Man-made climate change is making our climate warmer, causing the rise of sea level, and diminishing Arctic sea ice extent over time. These things are happening and human activity, primarily the result of fossil fuel use, has been shown to be the dominant cause. This is unequivocal, as in undeniable and demonstrated by multiple lines of evidence.
So how do we communicate that fact?
As this page has discussed many times, there are lobbyists who spend millions of dollars and terabytes of internet bandwidth to intentional misrepresent the science to the public. That is their job as fossil fuel, libertarian, and other corporate lobbyists; all to protect profits of industries and corporations that benefit from outsourcing the costs of their products to the public.
I've spoken already about how climate scientists can communicate with the public. Strategies include speaking at local libraries, churches, and schools; teaching classes at community colleges or online; making yourself available to the media, and even doing TV shows. While these are all good ideas, there are several things that all scientists must keep in mind when talking to the public.
1) Lose the jargon: I mentioned this in the above linked article but it's important to reiterate it. Anyone who has ever read a medical report knows that every profession has its own language for describing things. This language allows professionals to communicate using words that have precise meanings - to them. To everyone else they are gibberish. No one expects everyone to understand the jargon of anyone outside their profession. So don't talk to the public like you're talking to your fellow scientists at a scientific conference. Doing so makes you look clueless.
2) Make it personal: Gee, reduced albedo enhances thermal absorption...; say what? Albedo? Is like libido? Needless to say, this falls under the "lose the jargon" item above. Just say as less white ice means the darker water absorbs more heat from the sun and makes the remaining ice melt even faster. Then move on to why this matters to the person you're talking to. Explain that their favorite beaches may disappear, or that wine growing areas may shift, or their allergies may get worse. Know your audience and what is important to them, then explain how climate change effects them personally.
3) Have patience: Remember when you just couldn't understand what your PhD advisor was trying to tell you? Now think about what it must be like for people who haven't spent all those years studying in your field. Remind yourself that some of these concepts are pretty intense. Make it clear and take your time. And again, lose the jargon.
4) Don't explain everything: Seriously, dude. There is no reason to get all statistics and math on people. Sure, the devil is in the details, but only for fellow scientists. The public doesn't need to know exactly how many gigatonnes or gigawatts or gigawhatever are involved. Just explain that the massive amounts of CO2 we've added to the atmosphere are warming the climate, which leads to Arctic sea ice extent decreases, increasing sea levels, greater likelihood of more severe droughts, yada, yada, yada. Better yet, tackle one issue at a time, and leave out the math.
5) Don't waste time with trolls: Remember "have patience?" There is one exception - trolls. In pre-internet days trolls were just obnoxious people you could walk away from and keep out of your life; now they walk into your living space via Facebook and other online social networking vehicles. But guess what - you can still block them from your life. Do it. Trolls serve zero useful purpose. Their entire existence is a mission to disrupt, and frankly, it's a disservice to your readers and listeners to let trolls disrupt the right of honest people to learn.
6) Be polite: This can often be hard to do (see #5, Don't waste time with trolls). Descriptive terms like "denier" for someone who denies basic fact are okay (though some would disagree even on this point), but personal attacks allow trolls to whine about how they are being attacked and protect them from having to defend their statements. If you can't be polite, move on.
7) Tell them what they can do: Most people want to do their part, but figuring out what that part is can be daunting. Steer them to some solutions that they, as individuals and as local groups, can do. The USEPA has a nice page that gives some ideas for what to do at home, at the office, on the road, and at school. The David Suzuki Foundation offers 10 ways to stop climate change, and many others have ideas as well.
One way is to actively reach out to your elected officials at the local, state, and/or federal level. Learn about the effects that man-made climate change is having, or will have in the future, on your community. Reach out to your congressional representatives. Insist that rational actions be taken to ensure a future for your children and grandchildren.
No one person should think that they have to "save the world" by themselves, just that they can take one small step. If all of us each take a step, those steps become miles and, eventually, light-years.
Finally, one more:
8) It's already happening: Man-made climate change is here. It's already having impacts on our lives, and will continue to get worse without action. But action is also happening. The global community has begun taking steps to reduce CO2 emissions. The energy industry has begun taking steps to shift from fossil fuels to renewable sources of energy. The public has begun to take steps at the local and state levels - some small, some large. The federal government has begun shifting to renewables. Even corporations have begun to modify their behavior and investments to reduce carbon footprints, which they often find also decreases costs and improves corporate finances.
So all of us need to remind all the rest of us that we're already on our way to solving this problem. All it takes is for each of us to take that step.