The “dominant story of the next century” will be one of either gloom or redemption, says Steven Hamburg, depending on how humanity chooses to address climate change. To date, Earth’s inhabitants have not meaningfully acknowledged this choice. Yet Hamburg retains a streak of optimism, based on his belief that bringing the impact of climate change home to individuals may stimulate a constructive response.

First Hamburg sketches the dire facts: the planet is headed toward at least a 2 degree Celsius increase in temperature in coming decades, with consequences likely to include shifts in crop production, coral reef decline, and rising sea levels that threaten delta populations with devastating storm surges. From Hamburg’s perspective, there’s no serious argument that humans are major drivers of this rapid change, which is already negatively affecting many regions of the world. While affluent societies may discuss adaptation, it’s already clear that “the losers are those people living on a dollar a day, with no capital.” So “the question for each of us is how much change is too much change? … How much can we tolerate?”

Hamburg’s first climate change paper in 1988, which focused on a subject he knows intimately, the ecology of New Hampshire’s White Mountains, was met with “total silence.” He worries that scientists are still conducting climate change research in a kind of void, with most people relatively oblivious to an unfolding cataclysm. “It’s that dissonance that’s a challenge for us as a society,” he says. As a result, he’s working with groups that attempt to communicate how climate change affects the “places we live in and care about.” For instance, in Hamburg’s White Mountain territory, climate change has led to a much shorter winter, and a pattern of winter warming and cooling that has decimated the once dominant red spruce forests, leaving maples to thrive (for the moment).

People everywhere must be persuaded to become “agents of change.” Hamburg recounts how the CEO of Walmart enlisted him to help the corporation become more sustainable, which led to the sale of millions of compact fluorescent bulbs (replacing incandescents), major profits, and massive savings in carbon emissions. Corporations are getting it, believes Hamburg (even Rupert Murdoch’s chains are going green), seeing that “doing the right thing for society” can save money. But these moves must be accompanied by government regulations, in both developed and developing countries, which will require a “conversation…to link impacts in our own worlds and lives, with actions we can take.”