The Current Wisdom is a series of monthly articles in
which Patrick J. Michaels, Director for the Center for the Study of
Science, reviews interesting items on global warming in the
scientific literature that may not have received the media
attention that they deserved, or have been misinterpreted in the
popular press. Occasionally — as in this edition — we
examine recent global warming perceptions that are at odds with
Prior to April, 2011, issues of this Wisdom, which began in 2010, are available at our blog Cato@Liberty (www.cato-at-liberty.org/).
The Yale Project on Climate Change Communication in conjunction with the George Mason University Center for Climate Change Communication have just released the most recent of their periodic surveys on American’s thoughts about global warming. 1,061 adults across the country were questioned during September about it and extreme weather events across the U.S.
Given that we are supposed to know what we are talking about, we’re going to answer a few of the chief questions.
But first, a complaint. The Yale/GMU survey has many of the bad aspects of “push” polling, where the design assures a certain answer. Here’s a related example from a recent University of Illinois survey by Peter Doran:
We constantly hear the meme that this “96 per cent of climate scientists surveyed say global warming is real”. That’s based on Doran’s survey, and is an artifact of the way the question was asked, which was, “when compared with pre-1800 levels do you think that mean global temperatures have generally risen, fallen, or remained relatively constant?” Actually, 100% should have answered “risen”. It’s irrefutable that the 17th century was colder than the 20th. The subsequent question, on human attribution, was also worded in such a way that also guaranteed a lot of agreement. If properly designed, the survey would have asked how much was related to human activity, not just whether humans were involved in the temperature change.
The planet’s surface temperature is higher than it was 100 years ago, and so is the temperature of the U.S. It’s not whether or not it’s warmer, it’s “how much warmer” and “what are the implications?”.
So with that in mind, let’s move on to some of the main questions asked by the Yale/GMU pollsters.
Survey Question: “How much do you agree or disagree with the following statements [sic]: “Global warming is affecting weather in the United States?” (strongly agree, somewhat agree, somewhat disagree, strongly disagree, don’t know/no answer)
Answer: Somewhat agree. On a scale of 0 (completely disagree) to 100 (completely agree) we would score our answer at 55.
Brief Rationale: Global warming has to affect “the weather” in the United States, or anywhere else. Big deal. Changing the radiative properties of the atmosphere — which is what increasing carbon dioxide does — must alter the character of weather events as well as the climate. But how much? In reality, the amount of weather related to natural variability dramatically exceeds what is “added on” by global warming. This is obvious from a look at the “Climate Extremes Index” from the National Climatic Data Center (Figure 1).
Figure 1. Climate Extremes Index from the National Climatic Data Center
While it is true that this index has risen from a low point around 1970, it is also clear that it merely returned to values observed in the early 20th century. Did greenhouse gases raise the extremes index in the early 20th century? Obviously not.
Comments: The survey results seem to pretty much square with our opinion. “Somewhat agree” is the answer with the greatest percentage of response, and there is a relatively even split of respondents on either side of that. But our guess is that most of those who “somewhat agree” are probably thinking that global warming is affecting the weather in a way that can be perceived as separated from normal variability, which is not the case.
People are answering this Yale/GMU survey question correctly, but for the wrong reason. This is reflected in the next question.
Survey Question: Some people say that global warming made each of the following events worse. How much do you agree or disagree? (strongly disagree, somewhat disagree, somewhat agree, strongly agree)
• The current drought in the Midwest and the Great Plains?
Answer: Strongly disagree. Score: 0
Rationale: There is no correlation between global temperatures and drought in the United States (Figure 2). We wrote on this when NASA’s James Hansen was hyping this story: (http://www.worldclimatereport.com/index.php/2012/08/14/hansen-is-wrong/)
Figure 2. Percent of U.S. wet or dry shows no relationship whatever to global warming.
• The severe storm (known as a “derecho”) that knocked down trees and power lines from Indiana to Washington D.C. in June of 2012
Answer: Strongly disagree. Score: 0
Rationale: Derechos are thunderstorms with damaging straight-line winds, as opposed to tornadoes, which form from strong thunderstorms that have a rotational component. If there were any relationship between derechos and global warming, we would also be seeing an increase in tornadoes. While the new Doppler radars detect many more weak tornadoes than earlier technology, no one needs a radar to see a Fujita-scale 3, 4 or 5 storm, and there’s simply no trend in their frequency. Perhaps even more interesting is that constant-dollar and value-adjusted damages from tornadoes are going down, according to a paper recently accepted for publication by University of Colorado’s Roger Pielke, Jr.
• This year’s record forest fires in Colorado and elsewhere in the American West?
Answer: Strongly Disagree. Score: 20
Rationale: Historically, warm and dry periods are linked to more Western fires. While Colorado has experienced some substantial droughts since the turn of the century, the integrated dryness (moisture deficit multiplied by time) has yet to reach that of the 1930s, which was before substantial emissions of greenhouse gases. In the Northwest, another center of fire activity this year, there is simply no trend whatsoever in dryness in recent decades. Further, paleo-climatic indicators show much more severe and prolonged western droughts — particularly in the 17th century — than those currently being experienced.
• Record high Summer temperatures in the U.S. in 2012?
Answer: Somewhat agree. Score: 55
Brief Rationale: As its name implies, “global warming” puts an ongoing pressure on temperatures to increase, both in the global average, as well as in regions such as the U.S.
But the linkage, while statistically significant, is quite weak. Generally speaking, global average seasonal temperatures explain about 20% of the year-to-year variability in U.S. seasonal temperatures. While that is statistically significant, it also means that the 80% of the remaining variability is related to things other than global warming.
The largest number of statewide temperature records were set in the 1920s and 30s, and, warming or not, they have yet to be exceeded. In fact, what is peculiar about these state records is the lack of them during the relatively warm recent 15 years. What that shows is that single daily records are caused by atmospheric circulation anomalies of true rarity, and individual events cannot be scientifically related to a larger-scale global phenomenon except to note that the probability of an extreme temperature event should be elevated. “Should” &mndash; because of the odd paucity of recent state records.
• The unusually warm Spring across the United States in 2012?
Answer: Somewhat agree. Score: 60
Rationale: See explanation above. Score raised from 50 to 60 because greenhouse-gas-induced warming should concentrate more in cold air (i.e. the beginning of Spring) than in the hot air of summer.
• The unusually warm Winter across the United States in 2011-2012?
Answer: Somewhat agree. Score: 70
Rationale: See the explanations above. That does not mean that every winter will be warm and relatively snow-free, like last year. Everyone in the eastern U.S. still remembers the very cold and snowy winter of 2009-10.
Comments: The public’s perception of a single derecho as significant flies in the face of 60 years of good tornado data (the relationship between the two is noted above), and it is very easy to examine historical drought data for global warming-related trends. Averaged across the nation, there aren’t any. There has been an increase in drought frequency in the Southwest, but there is an equal and opposite tendency for increasing wetness in the Northeast.
Question: “In your opinion, over the past several years, has the weather in the U.S. been… (much worse, somewhat worse, about the same, somewhat better, much better)?”
Answer: About the same. Score: 50
Brief Rationale: This is a pretty subjective question. What is better or worse weather? Is more rain better or worse? Are higher temperatures better or worse? Perhaps some would consider the amount of damage that is caused by the weather to be an indication of weather quality (i.e., goodness or badness). In that case, once the damage estimates are adjusted to account for changes in inflation, wealth, and population, there are no detectable trends.
Comments: Most of the respondents seem to have got this answer wrong. Although, as we mentioned above, the question is a largely a qualitative one. We like big snowstorms, so we would consider a winter without them to be worse than a winter with many. Many other folks hold the opposite view. The same goes for virtually all weather events, with perhaps the exception of tornadoes (although the annual army of storm chasers may disagree).
Question: “Have each of the following types of extreme weather events become more or less common in your local area over the past few decades? Would you say much more common, somewhat more common, somewhat less common, much less common, or has it stayed about the same?
• Very heavy rainstorms?
• Heat waves?
Answer: The correct answer to the questions above depends on where you live. For instance, if you live in the Northeast, the frequency of heavy rains has been increasing, but that has not been in the case if you live in the Northwest.
The Southwest has seen an increase in drought conditions during the past few decades, while nearly everywhere else in the country has not, and the Northeast has gotten wetter. Averaged across the country, there is simply no trend in drought.
And while the Upper Midwest has seen little change in summer heat waves over the past several decades, residents of the Southeast may have noticed in increase over the same time period. Very few statewide temperature records are from recent years, with the largest number of decadal records set in the 1930s — and these still stand.
Again, the question “how much” should be asked. We (Pat Michaels and Chip Knappenberger) published a paper a few years back in which we examined precipitation on the heaviest day of the year around the country. Indeed, we found an increase. But before getting too worked up, consider the important question of “how much”. The fact is that rainfall on the heaviest day of the year, averaged across the country, has increased a grand total of 0.26 inches in the last 100 years, something no one could “notice.”
Figure 3. Average rainfall on the rainiest day of the year averaged across the U.S.
The Yale/GMU pollsters consistently produce results which suggest that American’s are much more concerned about global warming than is indicated by the results of most other polling agencies (see here for further examples, http://scienceandpublicpolicy.org/images/stories/papers/originals/no_energy_taxes.pdf).
Finally, a more telling measure of public concern is how much money people are willing to spend to mitigate global warming. According to a recent survey from Stanford University, the answer is not much: http://woods.stanford.edu/docs/surveys/GW-Policy-Trend-2010-2012-1.pdf.