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Question: Is bacon better for you than tilapia? Does tilapia cause cancer and/or Alzheimer’s disease?
Answer: No. These false claims, spread by multiple websites, are not supported by solid scientific evidence.
Full Question
What is the truth about warnings that eating tilapia may cause cancer and/or Alzheimer’s Disease? What is the nutritional value of tilapia fish?
Full Answer
Multiple websites, such as edrugsearch.com, eatthis.com and draxe.com, have claimed that scientists have found hamburgers and bacon are better for you than tilapia. Versions of these articles have spread through Facebook, with users flagging them as potentially fake. Our readers also have asked us about the dangers of eating tilapia.
Many of these alarming articles about tilapia claim that bacon is a better health option than tilapia because the fish lacks essential nutrients and can increase risk of cancer and Alzheimer’s disease. But there is no solid evidence that eating tilapia increases the risk of either of these diseases.
The fish is also a low-fat source of protein and a number of vitamins and minerals, including vitamin B12 and selenium. However, other fish, such as salmon, are a better source of omega-3 fatty acids, which are essential nutrients.
Experts told us there’s no debating whether or not bacon and hamburgers are better for you than tilapia — they’re not. Both bacon and hamburgers are high-fat sources of protein. Bacon is also high in added sodium.
Fishy Claims
Where did this idea that bacon is better for you than tilapia come from in the first place?
Some of the anti-tilapia articles point to a controversial scientific study published in the Journal of the American Dietetic Association in July 2008.
In that paper, Floyd H. Chilton, a professor of physiology and pharmacology at Wake Forest University, and his colleagues conclude that “tilapia is not a good choice” for “individuals who are eating fish as a method to control inflammatory diseases such as heart disease.” The researchers add: “All other nutritional content aside, the inflammatory potential of hamburger and pork bacon is lower than the average serving of farmed tilapia.”
Inflammation is the body’s response to toxins or unwanted substances; it can occur in the arteries when cholesterol forms plaque.
Shortly after the study was published, a number of experts wrote an open letter disputing the idea that tilapia was unhealthy. “Tilapia and catfish are examples of lower-fat fish that have fewer omega-3s” than oily fish, but “still provide more of these heart-healthy nutrients than hamburger, steak, chicken, pork or turkey,” they wrote. “Replacing tilapia or catfish with ‘bacon, hamburgers or doughnuts’ is absolutely not recommended,” they cautioned. In November 2008, Harvard Medical School wrote a letter similarly concluding that tilapia is a “good choice for dinner.”
Still, years later, Chilton’s finding about inflammatory potential, which did not concern “all other nutritional content,” continues to be twisted into claims that bacon is generally healthier than tilapia.
We reached out to Chilton for comment, but he didn’t respond. However, he told Fox News in April 2014 that his research was being taken out of context by those warning against tilapia’s risks.
“We never intended to paint tilapia as the cause of anything bad,” he said. But, he added, “If your doctor or cardiologist is telling you to eat more fish, then you should look for varieties that have higher levels of omega-3 and avoid those with high inflammatory potential.”
How did Chilton and his colleagues come to their conclusion that tilapia has a high inflammatory potential, higher than bacon and hamburgers?
Chilton and his team measured the content of omega-3 and omega-6 fatty acids in 30 “commonly consumed farmed and wild fish,” including tilapia, salmon, tuna, cod, catfish and trout. The researchers found that farmed trout and Atlantic salmon contained “relatively high concentrations” of omega-3 fatty acids, while farmed tilapia and catfish contained “much lower concentrations” of these essential nutrients.
They also found that farmed trout and Atlantic salmon had low ratios of omega-6 to omega-3 fatty acids, whereas farmed catfish and tilapia had high ratios of these compounds, meaning they had notably more omega-6 than omega-3 fatty acids.
Omega-3 and omega-6 fatty acids are two groups of chemical compounds that are essential to the normal functioning of the body, but that humans can only obtain through food. Among other things, the body uses these nutrients to form molecules that regulate the functioning of the heart, lungs and and immune system. These compounds are also found to regulate processes in the brain.
The science is clear that eating fish high in omega-3 fatty acids is associated with a lower risk of heart disease and failure, says the National Institutes of Health.
As for omega-6 fatty acids, the American Heart Association concluded that research indicates consumption of 5 percent to 10 percent of an individual’s energy from omega-6 fatty acids “reduces the risk” of coronary heart disease “relative to lower intakes.” The association added, “The data also suggest that higher intakes appear to be safe and may be even more beneficial.”
Some researchers argue that it’s the ratio of omega-6 to omega-3 fatty acids that matters most for preventing heart disease, not the absolute quantities of each, says the NIH. But no study has pinpointed an optimal ratio. The NIH adds that still other researchers argue the ratio theory isn’t a good measure for predicting or preventing disease.
So there’s no scientific consensus on the ratio theory. But Chilton and his team used tilapia’s high omega-6 to omega-3 ratio to argue that tilapia had a high inflammatory potential in their 2008 paper.
Chilton and his team also argue that omega-6 fatty acids, specifically one type, arachidonic acid, are generally inflammatory. Since they found that tilapia contained “high quantities of arachidonic acid,” the researchers concluded that tilapia is not a “good choice” for “individuals who are eating fish as a method to control inflammatory diseases such as heart disease.”
What about compared with bacon and hamburgers?
The researchers measured, on average, 134 milligrams of arachidonic acid in 100 grams of tilapia, with some samples reaching 300 mg per 100 g. They also say that 100 grams of bacon and hamburgers contain 191 mg and 34 mg, respectively, of arachidonic acid, based on the U.S. Department of Agriculture’s National Nutrient Database Standard Reference Release 20. This led Chilton and his team to conclude: “All other nutritional content aside, the inflammatory potential of hamburger and pork bacon is lower than the average serving of farmed tilapia.”
Other experts dispute the measurements in the Chilton study.
Chilton and his co-authors claim that tilapia “contain[s] some of the highest levels of arachidonic acid found in human beings’ food chain,” but William S. Harris, an expert in fatty acids and human nutrition at the University of South Dakota, told us that wasn’t accurate. Harris wrote a commentary criticizing Chilton’s study when it was published.
Harris, who is also the president of OmegaQuant, a company that performs fatty acid analysis for researchers, told us tilapia isn’t high in omega-3 or omega-6 fatty acids because the fish isn’t high in fat, period. The levels of fatty acids in fish correspond to the quantity of fat in fish, he explained.
Kevin Fitzsimmons, an expert in aquaculture at the University of Arizona, agreed with Harris.
“Despite the implications of [Chilton’s] paper, single slices of bacon and burgers would have way more total omega-6 fatty acids than ten tilapia fillets,” he told us by email. “I have no problem with theory that excessive amounts [of arachidonic acid] might lead to inflammation.” But he added, “the fact is that the very small amounts of arachidonic acid in tilapia (and many other fishes) would never amount to enough to harm humans, no matter what the ratio to omega-3 fatty acids.”
Harris also said that all other nutritional content is important when evaluating what’s better for cardiovascular health. Tilapia may not be the best source of omega-3 fatty acids, but “hamburgers and bacon have bad things in them,” he said, such as high levels of saturated fatand added sodium, both of which are linked to an increased risk of heart disease.
And compared with tilapia, both bacon and hamburgers are high-fat sources of protein. Foods high in fat contribute to obesity, which is linked to heart disease, stroke, type 2 diabetes and cancer, says the Centers for Disease Control and Prevention. Over one-third of U.S. adults are obese, adds the CDC.
In short, the idea that tilapia has high inflammatory potential rests on a debated link between arachidonic acid and inflammation. It’s also based on the theory that the ratio of omega-6 to omega-3 fatty acids corresponds to inflammation potential, a theory that lacks scientific consensus.
And the study in question didn’t say that bacon was generally healthier than tilapia. Since tilapia is low in fat, it’s not a good source of fatty acids, period. But it’s still a good source of protein and other nutrients. Given bacon’s high fat and sodium content, it’s clearly not a healthier option than tilapia.
Can Tilapia Cause Alzheimer’s Disease?
The purported connection between tilapia and Alzheimer’s disease also rests on the fish’s arachidonic acid content, even though other foods have higher levels of the fatty acid. There’s no strong evidence linking arachidonic acid to the onset of Alzheimer’s in humans.
Alzheimer’s is a neurological disease characterized by memory loss and other cognitive issues. The causes of the disease “probably include a combination of genetic, environmental, and lifestyle factors,” explains the NIH.
Richard Ransohoff, an expert in neurodegenerative disease at Biogen, a biotechnology company that develops treatments for neurological diseases, told us by email that “evidence for a relationship” between Alzheimer’s disease and dietary arachidonic acid “is weak and indirect.” He added, “Equal data support and contradict the assertion that high dietary” arachidonic acid promotes Alzheimer’s.
He pointed us to an analysis of the available research on the subject by Jean Luc Olivier, then at the University of Lorraine in France, and others published in the journal Biochimie in November 2016.
“Several studies” support arachidonic acid’s involvement in Alzheimer’s disease, the researchers found. This means the omega fatty acid likely plays a role in the mechanism of the disease. But it doesn’t mean eating foods containing arachidonic acid necessarily increases the risk of Alzheimer’s. In fact, Olivier and his team point out that there has been conflicting research on mice fed arachidonic acid-enriched diets.
One 2015 study published in the Journal of Alzheimer’s Disease and conducted by Takashi Hosono, an Alzheimer’s researcher at the National Center for Geriatrics and Gerontology in Japan, found that an arachidonic acid-enriched diet delayed memory impairment in mice with Alzheimer’s disease. In another study published in Brain Research in July 2015, Hosono’s research team also found that the mice’s brain tissue showed less evidence of Alzheimer’s.
However, another study published in Neurobiology of Aging three years earlier showed the opposite. Konrad Beyreuther, the director of Network Aging Research at the University of Heidelberg in Germany, and colleagues found that mice fed arachidonic acid-enriched diets had more evidence of Alzheimer’s in their brains than those fed normal diets. But many of the differences were not statistically significant, which means they could have been due to chance.
Why the conflicting research? Olivier and his team point out in their 2016 analysis that Beyreuther fed his mice “a 10-fold higher amount” of arachidonic acid than Hosono and his group fed their mice.
Harris, at OmegaQuant, said there’s no way a person could consume that much arachidonic acid relative to their diets, so Beyreuther’s analysis was “irrelevant” to human biology. Mouse studies don’t always translate to human beings, he emphasized.
Still, at least one anti-tilapia article cited Beyreuther’s study as proof that the fish increases the risk of Alzheimer’s disease.
Can Tilapia Cause Cancer?
Articlescirculating on the web also claim tilapia may have up to 10 times more carcinogens than other fish because of what farmers feed tilapia. The articles point to one particular carcinogen, dioxin. But tilapia hasn’t been found to contain high levels of dioxin or any other carcinogens.
Fitzsimmons, at the University of Arizona, told us this claim “makes absolutely no sense.” He explained that tilapia consume “mostly algae and aquatic plants in the wild and plant based ingredients in farm feeds.” This means they are lower in the food chain than carnivorous fish like salmon.
Dioxin is “bio-accumulated,” which means it becomes “more concentrated going up the food chain,” he explained. “So you would expect dioxin levels in carnivorous fishes like salmon and bass to be higher than tilapia or catfish or shrimp,” he said, adding, “that is what the real science confirms.”
Fitzsimmons pointed us to an April 2009 study by Stefan van Leeuwen, an expert in chemical pollutants at Wageningen University in the Netherlands, and others. Published in Environmental Science and Technology, the study analyzed the levels of a number of different carcinogens, including dioxin, in salmon, trout, tilapia, pangasius and shrimp.
The group found: “Carnivorous species contained higher contaminant concentrations than omnivorous species.” Tilapia had roughly the same amount of contaminants as pangasius and shrimp, but less than salmon and trout, which are both carnivores.
Still, all of the samples had “very low” contaminant levels, “far below the European and Dutch legislative limits,” the researchers concluded.
An October 2013 study published in the Journal of Food Processing & Technology came to similar conclusions about tilapia imported to the United States. Gulnihal Ozbay, an assistant professor in natural resources at Delaware State University, and another researcher found that tilapia had “safe levels” of mercury, cadmium, arsenic and lead by the Food and Drug Administration’s standards. All of these metals may cause, or are definitively known to cause, cancer.
Overall, there’s no evidence that tilapia contains high levels of carcinogens.
“I have no idea why anyone would spread an obvious falsehood that has absolutely no basis in science or a single study with data,” said Fitzsimmons. “Anyone who looks at the facts published in hundreds of peer reviewed literature can see the many obvious nutritional benefits of eating tilapia and virtually all other fishes.”
Trump made two claims about the Paris Agreement, a global accord aimed at addressing climate change, that require context:
Trump said that the U.S. “pays billions of dollars” for the Paris Agreement, but China, Russia and India have paid “nothing.” The U.S. has pledged $3 billion, but so far has paid $500 million. The agreement requires developed countries, such as the U.S., to help developing countries, including China and India, with mitigating climate change. Russia has not ratified the agreement.
He said that “the agreement could ultimately shrink America’s GDP by $2.5 trillion over a 10-year period.” But that estimate is over 20 years, not 10, and it comes from a conservative think tank. Another analysis described the potential economic impact as “modest” and the cost of delaying action as “high.”
Trump made his claims at a rally in Harrisburg, Pennsylvania, on his 100th day in office, April 29.
Trump, April 29: Our government rushed to join international agreements where the United States pays the costs and bears the burdens while other countries get the benefit and pay nothing. This includes deals like the one-sided Paris climate accord, where the United States pays billions of dollars while China, Russia and India have contributed and will contribute nothing. Does that remind you of the Iran deal? How about that beauty, right? On top of all of that, it’s estimated that full compliance with the agreement could ultimately shrink America’s GDP by $2.5 trillion over a 10-year period. That means factories and plants closing all over our country. Here we go again. Not with me, folks. Those are the facts, whether we like them or not.
The Paris Agreement entered into force on Nov. 4, 2016. It primarily aims to keep global average temperature “well below 2°C above pre-industrial levels,” but preferably “to limit the temperature increase to 1.5°C” above pre-industrial levels. The planet has warmed about 1 degree Celsius already, according to NASA.
The main aim of the UNFCCC is to stabilize greenhouse gas concentrations “at a level that would prevent dangerous anthropogenic (human induced) interference with the climate system,” a task that “should be achieved within a time-frame sufficient to allow ecosystems to adapt naturally to climate change, to ensure that food production is not threatened, and to enable economic development to proceed in a sustainable manner.”
Industrialized countries, which the UNFCCC calls Annex I countries, are expected to do the most to cut emissions because “they are the source of most past and current greenhouse gas emissions,” according to the UNFCCC. Annex I countries include the U.S. and Russia.
Under the UNFCCC, industrialized countries are also expected to help fund climate change initiatives in developing countries, or Non Annex I countries, which include China and India. The Paris Agreement itself follows much of the same logic, and it uses funding mechanisms set up under the UNFCCC.
Those funding mechanisms include grants and loans managed by the Global Environment Facility, which funds climate initiatives as well as projects related to other environmental issues, such as biodiversity, forests and chemical waste.
Countries could also contribute funds to the Green Climate Fund, a separate program for the transfer of funds from industrialized to developing countries. So far, this fund has backed 43 projects that help developing countries mitigate and adapt to climate change, such as projects to improve their renewable energy sectors.
To “pay” for the Paris Agreement, countries would contribute money to the above funds, in addition to spending money to combat climate change within their own borders.
But when we asked the White House for support for Trump’s claim that the U.S. “pays billions of dollars” for the Paris Agreement while China, Russia and India have paid and will pay “nothing,” White House spokesman Steven Cheung specifically referred us to the Green Climate Fund.
The U.S. has promised to contribute $3 billion to this fund, but as of March 3 it has contributed only $500 million. The fund’s website states that the U.S. contribution is “[s]ubject to the availability of funds.”
Even if the U.S. does provide $3 billion to this fund, it still wouldn’t have contributed the most on a per-capita basis. Sweden has already contributed $581 million, which is nearly $60 per person — the largest per-capita contribution of any country. And Luxembourg has pledged, but not fully contributed, nearly $94 per person, which would make it the largest. In fact, the U.S. ranked 11th in its pledged contribution per capita, after a number of European countries and Japan.
Meanwhile, China and India haven’t contributed to the Green Climate Fund. Of the 43 governments that have pledged money to the fund, only nine represent developing countries, the fund’s website says.
Russia hasn’t contributed any funds either, but it also hasn’t ratified the Paris Agreement or submitted an outline of what actions it will take to play a part in achieving the accord’s primary aim, namely, to keep global temperatures below 2 degrees Celsius above pre-industrial levels. This outline, what the UNFCCC calls a country’s “nationally determined contribution,” might include actions such as increasing its share of renewable energy or quantifying how much it will cut emissions overall. The U.S., for example, has pledged to cut emissions to 26 percent to 28 percent below its 2005 level by 2025.
China, India, Russia and the U.S. were all donors in the latest funding cycle for the Global Environment Facility. Out of a total of $4.43 billion for the 2014 to 2018 cycle, U.S. funds made up 14.7 percent, or just over $651 million; China contributed 0.54 percent, or almost $24 million; Russia gave 0.4 percent, or $17.7 million; and India provided 0.32 percent, or just over $14 million. The U.S. contributed the second most overall, topped by Japan, which contributed 16.34 percent, or almost $724 million.
It’s also important to mention that, per capita, the U.S. emitted more greenhouse gases than China and India combined in 2015, as we’ve written previously.
Each person living in the United States contributed 16.07 tons to the country’s total on average, while each person living in China and India contributed 7.73 and 1.87 tons on average, respectively. However, China still emits the most in total tons because its population is almost 1.4 billion people, while nearly 325 million live in the United States. Russia, on the other hand, emitted 12.27 tons per person on average in 2015, or the 5th most in total tons, after China, the U.S., the European Union and India.
Significant Economic Harm?
To support Trump’s claim that “full compliance with the agreement could ultimately shrink America’s GDP by $2.5 trillion over a 10-year period,” Cheung, the White House spokesman, pointed us to a March commentary piece on the Heritage Foundation’s website. That referred to work originally done by Heritage Foundation senior statistician Kevin D. Dayaratna and others in an April 2016 report. The Heritage Foundation’s mission is to “formulate and promote conservative public policies.”
Dayaratna and his group concluded that the Paris Agreement “will result in over $2.5 trillion in lost GDP by 2035,” which would be a 20-year period, not a 10-year period, as Trump said. GDP, or gross domestic product, is a measure of a country’s economic output.
We asked Roberton C. Williams III, a resource economist at the University of Maryland and a senior fellow and director of academic programs at the economic analysis group Resources for the Future, to review the Heritage Foundation’s report. He called the $2.5 trillion figure a “reasonable estimate,” given the numbers and methodology used in the report, but said it was “expressed in a misleading way.”
The standard, he said, is to express lost GDP as a percentage of total GDP. So the foundation’s total amount — $2.5 trillion in lost GDP by 2035 — would be equivalent to a 0.55 percent decrease on average in the total GDP per year, he calculated. Williams also emphasized that the annual 0.55 percent reduction in total GDP is not to be confused with a 0.55 percent drop in the real GDP growth rate, which was 1.6 percent in 2016. The total U.S. GDP was $18.6 trillion in 2016.
To estimate the effect of the Paris Agreement on U.S. GDP, Dayaratna and his colleagues at the Heritage Foundation plugged a carbon tax rate — which started at $36 (in 2007 dollars) in 2015 and increased 3 percent each year thereafter — into what they called the “Heritage Energy Model.” This model, the authors say, is a “clone” of the National Energy Model System used by the federal Energy Information Administration.
A carbon tax “directly sets a price on carbon by defining a tax rate on greenhouse gas emissions or – more commonly – on the carbon content of fossil fuels,” writes the World Bank. The specific carbon tax rate the Heritage Foundation authors used comes from the Environmental Protection Agency’s estimate for the social cost of carbon, which takes into consideration “long-term damage done by a ton of carbon dioxide,” including changes in agricultural productivity, human health and property damage.
Dayaratna and his colleagues say in their report: “Modeling tax changes as a substitute for quantifying the economic impact of regulatory proposals is a widely accepted practice.” Williams confirmed that this is in fact the case.
Williams told us economists consider multiple factors when choosing what specific carbon tax rate to use when estimating economic effects. Economists might use what he called a “politically viable” rate based on a carbon tax already proposed by a politician. They might also use a carbon tax rate associated with the social cost of carbon for a particular country or region, as the Heritage Foundation authors did. Or economists might use a carbon tax rate that would be needed to meet a specific emissions target.
When it comes to the Paris Agreement, Williams said going the third route makes the most sense; that is, calculating what carbon tax rate would be needed for the U.S. to meet its pledged emissions target of 26 percent to 28 percent below its 2005 level by 2025. In fact, Williams pointed us to a November 2016 report by Resources for the Future that did exactly that.
Yunguang Chen and Marc A.C. Hafstead, both fellows at the organization, found that a constant carbon tax of $21.22 (in 2013 dollars) starting in 2017 would allow the U.S. to meet its Paris Agreement target by 2025. The U.S. could alternatively use a carbon tax rate starting at $16.87 in 2017 and rising at 3 percent per year to meet its target. This, and similar carbon tax rates, would reduce the real GDP from 2017 to 2025 by between just under 0.10 percent and 0.35 percent per year, depending on how the revenue from the taxes are used and depending on the year. (See figure 4.) Those figures are lower than the equivalent 0.55 percent per year decrease in real GDP from the Heritage study.
The authors conclude that “the size of the 2025 carbon taxes and their corresponding economic costs are modest.” They also say that “the cost of delaying the implementation of a carbon tax is high.”
“Delaying implementation until 2020 raises the costs of using an economy-wide carbon tax to meet the 2025 targets by 12 percent relative to implementing the policy in 2017,” the report says. “Delaying until 2023 increases the costs relative to 2017 by over 29 percent.”
Geoffrey Heal, a resource and environmental economist at Columbia University, told us the cost of doing nothing would be “very expensive.”
“The Paris agreement will cost little or nothing and allowing climate change to proceed would be very expensive indeed,” Heal said, adding that “staying in Paris does not fully prevent climate change but it’s a good start.”
Editor’s Note: SciCheck is made possible by a grant from the Stanton Foundation.
While on the campaign trail in New Hampshire, Republican presidential candidate Ted Cruz gave a speech to local residents that contained inaccurate and misleading claims about climate science and its terminology:
Cruz claimed “none of the alarmists say ‘global warming’ anymore — now it’s ‘climate change.’ ” That’s inaccurate. Scientists still use both terms, but tend to use “climate change” more often because, in addition to warming, it refers to phenomena such as sea-level rise and changes in precipitation patterns.
Cruz also said “climate change is the perfect pseudoscientific theory because it can never, ever, ever be disproven.” This is false. It could be, but the chances are slim. Climate change rests on the veracity of the greenhouse effect, a theory which has been repeatedly verified since it was first proposed in 1824.
Cruz says “if it gets hotter or colder, wetter or drier — the climate has always changed since the beginning of time.” That’s misleading. The climate fluctuates due to natural causes, but it’s unlikely that these phenomena alone account for some more recent changes. The models do not predict uniform warming or cooling. Some places may be cooler, but overall warming is expected.
Cruz made his remarks in Conway, New Hampshire, on Jan. 19, the day before the National Oceanic and Atmospheric Administration and NASA released findings that strongly suggest 2015 was the hottest year on record by a long shot.
Cruz, Jan. 19: Has anyone noticed in the past couple of years, the theory has magically changed a third time? Now none of the alarmists say ‘global warming’ anymore — now it’s ‘climate change.’ … If you are a big government politician, if you want more power, climate change is the perfect pseudoscientific theory. How many of y’all remember high school biology? Remember the scientific method? You start with a hypothesis and then you use evidence to try to disprove the hypothesis, to test it to see if it’s true. Climate change is the perfect pseudoscientific theory because it can never, ever, ever be disproven. If it gets hotter or colder, wetter or drier — the climate has always changed since the beginning of time. It will continue to change till the end of time.
This isn’t the first time during the presidential campaign that Cruz has called climate change “pseudoscientific.”
On Dec. 8 2015, Cruz, in an NPR interview, said: “Climate change is the perfect pseudoscientific theory for a big government politician who wants more power. Why? Because it is a theory that can never be disproven.”
Climate Change vs. Global Warming
First of all, since “alarmists” include scientists, Cruz’s claim that “none of the alarmists say ‘global warming’ anymore — now it’s ‘climate change’ ” is inaccurate. Scientists still use both terms. “Climate change” has also been around in the scientific literature longer than “global warming,” though it didn’t always refer to both anthropogenic and natural climate change as it does today.
According to NASA and NOAA, “climate change,” “global warming” and the related term “greenhouse effect” can refer to both natural and human influences on the planet. Scientists at these organizations and others, such as the Intergovernmental Panel on Climate Change, tend to tack on adjectives like anthropogenic or enhanced when referring specifically to human-influenced atmospheric and climatic changes. But for the sake of simplicity, instances of these three terms will refer to human-related changes here, unless stated otherwise.
Michael Mann, a climatologist and geophysicist at Pennsylvania State University, also told us by phone that, to scientists, “climate change,” “global warming” and the “greenhouse effect,” refer to different, albeit closely-related, phenomena. As a result, scientists use all of these terms (and many more) to explain the phenomena they observe.
However, Mann did say (as does NASA — see entry for “climate change”) that scientists prefer the term “climate change” because it encompasses global warming as well as other phenomena, like sea-level rise and changes in precipitation patterns.
There is general consensus in the scientific community regarding the definitions of these three terms (compare NASA and NOAA‘s definitions, for example). The “greenhouse effect” is the process by which gases including carbon dioxide and methane act as a blanket over the planet, trapping the sun’s radiation, or heat. “Global warming” refers to an increase in the Earth’s average surface temperature because of rising greenhouse gas levels in the atmosphere from the burning of fossil fuels. Global warming then leads to other changes in the global climate, including those related to precipitation, the seasons and sea levels — a collection of phenomena, which, among others, fall under the title “climate change.”
In a nutshell, says Mann, the greenhouse effect facilitates global warming, which leads to climate change.
In a phone interview, Erik Conway, a historian at NASA since 1998, told us that the first usage of the term “global warming” in the scientific literature most likely occurred in 1975, when the journal Sciencepublished the geochemist Wallace Broecker’s paper “Climatic Change: Are We on the Brink of a Pronounced Global Warming?”
“Climate change,” on the other hand, probably dates back to the 19th century, said Conway, but for decades scientists used it to refer to natural changes in the climate, like ice ages. For this reason, pinpointing when the exact term was first used in an anthropogenic sense is tricky, he said.
However, the physicist Gilbert N. Plass did use the term “climatic change” — similar to “climate change” — in an anthropogenic sense in his 1956 paper titled “The Carbon Dioxide Theory of Climatic Change.” Plass’ paper discusses how the “extra CO2 released into the atmosphere by industrial processes and other human activities may have caused the temperature rise during the present century.”
For most of the 1970s, scientific publications regularly used the phrase “inadvertent climate modification” to describe human impact on the climate, Conway wrote on NASA’s website in 2008. At the time, scientists weren’t sure how increased greenhouse gases in the atmosphere would affect the global climate, so they used this more neutral term to describe their findings.
But in the 1979 document often called the Charney Report for its chairman, Jule Charney, the phrase “inadvertent climate modification” was dropped for the terms “global warming” and “climate change.” “When referring to surface temperature change, Charney used ‘global warming.’ When discussing the many other changes that would be induced by increasing carbon dioxide, Charney used ‘climate change,’ ” much like scientists use the terms today, explains Conway.
Conway also writes that the usage of “global warming” “exploded” in the popular media in June 1988 when James E. Hansen, a prominent NASA scientist, used the term during testimony to Congress about the subject. Hansen said, for example: “Global warming has reached a level such that we can ascribe with a high degree of confidence a cause and effect relationship between the greenhouse effect and the observed warming.”
In emails to us, both Anthony Leiserowitz, director of the Yale Program on Climate Change Communication, and Harvard historian Naomi Oreskes said Republican strategist Frank Luntz popularized the phrase “climate change” — at least among some politicians.
Prior to the 2002 midterm elections, Luntz wrote a then-confidential memo to the Bush administration urging it to avoid the “frightening” phrase “global warming,” and instead use the term “climate change.” In the memo Luntz wrote, “while global warming has catastrophic communications attached to it, climate change suggests a more controllable and less emotional challenge.”
Luntz’s advice did appear to have an effect on which terms the Bush administration used. Back in 2003 both the New York Times and the Guardian reported that while “global warming” appeared regularly in President Bush’s speeches on the environment in 2001, the term nearly disappeared during 2002 to be replaced by “climate change.”
Overall, Cruz’s claim that “none of the alarmists say ‘global warming’ anymore — now it’s ‘climate change’ “is inaccurate. Scientists still use both terms, but tend to use “climate change” more often because it refers to more phenomena. And it was Republican strategist Luntz who encouraged members of his party to use the term “climate change” over “global warming.”
Can Climate Science ‘Never, Ever’ Be Disproved?
As for Cruz’s claim that “climate change is the perfect pseudoscientific theory because it can never, ever, ever be disproven,” Mann told us that “absolutely” climate change could be disproved. “That’s true in any area of science,” he said. “It’s true in physics. It’s true in biology. It’s true in climate change.” As he explained above, the theory of climate change rests upon the accuracy of the theory of global warming, which, in turn, depends on the theory of the greenhouse effect.
One way to disprove climate change might be to disprove the greenhouse effect, Mann told us. This would entail finding strong evidence that suggests gases like carbon dioxide don’t trap the sun’s heat. But the likelihood of this occurring is slim to none, as the theory has been verified time and again since it was first proposed by the physicist Joseph Fourier in 1824.
Another way to disprove climate change would be to challenge the theory of global warming, adds Mann. Since global warming can be thought of as an enhanced greenhouse effect (see NASA’s definition of the term here), this method of falsification would be related to — though different from — disproving the greenhouse effect.
In other words, instead of finding strong evidence that suggests carbon dioxide, for example, doesn’t trap the sun’s heat point blank, scientists would have to show that higher average global temperatures aren’t the result of increased levels of greenhouse gases. But scientists have found no evidence to support this claim.
Alternatively, if over the past few decades the planet hadn’t warmed on average as much as scientists thought it would, this would also have given them cause to reevaluate their current understanding of both global warming and climate change. For example, Mann says that if James Hansen’s predictions back in 1988 had been wrong, scientists would have reevaluated their theories.
But Hansen’s predictions, which concerned how much the planet would warm on average based on three scenarios for fossil fuel emissions (and about which he spoke to Congress in 1988), were “more or less spot on,” Mann told us.
As we have written before, the U.N.’s Intergovernmental Panel on Climate Change’s fifth assessment report that was released in 2013 concluded that it is “extremely likely” that more than half of the observed temperature increase since 1950 is due to human activities.
Cruz is off the mark when he says climate change “can never, ever, ever be disproven.” It could be, but it becomes less and less likely each time scientists verify the greenhouse effect, global warming and global warming’s effect on climatic patterns around the planet.
Is Climate Change Human-Caused? Is it a Fallacy?
Cruz’s claim that “if it gets hotter or colder, wetter or drier — the climate has always changed since the beginning of time” can be examined in two ways: Can natural phenomena alone explain changes to today’s climate, like an increase in extreme weather events? And does the theory of climate change entail a fallacy? A “fallacy” is a general term that refers to an error in reasoning. In this case, the fallacy is unfalsifiability.
Regardless, Cruz’s claim is misleading at best and inaccurate at worst.
Can natural phenomena explain all of today’s climatic changes? Scientists have found strong evidence that suggests anthropogenic causes, like the burning of fossil fuels, contribute to changes in our climate in addition to natural causes.
U.S. Global Change Research Program, May 2014: Long-term, independent records from weather stations, satellites, ocean buoys, tide gauges, and many other data sources all confirm that our nation [the United States], like the rest of the world, is warming. Precipitation patterns are changing, sea level is rising, the oceans are becoming more acidic, and the frequency and intensity of some extreme weather events are increasing. Many lines of independent evidence demonstrate that the rapid warming of the past half-century is due primarily to human activities.
The 2014 National Climate Assessment was produced by “a team of more than 300 experts guided by a 60-member Federal Advisory Committee” and reviewed by “the public and experts, including federal agencies and a panel of the National Academy of Sciences.”
The IPCC’s fifth assessment report also found evidence to support the existence of human-induced climate change. For example, the U.N. panel writes (see page 2): “Human influence on the climate system is clear, and recent anthropogenic emissions of greenhouse gases are the highest in history. Recent climate changes have had widespread impacts on human and natural systems.”
NASA’s website also cites collective and individual statements from a number of American and international scientific societies, academies and government agencies that all agree global warming and climate change are due, in part, to human actions. For example, in 2006 the Board of the American Association for the Advancement of Science, publisher of the journal Science, said: “The scientific evidence is clear: global climate change caused by human activities is occurring now, and it is a growing threat to society.”
In short, when Cruz said “if it gets hotter or colder, wetter or drier — the climate has always changed since the beginning of time,” he implied climate change is only due to natural causes. This is inaccurate. Scientists have found plenty of evidence to suggest that humans have been contributing to climate change since the Industrial Revolution.
Lastly, Cruz implies that the theory of climate change entails a fallacy when he juxtaposes the line “if it gets hotter or colder, wetter or drier” with his claim that the theory can never be proved wrong. This is misleading. Scientists have found evidence that suggests climate change includes an increase in both wetter and drier, hotter and colder conditions — including more extreme weather events — and this evidence doesn’t entail a fallacy.
Along with large-scale reports like those of the IPCC, independent studies have also found that human-induced global warming is the likely cause of changes to the global climate, such as an increase in extreme weather events. In April 2015, for example, Nature Climate Change published a paper that found that extreme heat waves and heavy rainfall may already be occurring with increasing frequency due to anthropogenic causes.
Back in April 2015 we also wrote about the relationship between global warming and extreme weather when we fact-checked claims made by Lamar Smith, a Republican from Texas and chairman of the House Committee on Science, Space, and Technology.
To be clear, scientists do not claim that climate change is at the root of every recent drought, flood, heatwave and snowstorm. In December of last year, the American Meteorological Society published a collection of 32 studies that examined 28 extreme weather events in 2014. Collectively, the researchers found that whether climate change plays a role in extreme weather depends on the region and meteorological phenomenon of interest.
“When you start talking about individual regions, forecasts become much more uncertain,” Mann told us. But “when you talk about some of these more general principles, those are pretty rock solid.”
By “general principles” Mann is referring to the many different mechanisms underlying fluctuations in the planet’s climate. To explain why climate change doesn’t entail a fallacy, we will outline how one of those mechanisms relates to extreme weather, namely floods and droughts.
One way to understand the relationship between global warming and climate change, relies on how H2O reacts to heat. When H2O in the form of water is heated it evaporates and turns into water vapor. When H2O in the form of ice is heated, it melts and turns into water. So in areas where there are mountains with snow pack, global warming may lead to increased flooding, Mann told us. Whereas in areas where there are lakes or moisture in the soil, global warming may lead to more droughts. Again, this explanation is simplified, and many more mechanisms contribute to increased flooding and prolonged droughts, among other extreme weather events.
There are mechanisms to explain how on a global level climate change can entail both droughts and floods simultaneously. As a result, Cruz was misleading when he juxtaposed the line “if it gets hotter or colder, wetter or drier” next to his claim that the theory can never be proved wrong.
To sum up, Cruz’s speech in Conway on Jan. 19 included both inaccurate and misleading claims.
First, he said “none of the alarmists say ‘global warming’ anymore — now it’s ‘climate change.’ ” Scientists still use both terms. Next, he claimed climate change “can never, ever, ever be disproven.” This is false. It could be, but the chances are slim. Third, he misled when he said “if it gets hotter or colder, wetter or drier — the climate has always changed since the beginning of time.” Natural causes influence the climate, but it’s unlikely these phenomena alone account for some more recent changes. And given the global climate’s spatial and temporal complexity, scientists expect that some areas of the planet will change differently from others. So there’s nothing fallacious about the theory of climate change entailing more weather extremes, for example.
