海角大神

Readers who follow climate news might have noticed last week that scientists at the National Oceanic and Atmospheric Administration that the planet just had its 400^th consecutive month with above average temperatures 鈥� 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.聽Other milestones also regularly make news 鈥� 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.

鈥淚鈥檝e long thought that we don鈥檛 serve ourselves well by holding these things [like the 410 ppm threshold] up. It鈥檚 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鈥檛 respect the line anymore,鈥� says James White, a geology professor at the University of Colorado in Boulder. 鈥淏ut how do you get people to pay attention?... This to me is the fundamental question.鈥�

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.

鈥淭he challenge with climate change is that it鈥檚 a slow-moving crisis,鈥� says Katharine Hayhoe, director of the Climate Science Center at Texas Tech University in Lubbock. To keep it at the top of people鈥檚 consciousness frequently means needing to take note of such milestones, she says. 鈥淏ut at the same time, it does give the impression 鈥� people said it would be a disaster if we passed 400 ppm, and we passed 410, and the world hasn鈥檛 ended. It creates this false sense that it鈥檚 okay.鈥�

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 鈥� 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鈥檛 overcome all the hurdles to getting people鈥檚 attention, says Hayhoe. 鈥淚t鈥檚 also part of our psychology,鈥� she says. 鈥淲e as humans are built to look at and respond to the short term.鈥�

That鈥檚 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 鈥� particularly ones that are also good economically 鈥� are already being implemented.

鈥淭he two biggest myths are, it doesn鈥檛 matter to me, and there鈥檚 nothing we can do to fix it,鈥� says Hayhoe. 鈥淭his is what I talk about almost every single time.鈥�

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鈥檙e put in the right context.

鈥淎 random factoid that suggests the world is going to hell in a handbasket, or that it鈥檚 going there even faster than we thought, is likely to raise some people鈥檚 anxiety levels, but not likely to help them think about what options they have for doing something about it,鈥� says Edward Maibach, director of George Mason University鈥檚 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鈥檚 one way of understanding that 鈥渨e鈥檝e left the safety zone, and now are decidedly in the red zone.鈥� But what makes it meaningful is 鈥渋f we tie that to the actions we can collectively take to stop the needle moving upward.鈥�

At the same time, Maibach notes that it鈥檚 not as though most people are being deluged with more information about climate change than they can process. 鈥淢embers of the public tell us in response to surveys that they don鈥檛 talk about it, and they don鈥檛 hear friends and family and coworkers talk about it,鈥� he says. 鈥淭he average American sees about one story per month on climate change.鈥�

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

Hayhoe says she likes to point to Arctic sea ice as an indicator because of how visual it is 鈥� 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鈥檚 easy to visualize, and because of how drastically it鈥檚 likely to shift weather and climate systems, as reflective ice gets exchanged for absorbent blue ocean.

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 鈥渢he pulse of the planet:鈥� 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.聽聽

鈥淯nless we鈥檙e coupling these indicators with opportunities for change, then some of the message is lost,鈥� says Professor Kenney. 鈥淧art of what we see with these indicators is the future we鈥檙e committing our children to鈥�. That鈥檚 our moral imperative: to make the hard choices that our parents didn鈥檛 get around to making, so our children don鈥檛 have to experience a future that鈥檚 even more intense and extreme and difficult to manage than what we鈥檝e set up.鈥�