As governments around the world move closer to taking much-needed action on the climate, it's no surprise that those who don't want to see action have stepped up efforts to discredit the science behind global warming.  Sometimes the group of fossil fuel-friendly media pundits, bloggers, and even industry-paid scientists who try to cast doubt on global warming are referred to as "global warming skeptics."  In this post however, I use the term "denialist" instead of "skeptic" because, in my opinion, it is much more accurate.  Skepticism is an essential part of the scientific process, and real skeptics will weigh all the evidence objectively.  Most global warming deniers are not true skeptics at all.  They are selective in what evidence they look at (see the first and fourth question and answer below), misrepresent or misunderstand actual science (second question), engage in coordinated efforts to confuse the public in order to derail climate policy (third question), and ignore statistical data showing many of their claims are unfounded (last question).  It's important to understand the truth behind denialist tactics, and it's very natural that GreenAnswers member have questions about the reality of denialist claims.  In this post, I've compiled five questions which illustrate how and why global warming denialists have it so very wrong.

Why do people think cold weather disproves global warming?

This question from Edengilbert is a great one to start with, because probably the single most common argument you will hear from global warming denialists is that cold weather in winter "proves" global warming can't be real.  As seanm points out in an answer to this question, denialists using this argument overlook the fact that weather and climate are two different things, and that cold weather during a given month or year doesn't mean the overall climate of the Earth isn't getting warmer.  In fact, NASA studies revealed early this year that 2000-2009 comprised the warmest decade on record and that 2009 was the second warmest year since records began, with only 2005 coming in warmer.  Meanwhile, denialists are selective in the weather they draw attention to, talking on and on about cold weather in the eastern United States while ignoring the fact that this winter in the Pacific Northwest has been so warm extra snow has had to be trucked into Vancouver, British Columbia to make the Winter Olympics possible.  Unfortunately global warming denialists are likely to continue using every snowfall and blizzard as "proof" that global warming isn't real, but it's important to understand why such arguments are flawed. 

Why do climate change skeptics claim that the theory of global warming violates the second law of thermodynamics?

The answer to this question from seanm illustrates just how careful you must be when evaluating denialist claims that at first glance sound "scientific."  If you read a lot of online debates about global warming, you're likely to run into arguments that the concept of global warming is contrary to the second law of thermodynamics which states (among other things) that while heat will naturally dissipate from a warm object or body to a colder body, it will never do the opposite.  In other words, heat will never move spontaneously from a cool body to a warmer one.  According to denialists, a paper by German physicist Gerhard Gerlich is supposed to have shown global warming cannot be real because it would mean heat energy trapped by greenhouse gases in the atmosphere would have to be radiated in the direction of the Earth, which is warmer than the outer atmosphere.  In other words, the argument goes, global warming would require heat to be transferred from the cold outer atmosphere to the warmer surface of the Earth, violating the second law of thermodynamics.  This argument may sound convincing at first, but there are important problems with it.

First, if this argument were correct, then the second law of thermodynamics wouldn't just disprove global warming - it would mean no heat energy from the sun could reach the comparatively warm Earth, which obviously isn't true.  Indeed, in this case denialists fundamentally misunderstand the second law of thermodynamics, which states that heat will never move from a colder to a warmer body unless some outside force causes it to do so.  When heat is reflected off the Earth's surface and encounters greenhouse gases in the atmosphere, it bounces off the gas molecules in random directions - some of it out into space, and some back toward Earth.  In short, the theory of global warming makes no claim that heat spontaneously shifts from a cold body to a warmer body.  Rather, heat photons that would otherwise have all reflected back into space are propelled in random directions when they bounce off of greenhouse gases, roughly half of them heading back toward the Earth and making the planet warmer.  The second law of thermodynamics is never violated.  And what about the scientist supposed to have written that paper giving the denialists their backing?  It turns out Gerhard Gerlich is an industry ally who has also tried to discredit the dangers of pesticides and the negative health effects of smoking, and whose industry-biased arguments have been discredited many times by other scientists.

What do you think is the significance of "climate-gate"?

In late 2009 a group of global warming denialists broke into a lab belonging to the Climate Research Unit at the University of East Anglia, and gained illegal access to about 1,000 emails between climate scientists, some of which are supposed to cast doubt on the reality of global warming.  However as jneust1 points out in an answer to this question from Sierraaa, the truth is statements in the emails have been taken out of context by the media, and don't actually discredit the overwhelming evidence for global warming in any way.  It appears that the break-in incident, sometimes referred to as "Climate Gate," was a carefully orchestrated attempt by denialists to cast doubt on global warming science right before the Copenhagen climate negotiations in December.  The hacked emails were leaked in November of 2009, but the hackers waited over a month to release them, apparently seeking to undermine the integrity of the Copenhagen talks.  Unsurprisingly, denialist websites and news services like Fox News immediately picked up on claims that the emails discredit global warming.  But if you listen to what actual scientists are saying, the vast majority of climate researchers agree nothing in the "Climate Gate" emails disproves global warming or shows scientists intentionally manipulating data.

Should the UN be taken out of climate change debates?

This question from Jonathonlarson gets at recent efforts on the part of denialists to discredit the authority of the United Nations on climate issues.  After the "Climate Gate" debacle, many denialists latched onto findings that a UN statement about the rate at which glaciers in the Himalayas are retreating appears to have predicted an erroneously fast disappearance of glaciers.  It's true that a mistake on the part of UN researchers does seem to have caused an error in a 2007 report.  However, denialists are wrong again when they claim this discredits UN climate research.  While the mistake is unfortunate, the UN's Intergovernmental Panel on Climate Change is responsible for processing so much data that human error is bound to lead to occasional errors.  This one does not change the fact that the Earth is warming, and that glaciers around the world are retreating.  In fact, while in this case the UN overestimated the impact of global warming on Himalayan glaciers, the much more common trend has been for new studies to show the effects of global warming are being felt much faster than the UN predicted would happen.  But are findings that sea levels are rising faster than expected likely to be acknowledged by denialists?  Probably not.

Is global cooling as much of a risk as global warming?

With this question, guest hints at the recent media trend in claims that "global cooling" may be as much a concern as global warming - the implication being that if the world is getting cooler then regulating heat-trapping gases is unwise.  Pro-industry networks like Fox News have reported widely on claims about global cooling, giving the impression that there's real scientific doubt as to whether the planet is getting warmer.  Yet while year-to-year global temperatures are bound to fluctuate to a certain extent, there is no reliable basis for arguments that the climate is getting cooler overall.  In fact, trends in global temperatures clearly signal the opposite is true.  Unlike Fox News, Associated Press did the legwork to test whether claims about global cooling were based on hard evidence.  In an ingenious piece of objective testing, AP presented four independent statisticians with sets of yearly temperature data but did not tell the statisticians the numbers represented global temperatures.  The statisticians were simply asked to test the numbers for downward trends, and the fact that they didn't know what the numbers represented eliminated the possibility of bias toward a certain outcome.  The statisticians found no cooling trend at all, indicating claims about global cooling are unfounded.

Photo credits: Kathmandu, Nepal, Himalayas, Everest, Snow Storm: Road Being East Whiteland Township, PA