Most people who deny that human activity is warming the planet just dismiss a massive body of scientific evidence as a big hoax.

But there’s a more sophisticated set of climate “skeptics” who make arguments that, at least to the lay ear, sound like they’re grounded in scientific evidence. And because most of us lack the background to evaluate their claims, they can muddy the waters around an issue that’s been settled in the scientific community.

So, as a public service, we gathered eight of the most common of these pseudoscientific arguments and asked some serious climate scientists — all working climatologists who have been widely published — to help us understand what makes these claims so misleading.

1. No, the Earth Hasn’t Stopped Warming Since 1998 (or 1996 or 1997)

This claim was popularized by “Lord” Christopher Monckton, a prominent British climate “skeptic” with no scientific background who presented himself as a member of the House of Lords until the Parliament published a cease and desist order demanding that he stop. His so-called “research” relies on people’s confusion about the difference between weather, which fluctuates all the time, and climate, which speaks to long-term trends. With some careful cherrypicking of data, you get the argument that there’s been “no global warming for 17 years, 3 months.”

Kevin Trenberth Distinguished senior scientist, Climate Analysis Section, National Center for Atmospheric Research

What’s going on? “1998 was the warmest year in the last century,” explains Kevin Trenberth, a distinguished senior scientist in the Climate Analysis Section of the National Center for Atmospheric Research. “There was a big El Niño event in 1997 and 1998, and we have a lot of evidence that there was a lot of heat coming out of the ocean at that time. So that’s the real anomaly — the fact that we had what was perhaps the biggest El Niño event on record.”

“That’s one of the cherrypicking points for deniers — they take the highest value and then compare it” with lower points in the natural temperature fluctuation we know as “weather.” “If you choose the highest value,” says Trenberth, “then the odds are that all the other values are going to be lower — even in the presence of an overall warming climate.”

Here’s what the long-term warming trend looks like, according to both surface and ocean readings:

But the idea that the climate stopped warming at some point goes back even further. In the 1990s, two climatologists, Roy Spencer and Richard Lindzen, published a series of papers hypothesizing that global warming had stopped. Spencer and Lindzen are among the few climate contrarians with real scientific credentials, and have been widely cited by climate skeptics; Spencer has testified at a number of Republican congressional hearings on climate science.

Spencer also dismisses the theory of evolution, and has written: “I view my job a little like a legislator, supported by the taxpayer, to protect the interests of the taxpayer and to minimize the role of government.”

Of course, none of that matters if their science is sound. But according to John Abraham, a professor of thermal and fluid sciences at the University of St. Thomas School of Engineering, who has published over 130 papers in peer-reviewed journals, it isn’t. “It turns out that they made three serious errors in their data,” he explains. “It took years, and it took a lot of time from other scientists to find these errors in their calculations. In fact, they switched a positive sign for a negative sign in one of their equations.”

He adds that while warming has in fact slowed on the earth’s surface, “93 percent of the heat goes into the ocean, and the ocean continues to heat, so people are confusing temperature fluctuations in the atmosphere — the weather — with long-term climate change.”

This graphic shows the change in total heat content on the planet’s surface and in its oceans:

2. No, the IPCC Makes Projections, Not Predictions

In the real world, we have natural climate variability, and then we have human-caused warming,” says Ben Santer, a climate researcher at the Lawrence Livermore National Laboratory who ranked 12th in a 2002 study of the most frequently cited scientists in the field. “And that human-caused warming is embedded in the rich, day-to-day, month-to-month, year-to-year and decade-to-decade noise of natural climate variability.”

Ben Santer Climate researcher, Lawrence Livermore National Laboratory

Santer was explaining the misleading nature of the claim that because the earth hasn’t warmed as quickly as some previous projections from the Intergovernmental Panel on Climate Change (IPCC) suggested it would, the science is somehow suspect.

“Lord” Monckton and other skeptics make much of the fact that the IPCC’s first model projected that the planet would warm at a rate of 3.5 degrees Celsius, when real-world readings since then have shown a warming rate of 1.4 degrees per century.

According to Santer, “The inherent fallacy here is that they’re looking at very short-term changes over a decade or so and saying that if there’s some mismatch between modeled and observed changes over a short period of time, then that falsifies all climate models, and all of their projections of future climate change — but it does no such thing.

“What we do in our line of work is we beat down that short term noise of natural climate variability by looking at changes over long sweeps of time. This claim is classic cherrypicking — it’s treating IPCC results from previous assessments as predictions rather than projections, and exploiting short-term climate noise to argue that there’s some fundamental mismatch between the models and observations. If that were right, you’d see evidence of such a mismatch over long sweeps of time, but we don’t.”

John Abraham adds that “the atmosphere heated faster than the projections from about 1990 to 2000, and then they rose slower from 2000 to the present. And now, with a new El Niño forming, we’re probably going to see a new record and erase that slower trend.”

3. Yes, the Temperature Readings Are Reliable

Andrew Dessler Professor of atmospheric sciences, Texas A&M University

“The thing to remember here is that scientists aren’t idiots,” says Andrew Dessler, a professor of atmospheric sciences at Texas A&M University and winner of this year’s Louis J. Battan Author’s Award from the American Meteorological Society.

Dessler was responding to a study conducted by Anthony Watts, a former TV weatherman and prominent climate denier, for the Heartland Institute, which has received funding from the Koch brothers and ExxonMobil.

In 2009, Watts claimed that 90 percent of the stations used to monitor the earth’s surface temperature were positioned in places where they were prone to artificially inflated readings — near heat sources, for example.

“This was a big issue maybe four or five years ago,” says Dessler. “In fact, this was the issue the skeptics were touting. But if you look at the peer-reviewed literature, this was stuff that was answered years ago.

“It is true there are issues [with some surface monitoring stations], but you can make adjustments for them. For example, you can look at a station in a city, and say, ‘Okay, maybe there’s an urban effect,’ and then you compare the trend with a rural station nearby.” What matters most is the trend of rising temperatures measured at many different locations.

More to the point, says Dessler, “the surface temperature record is only one of eight or ten different data sets that we look at — and the others agree very well with the surface temperature record.” Scientists have compiled independent temperature data using weather balloons, satellite measurements and sea and ocean readings, and they all show the same thing: a warming planet.

4. Yes, There Is a Scientific Consensus

The most important thing to understand about the scientific consensus that human activities are causing the earth to warm is that it isn’t a result of peer pressure or someone policing scientists’ opinions. It results from the scientific method.

John Abraham Professor of thermal and fluid sciences, University of St. Thomas School of Engineering

“Scientists are very interested in theories that other factors may be causing climate change,” says John Abraham. “The contrarians put forward ideas and the consensus scientists investigate them honestly and find that they don’t withstand scientific scrutiny. This happens all the time. That’s how science works. In fact, showing that these guys are wrong makes the science better.”

A scientific consensus emerges when the weight of evidence for a proposition becomes so great that serious researchers stop arguing about it among themselves. They then move on to study and debate other questions. There’s quite a bit of scientific debate about lots of different aspects of climate change, but the question of whether humans are causing the planet to warm isn’t one of them.

There have been three studies, using different methodologies, that have shown that almost all working climate scientists — 97 percent — accept the consensus view.

But what if those three percent who reportedly reject the consensus are like Galileo, who challenged the 16th century view that the sun revolved around the Earth? John Abraham and five of his colleagues published a study earlier this year which found that studies authored by climate contrarians “were often found to be unsubstantiated by the data,” resulting in “criticisms, corrections, and in some cases, resignation of editors.” They add: “the same fate has not befallen the prominent consensus studies.”

But that hasn’t prevented climate deniers from compiling long lists of people they claim to be dissenting climatologists. The most prominent of these was the Oregon Petition, which was organized by a chemist named Art Robinson, founder of a group called the Oregon Institute of Science and Medicine (OISM), which also markets a home-schooling kit for “parents concerned about socialism in the public schools.”

The petition was supposedly signed by “31,000 American scientists” who opposed the consensus “entirely on scientific grounds published in peer reviewed journals.” But in fact, anyone could sign on, and according to Michael Mann, director of Penn State’s Earth System Science Center, the list ultimately included the Spice Girls and several Star Wars characters.

More recently, climate change denier Marc Morano, who in the past has worked for both Rush Limbaugh and Sen. James “Climate Change Is A Hoax” Inhofe (R-OK), compiled a smaller list that he says is proof that the consensus is “falling apart.”

Barry Bickmore, “a geochemistry professor at Brigham Young University, an active Mormon, and an active Republican,” looked at a sample of the names on Morano’s list and found mechanical engineers, a biochemist and a metallurgist working for US Magnesium, but no working climate scientists who had published in peer-reviewed journals.

5. It’s Not the Sun’s Fault

Henrik Svensmark is a physicist and professor at the Danish National Space Institute in Copenhagen. He’s published a number of papers, spanning a decade, arguing that the Earth is warming as a result of solar activity.

He hasn’t been persecuted for these beliefs, nor run out of the scientific community on a rail. Nobody has tried to censor his views. Rather, his theories have been tested by other scientists, repeatedly, and don’t stand up to scrutiny. That’s how the scientific method works.

“There’s no evidence to support Svensmark’s contention,” says Ben Santer of the Lawrence Livermore National Laboratory. “It’s a testable hypothesis, and we routinely look at whether Svensmark’s ‘the sun explains everything’ hypothesis is in accord with available observations. And it isn’t.”

Santer explains that if the sun were warming the planet, we would see heating “throughout the full vertical extent of the atmosphere.” Yet scientists have found that while the lower atmosphere is heating up, the upper atmosphere is actually cooling, and that finding is “fundamentally inconsistent” with the idea that the sun is to blame. But, says Santer, that pattern is exactly what was “predicted by the earliest computer model simulations” of a planet that’s warming due to increased greenhouse gases.

6. Doubling Down With “Global Cooling”

Climate change deniers seized on an op-ed Henrik Svensmark wrote in 2009 for a conservative Danish newspaper claiming that the sun had entered a cooling cycle, and therefore the Earth would begin to cool as well.

“There is no credible data nor any credible scientist who would make this claim,” says John Abrahams. “Perhaps Cliff Clavin from Cheers might say this but not even the few contrarian scientists would agree that this statement is correct.”

Several of the other scientists we spoke to agreed that this claim is simply bizarre.

7. Yes, It’s Been Warm Before

Katharine Hayhoe Director, Climate Science Center, Texas Tech

Katharine Hayhoe, director of the Climate Science Center at Texas Tech, says that on three occasions she came down with food poisoning after eating at a certain chain restaurant. For some reason, she tried the chain again, and once again suffered from the exact same stomach pains the next day. She assumed that she was dealing with another bout of food poisoning, but it didn’t go away. Finally, after two weeks, she discovered that she was actually pregnant — it was morning sickness.

“Just because something happened before for one reason, doesn’t mean that when it happens again it’s for the same reason,” says Hayhoe in response to a claim, popularized by “Lord” Monckton, that the fastest warming ever recorded occurred in central England in the 17th century. This, says Monckton, was before the industrial revolution began, so “it cannot have been our fault.”

Anthony Leiserowitz: Making People Care About Climate Change

“Our planet is running a fever,” says Hayhoe, “and I can think of six or seven reasons why it could be running hot. As a scientist, you don’t just jump to conclusions. You do the tests. You say, ‘OK, could it be a natural cycle this time? Could it be the sun? Could it be volcanoes? Could it be orbital cycles and ice ages?’ We run those tests and we see if it could be any of those things that caused the climate to change naturally in the past. And in this case, we’ve run those tests and the answer to all those questions is, ‘no.’ In fact, if our temperature were controlled by natural causes right now, we’d be getting cooler, not warmer.”

Hayhoe also notes Monckton’s reliance on temperatures in Central England during odd ranges of dates, like 1663-1762. “It’s cherry-picking in both space and time,” she says. “If you’re going to look at global climate change, you have to look at global temperatures. When it’s hot in one place, it’s cold in another. And when you see weird dates, you should be suspicious — there has to be a reason why someone chose those odd dates. Climate scientists tend to use nice round numbers like 1800 or 1900.”

8. No, Antarctic Ice Isn’t Increasing

The claim that Antarctic ice is increasing rather than melting is an interesting one given the two major studies released this week which found that six large West Antarctic glaciers are in an irreversible state of decline.

Kevin Trenberth of the National Center for Atmospheric Research explains the importance of distinguishing between sea ice and land ice. Ninety-eight percent of Antarctica’s land mass is covered by ice that accumulated over thousands of years. This ice is melting at an alarming rate.

Sea ice, on the other hand, builds up in the winter and melts almost entirely in the summer. The difference between the two is crucial — melting land ice increases ocean levels significantly, while sea ice melt has a lesser effect.

Trenberth says that the claim is based on the spread of sea ice, not overall ice volume. “This is a very important distinction because sea ice gets blown around by the winds, and around Antarctica there are very strong winds,” he says. “And we actually know why the sea ice changes from year to year — we have solid evidence. When there are southerly winds, winds blowing away from the continent, then the ice spreads out and almost creates an ice factory because it opens up little gaps between the ice and then more ice forms in the gaps. That sea ice is often very thin, and while it can spread a long way, it doesn’t amount to much in terms of volume.”

The Antarctic winds are changing, sea ice is spreading out, and scientists have several theories to explain why. But the important thing to understand is that a number of studies, using different methods to approach the question, have all concluded that we’re losing massive amounts of land ice, and that’s what’s driving the rise in sea levels.

And 168 more…

These are only some of the most common pseudoscientific climate arguments. The Skeptical Science website provides easy-to-understand scientific rebuttals to these and 168 others.

A correction was made to this post.