The Generational Experience
AUTHOR: Richard Cicone, Principal, ISCIENCES, L.L.C.
28 February 2017
Not My Grandfather's Climate
My granddaughter recently turned 22. Of course, every grandparent thinks, “How time flies.” (Quickly followed by “Ah, to be 22 again!”) Was it not yesterday that I recall her child’s smile and first words? I thought about my grandfather who was born in 1863, over 150 years ago. He was a blacksmith in the “old country” and then labored in the glassworks and steel mills in their heyday in the Monongahela Valley south of Pittsburgh. A long time ago, but his memory is still fresh. My father, born in 1904, carried on his father’s craft at Acorn Iron Works in Detroit. I like to think they would have been happy with the path I took directing research at ISciences, L.L.C. That work involved developing an understanding of the impacts of climate change on fresh water.
This got me to thinking. We are experiencing the warmest weather patterns recorded in the modern record. Does my granddaughter think it is warmer than usual? Would my grandfather have felt that it was generally colder during his lifetime? Is there some way to quantify their generational experience?
The Thirty-Year Rule
The generational experience is woven into temperature statistics. The average high and low temperatures that are posted daily in local newspapers are generally 30-year regional averages, updated every decade or so. Our daily experience is measured against these norms when we step outside and say "It's hotter (or colder) than usual." We understand well that climate can change regionally, so our point of reference is regularly updated to reflect our experience.
Climate scientists use global average temperature as an indicator to track climate trends, generally leaving the base period fixed to see what change has occurred relative to that period, and referring to the difference from normal as an “anomaly.” Since 1880 it is estimated that the global average temperature has increased by 1.7˚ Fahrenheit. My grandfather, a smith who worked next to a blazing coal fire, would have appreciated the cooler 1880 air, correct?
The use of global average temperature is but one of many indicators that climate scientists track. These indicators show we are experiencing a change in the global climate that is affecting the oceans, global ice masses, the weather, the hydrological cycle, and living things. Some argue that the warmer temperature is a welcome change, making summers and winters more pleasant in some places, lands more arable in others. This is debatable, but I will not tackle that here. Rather I will explain how we, living today, may be sensing a different condition than our forebears.
Our Perception of Climate Change
I borrow this subtitle, “Perception of Climate Change,” directly from the title of a 2012 paper written by James Hansen, Makiko Sato, and Reto Ruedy. These scientists sought some way to demonstrate that changes in average temperature could result in human risk. They surmised that the summer season was the time of year that climate temperature changes would have the biggest effect on us, and focused on extreme temperature as the appropriate metric to consider. Extreme temperatures can have significant impact on living things. Scientists have enumerated many concerns regarding human, plant and animal health resulting from extreme temperature trends and events., For example, a 2009 European Union study documented growing incidences in Europe of morbidity and mortality (cardiovascular, renal, respiratory and metabolic disorders) related to extreme heat events, with expectation of increased impacts in future decades due to the warming trend.
Hansen and his team employed a NASA Goddard Institute for Space Studies (GISS) historical temperature record called GISTEMP to examine trends in extreme temperature over six 11-year periods, from 1950 to 2015., These data document monthly average temperatures over land. Their analysis focused on the summer months in both Northern and Southern Hemispheres. The 30-year period from 1951 to 1980 was used to establish the average monthly temperature. Extreme average temperatures were defined as those that were three standard deviations above or below the average for 1951 through 1980. They point out that “the chance of exceeding this threshold is only 0.13% for a normal distribution of variability” (that is, chances are less than 1 every 740 years).
Though it seems intuitive, it is not necessarily the case that warmer averages will result in more extreme temperatures. Weather does not necessarily follow ordinary statistical patterns. In this case intuition is borne out. Driven mostly by unseasonably warmer low temperatures, the distributions of average monthly temperatures for each decade under consideration shifted toward warmer average temperatures - incrementally fewer cold extremes and more warm extremes as seen in Figure 1 (below).
The x-axis represents temperature anomalies measured by the standard deviations from 1951 to 1980 average; and the y-axis, frequency of occurrence. The peak appears near zero (the mean value of the baseline period) in the early decades, then shifts to the right. The distribution also broadens, implying a greater percentage of extreme conditions exceeding a given threshold. The scientists found that the land area affected by the extreme mean temperatures (using the three standard deviation threshold) in the last decade exceeded the land area affected in 1950 by ten-fold. That is, one would be 10 times more likely to experience a very hot month in 2015 than in 1950.
OK, But What About My Grandfather?
If you are willing to accept their data, means and methods, the Hansen team provides an ample demonstration that monthly average temperatures extremes, 3 standard deviation departures from the norm, are more common - ten times more common in 2015 summers than in 1950. But their analysis is based on the climate norms derived from 1951 to 1980. Those would be my father’s adult years and my formative ones. How different were my grandfather’s and granddaughter’s experiences?
Michael McElroy and D. James Baker addressed this question in a study about climate extremes that they conducted at the request of the US Government. Like Hanson, McElroy and Baker also analyzed the GISTEMP dataset, this time including data available back to 1910. Both annual and monthly temperature records were analyzed. The results for the annual analysis are displayed in Figures 2-4 below. Three overlapping statistical baselines were employed allowing comparison of three climatological periods, 1910 to 1970 (my grandfather’s lifetime), 1930 to 1990 (my father’s lifetime), and 1950 to 2010 (my lifetime). We will come back to my granddaughter.
The metric chosen for analysis was the “return period,” a statistical measure of how often one would expect to observe the anomalous condition to recur. A return period of 30 years would imply that one would expect to experience this condition once in 30 years, a relative rarity in one’s lifetime. Each bar depicts the fraction of the measured Earth's surface that experienced a 30-year anomaly in the given year. Red bars are for warmer than normal temperatures, blue bars are for colder than normal temperatures. In a normal year, one thirtieth would likely experience such an extreme temperature condition (that is, an average 3.33% of the terrestrial area). The x-axis is the year and the y-axis is the fraction of terrestrial land area that experiences a hot or cold 30-year anomaly. Analysis of the fraction of populated land area and the fraction of cultivated land area produced similar results. Analysis of monthly data by hemisphere also produced similar results for each month, regardless of season.
The first graphic, Figure 2 below, represents my grandfather’s experience. Throughout most of his lifetime, from 1910 to 1970, he did indeed experience the normal condition. Note that both the 30-year 'hot' and 'cold' anomalies affected a fraction of land area between 0.0 (0%) to 0.1 (10%). This is about what one would expect statistically, as indicated by the gray band labeled "Expected." 1917 stands out as an unusually cold year and 1934 stands out as an unusually warm year. Had he lived beyond 1970, he would have experienced 30-year 'hot year' anomalies much more often, and 'cold year' anomalies rarely. By 2000, the fraction is consistently above 33%, indicating he would have experienced 'hot year' anomalies about once every three years.
What About My Father?
Had my father, Figure 3 below, lived beyond 1990, he would have experienced many more occurrences of 30-year anomalies, on average as often as once every four years instead of once in thirty. And indeed, we who are senior citizens are now experiencing warm extreme conditions more often than in our youth, as much as six times more often.
What About My Granddaughter?
What about my granddaughter? She was born in the mid-1990s. None of the statistical baselines chosen for this analysis depict her lifetime experience. One would want to select a 30-year period, say 1980 to 2010 to represent the temperature norms during her lifetime. Looking at the graph in Figure 4, hot anomalies were much more frequent throughout this 30-year period, so the average temperature would also be higher. Relative to this measure, in her experience many fewer hot anomalies would have occurred. It is likely that she would say, “It has always been this way, as long as I can remember!” Had she lived in the early 1900s with memory of her current experience, she would have found the 1900s colder indeed.
What Can We Expect in the Future?
Certainly, relative to the early 20th century norms, my grandfather’s generation experienced far fewer temperature extremes than he would experience if he were alive today. Today’s climate is not my grandfather’s climate; mine is not my father’s; and for most of my earlier years, mine has differed notably from my granddaughter’s. This is demonstrated by the data, and explained by the scientists who observe what is happening in the context of the chemical, physical and geo dynamics that determine our climate. But we can trust our own experiences as well. We are surrounded by many clues - record breaking temperatures; harder rains; more frequent droughts; melting glaciers; changes in plant life, and in animal and insect behavior; earlier springs, later autumns. Climate has changed.
But climate is always changing, right? Will it change back to the climate of the early 1900s? To address this question, it serves us well to understand the relationship between global warming and climate change. The whole earth (especially the oceans and ice masses) is warming due to an imbalance between incoming energy supplied by the sun and outgoing radiation reflected off the ground and atmosphere or emitted from the Earth’s surface into space. Increasing levels of greenhouse gases are absorbing and then re-emitting about half of Earth’s emitted energy back to Earth. A common metaphor is that greenhouse gases like CO2 act like a blanket “trapping” the heat. Increased surface temperature, as land and oceans shed energy, is a natural response to energy imbalance. Increasing atmospheric temperatures will increase emissions to space, as required by the laws of thermodynamics that insist upon celestial bodies seeking energy equilibrium.
Scientists expect atmospheric concentrations of CO2 to climb, likely increasing average global temperatures by 3.7˚ F (about 2˚ C) since the industrial revolution began around 1750, and by about 2˚F more than today. This level could be reached as soon as 2050, depending on natural variations and our efforts to reduce emissions in coming decades.,,
Can we continue to expect severe weather conditions? More importantly, what will our children and grandchildren experience? Will extreme temperature conditions continue to become more extreme and more common? The warming trend will certainly continue. NASA tells us, among other things, “Droughts in the Southwest and heat waves (periods of abnormally hot weather lasting days to weeks) everywhere are projected to become more intense, and cold waves less intense everywhere. Summer temperatures are projected to continue rising, and a reduction of soil moisture, which exacerbates heat waves, is projected for much of the western and central U.S. in summer. By the end of this century, what have been once-in-20-year extreme heat days (one-day events) are projected to occur every two or three years over most of the nation.” NASA is not alone in this assessment, and if anything, NASA is holding back from more dire pronouncements that some others make.
Monitoring the Changes
Our dedication at ISciences is to serve our clients well, and to contribute to monitoring this unfolding process. We focus upon changes that we can observe affecting the hydrological cycle. So, monthly we report on anomalous surface water conditions at our web site, http://www.isciences.com. Occasionally we provide explanations such as this one as to what is happening and why. It is a small role that we can play.
But global warming is a transformational issue that impacts life on Earth. We need those who can play the big roles. I am hopeful that NASA, NOAA, NSF, EPA, and the many organizations and scientists worldwide involved in the study of global warming and climate change will continue to monitor and explain the changes we are witnessing. They play an indispensable role in educating our policy makers, that they may guide us along a path that will deter the worst effects of global warming upon us, and more importantly, upon future generations.
[ABOUT THE AUTHOR: Ric Cicone is co-founder and former president of ISciences. He is an expert in the application of imaging and information technologies to address social, environmental and national security issues. Throughout his 42-year career he has conducted R&D using remote sensing and geospatial analysis methods to address social security, sustainability, and environmental intelligence questions.]
 Global Climate Change: Vital Signs of the Planet, see http://climate.nasa.gov.
 Hansen, J., Sato, M., & Ruedy, R. (2012). Perception of Climate Change, PNAS, published online at http://www.pnas.org/content/109/37/E2415, August 6, 2012.
 McMichael, A.T. et al., Editors. (2003). Climate Change and Human Health: Risks and Responses, World Health Organization. [Online at http://www.who.int/globalchange/publications/climchange.pdf]
 Balbus, J., Crimmins, A., Gamble, J.L., Easterling, D.R., Kunkel, K.E., Saha, S., & Sarofim, M.C. (2016). Ch. 1: Introduction: Climate Change and Human Health. The Impacts of Climate Change on Human Health in the United States: A Scientific Assessment. U.S. Global Change Research Program, Washington, DC, 25–42. http://dx.doi.org/10.7930/J0VX0DFW
 EU Commission Staff Working Document. (2009). Human, Animal and Plant Health Impacts of Climate Change. [Online at http://ec.europa.eu/health/ph_threats/climate/docs/com_2009-147_en.pdf]
 Hansen, J., Ruedy, R., Sato, M., & Lo, K. (2010). Global surface temperature change. Rev Geophys 48:RG4004, doi:10.1029/2010RG000345. [Online at https://pubs.giss.nasa.gov/docs/2010/2010_Hansen_ha00510u.pdf]
 GISTEMP Team. 2016: GISS Surface Temperature Analysis (GISTEMP). NASA Goddard Institute for Space Studies. [On-line at http://data.giss.nasa.gov/gistemp/]
 Monthly mean temperatures can be calculated as an average of daily observations (e.g., the average of daily maximum and minimum temperature) or from daily averages of observations collected at various times during a day. These can include averages of observations taken every hour or an average of observations made at various times during a day (e.g., every three or six hours or at three fixed hours during the day). There are many other ways of calculating monthly mean temperature, and in many cases more than one method was used for calculating mean temperature for the same station" Source An overview of the Global Historical Climatology Network monthly mean temperature data set, version 3. [Online at: http://onlinelibrary.wiley.com/doi/10.1029/2011JD016187/full]
 The climate record shows that the average daily temperature has increased since the pre-industrial era mostly because of increases in the average daily low temperature. Information is inconclusive regarding trends in global daily high temperature events, though there appears little change over continental United States in recent decades. Increases in average monthly temperatures suggest longer heat waves which can affect human, plant and animal health. (see footnote 5, Balbus et al.)
 McElroy, M., & Baker, D.J. (2012). "Climate Extremes: Recent Trends with Implications for National Security,” Harvard University. [Online at http://environment.harvard.edu/climate-extremes] Note that the authors of "Climate Extremes" employed a code to examine temperature extremes and anomalous surface water conditions developed by ISciences analysts, Thomas Parris, Jon Boright, and Eric Crist, that is also used in ISciences’ Water Security Indicators Model (WSIM).
 GISTemp contains data back to 1880, but the sparseness of data in the early years limited analysis. Only grid cells with at least ten good months of data in 80% of the years being analyzed were used. Missing cell months were replaced with average values over the period of analysis to avoid potential bias due to sparse weather stations, especially in high latitude regions where warming is more pronounced.
 The baseline period was extended to 60 years to reflect lifetime experiences and to provide statistical validity to the return period metric chosen. Thus, the analysis is not directly comparable to the Hansen team’s analysis, though it does support the same general conclusions.
Watson, R., Carraro, C., Canzioni, P., Nakicenovic, N., McCarthy, J.J., Goldemberg, J., & Hisas, L. (2016). The Truth About Climate Change, The Universal Ecological Fund (FEU-US). [Online at http://pure.iiasa.ac.at/13837/1/The%20Truth%20About%20Climate%20Change.pdf]
 NASA Earth Observatory. How much more will Earth warm? [Online at http://earthobservatory.nasa.gov/Features/GlobalWarming/page5.php]
 Mann, M. (2014). Earth Will Cross the Climate Danger Threshold by 2036. Scientific American, April 1, 2014. [Online at https://www.scientificamerican.com/article/earth-will-cross-the-climate-danger-threshold-by-2036/]
 Global Climate Change: Vital Signs of the Planet. (2016). [Online at http://climate.nasa.gov/effects/]
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