The 5 telltale techniques of climate change denial

By John Cook

Updated 1725 GMT (0025 HKT) July 22, 2015

11 ways climate change affects the world 11 photos

Pollen allergies – Are you sneezing more often these days? Climate change may be to blame for that, too. Recent studies show that rising temperatures and carbon dioxide levels promote the growth of weedy plant species that produce allergenic pollen. The worst place in the United States for spring allergies in 2014, according to the Asthma and Allergy Foundation of America? Louisville, Kentucky.

Hide Caption

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11 ways climate change affects the world 11 photos

Deforestation – Climate change has not been kind to the world's forests. Invasive species such as the bark beetle, which thrive in warmer temperatures, have attacked trees across the North American west, from Mexico to the Yukon. University of Colorado researchers have found that some populations of mountain pine beetles now produce two generations per year, dramatically boosting the bugs' threat to lodgepole and ponderosa pines. In this 2009 photo, dead spruces of the Yukon's Alsek River valley attest to the devastation wrought by the beetles.

Hide Caption

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11 ways climate change affects the world 11 photos

Mountain glaciers – The snows capping majestic Mount Kilimanjaro, Africa's highest peak, once inspired Ernest Hemingway. Now they're in danger of melting away altogether. Studies suggest that if the mountain's snowcap continues to evaporate at its current rate, it could be gone in 15 years. Here, a Kilimanjaro glacier is viewed from Uhuru Peak in December 2010.

Hide Caption

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11 ways climate change affects the world 11 photos

Endangered species – Polar bears may be the poster child for climate change's effect on animals. But scientists say climate change is wreaking havoc on many other species -- including birds and reptiles -- that are sensitive to fluctuations in temperatures. One, this golden toad of Costa Rica and other Central American countries, has already gone extinct.

Hide Caption

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11 ways climate change affects the world 11 photos

Animal migration – It's not your imagination: Some animals -- mostly birds -- are migrating earlier and earlier every year because of warming global temperatures. Scholars from the University of East Anglia found that Icelandic black-tailed godwits have advanced their migration by two weeks over the past two decades. Researchers also have found that many species are migrating to higher elevations as temperatures climb.

Hide Caption

10 of 11

11 ways climate change affects the world 11 photos

Extreme weather – The planet could see as many as 20 more hurricanes and tropical storms each year by the end of the century because of climate change, according to a 2013 study published in the Proceedings of the National Academy of Sciences. This image shows Superstorm Sandy bearing down on the New Jersey coast in 2012.

Hide Caption

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11 ways climate change affects the world 11 photos

Melting polar ice caps – The consequences of climate change go far beyond warming temperatures, which scientists say are melting the polar ice caps and raising sea levels. Click through the gallery for a look at 10 other key effects of climate change, some of which may surprise you.

Hide Caption

1 of 11

11 ways climate change affects the world 11 photos

Drought – In the coming decades climate change will unleash megadroughts lasting 10 years or more, according to a new report by scholars at Cornell University, the University of Arizona and the U.S. Geological Survey. We're seeing hints of this already in many arid parts of the world and even in California, which has been rationing water amid record drought. In this 2012 photo, a man places his hand on parched soil in the Greater Upper Nile region of northeastern South Sudan.

Hide Caption

2 of 11

11 ways climate change affects the world 11 photos

Wildfires – There's not a direct link between climate change and wildfires, exactly. But many scientists believe the increase in wildfires in the Western United States is partly the result of tinder-dry forests parched by warming temperatures. This photo shows a wildfire as it approaches the shore of Bass Lake, California, in mid-September.

Hide Caption

3 of 11

11 ways climate change affects the world 11 photos

Coral reefs – Scientists say the oceans' temperatures have risen by more than 1 degree Fahrenheit over the last century. It doesn't sound like much, but it's been enough to affect the fragile ecosystems of coral reefs, which have been bleaching and dying off in recent decades. This photo shows dead coral off the coast of St. Martin's Island in Bangladesh.

Hide Caption

4 of 11

11 ways climate change affects the world 11 photos

Food prices – A U.N. panel found in March that climate change -- mostly drought -- is already affecting the global agricultural supply and will likely drive up food prices. Here, in 2010, workers on combines harvest soybeans in northern Brazil. Global food experts have warned that climate change could double grain prices by 2050.

Hide Caption

5 of 11

11 ways climate change affects the world 11 photos

Pollen allergies – Are you sneezing more often these days? Climate change may be to blame for that, too. Recent studies show that rising temperatures and carbon dioxide levels promote the growth of weedy plant species that produce allergenic pollen. The worst place in the United States for spring allergies in 2014, according to the Asthma and Allergy Foundation of America? Louisville, Kentucky.

Hide Caption

6 of 11

11 ways climate change affects the world 11 photos

Deforestation – Climate change has not been kind to the world's forests. Invasive species such as the bark beetle, which thrive in warmer temperatures, have attacked trees across the North American west, from Mexico to the Yukon. University of Colorado researchers have found that some populations of mountain pine beetles now produce two generations per year, dramatically boosting the bugs' threat to lodgepole and ponderosa pines. In this 2009 photo, dead spruces of the Yukon's Alsek River valley attest to the devastation wrought by the beetles.

Hide Caption

7 of 11

11 ways climate change affects the world 11 photos

Mountain glaciers – The snows capping majestic Mount Kilimanjaro, Africa's highest peak, once inspired Ernest Hemingway. Now they're in danger of melting away altogether. Studies suggest that if the mountain's snowcap continues to evaporate at its current rate, it could be gone in 15 years. Here, a Kilimanjaro glacier is viewed from Uhuru Peak in December 2010.

Hide Caption

8 of 11

11 ways climate change affects the world 11 photos

Endangered species – Polar bears may be the poster child for climate change's effect on animals. But scientists say climate change is wreaking havoc on many other species -- including birds and reptiles -- that are sensitive to fluctuations in temperatures. One, this golden toad of Costa Rica and other Central American countries, has already gone extinct.

Hide Caption

9 of 11

11 ways climate change affects the world 11 photos

Animal migration – It's not your imagination: Some animals -- mostly birds -- are migrating earlier and earlier every year because of warming global temperatures. Scholars from the University of East Anglia found that Icelandic black-tailed godwits have advanced their migration by two weeks over the past two decades. Researchers also have found that many species are migrating to higher elevations as temperatures climb.

Hide Caption

10 of 11

11 ways climate change affects the world 11 photos

Extreme weather – The planet could see as many as 20 more hurricanes and tropical storms each year by the end of the century because of climate change, according to a 2013 study published in the Proceedings of the National Academy of Sciences. This image shows Superstorm Sandy bearing down on the New Jersey coast in 2012.

Hide Caption

11 of 11

11 ways climate change affects the world 11 photos

Melting polar ice caps – The consequences of climate change go far beyond warming temperatures, which scientists say are melting the polar ice caps and raising sea levels. Click through the gallery for a look at 10 other key effects of climate change, some of which may surprise you.

Hide Caption

1 of 11

11 ways climate change affects the world 11 photos

Drought – In the coming decades climate change will unleash megadroughts lasting 10 years or more, according to a new report by scholars at Cornell University, the University of Arizona and the U.S. Geological Survey. We're seeing hints of this already in many arid parts of the world and even in California, which has been rationing water amid record drought. In this 2012 photo, a man places his hand on parched soil in the Greater Upper Nile region of northeastern South Sudan.

Hide Caption

2 of 11

11 ways climate change affects the world 11 photos

Wildfires – There's not a direct link between climate change and wildfires, exactly. But many scientists believe the increase in wildfires in the Western United States is partly the result of tinder-dry forests parched by warming temperatures. This photo shows a wildfire as it approaches the shore of Bass Lake, California, in mid-September.

Hide Caption

3 of 11

11 ways climate change affects the world 11 photos

Coral reefs – Scientists say the oceans' temperatures have risen by more than 1 degree Fahrenheit over the last century. It doesn't sound like much, but it's been enough to affect the fragile ecosystems of coral reefs, which have been bleaching and dying off in recent decades. This photo shows dead coral off the coast of St. Martin's Island in Bangladesh.

Hide Caption

4 of 11

11 ways climate change affects the world 11 photos

Food prices – A U.N. panel found in March that climate change -- mostly drought -- is already affecting the global agricultural supply and will likely drive up food prices. Here, in 2010, workers on combines harvest soybeans in northern Brazil. Global food experts have warned that climate change could double grain prices by 2050.

Hide Caption

5 of 11

11 ways climate change affects the world 11 photos

Pollen allergies – Are you sneezing more often these days? Climate change may be to blame for that, too. Recent studies show that rising temperatures and carbon dioxide levels promote the growth of weedy plant species that produce allergenic pollen. The worst place in the United States for spring allergies in 2014, according to the Asthma and Allergy Foundation of America? Louisville, Kentucky.

Hide Caption

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Story highlights

• John Cook: Climate deniers rely on a common set of techniques to dispute the science
• Cook: Knowing deniers' tactics can help inoculate people from a misleading view of reality

John Cook is the Climate Communication Fellow for theGlobal Change Institute at the University of Queensland. He created the website Skeptical Science.com, which won the 2011 Australian Museum Eureka Prize for the Advancement of Climate Change Knowledge. Cook co-authored the college textbook "Climate Change Science: A Modern Synthesis" and the book "Climate Change Denial: Heads in the Sand." In 2013, he published a paper analyzing the scientific consensus on climate change that gained worldwide media attention, being mentioned by President Barack Obama and U.S. Secretary of State John Kerry. It was awarded the best paper of 2013 published in Environmental Research Letters. The opinions expressed in this commentary are his.

(CNN)There is overwhelming scientific evidence that humans are causing global warming. Nevertheless, a small proportion of the population continues to deny the science. This can be problematic when the small number denying climate science includes half of the U.S. Senate.

John Cook

How do you identify climate science denial, and how do you respond to it? To address denial properly, you need to understand the telltale techniques used to distort the science. It turns out all movements that deny a scientific consensus, whether it be the science of climate change, evolution or vaccination, share five characteristics in common:

1. Fake experts

Ninety-seven percent of climate scientists agree that humans are causing global warming. This has been found independently in a number of studies, including surveys of Earth scientists,analysis of public statements about climate change and analysis of peer-reviewed scientific papers. How might one cast doubt on the overwhelming scientific consensus? One technique is the use of fake experts.

We see this in online petitions such as the Global Warming Petition Project, which features more than 31,000 scientists claiming humans aren't disrupting our climate. How can there be 97% consensus when 31,000 scientists disagree? It turns out 99.9% of the petition's signatories aren't climate scientists. They include computer scientists, mechanical engineers and medical scientists but few climate scientists. The Global Warming Petition Project is fake experts in bulk.

2. Logical fallacies

The reason why there's a 97% consensus is because of the many lines of evidence that humans are causing global warming. Human fingerprints are being observed in heat escaping out to space, in the structure of the atmosphere and even in the changing seasons. Another denialist technique used to counter the weight of evidence is the logical fallacy.

The most common fallacious argument is that current climate change must be natural because climate has changed naturally in the past. This myth commits the logical fallacy of jumping to conclusions. It's like finding a dead body with a knife sticking out of its back, and arguing that the person must have died of natural causes because humans have died of natural causes in the past. The premise does not lead to the conclusion.

3. Impossible expectations

While many lines of evidence inform our understanding of climate change, another source of understanding are climate models. These are computer simulations built from the fundamental laws of physics, and they have made many accurate predictions since the 1970s. Climate models have successfully predicted the loss of Arctic sea ice, sea level rise and the geographic pattern of global warming. However, one technique used to cast doubt on climate models is the tactic of impossible expectations.

Some people argue that climate models are unreliable if they don't make perfect short-term predictions. However, a number of unpredictable influences such as ocean and solar cycles have short-term influences on climate. Over the long term, these effects average out, which is why climate models do so well at long-term predictions.

4. Cherry-picking

Signs of global warming have been observed all over our planet. Ice sheets in Greenland and Antarctica are losing hundreds of billions of tons of ice every year. Global sea level is rising. Thousands of species are migrating toward cooler regions in response to warming. The ocean is building up four atomic bombs worth of heat every second. One way to avoid this overwhelming body of evidence is through the technique of cherry-picking.

For example, a persistent myth is that global warming stopped in recent decades. This is done by focusing on one slice of our climate system -- the surface temperature record. Further, it relies on cherry-picking short time periods. This ignores the long-term trend and more importantly, ignores the many warming indicators telling us that our planet continues to build up heat.

5. Conspiracy theory

The global surface temperature record is constructed by teams across the world, each compiling their own independent record. These different efforts, each using their own methods, paint a consistent picture of global warming. Climate science deniers reject this coherent evidence with conspiracy theories.

The thousands of scientists across the world who develop these temperature records are regularly accused of faking their data to inflate the global warming trend. Of course, critics produce no evidence for a global conspiracy. In fact, a number of investigations into the scientists' methodology has concluded that they conducted their research with robust integrity. How do the conspiracy theorists respond to each exoneration? By expanding their conspiracy theory to include the investigators!

The link between conspiratorial thinking and science denial has serious and practical consequences. Conspiracy theorists are immune to scientific evidence, as any evidence conflicting with their beliefs is considered part of a conspiracy. The implication is that the most effective approach is not changing the mind of the unchangeable. Rather a more fruitful approach is communicating the realities of climate change to the large, undecided majority who are open to scientific evidence. A crucial part of the puzzle is explaining the techniques of science denial. This has the powerful effect of inoculating people against the misinformation of climate science deniers.