Following climate news can mean taking note of a regular stream of indicators: when carbon dioxide levels pass various thresholds, record temperatures, record low levels of Arctic sea ice. But does noting such milestones keep the public engaged, or does it just raise anxiety levels or fade into a sea of data? Climate scientists differ on the answer to that question. Most agree that certain indicators are important to keep an eye on and also that it's key to put them in a meaningful context. “The challenge with climate change is that it’s a slow-moving crisis,” says Katharine Hayhoe, director of the Climate Science Center at Texas Tech University. Anytime she talks to the public, she not only includes facts and figures but also shares two central ideas: how climate change is already affecting people in the places they live and what solutions are being implemented. “The two biggest myths are, it doesn’t matter to me, and there’s nothing we can do to fix it,” says Dr. Hayhoe. “This is what I talk about almost every single time.”

Readers who follow climate news might have noticed last week that scientists at the National Oceanic and Atmospheric Administration announced that the planet just had its 400th consecutive month with above average temperatures – yet another record set in a steady stream of similar ones.

Earlier this month, there was a brief flurry of stories noting that, in April, atmospheric carbon dioxide concentration levels passed 410 parts per million averaged over the whole month. A year earlier, readings had first crossed 410 ppm. They breached 400 ppm in 2013. Other milestones also regularly make news – from record-low sea ice in the Arctic to record-high global temperatures.

To climate scientists, each milestone represents an opportunity to help the public visualize the changes that the Earth is experiencing, and to keep attention focused on the issue. But for average citizens, they can start to feel redundant or overwhelming. It can be difficult to discern which indicators are important to pay attention to, or just what they mean.

“I’ve long thought that we don’t serve ourselves well by holding these things [like the 410 ppm threshold] up. It’s sort of like us drawing a line in the sand, and then people step over it. So you step back and draw another line in the sand. After a while they don’t respect the line anymore,” says James White, a geology professor at the University of Colorado in Boulder. “But how do you get people to pay attention?... This to me is the fundamental question.”

Part of the difficulty, say Professor White and others, is the lack of general understanding for how warming works, and on what time scale: The amount of carbon dioxide in the atmosphere rises much quicker than the effects that will eventually be associated with it.

“The challenge with climate change is that it’s a slow-moving crisis,” says Katharine Hayhoe, director of the Climate Science Center at Texas Tech University in Lubbock. To keep it at the top of people’s consciousness frequently means needing to take note of such milestones, she says. “But at the same time, it does give the impression – people said it would be a disaster if we passed 400 ppm, and we passed 410, and the world hasn’t ended. It creates this false sense that it’s okay.”

Dr. Hayhoe likes to use a paleoclimate perspective to help people understand: records we have from the last time that carbon dioxide levels were as high as they are now. The most recent era with atmospheric concentrations of about 400 ppm was the Mid-Pliocene, some 3 million years ago – when sea levels were about 50-80 feet higher.

White often uses analogies like a pot of water on the stove: After turning up the temperature, it takes a while for the water to fully heat.

But better education and explanations can’t overcome all the hurdles to getting people’s attention, says Hayhoe. “It’s also part of our psychology,” she says. “We as humans are built to look at and respond to the short term.”

That’s why, anytime she talks to the public, she not only includes the facts, figures, and indicators, but also two central ideas: how climate change is affecting people in the places they live, already, and what attractive solutions – particularly ones that are also good economically – are already being implemented.

“The two biggest myths are, it doesn’t matter to me, and there’s nothing we can do to fix it,” says Hayhoe. “This is what I talk about almost every single time.”

Adrees Latif/Reuters On Tangier Island, a speck of grassland in Maryland's Chesapeake Bay, climate activists are struggling to get residents to pay attention to rising seas, which some scientists estimate could ultimately render the island uninhabitable.

Context matters

Other scientists agree that indicators like carbon dioxide levels or global temperature are most useful when they’re put in the right context.

“A random factoid that suggests the world is going to hell in a handbasket, or that it’s going there even faster than we thought, is likely to raise some people’s anxiety levels, but not likely to help them think about what options they have for doing something about it,” says Edward Maibach, director of George Mason University’s Center for Climate Change Communication. He likes to think about such numbers as metrics, rather than milestones, and put them in a context that helps people see solutions.

An indicator like carbon dioxide concentrations can be useful to watch, says Professor Maibach, since it’s one way of understanding that “we’ve left the safety zone, and now are decidedly in the red zone.” But what makes it meaningful is “if we tie that to the actions we can collectively take to stop the needle moving upward.”

At the same time, Maibach notes that it’s not as though most people are being deluged with more information about climate change than they can process. “Members of the public tell us in response to surveys that they don’t talk about it, and they don’t hear friends and family and coworkers talk about it,” he says. “The average American sees about one story per month on climate change.”

And noting milestones we keep passing, like the carbon dioxide levels, can be a useful reminder “that projections from the past really are coming true,” says Richard Alley, a geologist at Pennsylvania State University, writing in an email. “As we pass milestones of, say, CO2 concentration, we are seeing the warming that was projected for CO2 concentration, accurately and reliably,” he explains.

Hayhoe says she likes to point to Arctic sea ice as an indicator because of how visual it is – people can see, in photos, large areas disappearing. Carbon dioxide, by contrast, is invisible, and not well understood by most non-scientists.

White, at the University of Colorado, also watches Arctic sea ice, both because it’s easy to visualize, and because of how drastically it’s likely to shift weather and climate systems, as reflective ice gets exchanged for absorbent blue ocean.

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Melissa Kenney, an environmental decision scientist at the University of Maryland, says she generally cites five primary indicators people should keep an eye on to get “the pulse of the planet:” global temperature, carbon dioxide levels, global sea level rise, Arctic sea ice, and ice sheets and glaciers. But sounding the alarm does little good if it isn't accompanied by proposed actions, she says.

“Unless we’re coupling these indicators with opportunities for change, then some of the message is lost,” says Professor Kenney. “Part of what we see with these indicators is the future we’re committing our children to…. That’s our moral imperative: to make the hard choices that our parents didn’t get around to making, so our children don’t have to experience a future that’s even more intense and extreme and difficult to manage than what we’ve set up.”