I have had the general impression that in recent years, it has gotten cloudier. But that could be an incorrect impression, coming from the fact that, like everybody, I get older with each year. Or, it could come from the fact that my analyses for this blog have shown that there is marginally more precipitation in Missouri due to climate change. Perhaps I say “Ha!” to myself every time it is cloudy, “See, it’s because of climate change.”

Checking out one’s subjective impressions about clouds is not so easy. Clouds are very complex, and they provide the largest source of uncertainty in future climate projections. There are all kinds of clouds, and they exist at many levels of the atmosphere. Not only that, they are constantly changing: it can be overcast one moment and clear an hour later. The task of reducing this complexity to a simple measure of cloud cover has been difficult. Most weather stations do it, however. For instance, the daily climate report published by National Weather Service in St. Louis reports that for St. Louis, on July 21, 2019, the sky cover was 0.6. This means that on average for the whole day, 6/10ths (60%) of the sky was covered with clouds. (They measure the percent of the sky covered by clouds several times a day, and average the results.)

Finding a time series reporting this data over time is harder. I’ve been looking for it for some time, and I finally found it at NASA’s Giovanni Data Tool. This is a portal that provides access to satellite data for a large number of atmospheric variables, including cloud fraction. Without getting into the weeds, cloud fraction is the fraction of an area that is cloudy, roughly the same thing as sky cover, but from the sky down, rather than the ground up. The scale runs from 0, meaning none of the area was covered by clouds, to 1, which means all of the area was covered by clouds. Thus, as in the example above, 0.6 would mean that 6/10ths of the area (60%) was covered by clouds.

Figure 1: Cloud Fraction Search Area. Map Created on Google Earth.

Giovanni did not permit searching for cloud fraction by state, but it would search within a rectangle that I could define. So, as I usually do in such cases, I defined a rectangle that just barely enclosed the whole state. Figure 1 shows the search area.

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Figure 2. Data source: NASA Giovanni.

Figure 2 shows the monthly cloud fraction for that rectangle from 1/1/1980, through 6/1/2019. To justify my impression that it is cloudier, you can notice that from about 2010, there has been a noticeable increase in cloud fraction. However, it is an anomaly, and the trend line, in black, shows that the cloudiness has not changed much since 1980; if anything, it has decreased a little bit, the trend line being down about 0.02 over the whole time period.

Thus, my impression was both right and wrong. I was right that, since 2010, it has gotten more cloudy over Missouri. But that hides the long-term fact that, since 1980, it has not. It is common for subjective impressions to favor recent experience over the far past, but it can hide the truth.

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Figure 3. Data source: NASA Giovanni.

What about the Continental United States (CONUS) as a whole? Again, Giovanni wouldn’t let me search by the boundaries of the CONUS, so I searched in a rectangle that barely enclosed it. Figure 3 shows the data. Notice first that the year-to-year variation is less than for Missouri. Where cloud fraction in Missouri has bounced around between 0.2 and 0.6, cloud fraction for the CONUS has bounced around between 0.3 and 0.5. We have seen this before with other environmental data: large areas tend to average out variations in one area with opposite variations in another. However, here, too, we see the slightly declining trend in cloud fraction. The CONUS as a whole is becoming slightly less cloudy, and the difference in the trend line is about 0.02, similar to what it was for Missouri.

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Figure 4. Data source: NASA Giovanni.

The world, however, shows a markedly different trend (Figure 4). Again, because it is an even larger area, the year-to-year variation is now only between 0.44 and 0.5. Don’t be fooled because Excel has spread out the y-axis. However, this time the trend is slightly up, the trend line increasing slightly less than 0.02. The world is becoming very slightly more cloudy. I don’t know for sure, but I would bet you that the increase is happening primarily over the oceans. That would be an interesting research project.

The changes are very small. However, the world has become slightly cloudier over the last 40 years, while both Missouri and the Continental United States have become slightly less cloudy.

Sources:

“Analyses and visualizations used in this article were produced with the Giovanni online data system, developed and maintained by the NASA GES DISC.” Data downloaded 7/22/2019 from https://giovanni.gsfc.nasa.gov/giovanni.

Map created with Google Earth on 7/22/2019.

Tropical Storm Barry formed in the Gulf of Mexico on July 11. It strengthened, and churned ashore as a Category 1 hurricane in western Louisiana on July 13. It weakened, and moved northward, causing rain in Arkansas and here in Missouri.

Figure 1. Data source: Landsea, downloaded 2019.

As Figure 1 shows, land-falling hurricanes in July are uncommon, though not unknown: there have been 26 in the 167 years that records have been kept. That’s one every 6.4 years. It seems like a good time to ask whether climate change has been affecting tropical cyclones?

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Figure 2. Source: Weather.gov.

Why might we expect climate change to affect tropical cyclones? To answer that question, you have to understand the “engine” that drives a tropical cyclone (see Figure 2). Tropical cyclones get their energy from warm, humid air on the surface of the ocean. Convection causes the warm, humid air to rise, and as it does so, it enters cooler regions of the atmosphere. This causes the humid air to condense into clouds and rain (often thunderstorms). Condensation is an exothermic process – that means that the water gives off heat as it condenses. The heat keeps the humid air rising, condensing more water, and giving off more heat. This process continues. As the air rises, it leaves an empty place where it used to be, so more air rushes in from the sides to take its place. If this air is also warm and humid, then it will rise, too, and condense into rain. If this process strengthens, then the air rises faster and faster, and the air moving in to take its place moves faster and faster. The air begins to rotate, and presto, you have your tropical cyclone.

The energy that drives all of this is the warm humid air on the surface of the ocean. Thus, it is easy to understand that anything that causes the air on the surface of the ocean to be warmer and more humid can provide more energy to a storm that might form.

What if, over the decades, the water in the oceans got warmer? Well, it would make the air above it warmer. It would also evaporate into the air more effectively, as we all know that warm water evaporates more quickly than does cold water. So warming oceans would seem to be a perfect recipe for providing more energy to tropical cyclones, making them more intense. Climate change is projected to cause the oceans to warm, and this brings us to the first article I wanted to report.

Multiple studies have reported that the heat content of the oceans has been rising. The IPCC 5th Assessment Report put the rate at 0.20-0.32 watts per square meter. However, there were many uncertainties. A recent article by Cheng, Abraham, Hausfather, and Trenberth (2019) reports that since the 5th Assessment Report, scientists have made progress in identifying and resolving the uncertainties. They review 3 studies that incorporated the advances, and find that the rate has actually been 0.36-0.39 watts per square meter. Compared to the IPCC estimate, that represents an increase of somewhere between 0.04-0.19 watts per meter.

Doesn’t sound like much, does it? The oceans are huge, however, 361,900,000 square kilometers, which translates to 361,900,000,000,000 square meters. So, the increase represents an increase of 14,476,000 – 68,761,000 megawatts. The Callaway Nuclear Generating Station in Missouri is rated at 1,190 megawatts, so the increase is equal to 12,164 – 57,782 Callaway Nuclear Generating Stations. That’s a lot of heat!

So, have tropical cyclones become more severe? Well, that is really two questions. One involves wind speed, the other involves rainfall amounts. Too many other factors affect wind speed and rainfall amounts to permit a simple comparison across storms. There is no scientific consensus regarding how climate change has affected tropical cyclones, or how it may do so in the future.

Patricola and Wehner (2019) recently published a study where they modeled the wind speed and rainfall in a suite of 15 tropical cyclones from around the world under different climates. Thus, this study doesn’t really prove anything. Rather, it clarifies what kind of effects our current theories might predict. From coolest to warmest they simulated pre-industrial climate, historical climate, RCP 4.5, RCP 6.0, and RCP 8.5. (The RCPs are standardized emission scenarios used to project the effects of climate change. The terms 4.5, 6.0, and 8.5 represent the level of radiative forcing caused by climate change. All are projected to be warmer than current climate.) They then made comparisons between the models.

Table 1. Source: Patricola and Wehner, 2018.

Table 1 presents the results for peak wind speed measured for at least 10 minutes. The 1st column lists the name of the storm. The 2nd column gives the difference between the result of the historical and pre-industrial models. The 3rd column gives the difference between the result of the RCP 4.5 and historical models. The 4th column gives the difference between the result of the RCP 6.0 and historical models. The 5th column gives the difference between the result of the RCP 8.5 and historical models. The 6th column gives the wind speed projected by the historical model. The 7th column gives the wind speed as it was actually observed in the real storm.

Remember that the goal here is not to actually predict wind speed, but to understand the kind of effects our climate models project. The average difference in wind speed projected for RCP 4.5 vs. historical climate was 6.7 knots. The average difference in wind speed projected for RCP 6.0 vs. historical climate was 7.8 knots. The average difference in wind speed projected for RCP 8.5 vs. historical climate was 13.0 knots. Thus, for those comparisons, the hotter the climate scenario, the higher the wind speed. The outlier was for pre-industrial climate. Being cooler, the pre-industrial climate scenario should have resulted in lower wind speeds than the historical climate, yet the projection resulted in higher wind speed. Why, I’m not sure.

Table 2. Source: Patricola and Wehner, 2018.

Table 2 presents the results for rainfall. The average difference in rainfall projected for RCP 4.5 vs. historical climate was 10.9 inches. The average difference in rainfall projected for RCP 6.0 vs. historical climate was 13.5 inches. The average difference in rainfall projected for RCP 8.5 vs. historical climate was 18.4 inches. Here, pre-industrial climate was not an outlier: the average rainfall projected for pre-industrial climate was 5.8 inches less than for historical climate.

Thus, the study shows that modeling projects that climate change will result, on average, in more rainfall per storm. The trend was linear and consistent, and no storm bucked the trend. For wind speed, results were less consistent.

Hurricane Harvey was a great example of what is projected for rain. The storm parked itself over Houston and Eastern Texas, dropping 40 inches of rain in some areas, causing extensive flooding.

But what about Hurricane Barry? It’s storm path initially projected that it would come very close to New Orleans, and it would dump 15-20 inches of rainfall. Would there be another Katrina-like disaster?

The reality turned out to be much less dire. The storm came ashore west of New Orleans, and though there were some spots that received heavy rain, most areas received much less. According to the official weather service reports from New Orleans, Baton Rouge, and Shreveport, between July 1 and July 15 they received 3.66 inches, 4.41 inches, and 0.42(!) inches. It sounds like most of the rain came from scattered thunderstorms associated with Barry, not from a widespread downpour.

Sources:

Cheng, Lijing, John Abraham, Zeke Hausfather, and Keven E. Trenberth. 2019. “How fast are the ocearns warming?” Science. Vol 363 (6423), pp. 128-129. Downloaded 1/20/2019 from http://science.sciencemagazine.org.

Landsea, Chris. “Frequently Asked Questions: How many hurricanes have there been in each month?” Atlantic Oceanographic & Meteorological Laboratory. Data downloaded 7/16/2019 from https://www.aoml.noaa.gov/hrd/tcfaq/E17.html.

National Centers for Environmental Information. “Volume of the World’s Oceans from ETOPO1.” Viewed online 7/15/2019 at https://ngdc.noaa.gov/mgg/global/etopo1_ocean_volumes.html.

National Weather Service Forecast Office, New Orleans/Baton Rouge, LA. Daily Climate Report.Viewed online 7/16/2019 at https://w2.weather.gov/climate/index.php?wfo=lix.

National Weather Service Forecast Office, Shreveport, LA. Daily Climate Report. Viewed online 7/16/2019 at https://w2.weather.gov/climate/index.php?wfo=shv.

Patricola, Christina M. and Michael F. Wehner. 2018. “Anthropogenic Influences on Major Tropical Cyclone Events.” Nature. 563, 11/15/18., pp. 339-346.

Weather.gov. “Hurricane Facts”. Downloaded 7/16/2019 from https://www.weather.gov/source/zhu/ZHU_Training_Page/tropical_stuff/hurricane_anatomy/hurricane_anatomy.html.

Wikipedia contributors, “Hurricane Barry (2019),” Wikipedia, The Free Encyclopedia, https://en.wikipedia.org/w/index.php?title=Hurricane_Barry_(2019)&oldid=906405193 (accessed July 15, 2019).

Wikipedia contributors, “Tropical cyclone,” Wikipedia, The Free Encyclopedia, https://en.wikipedia.org/w/index.php?title=Tropical_cyclone&oldid=906385211 (accessed July 15, 2019).

Figure 1. Data source: Office of Climate, Water, and Weather Services, National Weather Service.

Damage from severe weather in Missouri shows a different pattern than does damage nationwide. As Figure 1 shows, the cost of damage from hazardous weather events in Missouri spiked in 2007, then spiked even higher in 2011. Since then, it has returned to a comparatively low level. The bulk of the damage in 2011 was from 2 tornado outbreaks. One hit the St. Louis area, damaging Lambert Field. The second devastated Joplin, killing 158, injuring 1,150, and causing damage estimated at $2.8 billion. The damages in 2007 came primarily from two winter storms, one early in the year, one late. In both cases, hundreds of thousands were without power, and traffic accidents spiked.

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Office of Climate, Water, and Weather Services, National Weather Service.

Figure 2 shows deaths and injuries in Missouri from hazardous weather. Deaths are in blue and should be read on the left vertical axis. Injuries are in red and should be read on the right vertical axis. The large number of injuries and deaths in 2011 were primarily from the Joplin tornado. In 2006 and 2007, injuries spiked, but fatalities did not. The injuries mostly represented non-fatal auto accidents from winter ice storms. The fatalities in 1999 resulted from a tornado outbreak.

I understand the trends in both figures this way: once in a while, Missouri has been struck with catastrophic weather events. They cause lots of deaths and a lot of damage, at a whole different scale from years with no catastrophic weather event. In years with no such event, weather-related deaths in Missouri have been around 40 or fewer, and injuries have been roughly 400 or fewer. Damages in such years have been about $150 million or less. In years with catastrophic weather events, the totals can be much higher.

2017 was a year in which Missouri saw no weather disasters that caused such high damages, or killed or injured so many people. That does not mean that Missouri was unaffected, however. The state was included in several billion-dollar weather disasters, the most costly of which was probably the flood of April 25-May 7. That was a historic flood for many of the communities that were affected.

The Missouri data covers fewer years than the national data discussed in my previous post. It also covers all hazardous weather, in contrast to the national data, which covered billion dollar weather disasters only. In addition, for some reason the Missouri data for 2018 has not yet been posted.

While the national data shows a clear trend towards more big weather disasters, Missouri’s data does not. The Missouri data seems to reflect the kind of disaster and where it occurred. Tornadoes, if they hit developed areas, cause injuries, deaths, and lots of damage. Floods cause fewer injuries and deaths; damage can be significant, but it is limited to the floodplain of the river that flooded. Ice storms affect widespread areas; damages come mostly through loss of the electrical grid, which can cause widespread economic loss and from car crashes, which cause many injuries but fewer deaths.

Sources:

Office of Climate, Water, and Weather Services, National Weather Service. 2016. Natural Hazard Statistics. Data for Missouri downloaded at various dates from https://www.nws.noaa.gov/om/hazstats.shtml#.

CPI inflation Calculator. 2019. 2017 CPI and Inflation Rate for the United States. Data downloaded 4/6/2019 from https://cpiinflationcalculator.com/2017-cpi-and-inflation-rate-for-the-united-states.
National Centers for Environmental Information. 2019. Billion-Dollar Weather and Climate Disasters: Table of Events. Viewed online 4/6/2019 at https://www.ncdc.noaa.gov/billions/events/US/1980-2018.

Descriptions of specific weather events, if they are large and significant, can be found on the websites of the Federal Emergency Management Administration, the Missouri State Emergency Management Agency, and local weather forecast offices. However, in my experience, the best descriptions are often on Wikipedia.

The number of natural disasters in the USA in 2018 declined from 2017, and the amount of damage they did also declined.

Figure 1. Source: National Centers for Environmental Information, 2019.

Since 1980, there have been 241 severe weather and/or climate events in the USA that have caused damages exceeding $1.6 trillion dollars. The most important of these are the “billion-dollar disasters,” events that caused damages in excess of $1 billion. Figure 1 shows the data. The columns represent the number of events, with each color representing a different type of event. The black line represents a moving 5-year average number of events. They gray line represents the cost of damages, in billions of dollars.

In 2018, there were 14 billion-dollar disasters. That is more than double the long-term average. The 4 years with the most billion dollar disasters have all occurred in the last 8 years, and the last 3 years have ranked #1 (tie), #3, and #4. The last 3 years have been significantly higher than any other years except 2011. The increase comes primarily from severe storms, a category that excludes hurricanes and tropical cyclones, flooding and winter storms. These are tornadoes, thunderstorms, hail, and similar kinds of storms.

The estimated CPI-adjusted losses in 2018 were $91 billion. That’s quite a chunk of change, but it much less than the costs in 2017 ($312.7 billion), 2005 ($220.8 billion), or 2012 ($128.6 billion). 2017 was a terrible year (see here): Hurricanes Harvey, Irma, and Maria struck in 2017, and not only was it far-and-away the most costly year, it also tied for the highest number of disasters. Hurricane Katrina struck in 2005, and Hurricane Sandy struck in 2012. Hurricane Katrina is still the single event that caused more damage than any other, followed by Hurricanes Harvey and Maria. Last year, the most costly natural disaster was the series of wildfires in California, especially the Camp Fire. The fires caused an estimated $24 billion in damage.

Looking at Figure 1, starting somewhere around 2005, the number of billion-dollar disasters starts to trend upward. The amount of damage does, too, though the variation from year-to-year is much greater. The National Centers for Environmental Information, which keeps this data, factors the Consumer Price Index into it, so the change is probably not due to inflation.

Three factors probably account for most of the increase. First, climate change has caused an increase in the amount of energy in the atmosphere, energy that is available to power more and bigger storms. I once calculated that the increased radiative forcing from climate change was equal to the energy output of 1.6 million nuclear power plants. (See here) That’s a lot of energy available to power storms. Second, climate change has caused an increase in droughts throughout the western United States. Even in years like this one, when there has been an abundance of winter snow, the warm temperatures cause the snow to melt earlier in the spring, and they dry out the land faster during the summer. The result is a tinder box, perfect conditions for huge wildfires. And finally, we keep putting ourselves in harm’s way. Development has increased along the Atlantic and Gulf Coasts, where it is in the path of any hurricane that comes ashore. Development has also increased along the fringes of forests, where it is vulnerable to wildfire. And even in the middle of the country, sprawl has increased the built-up area, making tornadoes more likely to grind over it, as opposed to farmland.

Missouri was in the region damaged by some of the big weather events of 2018, so the next post will look at how we fared here in the Show Me State.

Sources:

The National Centers for Environmental Information Billion-Dollar Weather and Climate Disasters portal has 5 pages available, and I used them all for this post: Overview, Mapping, Time Series, Summary Stats, and Table of Events. Downloaded and viewed online 4/3/2019 at https://www.ncdc.noaa.gov/billions.

2018 was the 3rd wettest year on record across the contiguous USA.

Figure 1. Source: NOAA Climate-at-a-Glance

So says data from Climate-At-A-Glance, the data portal operated by the National Oceanographic and Atmospheric Administration (NOAA). Figure 1 shows the data, with the green line representing actual yearly precipitation, and the blue line representing the trend across time. The left vertical scale shows inches of precipitation, while the right shows millimeters of precipitation. In 2018, the average precipitation across the contiguous USA was 34.62 inches, which was the 3rd highest amount in the record. Over time, precipitation seems to be increasing at about 0.18 inches per decade. The trend towards more precipitation is present in the Eastern Climate Region (+0.30 inches per decade), the Southern Climate Region (+0.24 inches per decade), and the Central Climate Region (+0.23 inches per decade). It is almost absent in the Western Climate Region, however (+0.02 inches per decade). In fact, 2018 was a below-average precipitation year in the West. (Except where noted, data is from the Climate-at-a-Glance data portal.)

(Click on figure for larger view.)

Figure 2. Source: NOAA Climate-at-a-Glance.

In Missouri, 2018 was the 41st wettest year on record, with 43.04 inches of precipitation. (Figure 2) This puts the year 2.54 inches above the long-term average. As expected, the variation from year-to-year is much larger than the change in precipitation over time, but since 1895 Missouri has trended towards about 0.24 inches more precipitation per decade.

Unlike 2016 and 2017, 2018 did not bring epic flooding to Missouri. Perhaps the most notable thing about Missouri precipitation in 2018 were two almost out of season snow events – one over the Easter weekend in April, and one in mid-November. The latter heralded what has been a very snowy winter so far in 2019 for Missouri and much of the Midwest.

Figure 3. Source: Source: NOAA Climate-at-a-Glance.

The Northern Rockies and Plains are where most of the water that flows into the Missouri River originates, and the Missouri River provides water to more Missourians than any other source. This region saw 24.83 inches of precipitation in 2017, some 5.82 inches above average. (Figure 3) As expected, the variation between years is much larger than the change over time, but here, too, precipitation has been increasing, though the change has only been +0.07 inches per decade.

What to watch for in Missouri, then, does not appear to be a decrease in average yearly precipitation, but two other issues. First, demand for water has been increasing. Will it grow to outstrip the supply? Second, this winter notwithstanding, climate change is causing precipitation that once fell as snow to fall as rain. This changes the timing of when the Missouri River receives the runoff. Will that affect the ability of the river to supply water to meet the various demands? So far, these answers are not known. (For a more extended discussion, see here.)

Figure 4. Source: Source: NOAA Climate-at-a-Glance.

The water situation in California is more serious than it is in the Northern Rockies and Plains, Missouri, or contiguous USA. California has a monsoonal precipitation pattern, and it has regions that receive a great deal of precipitation, while other regions receive little, if any. Consequently, the state relies on snowfall during the winter, which runs off during the spring and early summer, and is collected into reservoirs. This water is then distributed around the state. Thus, the amount of water contained in the snowpack on April 1, which is when it historically started melting in earnest, has been seen to be crucial to California’s water status.

After a big water year in 2017, 2018 returned to below-average precipitation. It was the 34th driest year on record, with precipitation 4.54 inches below average. (Figure 4)

As I reported previously, the California snow season started slowly this winter. It has been catching up, and is now nearly average for this date. The snowpack is above average in the Colorado River Basin above Lake Powell, the other major source for California’s water. The snowpack is 110% of the average for this date. (National Resource Conservation Service, 2/14/2018).

Sources:

California Data Exchange Center, Department of Water Resources. Current Year Regional Snow Sensor Water Content Chart (PDF). Downloaded 1/22/2018 from https://cdec.water.ca.gov/water_cond.html.

Mammoth Mountain Ski Area. 2018. Snow Conditions and Weather: Snow History. Viewed online 1/15/2018 at NOAA National Centers for Environmental information, Climate at a Glance: U.S. Time Series, published January 2018, retrieved on January 15, 2018 from http://www.ncdc.noaa.gov/cag.

Natural Resource Conservation Service, U.S. Department of Agriculture. Upper Colorado River Basin SNOTEL Snowpack Update Report. Viewed online 1/28/2018 at https://wcc.sc.egov.usda.gov/reports/UpdateReport.html?textReport.

NOAA National Centers for Environmental information, Climate at a Glance: U.S. Time Series, published January 2018, retrieved on January 15, 2018 from http://www.ncdc.noaa.gov/cag.

2018 was the 4th warmest year on record globally, and the 14th warmest for the contiguous USA.

Figure 1. Source: NOAA Centers for Environmental Information.

Figure 1 shows the average annual temperature for the Earth for each year from 1880-2018. The chart shows the temperature as an anomaly. That means that they calculated the mean annual temperature for the whole series, and then presented the data as a deviation from that mean. Degrees Celsius are on the left vertical axis, and degrees Fahrenhiet are on the right. Because the earth contains very hot regions near the equator and very cold polar regions, the actual mean temperature has relatively little meaning, and Climate-at-a Glance does not include it in their chart. (All data is from NOAA, Climate at a Glance.) 2016 was the highest on record, and the 4 highest readings have all occurred within the last 4 years. You can see that the Earth appears to have been in a cooling trend until around 1910, then a warming trend until mid-Century, then a cooling period until the late 1960s or early 1970s, and then a warming period since 1970. Over the whole series, the warming trend has been 0.07°C per decade, which equals 0.13°F per decade. Since 1970, however, the warming has accelerated to 0.17°C per decade (0.30°F).

(Click on chart for larger view.)

Figure 2. Source: NOAA Centers for Environmental Information.

Figure 2 shows the average yearly temperature for the contiguous United States from 1895 to 2018. In this chart and those that follow, the vertical axes are reversed, with °F on the left vertical axis, and °C on the right. The purple line shows the data, and the blue line shows the trend. 2018 was the 14th highest in the record at 54.58°F. The 4 highest readings have all come within the last decade. Over the whole series, the average temperature has increased 0.15°F per decade. Since 1970, however, the rate has increased substantially.

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Figure 3. Source: NOAA Centers for Environmental Information.

Figure 3 shows the average temperature across Missouri for 2018. Across the state, it was the 35th warmest year on record, with an average temperature of 55.2°F. In Missouri, the warming trend from 1930-1950 was more marked than it was nationally; across the whole time period, the trend has been for a 0.1°F increase in temperature each decade. As was the case nationally, since 1970 the increase has accelerated.

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Figure 4. Source: NOAA Centers for Environmental Information.

Because conditions in the Northern Rockies and Plains affect how much water flows into the Missouri River, which provides more of Missouri’s water supply than any other source, I have also tracked climate statistics for that region. Figure 4 shows the data. Last year was slightly above average for this region. This region has been warming at a rate of 0.2°F per decade over the whole period, and, since 1970, the rate has accelerated substantially.

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Figure 5. Source: NOAA Centers for Environmental Information.

Because I have been concerned about the water supply in California, I also track the climate statistics for that state. Figure 5 shows the data. Last year was the 3rd warmest year in the record, with an average temperature of 60.2°F. California has been warming at a rate of 0.2°F each decade. Since 1970 the rate of increase has accelerated substantially.

In all 4 locations the average yearly temperature seems to have increased significantly for several decades, then paused during mid-Century, and then resumed climbing, but at an accelerated rate. There seems to be little doubt that across the country it is warmer than it was. In Missouri, the average yearly temperature has been increasing, but at a rate that is somewhat less than in the other locations I looked at.

Sources:

NOAA National Centers for Environmental Information, Climate at a Glance. Retrieved on February 1, 2019, from http://www.ncdc.noaa.gov/cag.

Followers of this blog know that I usually report on the snowpack conditions in California once or twice during the winter. I do this because I have family living in California, and because California constitutes an incredibly large percentage of this nation’s economy, and because it provides an incredibly large percentage of the fruits and vegetables we eat.

California depends on its snowpack for about 30% of its water supply. Climate change will reduce the California snowpack by as much as 40%, it is projected, putting the state’s water supply at risk. The snowpack is projected to decline mostly because the increased temperature will cause precipitation to fall as rain instead of snow, and because it will cause increased melting during the winter months.

Figure 1. Source: California Data Exchange Center, 2019.

The snow year got off to a slow start in California this year. The January 24 measurements showed the snowpack at 56-63% of average for that date, depending on which hydrologic region was measured. (See Figure 1.)

(Click on figure for larger view.)

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Figure 2. Data source: Mammoth Mountain Ski Resort, 2019.

The snowpack is below average despite the fact that California has had significant precipitation. November and December were slow, but at Mammoth Mountain, a ski resort located in the Sierra Nevadas, they have had 93 inches of snow this January. That puts the total for the winter within 2 inches of average for this date, and the month still has 4 days to go as I write.( See Figure 2.)

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Figure 3. Source: California Department of Water Resources, 2019.

Because California receives most of its water during the winter, but needs it most during the summer, the state operates many reservoirs. The water content of the most important are shown in Figure 3. The Lake Shasta, Trinity, and Oroville Reservoirs are the three largest, and thus, the most important. In general, the reservoirs appear to be close to normal levels for this time of year. The one exception is the Oroville Reservoir, which is at 39% of capacity. This reservoir was severely damaged in 2017, when storms caused emergency releases, which eroded away major portions of the dam. Repairs were completed last fall, but the dam has yet to refill. Whether it will ever refill given California’s reduction in snowpack is an interesting question to which I don’t know the answer. Oroville is the major water source for the California State Water Project, and, thus, it is important.

The Colorado River is another important source of water for California, and Lake Mead is the principal reservoir at which its level is measured. It is at 1085.21 ft. above sea level, or 40% of its capacity. For this date the average is 1159 ft. above sea level, and the historical low was 1083.46 ft. above sea level, reached in 2016. Lake Mead can be recharged with water from Lake Powell, and that reservoir is also at 40% of capacity. It is usual for these reservoirs to be low during the late fall, and then recharge during the winter. However, Lake Mead continues to flirt with historical lows and with the level at which mandatory water restrictions go into effect.

The bottom line here is that California’s water supply continues to be below historical levels, though not quite as low as during the terrible drought a few years ago. As of right now, signs do not point to a severe water crisis this year, but the state continues to walk a rather fine line. Should drought recur, a severe crisis is likely to occur..

Sources:

Alexander, Kurtis. 2018. “Oroville Dam Fixed and Ready to Go, Officials Say – But at a Big Price.” San Francisco Chronicle. 10/31/2018.

California Data Exchange Center. California Snowpack Water Content, January 24, 2019, Percent of April 1 Level. Downloaded 1.27.2019 from https://cdec.water.ca.gov/reportapp/javareports?name=PLOT_SWC.pdf.

California Department of Water Resources. Current Reservoir Conditions. Downloaded 1/27/2019 from http://cdec.water.ca.gov/reportapp/javareports?name=rescond.pdf.

Lake Mead Water Database. Viewed online 1/27/2019 at http://lakemead.water-data.com.

Mammoth Mountain Ski Resort. Snow & Weather Report. Viewed online 1/27/2019 at https://www.mammothmountain.com/winter/mountain-information/mountain-information.

The last post reported on 33 climate trends discussed in “State of the Climate 2017,” a report published in the Bulletin of the American Meteorological Society. This post characterizes the 2017 climate in the United States. Be sure to catch that this is for 2017, not 2018, the year just ended. In what follows, “CONUS” means the continental United States. All anomalies compare to the 1981-2010 average.

Figure 1. 2017 Temperature Anomalies Across the CONUS. Source: Blunden, Arndt, & Hartfield, 2018.

The annual average temperature in 2017 for the contiguous United States (CONUS) was 12.5°C or 1.0°C above the 1981–2010 average—its third warmest year since records began in 1895, 0.2°C cooler than 2016 and 0.4°C cooler than 2012. Figure 1 shows a map of 2017 temperature anomaly across the United States. Every state was warmer than average except for Washington. Most of Missouri was 1.0-1.5°C warmer than average (1.8-2.7°F). A few areas were even warmer, but the map isn’t sufficiently detailed to determine for sure which areas they were.

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Table 2. 2017 Precipitation Anomalies Across the CONUS. Source: Blunden, Arndt, and Hartfield, 2018.

Averaged nationally, precipitation was 104% of average, making 2017 the 20th wettest year in the record. The pattern was variable, however, as shown in Figure 2. In particular, winter precipitation was higher than average, with Nevada and Wyoming each having the wettest winters on record. The California mountains were wetter than average (I reported on the large snowpack in the winter of 2017 in previous posts). So was eastern Colorado-New Mexico. On the other hand, much of the Southwest and the northern Plain States were in drought. It was also dry along the Mississippi River from the Missouri Bootheel into central Iowa.
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Figure 3. Source: Blunden, Arndt, and Hartfield, 2018.

There were 16 weather-related events in 2017 which resulted in damage of more than $1 billion. That tied with 2011 for the highest number of billion-dollar disasters. The total damages they caused was $306 billion, a new record. Figure 3 shows a map of where they were roughly located. There were three major hurricanes across the southern United States, plus catastrophic fires in California and other western states. Missouri and Arkansas were affected by flooding in late April-early May 2017.

Missouri had 13 fatalities and 155 injuries from weather-related disasters in 2017, and a total of $156.20 million in damages. There have been many years when the Missouri’s weather-related damage has been below $100 million, but in 2011 it was over $3.4 billion.

Sources:

Blunden, J., D. S. Arndt, and G. Hartfield , Eds., 2018: State of the Climate in 2017. Bull. Amer. Meteor. Soc., 99 (8), Si–S332, doi:10.1175/2018BAMSStateoftheClimate.1. Downloaded 12/15/18 from https://www.ametsoc.org/index.cfm/ams/publications/bulletin-of-the-american-meteorological-society-bams/state-of-the-climate.

Office of Climate, Water, and Weather Services, National Weather Service. 2016. Natural Hazard Statistics. Data downloaded 2/10/16 from http://www.nws.noaa.gov/om/hazstats.shtml#.

Recent weeks have been very active for tropical storms. At one time in the Atlantic, there were 3 hurricanes (Florence, Helene, and Isaac) and 2 tropical storms (Gordon and Joyce). In the Eastern Pacific, August saw 4 tropical cyclones active at the same time (Hector, Kristy, John, and Lleana). and in September, Hurricane Hector and a new storm, Hurricane Olivia, impacted Hawaii. In the Western Pacific there have been 28 named storms. One of them, Super-Typhoon Mangkhut, caused extensive damage in the Philippenes.

Is this normal, or are tropical storms getting worse?

Tropical cyclones are rotating, organized storm systems that originate over tropical or subtropical waters. They have a center of low pressure around which they rotate that can develop into an “eye” if the storm is sufficiently intense and well organized. The thunderstorms tend to get organized into bands of thunderstorms that spiral out from the center. Even outside the thunderstorms, however, they have high sustained winds. In the Northern Hemisphere, they rotate counter-clockwise. In the Southern Hemisphere, they rotate clockwise.

Tropical cyclones are classified by the speed of their winds:

• Tropical Depressions have maximum sustained winds of 38 mph or less.
• Tropical Storms have maximum sustained winds of 39 to 73 mph.
• Hurricanes have maximum sustained winds of 74 mph or higher. In the Western Pacific, hurricanes are called typhoons. In the Indian Ocean and Southern Pacific, they are called cyclones.
• Major Hurricane have maximum sustained winds of 111 mph or higher.

Hurricanes are further classified according to the Saffir-Simpson Hurricane Wind Scale:

• Category 1: winds 74-95 mph., capable of causing damage even to well-constructed wood frame homes.
• Category 2: winds 96-110 mph., capable of causing damage to roofs and siding, blowing shallowly rooted trees over, and causing power loss.
• Category 3 (major hurricane): winds 111-129 mph., capable of causing structural damage to even well-built homes, snapping or uprooting lots of trees, and causing power outages that last for days.
• Category 4 (major hurricane): winds 130-156 mph., capable of causing catastrophic damage, ripping whole roofs off houses or blowing down walls. Regions impacted may be uninhabitable for weeks or months.
• Category 5 (major hurricane): winds 157 mph. or higher, capable of destroying most houses, blowing down most trees, cutting off access to whole regions, and making whole regions uninhabitable for weeks or months.

Figure 1. Source: National Oceanographic and Atmospheric Administration

Tropical cyclones generally originate near the equator. Figure 1 shows the major regions where tropical cyclones tend to form, and their typical paths. I’m not sure what sends so many of them up the U.S. coast, rather than coming ashore. Perhaps it is the jet stream, or the Gulf Current, or the Mid-Atlantic High.

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Figure 2: Cyclone Formation by Time of Year. Source: National Oceanic and Atmospheric Admiinistration.

Figure 2 divides the year into 10-day intervals, and counts the number of tropical storms, hurricanes, and major hurricanes that form in the Atlantic Basin per 100 years during each interval. August and September are “hurricane season,” and the 10 days from September 10-19 are the peak. This chart would seem to indicate that during that interval, between 90 and 100 tropical storms originate every 100 years in the Atlantic Basin. That averages out to about 0.9-1.0 per year. Thus, it would appear that the last several weeks have been unusually active.

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Figure 3. Data source: National Oceanographic and Atmospheric Administration

Figure 3 shows the number of tropical storms, hurricanes, and major hurricanes that have formed in the Atlantic Basin annually since 1851. The blue area shows the number of tropical storms, the red area shows the number of hurricanes, and the green area shows the number of major hurricanes. To each series I have fitted a polynomial regression line.

First, the variation between years is large for all of the series. Second, there are more tropical storms than hurricanes, and more hurricanes than major hurricanes. Third, all three series show an increasing trend over time. There are more tropical storms than there used to be, more hurricanes, and more major hurricanes. HOWEVER, in viewing these trends, one must keep in mind that today we have weather satellites, air travel, and a good deal more shipping density across the Atlantic Ocean. It is quite possible that some storms went undetected or unmeasured in the past, but that is no longer the case. Thus, the observed change could easily be due to better observations, not a real increase in the number of storms. I don’t have the ability to make that correction, but The Fifth Assessment Report of the Intergovernmental Panel on Climate Change concluded that evidence for an increase in the number of tropical cyclones is not robust.

Figure 4. Data source: Wikipedia Contributors, 9/14/18.

As noted above, tropical cyclones can form in 8 basins around the world. One might ask which produces the most severe storms? Figure 4 shows the data. All of the basins have produced storms with sustained winds above 150, but the highest ever recorded was 215 mph. in Hurricane Patricia in the Eastern Pacific in 2015. In terms of lowest central pressure, the lowest ever recorded was in Typhoon Tip in the Western Pacific in 1979.

One might also ask which basin produces the most severe storms. Record keeping began in a different year in each basin, however, there appears to be a clear answer: the Western Pacific. Counting only storms with a minimum central pressure below 970 kPa, this basin has produced more than twice as many as any other basin.

Large cyclonic storms most often form in the tropics during hurricane season, but they don’t have to. For instance, the so-called “Perfect Storm” (they made a movie about it starring George Clooney) was a 1991 storm that formed in the Atlantic off the coast of Canada on October 29. It developed into a Category 1 hurricane, with a well defined eye, not dissipating until after November 2. Similarly, the remnants of Tropical Storm Rina (2017) travelled north across the Atlantic, crossed the British Isles, and crossed Central Europe. Entering the Mediterranean Sea, it re-strengthened into a tropical storm, now called Numa, which developed an eye and other characteristics typical of a hurricane. It’s strength peaked on November 18, with maximum sustained winds of 63 mph., not quite hurricane strength, but close.

Sources:

Hartmann, D.L., A.M.G. Klein Tank, M. Rusticucci, L.V. Alexander, S. Brönnimann, Y. Charabi, F.J. Dentener, E.J. Dlugokencky, D.R. Easterling, A. Kaplan, B.J. Soden, P.W. Thorne, M. Wild and P.M. Zhai, 2013: Observations: Atmosphere and Surface. In: Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Stocker, T.F., D. Qin, G.-K. Plattner, M. Tignor, S.K. Allen, J. Boschung, A. Nauels, Y. Xia, V. Bex and P.M. Midgley (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA.
NASA Space Place. 2018. How Do Hurricanes Form. Downloaded 9/18/2018 from https://spaceplace.nasa.gov/hurricanes/en.

National Oceanic and Atmospheric Administration. 2018. Tropical Cyclone Climatology. Viewed online 9/18/2018 at https://www.nhc.noaa.gov/climo.

Wikipedia contributors. (2018, July 21). Cyclone Numa. In Wikipedia, The Free Encyclopedia. Retrieved 19:26, September 18, 2018, from https://en.wikipedia.org/w/index.php?title=Cyclone_Numa&oldid=851259614

Wikipedia contributors. (2018, September 14). List of the most intense tropical cyclones. In Wikipedia, The Free Encyclopedia. Retrieved 22:23, September 18, 2018, from https://en.wikipedia.org/w/index.php?title=List_of_the_most_intense_tropical_cyclones&oldid=859553932.