For the first Earth Day in 1970, cartoonist Walt Kelly trenchantly captured the core tension of humanity’s relationship to its home world as expressed through environmentalism and climate change: “We have met the enemy and he is us.”

This tagline was incorporated into a poster specifically created for the inaugural Earth Day and featured his main cartoon persona, Pogo.

The tagline, with its use of the strong word “enemy,” was a rephrasing of Commodore Oliver Perry’s declaration during the War of 1812 that “we have met the enemy and they are ours.” Undoubtedly, too, Kelly’s language drew on this particular moment in history, reflecting the deep social and political tensions over the Vietnam War.

In the succinctness of this tagline, Kelly expressed the foundational problem of environmentalism — and the present climate crisis — that looms ever larger over the human present and future: What are we to do about the foundational disruptions to our home world for which we are responsible? Over more than 50 years, each Earth Day has been a reenactment of this question—and of the ever-increasing stakes in addressing it.

Yet how has engagement with this question changed with time?

In 1970, the focus of environmentalism was on smog, trash, and despoiling of land and water resources, by-products of consumer and disposable lifestyles that took off after World War II. Today, primary attention goes to a deeper issue: That such consumption, and how it is sustained, has resulted in ever-increasing release of greenhouse gases into the atmosphere, especially carbon dioxide. This planetary atmospheric warming is pushing major Earth systems into changes not seen in millennia. We are, in short, in a crisis of our own doing.

As one example, ocean circulation, which through planetary-scale currents distributes energy between the cold polar regions and warm equatorial waters, is essential in maintaining temperatures hospitable to human existence. As highlighted in data gathered by NASA, NOAA, and other nations’ satellites, this vital mechanism is in danger of breaking down. As ice cover and glacial sheets melt, they disgorge freshwater into the salty ocean. Freshwater is lighter and does not sink to lower ocean depths at which the cold polar water flows back to the equator.  This seemingly small change in water composition can disrupt this critical means for regulating planetary temperatures.

Such a change, as radical as it would be, would not be isolated. The ocean interacts with the atmosphere, influencing its circulation. That change, coupled with a warming atmosphere, would intensify severe weather events such as heat waves and droughts. This is indicative of how all earth systems, including plant and animal life, are interdependent and work together in shaping climate.

This deepened knowledge of climate change has made clear that Kelly’s “we have met the enemy and he is us” obscures the vast differences between those parts of the world that have been the drivers of the climate predicament and those that have not—but who already are and will bear disproportionately the consequences of a warming world. Though the climate crisis will affect humanity in its entirety, some bear a greater responsibility for its resolution.

Organizing and committing to responsible action to address the crisis is the single, overriding issue of our time—who, how, and with what resources will such action be accomplished to ensure the future of all life on the planet? In climate science, the concept of “tipping points” is used to clarify the stakes of our Earth edging toward an inhospitable state. The change to ocean circulation sketched above is one example. One might apply this concept to the individual and collective response to the climate crisis: Are we at a tipping point in mobilizing the political and social commitment to mitigate the crisis? Or, will conflicts over political values delay action to the detriment of the planet and its peoples?

As part of our new slate of exhibitions, the Museum is devoting greater attention to climate change and the complex of issues connecting science, politics, and a viable human future. As the fundamental issue of our time, we look to bring our visitors into this conversation to share the stakes for them as individuals and for their communities—and to hear their voices. We are collecting objects that convey the scientific and technical dimensions of climate research. And we are collaborating with other Smithsonian museums and research centers to bring forward the social and cultural challenges caused by climate change.