How to discuss climate change with your uncle during the holidays

If your holiday dinner conversation turns into a debate over global warming, here are a few tips for staying cool while standing up for science.

Most people know better than to bring up politics, religion or climatology in polite company. It's a recipe for arguments, or at least for awkwardness.

But when families get together for big holiday meals like Thanksgiving and Christmas, that recipe is often dusted off anyway. And whether it's your nephew demonizing the Tea Party, your niece deifying Tim Tebow, or your aunt and uncle arguing about polar bears, no one wants squabbling to overshadow gobbling at a holiday feast.

Still, not all taboo topics are the same. Fuzzier issues like politics and religion are often sensitive, since they're largely matters of opinion and faith. But climate science is a little different, thanks to the "science" part. It's one thing to bite your tongue while a relative rants about taxes or morality, but what if the conversation turns to coral bleaching or glacier loss? Is it worth risking an argument to set the record straight?

In most cases, probably not. It's not like your relative is addressing the United Nations, and you might just come off as uptight and self-righteous for trying to squelch dissent. If your uncle had two glasses of wine and wants to grumble about Al Gore, you're probably better off letting him. Otherwise, you could just end up convincing him even further that environmentalists want to control his life.

But that's not to say you should never speak up for science at family gatherings. Polite enlightenment is possible; it just requires being knowledgeable and confident without seeming nitpicky or condescending. And even if you can do that, it still depends on your audience, which may have little patience for a science lesson.

If you decide it's worth the risks, though — maybe your uncle can be open-minded, or you know your cousin will back you up — here's a quick guide for explaining climate change without raining on everyone's parade:

1. Don't blow hot air: Whether you're debating your uncle or a stranger, it helps to know what you're talking about. Doing your homework will help ensure you always have a response ready without resorting to hyperbole. Below are a few examples of claims you might hear from a climate-change denier, along with a rebuttal to each (and links to more comprehensive lists). If you want a cheat sheet, consider printing out this guide or loading it on your smartphone for easy reference.

•"There's no evidence of global warming, and computer models are unreliable."
Scientists don't need computer models to tell them global warming is under way. For that, they can look to surface-temperature records, satellite data, ice-sheet borehole analysis, measurements of sea-level rise and sea-ice extent, and observations of permafrost loss and glacier melting. Computer models are helpful for predicting future climate patterns, and they're becoming increasingly accurate, but they're hardly the only evidence we have.

•"Global temperatures stopped rising in 1998."
This argument has lost some steam lately, especially since 2005 and 2010 tied as the hottest years on record. But it was never very convincing to begin with, since it implies that only a linear year-to-year rise indicates a trend. 1998 was hot, but it's considered an outlier because a strong El Niño skewed it even hotter. This graph shows yearly variability of global temperature anomalies (thin line) as well as as the "smoothed" average (bold line) from 1880 to 2010:

•"Glaciers are actually growing."
There are about 160,000 glaciers on Earth, and since scientists can't monitor them all collectively, they study groups of "reference glaciers." According to the World Glacier Monitoring Service, the average reference glacier has lost 12 meters (39 feet) of water-equivalent thickness since 1980. Some glaciers are stable, and a few are even growing, but many that provide key freshwater supplies are melting at an alarming rate. As glaciologist Bruce Molnia told MNN in 2010, warming affects low-elevation glaciers first, since temperatures are cooler in the mountains. "The lower the elevation of origin, the more dire the time period when the glacier will be affected," Molnia said.

•"The climate has changed before, so we can't be blamed for changing it now."
Earth's climate has changed lots of times without human help, but does that really mean humans are incapable of changing it? As Skeptical Science points out, that's "like arguing that humans can't start bushfires because in the past they've happened naturally." When the climate changed eons ago, it was because something made it change — extra sunshine warmed it up, volcanic clouds cooled it down. We know carbon dioxide and other greenhouse gases trap heat in the atmosphere, and we're now releasing those gases at a record pace. And the main problem is that modern-day climate change is happening faster than in the past, potentially outpacing some species' ability to adapt.

•"Global warming is good for humans."
CO2 does help plant growth, and warmer weather can initially boost crops in northern regions. But this view ignores widespread, long-term dangers in favor of scattered, short-term benefits. Climate change encourages extreme weather — including longer droughts in some places and bigger storms in others — that can decimate crops, and it also helps some pests expand their range. Global warming poses too many threats to list here, but they include: the loss of fisheries and marine ecosystems to ocean acidification; the loss of coastal communities to rising seas; the loss of freshwater supplies due to melting glaciers; and increased conflict due to droughts, floods and famine.

For a full list of responses to these and other climate claims, check out this 2009 report by the University of Oregon's Climate Leadership Initiative, this guide for "How to talk to a climate skeptic" by journalist Coby Beck, and this list of arguments and myths by Skeptical Science. A wealth of information about climate change can also be found at NOAA's climate.gov as well as climate.nasa.gov and epa.gov/climatechange.

2. Don't be insulting:
There's no going back from ad hominem attacks. Don't treat your uncle like he's dumb, and don't be rude or condescending. Admit it when you don't know something; give your uncle credit when he's right. This will help your credibility, and maybe even help prevent a holiday fracas with your family.

3. Cite your sources:
No one expects you to bring a bibliography to Thanksgiving but it would help if you could at least rattle off a few reputable sources of your information. That shouldn't be too hard, since most major scientific organizations around the world have reached a consensus that global warming is real and human activity contributes to it. NOAA, NASA and the EPA are good places to start, as is the U.N. Intergovernmental Panel on Climate Change (which, coincidentally, is holding a big climate summit next week in South Africa). Be respectful of your uncle's sources, too, but if he brings up "Climategate," feel free to point out it's been debunked.

(UPDATE: As MNN's Karl Burkart reports, a new campaign dubbed "Hackergate" has just surfaced two years after Climategate. Nothing revelatory has emerged from the newly leaked emails so far, but if your uncle wants to press the issue, just remind him that climate change has been confirmed by far more scientists than the ones who wrote these emails — and they haven't actually been discredited, either.)

4. Don't mix science and politics:
Climate change will never be solved without broad, coordinated political action, but that doesn't mean it needs to start at your dinner table. Opposition to climate science is largely born from deeply entrenched political attitudes about government regulation, so subjects like cap and trade are often even more sensitive than the polar ice caps. Try to keep the conversation light-hearted, or at least civil, and steer it away from politics if you can.

5. Take a break:
Your family is a captive audience during a holiday meal, so don't bore them with endless bickering. Even if your uncle wants to keep debating solar flares and the heat-island effect, spare your relatives and suggest continuing the discussion later, maybe via email so you can both provide links to your sources.

However you decide to handle a climate-change denier at the dinner table, don't forget the reason you're both sitting there. Holiday meals are a celebration of family and friends, and you shouldn't let a scientific debate kill the good vibes. It's a smart strategy to apply elsewhere, too — if you can explain global warming without losing your cool, you might give environmentalists everywhere something to be thankful for.

For a more detailed read on the above: http://www.mnn.com/family/family-activities/blogs/how-to-discuss-climate-change-with-your-uncle-during-the-holidays