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, friends and other acquaintances get together to socialize, that recipe is sometimes dusted off anyway. And whether it's your uncle disrupting a dinner conversation or co-workers co-opting a birthday lunch, no one wants squabbling to overshadow the festivities and food.

Still, not all taboo topics are the same. Fuzzier issues like politics and religion may be sensitive, considering they're largely matters of opinion and faith. But climate science is a little different, due to the "science" part. It's one thing to bite your tongue while a relative rants about tax codes or ancient texts, but what if the conversation somehow turns to sea ice or glacier loss? Is it worth risking a debate to set the record straight?

In many cases, probably not. It's not like your relative is addressing the United Nations, and you might come off as uptight and self-righteous for trying to squelch dissent. If your uncle had two glasses of wine and wants to grumble, it might be wiser to give him a little space. 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 events or social 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.

While computer models help us anticipate how climate change will unfold in the future, we already have an abundance of evidence that climate change is already happening today. (Photo: NASA [public domain]/Flickr)

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 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 keeping this guide accessible 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.

"The climate is changing because of the sun, not humans."

The sun does hold significant sway over Earth's climate, of course, but our star alone can't explain what's happening now. Earth's tilt and orbit around the sun vary in predictable cycles, and while these variations do nudge the planet in and out of ice ages, that happens over tens of thousands of years. Modern warming, on the other hand, has exploded in just 150 years, mostly in the last few decades.

Plus, as NASA points out, if the sun were responsible for the current trend, we'd expect to see warming across all layers of the atmosphere, from the surface up to the stratosphere. Instead, Earth is warming closer to the surface while the stratosphere is cooling off. In fact, solar irradiance has actually decreased slightly since a peak in the 1950s, as you can see in the NASA graph below. All of this is consistent with the scientific consensus, NASA explains: The current warming is caused by a buildup of heat-trapping gases near the surface, not by the sun getting "hotter."

This graph shows global surface temperatures changes (red) and solar energy reaching the Earth in watts per square meter (yellow) since 1880. (Photo: climate.nasa.gov)

"Global temperatures stopped rising in 1998."

This once-common argument has lost a lot of steam lately, especially since the 10 hottest years on record have now all occurred since 1998, and the five hottest years on record have all occurred since 2015. But it also wasn't 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 global temperature anomalies from 1880 to 2020, based on their divergence from the 1951-1980 average:

This graph shows the global average temperature anomaly (diverging from the 1951-1980 baseline average) since 1880. (Photo: NASA/GISS/GISTEMP)

This graph shows the global average temperature anomaly (diverging from the 1951-1980 baseline average) since 1880. (Image: NASA/GISS/GISTEMP)

And to look at that concept another way, here's a video from NASA that shows global temperature anomalies from 1880 to 2017:

"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 more quickly than in the past, potentially outpacing some species' ability to adapt.

Levels of carbon dioxide in Earth's atmosphere have skyrocketed in recent history. (Photo: NASA)

Levels of carbon dioxide in Earth's atmosphere have skyrocketed in recent history. (Image: NASA)

"Glaciers are actually growing."

There are about 160,000 glaciers on Earth, and since scientists can't monitor all of them, 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 a wild rate. As glaciologist Bruce Molnia told MNN, 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.

Clouds undulate around Hawaii's Mauna Loa Observatory, where scientists keep track of CO2 levels in Earth's atmosphere. (Photo: LCDR Eric Johnson [CC BY 2.0]/U.S. National Oceanic and Atmospheric Administration/Flickr)

"There isn't enough carbon dioxide in the atmosphere to make a difference."

Carbon dioxide does only constitute a tiny fraction of all the gases in our atmosphere, but along with methane and other greenhouse gases, it has an outsized effect on the climate. Humans have increased the abundance of CO2 in the atmosphere by about 45% since the Industrial Revolution, according to NASA, and aside from directly trapping heat on its own, that CO2 also has ripple effects. The largest greenhouse gas by volume is water vapor, for example, and its concentration in the atmosphere varies by temperature, with warmer air favoring higher humidity. So, as our CO2 emissions accumulate overhead, their warming effect allows the air to hold more water vapor, NASA explains, "further heating our planet in a vicious cycle."

"Carbon dioxide is a beneficial gas."

This statement is true, but the dose makes the poison. Plants need carbon dioxide to survive, and since we and most other animals rely on plants, it obviously would be foolish to suggest CO2 is inherently bad. But in addition to sustaining plant life, CO2 is also known to be a potent greenhouse gas, trapping solar heat near the planet's surface and lingering in the atmosphere for centuries. As the NASA graph above illustrates, the atmosphere now contains more CO2 — and is experiencing faster growth in CO2 levels — than it ever has in human history.

Hurricane Dorian demolished these buildings as it went through Marsh Harbour on Great Abaco Island in the Bahamas. (Photo: Scott Olsen/Getty Images)

"Global warming is good for humans."

CO2 does boost plant growth, and warmer weather can initially benefit crops in northern regions. But this view ignores vast, long-term dangers in favor of scattered, short-term benefits. Climate change promotes extreme weather — including longer dry spells like California's droughts, and bigger storms like Superstorm Sandy — that can kill people, destroy property and decimate crops. 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 and stronger hurricanes; the loss of freshwater due to melting glaciers; and increased conflict due to drought, floods and famine.

For a full list of responses to these and other climate claims, check out this 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.

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 fracas with your family.

3. Cite your sources.

No one expects you to bring a bibliography, but it would help if you could rattle off a few reputable sources. 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 feeds it. NOAA, NASA and the EPA are good places to start, as is the U.N. Intergovernmental Panel on Climate Change. Be respectful of your uncle's sources, too, but if he brings up "Climategate" or one of its spin-off scandals, feel free to point out they've been debunked.

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 and friends are often a captive audience at meals and other social events, so don't bore them with endless bickering. Even if your uncle wants to keep debating solar flares and sea levels, 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 deal with a climate-change denier, and in whatever context, try to keep things civil and substantive as much as possible. That might mean quietly tolerating someone's ignorance in some situations, or politely correcting outlandish claims in another. It won't work all the time, but if you can find ways to explain global warming without losing your cool, you could provide a valuable service for your social climate as well as that of your planet.