For 70 years, UNICEF has been on the front lines of the defense of children’s rights in every region of the world. The organization was founded in 1946, in the aftermath of World War II, and its first projects involved providing food and clothing to child refugees. Since then, it’s battled child disease, famine, female genital mutilation, and child marriage. The United Nations agency for children knows what it is talking about and doesn’t mince its words.

Now, as global leaders descend on Paris for the critical COP21 global climate summit, UNICEF has made it clear what is truly at stake. In a new report titled Unless We Act Now, UNICEF expresses those stakes bluntly: “There may be no greater, growing threat facing the world’s children—and their children—than climate change.” No one has made a stronger case that our children, and future generations of children, belong at the center of the global conversation about the climate crisis and what we must do to combat it.

By combining state-of-the-art demographic data on the world’s child population with scientific projections on the likely impacts of climate change in the decades ahead, UNICEF has created a chilling projection of what’s at stake. It also lays out three clear and urgent reasons why the hazards for children are so high.

The first is that the world’s children live disproportionately in areas on the front lines of climate change’s most dire impacts. There are 2.3 billion children (defined as people under 18) living on Earth and they are most concentrated in the parts of the world most at risk: sub-Saharan Africa with its growing drought crisis, the areas of East Asia in the path of increasing killer storms, and the parts of South Asia most at risk for flooding. In short, climate change’s triple threat has the world’s children squarely in its path.

As drought, floods, and other extreme weather events increase, children suffer the impacts even more deeply than adults. As UNICEF observes, when droughts decimate local food supplies, the nutritional crisis for children is not only of that moment, but impacts their development and health for a lifetime. When flooding invades vulnerable communities, children are the first to be swept to their deaths by raging currents, and they are more vulnerable than adults to communicable disease.

As UNICEF writes, “These pernicious impacts on children are not just theoretical; they have occurred in recent floods around the world. The 2010 floods in Pakistan affected more than 2.8 million children under 5 years of age, many severely. Rates of under-5 mortality were notably higher in flood-affected areas than the national average.”

A second reason why the stakes of the climate crisis are so high for children is the ways in which climate change radically amplifies the already deep inequalities that exist among the world’s children, threatening to wipe out decades of hard-won progress. In its comparison of climate impacts between poor and affluent children, UNICEF lays out a set of stark differences. Children living in poverty are less able to migrate from high-impact areas, less able to buy food as prices rise from scarcity, and less able to secure clean water. Poor children are also more vulnerable to disruptions in the health care system and—girls especially—are more likely to have their education interrupted when crises strike.

“The children and families who are already disadvantaged by poverty—those with the fewest resources for coping—are likely to face some of the most immediate dangers of climate change,” writes UNICEF. “Unaddressed, climate change will harm the poorest and most vulnerable children first, hardest, and longest.”

Finally, when we look at the impact of climate change on the human beings who will be the planet’s children 10 years, 20 years, and 30 years from today, it is clear that the time for action is now. Climate change is very different from a child vaccination program, for example. In 20 years, if the need is clear for an accelerated program to inoculate children once again against polio, we can still create the program at that time. Because the carbon emissions that will drive climate change in 20 years are being locked into the atmosphere today, the only thing that will save future generations of children will be a time machine—an unlikely option.

That being said, I think that moving the focus on climate issues to children is also a reason for political hope. It is akin to something I learned many years ago, when I was working with an amazing leader in Oakland’s African American community who had set up the first drug-treatment programs for pregnant women during the crisis of “crack” cocaine in the 1980s. She told me that the maternal instinct was the one force she saw as powerful enough to compete with that extreme addiction.

If we are fortunate, we will discover that humanity in this critical moment possesses a similar protective instinct toward our children in the midst of the climate crisis and toward the children of the next generation. To do that, we must redefine climate change, not just as an environmental crisis but as the most urgent children’s issue of our time.

UNICEF has given us the information and arguments the climate change movement needs to make that case in a serious way. Now it is up to climate activists to carry that message forward and to use it to build pressure for the action our children need now, and will need even more urgently in the future. The stakes, in Paris and beyond, could not be higher.