Observed Climate Change and the NegligibleGlobal Effect of Greenhouse-gas Emission

Limits in the State of Tennessee

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Observed climate change in Tennessee

HERE IS no observational evidence of unusual long-termclimate changes in Tennessee. No emissions reductions byTennessee will have any detectable regional or global

effect whatsoever on climate change.

Annual temperature: Long-term temperature records began in Tennessee in 1895. Overthe entire record, there is no statistically significant trend. Instead, the record isdominated by annual and decadal-scale variability. Temperatures during the past decadeor so have been similar to those of 1920-1940. They follow 40 years from the late 1950sthrough the mid-1990s when statewide average temperatures were cooler than average.Therefore there is nothing unusual about recent temperatures when set against the state’slong-term climate history:

Tennessee annual temperatures, 1895-2007Annual mean temperatures and secular trend

Figure 1. Annual statewide average temperature history for Tennessee, 1895-2007. Source: USNational Climatic Data Center: http://www.ncdc.noaa.gov/oa/climate/research/cag3/tn.html.

Seasonal temperatures: Likewise, there are no long-term seasonal trends. Instead, year-to-year and/or decade-to-decade variability is most evident. In no season do recenttemperatures appear unusual compared with observed temperature history. There is noevidence of “climate change”:

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Tennessee seasonal temperatures, 1895-2007Seasonal mean temperatures and secular trends

Figure 2. Seasonal mean temperatures in Tennessee, 1895-2007. Source: US National Climatic DataCenter: http://www.ncdc.noaa.gov/oa/climate/research/cag3/tn.html

Precipitation: There is also no statistically-significant trend and, again, the record isdominated by large interannual variations—ranging from as much as 66.68 inches of rainin 1979 to as little as 35.67 inches in 1941. Certainly, 2007 stands out as a very dry year,but there is no drying trend: 2007 merely reflects natural variability:

Tennessee annual precipitation, 1885-2007Total annual precipitation and secular trend

Figure 3. Total annual precipitation in Tennessee. Source: National Climatic Data Center:http://www.ncdc.noaa.gov/oa/climate/research/cag3/tn.html.

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Drought: Since 1895, there has been no long-term trend of drought in Tennessee.Instead, annual and decadal variability prevail:

Tennessee drought severity, 1885-2007Palmer drought-severity index

Figure 4. Monthly mean Palmer Drought Severity Index (PDSI) in Tennessee, 1895-2007.Source: National Climate Data Center, www.ncdc.noaa.gov.

Monthly mean Palmer Drought Severity Index values—a standard measure of moistureconditions that reconciles inputs from precipitation and losses from evaporation—showno trend during the past 113 years. The period of record is dominated by short-termvariations, although there was a drought in the mid-1950s and a period of high rainfall inthe mid-1970s. There were more droughts before 1950 than after.

Tornadoes: Tennessee lies close to “tornado alley” and experiences some tornadoes.However, an apparent increase is probably an artifact of better technology, a largerorganized network of tornado-spotters, and a growing population:

Figure 5. Tornado activity in the United States per 1,000 square miles. Source: National ClimaticData Center, http://lwf.ncdc.noaa.gov/oa/climate/severeweather/tornadoes.html.

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During the super-tornado outbreak of April 3-4, 1974—the worst tornado outbreak inU.S. history—at least 28 tornadoes passed through Tennessee, leaving 50 people dead,635 injured and $30 million in damages. It has been suggested that the frequency ofextreme weather events such as tornadoes will increase as a result of “global warming”.

However, in Tennessee, as in the United States as a whole, the recent increase in tornadoobservations can be explained by non-climate factors. Small tornadoes that were oncemissed are now being detected by Doppler radar and the larger network of observers. Areport by the Nashville Tennessee Office of the National Weather Service found:

“Population growth and warning coordination and awareness efforts have dramaticallyincreased the number of documented tornadoes—especially weak tornadoes—in recentyears, while simultaneously lowering the number of tornado-related fatalities.”

The number of major tornadoes across Tennessee—those less likely to have passedunnoticed owing to the damage they cause—shows no long-term increase, furtherindicating that the apparent increase in the occurrence of all tornadoes is probably areflection of our growing ability to detect them.

Figure 6. Top: Total number of tornadoes observed in Tennessee, 1950-2007. Middle: annual numberof major (F3-F5) tornadoes observed. Bottom: annual number of fatalities resulting from tornadoes.

Source: NOAA Storm Prediction Center: http://www.spc.noaa.gov/climo/historical.html)

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Hurricanes: Hurricanes play a largely beneficial part in Tennessee’s summer climate.The remnants of tropical cyclones that pass near Tennessee have usually lost the ferocityof their winds and deliver late-summer rainfall when it is most needed:

Figure 7. Proportion of total June-November rainfall from tropical systems. Source: Knight et al., 2007.

When a strong tropical cyclone strikes the U.S. coastline, the result can be devastating.However, further inland, the remnants of tropical systems produce good rainfall which isoften helpful to agriculture, forestry, and other water interests in the state. Recentresearch shows that Tennessee, on average, receives 4-8% of its total June-Novemberrainfall, and 6-15% of its normal September rainfall, from tropical storms.

Heatwaves: Heatwaves affect people less than before, thanks to air-conditioning andsocial programs to protect high-risk individuals, despite rising urban temperatures:

Figure 8. Annual heat-related excess deaths per million. Bars (left to right) indicate1970s, 1980s, 1990s. Source: Davis et al., 2003b.

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Several studies (e.g. Davis et al., 2003ab) show that U.S. urban populations are betteradapted to heatwaves than formerly. In Figure 8, each bar represents the annual numberof heat-related deaths in 28 major U.S. cities. For nearly all cities, heat-related deaths aredeclining. Though no cities from Tennessee were included in the studies by Davis et al.,in neighboring cities the number of heat-related deaths in the 1990s was negligible. Thissuccessful adaptation is the result of improvements in medical technology, air-conditioning, better public awareness, and proactive responses by municipalities toextreme weather events.

In the southern states, where heatwaves are more common, heat-related mortality is muchlower than in regions where heatwaves are rarer, such as the north-eastern U.S – furtherevidence that populations adapt to their prevailing climate. If heatwaves become morecommon, adaptations will occur without difficulty.

Vector-borne diseases: Malaria, dengue fever, and West Nile Virus, which have beenerroneously predicted to spread owing to “global warming”, are not tropical diseases.Climate change will accordingly have a negligible effect on their transmission rates.These diseases are readily controlled by well-known public health policies.

Malaria epidemics occurred as far north as Archangel, Russia, in the 1920s, and in theNetherlands. Malaria was common in most of the United States until the 1950s (Reiter,1996). In the late 1800s, when the United States was colder than today, malaria wasendemic east of the Rocky Mountains—a region stretching from the Gulf Coast all theway up into northern Minnesota, including the non-mountainous counties of Tennessee.

In 1878, 100,000 Americans were infected with malaria, and some 25,000 died. Malariawas eradicated from the United States in the 1950s not because of climate change (it waswarmer in the 1950s than in the 1880s), but because of technological advances. Air-conditioning, the use of screen doors and windows, and the elimination of urbanoverpopulation brought about by the development of suburbs and automobile commutingwere largely responsible for the decline in malaria (Reiter, 1996).

Figure 9. In the late 19th century malaria was endemic in shaded regions, includingthe western two-thirds of Tennessee. Source: Reiter, 2001.

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The effect of technology is also clear from statistics on dengue fever outbreaks, anothermosquito-borne disease. In 1995, a dengue pandemic hit the Caribbean and Mexico.More than 2,000 cases were reported in the Mexican border town of Reynosa. But in thetown of Hidalgo, Texas, located just across the river, there were only seven reportedcases (Reiter, 1996). This is just not an isolated example. Data collected over the pastdecade have shown a similarly large disparity between incidence of disease in northernMexico and in the southwestern United States, though there is very little climatedifference.

Another “tropical” disease that is often wrongly linked to climate change is the West NileVirus. The claim is often made that a warming climate is allowing the mosquitoes thatcarry West Nile Virus to spread into Tennessee. This reasoning is incorrect. West NileVirus, a mosquito-borne infection, was introduced to the United States through the portof New York in summer 1999. Since its introduction, it has spread rapidly, reaching theWest Coast by 2002. Incidence has now been documented in every state as well as mostprovinces of Canada. This is not a sign that the U.S. and Canada are progressivelywarming. Rather, it is a sign that the existing environment is primed for the virus. In theinfected territories, mean temperature has a range more than 40ºF. The virus can thrivefrom the tropics to the tundra of the Arctic – anywhere with a resident mosquitopopulation. The already-resident mosquito populations of Tennessee are appropriatehosts for the West Nile virus—as they are in every other state.

Since there are no climate trends in Tennessee, climate changes cannot have beenresponsible for the establishment of West Nile Virus. Mean annual temperature inTennessee could change by many degrees in either direction, or the precipitation regimecould vastly change, without affecting distribution of the West Nile Virus.

Impacts of climate-mitigation measures in Tennessee

lobally, in 2003, humankind emitted 25,780 million metric tons of carbon dioxide(mmtCO2: EIA, 2007a), of which Tennessee accounted for 120.1 mmtCO2, or only

0.47% (EIA, 2007b). The proportion of manmade CO2 emissions from Tennessee willdecrease over the 21st century as the rapid demand for power in developing countriessuch as China and India outpaces the growth of Tennessee’s CO2 emissions (EIA,2007b).

During the past 5 years, global emissions of CO2 from human activity have increased atan average rate of 3.5%/yr (EIA, 2007a), meaning that the annual increase ofanthropogenic global CO2 emissions is more than 7 times greater than Tennessee’s totalemissions. Even a complete cessation of all CO2 emissions in Tennessee will beundetectable globally. A fortiori, regulations prescribing a reduction, rather than acomplete cessation, of Tennessee’s CO2 emissions will have no effect on global climate.

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Wigley (1998) examined the climate impact of adherence to the emissions controlsagreed under the Kyoto Protocol by participating nations, and found that, if all developedcountries meet their commitments in 2010 and maintain them through 2100, with a mid-range sensitivity of surface temperature to changes in CO2, the amount of warming“saved” by the Kyoto Protocol would be 0.07°C by 2050 and 0.15°C by 2100. The globalsea level rise “saved” would be 2.6 cm, or one inch. A complete cessation of CO2

emissions in Tennessee is only a tiny fraction of the worldwide reductions assumed in Dr.Wigley’s global analysis, so its impact on future trends in global temperature and sealevel will be only a minuscule fraction of the negligible effects calculated by Dr. Wigley.

We now apply Dr. Wigley’s results to CO2 emissions in Tennessee, assuming that theratio of U.S. CO2 emissions to those of the developed countries which have agreed tolimits under the Kyoto Protocol remains constant at 39% (25% of global emissions)throughout the 21st century. We also assume that developing countries such as China andIndia continue to emit at an increasing rate. Consequently, the annual proportion ofglobal CO2 emissions from human activity that is contributed by human activity in theUnited States will decline. Finally, we assume that the proportion of total U.S. CO2

emissions in Tennessee – now 2.1% – remains constant throughout the 21st century. Withthese assumptions, we generate the following table derived from Wigley’s (1998) mid-range emissions scenario (which itself is based upon the IPCC’s scenario “IS92a”):

Table 1

Projected annual CO2 emissions (mmtCO2)

YearGlobal

emissions:Wigley, 1998

Developedcountries:

Wigley, 1998

U.S. (39% ofdevelopedcountries)

Tennessee(2.1% of U.S.)

2000 26,609 14,934 5,795 1202025 41,276 18,308 7,103 1492050 50,809 18,308 7,103 1492100 75,376 21,534 8,355 175

Note: Developed countries’ emissions, according to Wigley’s assumptions, do notchange between 2025 and 2050: neither does total U.S or Tennessee emissions.

In Table 2, we compare the total CO2 emissions saving that would result if Tennessee’sCO2 emissions were completely halted by 2025 with the emissions savings assumed byWigley (1998) if all nations met their Kyoto commitments by 2010, and then held theiremissions constant throughout the rest of the century. This scenario is “Kyoto Const.”

Table 2

Projected annual CO2 emissions savings (mmtCO2)

Year Tennessee Kyoto Const.2000 0 02025 149 4,6972050 149 4,6972100 175 7,924

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Table 3 shows the proportion of the total emissions reductions in Wigley’s (1998) casethat would be contributed by a complete halt of all Tennessee’s CO2 emissions(calculated as column 2 in Table 2 divided by column 3 in Table 2).

Table 3

Tennessee’s percentage of emissions savings

Year Tennessee2000 0.0%2025 3.2%2050 3.2%2100 2.2%

Using the percentages in Table 3, and assuming that temperature change scales inproportion to CO2 emissions, we calculate the global temperature savings that will resultfrom the complete cessation of anthropogenic CO2 emissions in Tennessee:

Table 4

Projected global temperature savings (ºC)

Year Kyoto Const Tennessee2000 0 02025 0.03 0.0012050 0.07 0.0022100 0.15 0.003

Accordingly, a cessation of all of Tennessee’s CO2 emissions would result in aclimatically-irrelevant global temperature reduction by the year 2100 of no more thanthree thousandths of a degree Celsius. Results for sea-level rise are also negligible:

Table 5

Projected global sea-level rise savings (cm)

Year Kyoto Const Tennessee2000 0 02025 0.2 0.0062050 0.9 0.032100 2.6 0.06

A complete cessation of all anthropogenic emissions from Tennessee will result in aglobal sea-level rise savings by the year 2100 of an estimated 0.06 cm, or two hundredthsof an inch. Again, this value is climatically irrelevant.

Even if the entire Western world were to close down its economies completely and revertto the Stone Age, without even the ability to light fires, the growth in emissions fromChina and India would replace our entire emissions in little more than a decade. In thiscontext, any cuts in emissions from Tennessee would be extravagantly pointless.

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References

Davis, R.E., et al., 2003a. Decadal changes in summer mortality in the U. S. cities.International Journal of Biometeorology, 47, 166-175.

Davis, R.E., et al., 2003b. Changing heat-related mortality in the United States.Environmental Health Perspectives, 111, 1712-1718.

Energy Information Administration, 2007a. International Energy Annual, 2005. U.S.Department of Energy, Washington, D.C., http://www.eia.doe.gov/iea/contents.html

Energy Information Administration, 2007b. Emissions of Greenhouse Gases in theUnited States, 2006. U.S. Department of Energy, Washington, D.C.,http://www.eia.doe.gov/oiaf/1605/ggrpt/pdf/0573(2006).pdf

Intergovernmental Panel on Climate Change, 2007. Summary for Policymakers,(http://www.ipcc.ch/SPM2feb07.pdf)

National Climatic Data Center, U.S. National/State/Divisional Data,(www.ncdc.noaa.gov/oa/climate/climatedata.html)

National Weather Service, Nashville Tennessee, A Tornado Climatology of MiddleTennessee (1830-2003), http://www.srh.noaa.gov/ohx/research/torcli.htm

Reiter, P., 1996. Global warming and mosquito-borne disease in the USA. The Lancet,348, 662.

Wigley, T.M.L., 1998. The Kyoto Protocol: CO2, CH4 and climate implications.Geophysical Research Letters, 25, 2285-2288.