Midwest Floods Becoming More Frequent

I have noticed over recent years how often a storm is described as being a "100-year" or "500-year" or even a "1000-year" event. If something is supposed to happen only once in centuries, how come we're getting them every few years. For instance, there have been record floods in the Midwest U.S. in 1993, 2008, 2011, 2013 and again in 2014. Maybe we need to redefine what it means to be a 100-year flood.

Or, maybe the definition of a 100-year flood isn't wrong at all - at least under previous conditions. Maybe the problem is the conditions have changed.

Researchers at the University of Iowa used river gauge data from the U.S. Geological Survey to determine the flood rate in the Midwest U.S. to examine that very question. What they found is that 34% of the stations they examined recorded an increased amount of flooding, while only 9% recorded a decrease.

The researchers just reported the findings without attempting to link them to climate change. However, these findings are exactly what we would expect, and have been predicted, as a result of climate change. As the air gets warmer it can hold more moisture. Then, when it gives it up, this will result in more severe precipitation events - flooding.

By the way, the economic cost of these floods runs into the billions of dollars. For those claiming climate change is good for us, would you mind explaining this, please?

Tropical Storms in the Southwest

The remnants of Hurricane Norbert hit the Southwestern U.S. this week and caused havoc. Record rainfall in the region caused flooding, closed roads and led to at least two deaths. To really add injury to injury, the flooding is not likely to help with the drought. The system missed the areas hardest hit by the drought and didn't help at all. Even in areas that got rain, the rain came so hard and fast that it ran off rather than soak in. Some, of course, will be caught in the reservoirs and will provide some help, but most will lost.

A tropical storm system hitting this region is very unusual. Just look at the fact that it was not only the single day record rain, but it really shattered the old record. Norbert dumped 3.29 inches on Phoenix on Monday. The old single day record was 2.91 inches and was 81-years old. The new record is more than 13% higher than the old one. (There was also a 4.98 inch rainfall in 1911 that occurred over two days, but within a 24-hour period, making it the 24-hour record holder.) What isn't revealed in that statistic is that the 3.29 inches fell in just seven hours. You don't see this kind of record history very often in places that get tropical storms on a regular basis.

According to Wikipedia, there have been four tropical storms that have hit the Southwester U.S. with gale force winds since 1900. Norbert was not the fifth. Storm organization had degraded quickly when the storm hit Mexico and wind speeds dropped precipitously.

So, why do so few storms hit this region? After all, there are lots of Pacific storms that form in this region and tropical cyclones in the Northern Hemisphere tend to hook towards the Northeast. You would think this would create a situation conducive for West Coast storm strikes.

The answer lies in the ocean temperature. The California Current along the West Coast originates in the north and moves southwards along the continental margin.  Take a look at this plot from Climate Reanalyzer showing the ocean temperature for September 11, 2014:

Source: Climate Reanalyzer

The light blue band along the coast line clearly shows how the waters in this region are cooler than ocean waters farther out to sea (to the left, or west). There are two things that are needed for tropical cyclone development: warm ocean water and a lack of high-altitude wind shear. As it turns out, the California Current not only cools the water, it also leads to high-altitude wind shear. Storms that form and move into this region run right into a hurricane killer. The U.S. West Coast has it very own hurricane-barrier.

But, what is going to happen as the ocean gets warmer as a result of climate change? We don't need to speculate, we can look at the record and we can see what is already happening.


While Norbert didn't bring gale force winds, it did fall in the category of tropical storm remnant affecting the Southwest. Again, according to Wikipedia (not a research quality source, but adequate for our purpose here), there have been 67 storms (not including Norbert) that are recorded to have had an impact on California.

Number of recorded storms impacting California

Period	Number of storms
Pre-1930	11
1930s	7
1940s	3
1950s	5
1960s	3
1970s	7
1980s	9
1990s	7
2000s	10
2010s	5

Adding Norbert, this list indicates that there have been 39 of the 68 storms since the beginning of the 1970s, over 57% of all of the storms on this list. Why did I use that time span? Take a look at this graph for the answer:

Source: NOAA

This graph shows the ocean temperature started a significant increase in the late-1960s. Remember, tropical storms need warm water. We would expect, if all things remain equal (a bad assumption, but a good starting point) that the California hurricane barrier would start to break down and that is what the data seems to be indicating.

Take a look at this plot, also from Climate Reanalyzer:

Source: Climate Reanalyzer

This plot shows the temperature anomaly for September 11, 2014, the same day as the other ocean temperature plot. The difference between the two is the first plot showed the actual water temperature and this one shows the difference between the actual temperature and the average temperature. Just as the above plot clearly showed the California Current to provide cooler waters along the West Coast, this one shows, equally clearly, that the waters along the West Coast are getting warmer. Quite a bit so, in fact.

Does this mean California and the Southwest can expect more tropical storm remnants? I believe the data shows that is already happening. Does this mean there is a possible relief for the long-term drought? Again, I believe the data already shows this is not the case. Droughts are relieved, and caused, by long-term changes in the precipitation pattern. Flash floods with large amounts of runoff are not going to provide the relief needed. That will take long, soaking rains and heavy snowfall in the mountains. In fact, there is evidence the warming oceans is what is actually causing the drought.

The conclusion I reach from this is that this region is already experiencing severe effects from global warming and will continue to see them into the future.

Precipitation Data Available Online

One of the common false arguments contrarians make is that climate change data is not available to anyone but climate scientists and they could prove the scientists wrong if they just had access to the data. This, of course, is false in multiple ways. The first being they are not going to prove climate scientists wrong, no matter how much data they have. The second being, the data is freely available to anyone with a Internet connection.

The National Climatic Data Center (NCDC) has all available climate data online for anyone to access. The National Snow and Ice Data Center (NSIDC) has ice and snow data. And, NASA Goddard Institute for Space Studies (NASA GISS) has satellite data. These are just a sample of the data available. So, anyone that claims they are denied the data clearly has not done their homework.

Now, this amount of data has just been increased. NASA and JAXA have made the data from the Global Precipitation Measurement (GPM) satellite available to the public. This mission is a joint mission between NASA and the Japan Aerospace Exploration Agency (JAXA), with contributions from other countries, was launched this past February 27 and measures worldwide precipitation.

If you would like to access the data you can find it here.