As the event progressed, however, "it was really clear that we were not going to achieve what we’d hoped," she said.

What she and her colleagues had hoped for was a deal to limit global temperature rise to 1.5 degrees Celsius this century and a binding mechanism to enforce that. What they got was the Paris Agreement, which aims to keep global temperature rise to "well below 2 degrees Celsius" — and which countries have signed on to through voluntary pledges.

Instead of celebrating in the streets, she found herself curled up in her hostel bed, crying.

The depression that struck Jornsay-Silverberg, 34, in 2015 still comes and goes today. She worries about ecosystems, native people and their habitats, the Amazon. She is also grieving a vision of her future that may no longer become a reality.

"People like myself are deciding whether [we] even want to have children," she said. When she was younger, she always assumed that she would.

The Rise of Eco-Anxiety

Environmental activists like Jornsay-Silverberg are not the only ones feeling overwhelmed with despair as the climate changes. While "eco-anxiety" is most commonly used to describe these feelings, therapists and others have bandied about different labels, too: climate anxiety, climate despair, eco-despair and eco-grief.

The American Psychological Association even published a guide for therapists to help them assist their patients. In it, they wrote, "the psychological responses to climate change, such as conflict avoidance, fatalism, fear, helplessness and resignation are growing. These responses are keeping us, and our nation, from properly addressing the core causes of and solutions for our changing climate, and from building and supporting psychological resiliency."

Robin Cooper, of San Francisco, is one of the founders of the Climate Psychiatry Alliance, a group of psychiatrists working to highlight how climate change impacts mental health, and how to help those affected.

She said she and her colleagues are seeing more patients with "tension, anxiety, worry, depression" about the climate.

In cases like this, one of the first things Cooper said she does is acknowledge the realistic nature of a patient's concerns. Unlike an irrational fear, eco-anxiety is a healthy response to a serious risk, she said.

"We are biologically wired to respond with anxiety to alert us to respond to real threats," she said.

Despair’s Antidote

So if the negative aspects of climate change won't be going away, how do we “treat” eco-anxiety?

Experts seem to agree on a three-part strategy:

Come together in community. "Find allies who understand what [you're] feeling… and get together with them," said Craig Chalquist, a psychologist and professor at the California Institute of Integral Studies. He said it can even be something informal. Often, people struggle with these feelings in isolation, since bringing up climate change is taboo in many social situations. Process your feelings. This can happen through talking, grief groups and spending time in nature. Really? Just talk about such a huge issue? Chalquist said yes, adding that people with eco-anxiety then "quickly move from that phase into, 'What can I do?'" Identify what specific problems speak to you, and get to work. Interested in oceans? Food systems? Reforestation? Chalquist said because all these aspects of the environment are connected, "to work on one is actually to bring some healing to the whole thing."

Sarah Jornsay-Silverberg said these steps have been crucial for her mental health.