey rainfall amount by at least 19%.

Figure 1, source Risser and Wehner, 2017

The model assumes that specific humidity increases, according to the Clausius-Clapeyron relationship, by 6-7% per degree of local warming in the absence of dynamical (wind) changes. They expect extreme precipitation to increase by the same amount.

Finally, they assume that the only influences on temperature are the atmospheric carbon dioxide concentration and ENSO (the Niño3.4 index to be specific). The modeling was done for the Houston area alone. They conclude that:

“[A 316 mm day rainfall] total has become much more commonplace: from a several hundred year storm in 1950 to a 25-50-year storm in 2017. Our covariate-based analysis indicates that this change is due to the anthropogenic increase in atmospheric CO2 concentrations and not natural ENSO variability.”

While I applaud Risser and Wehner for using actual data in their study, I find fault with their assumption that temperature is the only driver for precipitation and that the Clausius-Clapyron relationship is the only driver for specific humidity. These assumptions are speculative. Finally, assuming that the only drivers for temperature are CO2 and ENSO is extremely speculative. Other natural drivers for both global and local temperatures are well known, non-trivial, and should be considered. In particular, the Bray cycle is important as we exit the Little Ice Age and the shorter Atlantic Multidecadal Oscillation and other oceans cycles are important as discussed here.

Besides, modeling precipitation using such a simple natural model and then assigning all the excess precipitation to humans is not reasonable.

Van Oldenborgh, et al., 2017, Environmental Research Letters, December 2017, also compares historical precipitation data to the Clausius-Clapyron (CC) expected rainfall for observed warming. This paper is very similar to Emanuel, 2017, and they also conclude that the positive trend in excess precipitation (above the expected CC precipitation) is caused by man-made climate change. They claim that humans made the precipitation 8% to 16% more intense. This is like the conclusions of Emanuel, 2017 because they used the very similar data and procedures. This conclusion is model-based and presented no evidence of human influence on the storm. Again, like Emanuel, 2017, the storm is one point, they fit a model to the single point, limited the inputs to CO2 and their interpretation of “nature” and then attributed everything above their “cyber-nature” to human influence.

We should point out that the two models used in this study do not agree very well and the difference is a factor of two, the authors mention this, but do not provide an explanation, other than to say the models must have systemic differences. They accept the model that matches observations better, meaning it models Harvey.

They also conclude that Houston’s flood protection system must be improved and that the frequency of heavy rainstorms in the Houston area has increased. Both conclusions are well supported with data. The problem with the study is the same as the problem with Emanuel, 2017. They use a very over-simplified model of nature, then simply assign all excess to humans without any justification.

Historical hurricane data

Our subject is hurricanes and not models of hurricanes. The historical data for Atlantic hurricanes impacting the United States suggests that their intensity, as defined by their central pressure, is declining, see figure 2.

Figure 2, data source: NOAA Hurricane Research Division

In figure 2, we have subtracted the NOAA estimated hurricane central pressures from 1020 mb and summed the values for all U.S. landfall hurricanes over 10-year periods, these values are plotted at the midpoint of each 10-year period. Each 10-year period starts with the zero year and ends with the ninth year and is plotted at “5.” The central hurricane pressure is a good indicator of hurricane strength and it is a value available for nearly all hurricanes. We had to estimate the pressure from wind speed for three early hurricanes (in 1918, 1920, and 1953).

By subtracting the value from 1020, we make higher values a strong hurricane and smaller values a weaker hurricane. The trend shows that hurricane strength waxes and wanes over time in a 40 to 60-year pseudo-cycle. Although Irma and Harvey were strong hurricanes, we still seem to be in a hurricane lull in 2017. 2017 hurricanes, from Wikipedia, are included in figure 2. Table 1 shows the breakdown for the 294 U.S. hurricanes plotted in figure 2. “P” is the hurricane central pressure from NOAA.

Table 1, data source: NOAA Hurricane Research Division

Pielke Jr. and Lomborg have made similar plots. Lomborg plots the same hurricanes by category and it can be found here. Pielke’s plot for global cyclone and hurricane landfalls is presented as figure 3, it also shows a decline.

Figure 3, source: Pielke, Jr. House of Representatives testimony.

Further, Pielke, Jr. also plotted weather-related disaster costs for the world since 1990, the costs are declining as a percent of GDP.

Figure 4, source: Pielke, Jr. House of Representatives testimony.

As the world becomes more affluent, the GDP goes up and we are better able to handle natural disasters. The data suggests that the severity of hurricanes has gone down recently, not up. It also shows that weather-related disasters are becoming less expensive for society to deal with. But, we still hear that they are getting worse:

“Stronger and more frequent hurricanes have become one of the standard exhibits of the global-warming concerns. The Natural Resources Defense Council tells us that “global warming doesn’t create hurricanes, but it does make them stronger and more dangerous.” The group Friends of the Earth proclaims, “Hurricanes in Florida. Storms in the UK. Extreme weather events are predicted to become more frequent because of climate change.” Greenpeace tells us “there is strong evidence that extreme weather events—such as hurricanes—are increasing (and becoming more severe and frequent) because of climate change.” The solution offered is invariably CO2 cuts and adoption of Kyoto.” Lomborg, Bjorn. Cool It (Kindle Locations 1126-1132).

In 2006, tropical cyclone researchers and forecasters met at a WMO conference and agreed on the following:

“1. Though there is evidence both for and against the existence of a detectable anthropogenic [human-caused] signal in the tropical cyclone climate record to date, no firm conclusion can be made on this point.”

“2. No individual tropical cyclone can be directly attributed to climate change.”

“3. The recent increase in societal impact from tropical cyclones has largely been caused by rising concentrations of population and infrastructure in coastal regions.”

The theoretical debate over whether hurricanes are increasing in severity is unlikely to be resolved soon, most alarmist observers end up pointing out how damages from hurricanes are rising dramatically and quickly. This is correct, but attributing them to human-caused global warming is wrong. The global costs of weather-related disasters have increased over the past century because the population in dangerous areas has increased, as well as the value of buildings and infrastructure in those areas.

The Clausius-Clapeyron relationship

The recent studies of Hurricane Harvey, cited above, all compare the expected rainfall from the Clausius-Clapeyron relationship to actual data. The Clausius-Clapeyron relationship shows that the vapor pressure of a liquid is only related to temperature. As vapor pressure, the pressure just above a liquid surface, increases more evaporation occurs. So, all else equal (which it never is) as sea surface temperatures go up one-degree C, evaporation increases and the specific (or absolute) humidity in the air goes up about 6%. The next assumption is that as the specific humidity goes up precipitation increases by the same amount. These are all reasonable assumptions depending upon air and water circulation patterns and speed which are unknown.

But, being reasonable, is not enough. It is important to compare model results to observations and none of the studies do that. Risser and Wehner do the best job of tying their results to data, but by assuming that ENSO is the only natural influence on precipitation and temperature; and that man-made CO2 is the only other influence, their conclusions are suspect, other factors may be important as well.

Real world data do not support the Clausius-Clapeyron relationship between specific humidity and temperature. The relationship is sound in the laboratory, but observations show the relationship between humidity, temperature and precipitation is more complex. Benestad (2016) has reported that the European Centre for Medium-range Weather forecasts (ECMWF) interim reanalysis shows the total volume of water vapor in the atmosphere decreasing by -0.018 kg/m2 per decade from 1979-2011. According to RSS (Smith, et al., 2013) the atmosphere contains an average of about 28.5 mm of water vapor or 28.5 kg/m2 of water vapor (the conversion is 1:1 according to Hanssen, 2000), so the decrease seen by ECWMF is about .06%/decade or 0.006%/year (1979-2011). Miskolczi (2014) reports that The NOAA R1 dataset shows that global surface air temperature has increased 0.687K between 1948 and 2008, but the water content has decreased by 0.636% or -0.0106%/year, similar to what is seen in the ECWMF dataset.

The reason why the global specific humidity is decreasing as global temperatures are rising is unknown and hotly debated, but it seems to be happening. This observation casts doubt on any study that assumes the Clausius-Clapeyron relationship works alone to control humidity and precipitation. The physical relationship exists, and it will affect humidity to some degree, but there must be other confounding processes at work in the atmosphere.

Global warming will increase flooding

Warming may well result in increasing rain, but it doesn’t seem to translate into increasing flooding. A global sample (Kundzewicz, et al., 2005) of 200 rivers showed 27 had increasing high flows, 31 had decreasing flows and 137 showed no change.

In recent times, summer flooding shows no increasing or decreasing trend. Winter flooding has decreased since the Little Ice Age. During the Little Ice Age, it was much colder and ice dams formed in major rivers. This caused catastrophic flooding when temperatures increased, and the dams melted enough to give way. All but two major floods affecting Florence since 1177 occurred before 1844, Lomborg reports.

Economic losses due to floods have increased, but this is due to more building in flood prone areas. Oddly, it is also due to the increased construction of levees. Levees reduce the size of the floodplain and the extra water storage they provide. People also tend to build on the dry side of levees, a dangerous area.

Yet, modern flood control measures are working overall:

“In 1929, $200 of each $1 million worth of goods got damaged, whereas today only $70 of each $1 million is lost. This indicates that as society has more tangible wealth, while more goods will get damaged in floods, the damage will constitute a smaller and smaller proportion of the total wealth. Overall, floods are not getting more damaging but less.” Lomborg, Bjorn. Cool It (Kindle Locations 1300-1303).

Lomborg and Pielke also discuss flood prevention costs vs benefits:

“Using the United Kingdom example, for about 0.01 percent of GDP you get a benefit from damage reduction of 0.12 percent of GDP—a benefit-to-cost ratio of 11. From Kyoto, at the cost of 0.5 percent of GDP, you get a benefit of 0.00009 percent of GDP. Or, expressing it in equal terms, a dollar spent on flood management will reduce flooding 1,300 times better than a dollar spent on Kyoto. Flooding is not getting out of hand; the costs are declining compared to total wealth. It is not predominantly a signal of global warming or of increasing heavy rains.” Lomborg, Bjorn. Cool It (Kindle Locations 1316-1321).

From The Climate Fix by Roger Pielke Jr.

“Research on floods does not support the hypothesis that greenhouse gas emissions have led to a discernible increase in flood losses. Hans Jochim Schellenhuber, a prominent climate scientist and scientific adviser to German chancellor Angela Merkel, coauthored a 2004 paper that summarized the 2001 IPCC assessment and subsequent scientific discussions of floods. It concluded: ‘There has been no conclusive and general proof as to how climate change affects flood behavior, in the light of data observed so far…. It is difficult to disentangle the climatic component from the strong natural variability and direct, man-made, environmental changes.'” Pielke Jr., Roger. The Climate Fix: What Scientists and Politicians Won’t Tell You About Global Warming (p. 174).

Global warming will increase the frequency of droughts and their severity

The Clausius-Clapeyron relationship may not control the amount of precipitation or the global atmospheric specific humidity, but generally we would expect more evaporation with warmer temperatures and, as a result, more precipitation. Specific humidity is determined by the difference between evaporation and precipitation, which are separately controlled by complex processes, and the Clausius-Clapeyron relationship is only one. Climate models predict 5 percent more precipitation by 2100, which is our only estimate today.

Al Gore and others have told us that drought and hunger in the Sahel region of Africa are caused by global warming, yet Reuters reported in 2015:

“Rising greenhouse gases have boosted rainfall in the Sahel region of Africa, easing droughts that killed 100,000 people in the 1970s and 1980s, in a rare positive effect of climate change …. The report adds to debate about the causes of a greening of the Sahel region, south of the Sahara Desert from Senegal to Sudan. It said a continued rise in greenhouse gas emissions was likely to help more rainfall in the region in future. … Amounts of rainfall have recovered substantially,” said Rowan Sutton, a professor at the National Centre for Atmospheric Science at Britain’s Reading University and co-author of the study in the journal Nature Climate Change. And it was a surprise that the increase in greenhouse gases appears to have been the dominant factor, …. Sahel summer rainfall was 0.3 mm (0.01 inch) a day higher from 1996-2011 than the drought period of 1964-93.” Reuters, 2015


Damages from extreme weather events, whether heat waves, cold, droughts, tornados or forest fires are largely a function of the “societal” part of the equation. That is who lives in the area and how affluent they are. The damages are not due to human-caused climate change. According to Pielke, Jr.:

“Other sorts of extreme events— such as heat waves, cold spells, droughts, and forest fires— have similarly complex stories. In all cases, the societal part of the equation that leads to losses is the dominant factor, not climate change. Yet for some phenomena there are indications that a signal of climate change, and possibly related to greenhouse gas emissions, can be seen in the record of impacts. For instance, some recent research is suggestive that regional warming in the western United States can be associated with increasing forest fires, even in the context of complex patterns of forest management over the past century. If that pattern of warming can be directly attributed to greenhouse gas emissions, then it would be possible to attribute human-caused climate change with a demonstrated impact.” Pielke Jr., Roger. The Climate Fix: What Scientists and Politicians Won’t Tell You About Global Warming (p. 175).

Is the warming of the southwestern part of the U.S., which is making forest fires worse, a result of CO2 emissions? Or is it a natural climate trend? Even when warming can be identified as a cause somewhere, how do you separate the man-made component from the natural component? This is particularly difficult when we are in the midst of recovering from the Little Ice Age, which is the coldest period in the Holocene and we are still on a Bray cycle upswing.

Extreme weather risks are always present, wherever one lives. They vary with location, flooding is a serious risk in the Houston area, drought and wild fires are a serious risk in California, storm surges are a risk in the North Sea. Each location needs to assess their risks and build appropriate infrastructure to counter the risk as best they can. Trying to prevent so-called “climate change” with a world-wide imagined man-made remedy is a fool’s errand. Deal with the specific problem in your own neighborhood and let others deal with theirs. There is no universal solution to the “boogyman.” Oops, I mean extreme weather events.