Enter a term in the search box to find its definition.
Settings
Use the controls in the far right panel to increase or decrease the number of terms automatically displayed (or to completely turn that feature off).
Term Lookup
Settings
All IPCC definitions taken from Climate Change 2007: The Physical Science Basis. Working Group I Contribution to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Annex I, Glossary, pp. 941-954. Cambridge University Press.
Explaining climate change science & rebutting global warming misinformation
Scientific skepticism is healthy. Scientists should always challenge themselves to improve their understanding. Yet this isn't what happens with climate change denial. Skeptics vigorously criticise any evidence that supports man-made global warming and yet embrace any argument, op-ed, blog or study that purports to refute global warming. This website gets skeptical about global warming skepticism. Do their arguments have any scientific basis? What does the peer reviewed scientific literature say?
As Politico reported, Trump’s deputy national security adviser, KT McFarland, gave him a fake 1970s Time magazine cover warning of a coming ice age. The Photoshopped magazine cover circulated around the internet several years ago, but was debunked in 2013. Four years later, McFarland put the fake document in Trump’s hands, and he reportedly “quickly got lathered up about the media’s hypocrisy … Staff chased down the truth and intervened before Trump tweeted or talked publicly about it”.
A real Time magazine special issue cover from 2007 (left frame), and the faked version (right frame). Illustration: Time Magazine; climate denier with Photoshop
Story of the Week... El Niño/La Niña Update... Toon of the Week... Quote of the Week... SkS in the News... SkS Spotlights... Video of the Week... Coming Soon on SkS... Poster of the Week... Climate Feedback Reviews... SkS Week in Review... 97 Hours of Consensus...
Story of the Week...
April 2017: Earths 2nd Warmest April on Record
April 2017 was the planet's second warmest April since record keeping began in 1880, said NOAA's National Centers for Environmental Information (NCEI) on Thursday; NASA also rated April 2017 as the second warmest April on record. The only warmer April was just last year, in 2016. April 2017 ranked as the eighteenth warmest month (expressed as the departure of temperature from average) of any month in the global historical record in the NASA database. The extreme warmth of January 2017 (thirteenth warmest month of any month in NASA’s database), February 2017 (sixth warmest), March 2017 (fifth warmest) and now April gives 2017 an outside chance of becoming Earth’s fourth consecutive warmest year on record--if an El Niño event were to develop this summer and continue through the end of the year, as some models are predicting. It's more likely, though, that 2016 will remain as the warmest year in Earth's recorded history. For the year-to-date period of January–April 2017, Earth's temperature was 0.95°C (1.71°F) above the 20th century average of 12.6°C (54.8°F). This was the second highest such period since records began in 1880, behind 2016 by 0.19°C (0.34°F.)
Global ocean temperatures last month were the second warmest on record for any April, and global land temperatures were the fourth warmest on record. Global satellite-measured temperatures for the lowest 8 km of the atmosphere were the fifth warmest for any April in the 39-year record, according to the University of Alabama Huntsville (UAH).
Figure 1. Departure of temperature from average for April 2017, the second warmest April for the globe since record keeping began in 1880. Warmer-than-average temperatures during the month were observed across much of the world's land surfaces, with the most notable warm temperature departures from average across the Northern Hemisphere higher latitudes, specifically across much of central and eastern Asia, Alaska and the eastern half of the contiguous U.S., where temperatures were 3.0°C (5.4°F) above average or higher. Image credit: National Centers for Environmental Information (NCEI).
A chronological listing of news articles posted on the Skeptical Science Facebook page during the past week. Articles of high signifigance are highlighted in the Editor's Picks' section.
Editor's Picks
Receding forest on a mountainside in West Kalimantan province in Borneo
Receding forest on a mountainside in West Kalimantan province in Borneo.ROMEO GACAD/AFP/GETTY IMAGES
Palm oil is the second-most important oil in the modern consumer society, after petroleum. Producing it is a $50-billion-a-year business. It’s in a multitude of the household products in North America, Europe, and Australia: margarine, toothpaste, shampoo, lipstick, cookies, Nutella, you name it. Doritos are saturated with palm oil. It’s what gives chocolate bars their appetizing sheen – otherwise, they would look like mud. Palm oil has replaced artery-clogging ghee as India’s main cooking oil. India is now the major consumer of this clear, tasteless oil squeezed from the nuts of the oil-palm tree, Elais guyanensis,originally from West Africa, but now grown pantropically, mainly within ten degrees north and south of the Equator.
Indonesia and Malaysia chose palm oil as their main economic engine after independence in the 1960s, and they together account for 85 percent of world production, which is expected to double by 2050. As oils go, palm oil gives you the best bang for your buck. Soy fields yield far less than rows of oil-palm trees and have to be replanted annually, while the palms keep bearing huge clusters of oil-rich nuts for 20 years, and can then be replaced. In 2015 17 million hectares of oil palm yielded a total of 62 million tons of oil, while the 120 million hectares planted in soy yielded 48 million tons. Palm oil doesn’t lose its properties when it’s heated, or become rancid at room temperature, and it has multiple industrial uses. It is the edible vegetable oil of choice and is not going away.
Borneo is ground zero for oil-palm devastation. Nowhere has more native rain forest been wiped out. The world’s third-largest island, Borneo’s lower 73 percent is in Indonesia— the territory of Kalimantan— and its upper portion consists of two states in Malaysia, Sarawak and Sabah, separated by the small, oil-rich sultanate of Brunei. Fifty percent of the lowland Borneo rain forest, which once covered all of the island up to 10,000 feet, is gone, but it’s still the third-largest in the world, after the Amazon and Equatorial Africa’s. It is part of the most ancient rain forest— forest, period— on earth: 130 million years old, more than twice as old as the Amazon’s, and has the greatest density of higher plant species, an estimated 15,000 flowering species. Each new botanical or entomological expedition comes back with new species. Some 20,000 insect species have been found in Sarawak’s Gunung Mulu National Park alone.
We know humans are causing climate change. That is a fact that has been known for well over 100 years. We also know that there will be significant social and economic costs from the effects. In fact, the effects are already appearing in the form of more extreme weather, rising sea levels, ocean acidification, and so on.
So why haven’t humans done much about the problem? Answering that question may be more challenging than the basic science of a changing climate. Fortunately, a new review just out in Science helps us with this question. Lead author, Dr. Elise Amel, a colleague of mine, completed the review with colleagues Drs. Christie Manning, Britain Scott, and Susan Koger. Rather than focusing solely on the problems with communicating the science of climate change, this work takes a wider view on the hurdles that get in the way of meaningful action.
The review points out that since the 1970s, extensive efforts to educate people have not lead to significant shifts in behavior. They also acknowledge that using fear or guilt has not been effective in getting people to act. So, what can help?
Well, first we must understand that it is not just internal forces (emotions, beliefs, attitudes, etc.) that affect human behavior, but external influences as well. External factors, like social networks, societal roles, cultural worldviews, habits, infrastructure, investments, etc, are often severely underestimated in the extent to which they steer behavior. One fault of prior messaging is an almost exclusive focus of the first (internal) set of factors and a near-complete neglect of the latter (externals). The authors write:
Change is hard. Human beings are reticent to change their behavior even under the most compelling of circumstances, and environmental dangers do not tend to arouse the kind of urgency that motivates individuals to act. Mass transformation of unsustainable systems will be even more difficult than shifting individual behaviors, for unlike ants and bees, humans are not well equipped to coordinate behavior for common benefit.
Greenhouse gases (GHG) determine amountof warming, but oceans delaythe warming.
Elevator Statement
To see how the oceans delay warming of the atmosphere, try the following thought experiment.
Imagine a pot that holds about 8 liters/quarts.
Hang a thermometer from the center of the lid so that it hangs in the middle of the pot.
Put the pot on the stove with no water, just air.
Turn the burner on your stove on very low heat.
Measure the time it takes for the thermometer to reach 60°C (about 140°F).
Remove the pot from the stove, let it cool, fill with water, and place it on the stove on very low heat.
How much longer does it take to reach 60°C (about 140°F) with water instead of air in the pot? A lot longer!
If you wanted to heat the water to 90°C (about 195°F) in the same amount of time, you would need to start this experiment with the burner on higher heat.
The longer time it takes to heat the pot of water than a pot of air explains why there is a delay between GHG emissions and a rise in temperature of the atmosphere: the oceans absorb a lot of heat, requiring a long time to heat up. This is why scientists such as James Hansen refer to global warming as an inter-generational issue, because the heating due to our emissions are only fully felt by the next generation, due to the time lag created by the oceans.
Climate Science
The earth is covered mostly in water. The large heat capacity of the oceans mean they soak up a lot of energy and slow down the heating of the atmosphere. Just how long is the delay between the time we inject CO2 and other GHG's into the atmosphere and when the effect is felt? The CO2 concentration is like the burner setting in the above example: more CO2 is like a higher burner temperature. However, even though turning up the heat creates hotter water, it takes a while for the water to heat up.
We can estimate the final temperature the atmosphere will reach for a given CO2 concentration by using the average IPCC estimate of 3°C warming for doubling CO2 concentration (this is called the “climate sensitivity”). Using the estimate of pre-industrial CO2 concentration of 280 ppm (parts per million), a climate sensitivity of 3°C implies that CO2 concentrations of 350, 440, and 560 ppm yield 1, 2, and 3°C warming, respectively. Using this estimate of climate sensitivity together with measurements of CO2 from 1970 to today, we can estimate the warming that has been locked in due to recent CO2 emissions. That is, knowing the burner setting, we can estimate the final temperature of the pot of water, even though we will have to wait some time for it to heat up.
We also use the GISS (Goddard Institute for Space Studies) data to plot measured global mean temperature above preindustrial to estimate the time lag between the temperature anomaly suggested by a particular CO2 concentration and the time when that temperature is observed. This and CO2 concentrations for 4 selected years are shown in the following figure.
As a psychologist researching misinformation, I focus on reducing its influence. Essentially, my goal is to put myself out of a job.
Recent developments indicate that I haven’t been doing a very good job of it. Misinformation, fake news and “alternative facts” are more prominent than ever. The Oxford Dictionary named “post-truth” as the 2016 word of the year. Science and scientific evidence have been under assault.
Fortunately, science does have a means to protect itself, and it comes from a branch of psychological research known as inoculation theory. This borrows from the logic of vaccines: A little bit of something bad helps you resist a full-blown case. In my newly published research, I’ve tried exposing people to a weak form of misinformation in order to inoculate them against the real thing – with promising results.
Two ways misinformation damages
Misinformation is being generated and disseminated at prolific rates. A recent study comparing arguments against climate science versus policy arguments against action on climate found that science denial is on the relative increase. And recent research indicates these types of effort have an impact on people’s perceptions and science literacy.
A recent study led by psychology researcher Sander van der Linden found that misinformation about climate change has a significant impact on public perceptions about climate change.
The misinformation they used in their experiment was the most shared climate article in 2016. It’s a petition, known as the Global Warming Petition Project, featuring 31,000 people with a bachelor of science or higher, who signed a statement saying humans aren’t disrupting climate. This single article lowered readers’ perception of scientific consensus. The extent that people accept there’s a scientific consensus about climate change is what researchers refer to as a “gateway belief,” influencing attitudes about climate change such as support for climate action.
At the same time that van der Linden was conducting his experiment in the U.S., I was on the other side of the planet in Australia conducting my own research into the impact of misinformation. By coincidence, I used the same myth, taking verbatim text from the Global Warming Petition Project. After showing the misinformation, I asked people to estimate the scientific consensus on human-caused global warming, in order to measure any effect.
I found similar results, with misinformation reducing people’s perception of the scientific consensus. Moreover, the misinformation affected some more than others. The more politically conservative a person was, the greater the influence of the misinformation.
Response to misinformation about climate change.Cook et al. (2017), CC BY-ND
There was tremendous outcry when the New York Times hired opinion columnist Bret Stephens, who has a long history of making misinformed comments about climate change. Stephens didn’t assuage those fears when he devoted his first column to punching hippies, absurdly suggesting that our lack of progress on climate policy is a result of greens being too mean to climate deniers.
Stephens lamentably stayed on the subject of climate change in his second and third Times columns as well. In those pieces, he used corn-based ethanol subsidies as an example of where climate policy has gone wrong:
So let’s talk about ethanol and other biofuels, a subject some climate-change activists might prefer to forget. In 2007, George W. Bush used his State of the Union speech to call for huge increases in the production of renewable and alternative fuels such as ethanol. Democrats were firmly on board, and President Barack Obama pursued a largely similar course in his first years in office.
This is a clear case of cherry picking. There are hundreds of examples of climate policies with varying degrees of effectiveness; why focus on just one? Many environmental groups and “climate-change activists” have long opposed corn-based ethanol subsidies, as Stephens himself noted. Politicians of both political parties supported those subsidies because they were popular in corn-growing Midwestern states. It had little if anything to do with climate efficacy. So why blame “climate-change activists” for these politically-motivated subsidies?
For his next misleading argument, Stephens shifted to German electricity costs:
The country is producing record levels of energy from wind and solar power, but emissions are almost exactly what they were in 2009. Meanwhile, German households pay nearly the highest electricity bills in Europe, all for what amounts to an illusion of ecological virtue.
Stephens’ comparison to 2009 is another example of blatant cherry picking. German carbon emissions that year were particularly low, due in part to the global recession. The long-term trend is unmistakable.
National Review recently published an article by Oren Cass that misrepresents a 2016 paper on the scientific consensus on climate change, written by coauthors of 7 leading consensus studies and members of the Skeptical Science team (coauthors include Naomi Oreskes, Peter Doran, William Anderegg, Bart Verheggen & Stuart Carlton). I asked National Review for a right-of-reply and to their credit, they agreed. Here is my reply to Oren Cass: How to Recognize ‘Science Denial’.
National Review also published a reply-to-my-reply from Oren Cass: John Cook’s Leap of Faith. Unfortunately, Cass justifies his use of the fake expert strategy because, well, Bernie Sanders. He also misrepresents Gavin Schmidt and the IPCC, attempting to argue that I am an outlier compared to them
Interestingly, this is the same strategy that Richard Tol once tried in arguing our 97% was an outlier compared to other consensus studies, which led to my co-authoring the 2016 consensus-on-consensus study with other consensus researchers (which was the paper that Cass misrepresents, everything is coming full circle). The position of the IPCC, Gavin Schmidt and myself are in perfect agreement: our best estimate of human contribution to global warming is 100% with the lowest bound being around 50%.
Anyway, I also recorded an Evidence Squared podcast with Peter Jacobs, where we critique the original National Review article. We discuss the techniques of climate science denial, focusing on the technique of fake experts that Cass uses to cast doubt on expert agreement.
Story of the Week... El Niño/La Niña Update... Toon of the Week... Quote of the Week... Graphic of the Week... SkS in the News... Photo of the Week... SkS Spotlights... Video of the Week... Coming Soon on SkS... Poster of the Week... Climate Feedback Reviews... SkS Week in Review... 97 Hours of Consensus...
Story of the Week...
Did Global Warming Really 'Pause' During the 2000s?
Flames whip from the Morgan fire near Clayton, California, in September 2013, right as the “hiatus” was ending. Photo: Noah Berger / Reuters
It is the first year of the new Republican president’s term. He has taken over a healthy economy from his Democratic predecessor, and, with it, the freedom to branch out beyond the typical Reaganism. He has also inherited a slew of environmental policies, many of which combat global warming.
Most important among these is a fledgling UN treaty, a global agreement to restrict greenhouse-gas emissions. It was never ratified by the Senate, so the new president—whose Cabinet members have deep ties to the oil and gas industry—must decide whether to stay in the agreement or abandon it.
Global warming does not obsess most Americans, but it frightens the scientists who study it. Just before the new president took office, an unprecedented and monstrous El Niño, the largest ever recorded, set a new annual global temperature record—“the hottest year ever measured,” as the newspapers put it. Ocean temperatures surged around the world, bleaching the Great Barrier Reef and inducing a mass coral die-off . Great cracks are even appearing in ancient Antarctic ice shelves. Climate change seems to be already under way.
A chronological listing of news articles posted on the Skeptical Science Facebook page during the past week.
Editor's Pick
Global Climate Policy in an Uncertain State of Flux
What would happen if the US leaves the Paris agreement? It would be a big blow to global cooperation, especially since the US is the top emitter after China, and is also by far a bigger emitter per capita than China and most other countries. Credit: Bigstock.
It was thus heartening that US citizens are protesting against their government’s climate change policies.
It is also important for people and governments in the rest of the world to strengthen their resolve to fight climate change, rather than to relax now that the US leadership is refusing to do its part.
The best solution would be for the US to remain in the Paris agreement, and go along with other countries to meet and improve on their pledges and enable international cooperation to thrive.
That is not going to happen. So we may have to wait at least four years before another US administration rejoins the rest of the world to tackle climate change. Let’s hope it will not be really too late by then to save the world.
This blog post provides an update to Dana Nuccitelli’s article from June 2013 about Citizens’ Climate Lobby (CCL) as a lot has happened in the almost four years since it was published.The basics about CCL as explained in Dana’s post haven’t changed and because of that won’t be repeated here.
In 2013, CCL had been active mostly in the U.S. and Canada and the rest of the world didn’t yet play much of a role as shown in this snippet from Dana’s article:
“CCL is also exploring the possibility of launching some UK chapters. Although the UK is part of the European carbon cap and trade system, that system is experiencing difficulties, and CCL aims to maintain UK support for carbon pricing.”
Worldwide presence and impressive number
But, as this current map illustrates, CCL has by now gone global and has chapters on all continents except Antarctica:
Blue pins designate active chapters and yellow pins show chapters in development. Link to live map
The following video is a snippet from last year’s CCL conference in Washington D.C. and gives a glimpse of why people from around the world are joining this effort to get a meaningful price on carbon:
Human emission of heat-trapping gases is causing the Earth to warm. We’ve known that for many decades. In fact, there are no reputable scientists that dispute this fact. There are, however, a few scientists who don’t think the warming will be very much or that we should worry about it. These contrarians have been shown to be wrong over and over again, like in the movie Groundhog Day. And, a new study just out shows they may have another error. But, despite being wrong, they continue to claim Earth’s warming isn’t something to be concerned about.
Perhaps the darlings of the denialist community are two researchers out of Alabama (John Christy and Roy Spencer). They rose to public attention in the mid-1990s when they reportedly showed that the atmosphere was not warming and was actually cooling. It turns out they had made some pretty significant errors and when other researchers identified those errors, the new results showed a warming.
To provide perspective, we know the Earth is warming because we can measure it. Most of the heat (93%) goes into the oceans and we have sensors measuring ocean temperatures that show this. We also know about warming because we have thermometers and other sensors all over the planet measuring the temperature at the surface or in the first few meters of air at the surface. Those temperatures are rising too. We are also seeing ice melting and sea level rising around the planet.
So, the evidence is clear. What Christy and Spencer focus on is the temperatures measured far above the Earth’s surface in the troposphere and the stratosphere. Generally, over the past few decades these two scientists have claimed the troposphere temperatures are not rising very rapidly. This argument has been picked up to deny the reality of human caused climate change – but it has been found to be wrong.
Used correctly, Null Hypothesis Statistical Testing (NHST) provides a valuable sanity check in science, requiring scientists to question the support their theories receive from the data, such that they only proceed with their research hypothesis if it can overcome this (often minimal) hurdle. This enforces an element of healthy self-skepticism that helps science to be self-correcting in the long term. Unfortunately, however, statistical hypothesis testing is widely misunderstood amongst the general public, working scientists and even professors of statistics [1]. It isn't unduly surprising then, that misunderstandings of statistical significance have cropped up rather frequently in the climate debate. The aim of this post is to give an idea of what statistical significance actually means, and more importantly, what it doesn't mean and why this should matter.
The Basic Null Hypothesis Statistical Testing Recipe
Flipping a coin is the traditional way of deciding between two arbitrary options, for instance which side should have the option of batting or fielding first in a game of cricket. A classic example of statistical hypothesis testing is deciding whether a coin is fair (the probability of a head is the same as that of a tail) or whether it is biased. Say we observe the coin being flipped four times and it comes down heads each time. The usual recipe for statistical hypothesis testing is to first state your null hypothesis (known as H0), which is generally taken to be the thing you don't want to be true. Say we think the captain of the opposition is a cheat and he is using a biased coin to gain an unfair advantage. In that case, our null hypothesis ought to be that we are wrong and that his coin is fair (i.e. q = p(head) = p(tail) = 0.5).
H0: The coin is fair, q = 0.5
We then state our experimental hypothesis, for which we want to provide support
H1: The coin is biased, q ≠ 0.5
We then need a test statistic, z, that we use to measure the outcome of the experiment. In this case, we record the number of heads in n = 4 trials, so z = 4.
The greenhouse effect is like a warm, cloudy night.
Elevator Statement
At night clouds trap infrared radiation emitted from the ground, similar to greenhouse gases, and re-emit some of the absorbed radiation back to the ground.
More nighttime cloud cover means more trapped heat, and warmer temperatures near the ground, just as more CO2 in the atmosphere means more trapped heat, and warmer temperatures.
Because clouds are big and thick, their radiation-trapping effect is felt immediately, within a single night.
Because CO2 is diffuse, its effect is felt slowly, over many decades.
Increasing the concentration of CO2 in the atmosphere is like increasing the cloud cover at night: both warm the Earth by trapping infrared radiation.
Climate Science
The greenhouse effect describes the trapping of energy by Earth’s atmosphere: infrared radiation from the ground is absorbed by gases in the atmosphere such as CO2, H2O, CH4, and others. Although the greenhouse effect is active 24/7, it is most apparent at night. This is because with no background solar radiation, nighttime warmth occurs mostly by greenhouse gases and clouds grabbing and storing some of the infrared radiation emitted from the ground that is trying to make it to outer space. This is partly why nighttime temperatures have been steadily increasing as greenhouse gases increase: more greenhouse gases implies more heating.
After receiving misinformation from the anti-vaccine movement, including its founder Andrew Wakefield, immunization rates plummeted in a community of Somali immigrants in Minnesota, causing a measles outbreak among their children. It’s a disturbing trend on the rise in America that shows the importance of immunization and the dangerous power of misinformation.
A new paper published in PLOS One by John Cook, Stephan Lewandowsky, and Ullrich Ecker tests the power of inoculation; not against disease, but against the sort of misinformation that created the conditions leading to Minnesota measles outbreak. Inoculation theory suggests that exposing people to the tricks used to spread misinformation can equip them with the tools to recognize and reject such bogus claims.
The two issues are connected – in climate stories, journalists will often present arguments by climate scientists and climate deniers with equal weight, creating the perception of a 50/50 split when in reality, 97% of experts are on one side, as elegantly illustrated by John Oliver in this clip with over 7 million views from his HBO program Last Week Tonight:
Story of the Week... Video of the Week... Quote of the Week... Graphic of the Week... SkS in the News... Photo of the Week... SkS Spotlights... Toon of the Week... Coming Soon on SkS... Poster of the Week... Climate Feedback Reviews... SkS Week in Review... 97 Hours of Consensus...
Story of the Week...
The great climate silence: we are on the edge of the abyss but we ignore it
‘How can we understand the miserable failure of contemporary thinking to come to grips with what now confronts us?’ Photograph: Piyal Adhikary/EPA
After 200,000 years of modern humans on a 4.5 billion-year-old Earth, we have arrived at new point in history: the Anthropocene. The change has come upon us with disorienting speed. It is the kind of shift that typically takes two or three or four generations to sink in.
Our best scientists tell us insistently that a calamity is unfolding, that the life-support systems of the Earth are being damaged in ways that threaten our survival. Yet in the face of these facts we carry on as usual.
Most citizens ignore or downplay the warnings; many of our intellectuals indulge in wishful thinking; and some influential voices declare that nothing at all is happening, that the scientists are deceiving us. Yet the evidence tells us that so powerful have humans become that we have entered this new and dangerous geological epoch, which is defined by the fact that the human imprint on the global environment has now become so large and active that it rivals some of the great forces of nature in its impact on the functioning of the Earth system.
A chronological listing of news articles posted on the Skeptical Science Facebook page during the past week. Articles of high signifigance are highlighted in the Editor's Picks' section.
Editor's Picks
No country on Earth is taking the 2 degree climate target seriously
One of the morbidly fascinating aspects of climate change is how much cognitive dissonance it generates, in individuals and nations alike.
The more you understand the brutal logic of climate change — what it could mean, the effort necessary to forestall it — the more the intensity of the situation seems out of whack with the workaday routines of day-to-day life. It’s a species-level emergency, but almost no one is acting like it is. And it’s very, very difficult to be the only one acting like there’s an emergency, especially when the emergency is abstract and science-derived, grasped primarily by the intellect.
This psychological schism is true for individuals, and it’s true for nations. Take the Paris climate agreement.
In Paris, in 2015, the countries of the world agreed (again) on the moral imperative to hold the rise in global average temperature to under 2 degrees Celsius, and to pursue "efforts to limit the temperature increase to 1.5 degrees." To date, 62 countries, including the United States, China, and India, have ratified the agreement.
Are any of the countries that signed the Paris agreement taking the actions necessary to achieve that target?
As a climate scientist, I spend time and energy studying how fast the Earth is warming and what is causing the warming. This knowledge helps us predict what the future will look like. But, what most people are interested in is, “how will it affect me?”
Some impacts we are pretty clear about, like the impacts related to sea level rise, increased storms and heavy precipitation, and increased drought and heat waves – particularly the impacts these events have on the economy. But climate change will affect us personally as well (by personally, I mean our physical person).
In fact, climate change is already affecting personal human health around the world. This subject was the focus of a summary report just published by the Medical Society Consortium. What I really liked about this report is that it breaks down some of the key impacts by region. Unfortunately, the report is limited in scope to the USA. However, the general conclusions and trends can be illuminating for people outside the USA as well.
What was also welcome is that this report was prepared by physicians (not climate scientists) of major medical societies and the conclusions are based on the best available and current information of both the climate and health fields.
Four years ago, my colleagues and I published a paper finding a 97% consensus in the peer-reviewed literature on human-caused global warming. Since then, it’s been the subject of constant myths, misinformation, and denial. In fact, last year we teamed up with the authors of six other consensus papers, showing that with a variety of different approaches, we all found the expert consensus on human-caused global warming is 90–100%.
Most of the critiques of our paper claim the consensus is somehow below 97%. For example, in a recent congressional hearing, Lamar Smith (R-TX) claimed we had gone wrong by only considering “a small sample of a small sample” of climate studies, and when estimated his preferred way, it’s less than 1%. But in a paper published last year, James Powell argued that the expert consensus actually higher – well over 99%.
We thus had three quite different estimates of the expert consensus on human-caused global warming: less than 1%, 97%, or 99.99%. So which is right?
In his critique of our study, Powell argued that on scientific theories as settled as human-caused global warming or plate tectonics, scientists don’t bother to state the obvious. In our 97% paper, we examined how many studies endorsed, rejected or minimized, or took no position on human-caused global warming.
In his study, Powell only looked at papers explicitly rejecting the human cause; he assumed that the rest endorsed the consensus. And, he argued, applying our approach to another settled scientific theory like plate tectonics wouldn’t yield any results, because Powell assumed no scientist would bother to state something so obvious. If our approach weren’t valid for plate tectonics, Powell argued that it wouldn’t be valid for global warming either.
The 97% consensus on anthropogenic global warming (AGW) reported by Cook et al. (2013) (C13) is a robust estimate. Alternative methods, such as James Powell's, that identify only explicit rejections of AGW and assume that all other instances are endorsements, miss many implicit rejections and overestimate the consensus.
The C13 method can be modified and used to estimate the consensus on plate tectonics in a sample of the recent geological literature. This limited study—not surprisingly to anyone familiar with the field—produces a consensus estimate of 100%. However, among the abstracts that expressed an opinion. only implicit endorsements of the theory were found: this underlines the importance in consensus studies of identifying implicit statements. The majority of the abstracts expressed no position. Assuming that these cases suggest either uncertainty about, or rejection of, plate tectonics (as some critics of C13 have claimed about AGW) would lead to the absurd conclusion that the theory is not widely accepted among geologists.
Opinion surveys show that the public is misinformed about true state of consensus among climate scientists, with only a minority aware that it is greater than 90%. The difference between 97% and 99.99% is tiny compared to this gap. The 3% of published papers that reject AGW are contradictory and have invariably been debunked. They do not therefore provide a coherent alternative account of climate science. Despite this, dissenters are awarded disproportionate attention by ideologically and commercially motivated interests, as well as by false balance in the media. Countering this public confusion requires both communicating the consensus and debunking bad science.
We have previously responded to Powell’s arguments. John Cook published an article for Skeptical Inquirer and I wrote a piece on my blog Critical Angle. Yesterday, a team of eight co-authors (Andy Skuce, John Cook, Mark Richardson, Bärbel Winkler, Ken Rice, Sarah Green, Peter Jacobs and Dana Nuccitelli) published a more formal, peer-reviewed rebuttal: Does it matter if the consensus on anthropogenic global warming is 97% or 99.99%? in the Bulletin of Science, Technology & Society. The article is also paywalled, but the publisher allows us to post a version of the revised submitted manuscript, which can be read here.
In his BST&S paper, Powell makes four main arguments against C13:
Consensus studies by Doran & Zimmerman (2009), the Pew Research Center (2015) and Anderegg et al. (2010) fail to reveal a near-unanimous consensus on AGW “…because of some combination of small sample size, reliance on fallible opinion, and inclusion of nonexperts…”
The C13 study of 11,944 articles in the peer-reviewed literature from 1991-2011 failed to adequately measure the consensus because it ignored the abstracts and papers that did not express an opinion on AGW.
Applying the C13 methodology to a universally accepted theory like plate tectonics would yield misleading or absurd results.
If it were true that 3% of scientists rejected or were uncertain about AGW, then the case for action to prevent global warming would be weakened, since, by comparison with now-settled scientific questions like continental drift and the origin of lunar craters, the existence of dissenters might suggest that AGW theory was about to be overthrown
We respond in detail to these objections in the paper. I will summarize the main points below. Complete references are provided in the paper.
Arguments
‘How can we understand the miserable failure of contemporary thinking to come to grips with what now confronts us?’ Photograph: Piyal Adhikary/EPA
(
