Climatologist Dr. John Christy demolishes warmists' claims in testimony to Congress

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John R. Christy, PhD – Alabama State Climatologist

Recently it has become popular to try and attribute certain extreme events to human causation. The Earth however, is very large, the weather is very dynamic, especially at local scales, so that extreme events of one type or another will occur somewhere on the planet in every year. Since there are ennumerable ways to define an extreme event (i.e. record high/low temperatures, number of days of a certain quantity, precipitation total over 1, 2, 10 … days, snowfall amounts, etc.) this essentially assures us that there will be numerous “extreme events” in every year because every year has unique weather patterns. The following assesses some of the recent “extreme events” and demonstrates why they are poor proxies for making claims about human causation.

Midwestern Drought

To put it simply, Andreadis and Lettenmaier (2006) found that for the Midwest, “Droughts have, for the most part, become shorter, less frequent, less severe, and cover a smaller portion of the country over the last century.” In other words, droughts have always happened in the Midwest and they are not getting worse (more on Midwest heat waves below and on Midwest drought in Section 2). The figure below indicates no longterm changes in drought in the primary corn and soybean belt.

Extreme High and Low Temperatures

Another extreme metric is the all-time record high temperature for each state. The occurrence of the records by decade (Figure 1.1 below) makes it obvious that the 1930s were the most extreme decade and that since 1960, there have been more all-time cold records set than hot records in each decade.

However, there are only 50 states, and this is a number that isn’t large enough to give the best statistical results. Below in Fig. 1.2 are the year-by-year numbers of daily all-time record high temperatures that stood as of 2011 from a set of 970 weather stations with at least 80 years of record (NOAA/NCDC/USHCNv2). There are 365 opportunities in each year (366 in leap years) for each of the 970 stations to set a record high (TMax).

The clear evidence is that extreme high temperatures are not increasing in frequency. The recent claims about thousands of new record high temperatures were based on stations whose length-of-record could begin as recently as 1981, thus missing the many heat waves of the 20th century. So, any moderately hot day now will be publicized as setting records for these young stations because they were not operating in the 1930s.

The figure below gives what a climatologist would want to know because it uses only stations with long records.

A more meaningful result comes if we take the total record highs by ten-year totals, i.e. 1895-1904, 1896-1905, … 2002-2011. In Figure 1.3 below are the record daily highs for 704 stations with at least 100 years of data. Note that the value for the most recent decade is less than half of what was observed in the 1930s.

Regarding the heat wave of 2012, I calculated the number of record high temperatures that stand as of 2012 (Fig. 1.4) for stations in the 8 hardest-hit central states (AR-IL-IN-IA-KS-MO-NE-OK) and stations on the West Coast (CA-OR-WA). Notice that the Central-US and West Coast both felt the heat waves of the 1930s when the highest number of events occurred for both regions. However, the current 2012 event shows high numbers in the Central-US, but a dearth of record highs along the West Coast, indicating the heat wave is smaller and less severe than previous events.

Record cold temperatures are shown in Fig. 1.5 (TMin). Through the 1980s there was an even distribution with a fairly noticeable drop-off in record lows over the past 25 years. The cause for this drop-off is discussed in Section 3 of this testimony.

An interesting result is produced by taking the ratio year-by-year of the number of TMax daily records divided by the number of TMin daily records (Figure 1.6 below). The two large periods of more record highs than lows are in the 1930s and the last 15 years. The first high-ratio period in the 1930s was due to numerous TMax records while the more recent period was due to fewer TMin records. This decline in the record low temperatures (TMin) in the past 25 years is likely related to the general disturbance by human development around the thermometer stations (again, discussed in Section 3). Meehl et al., 2009 did a similar analysis, but started later, in 1950. This led to the claim of a rapidly rising ratio of record highs to record lows. Had the authors gone back only
two more decades to look at a more complete climate record, and had taken into account the contamination of TMin values, the claim of rapidly increasing ratios would not hold.