The two words “climate” and “change” are so routinely strung together that just saying them as a pair—“climate change”—seems to somehow obscure the full weight of the phenomenon they describe, to say nothing of its consequences. But in those moments when one pauses to consider the ramifications of human activity on the planet for generations and generations ahead, things can feel beyond bleak. And yet: This past year saw the nations of the world reached their first-ever agreement on an ambitious plan to rein in emissions, perhaps the most significant progress yet made on this issue.

We reached out to some of the leading scholars of climate change, conservation, and ecology, and asked them what, as the Earth begins yet another trip around the sun, is giving them cause for hope and despair. Below are their answers, lightly edited for length and clarity.

Robert Glennon, professor of law and public policy at the University of Arizona

Reason for despair: I despair that we don’t consider water to be scarce or valuable. A century of lax water laws and regulations has spoiled most Americans. We turn on the tap and out comes as much water as we want for less than we pay for cable television or cellphone service. When most Americans think of water, they think of it as similar to air—as infinite and inexhaustible. In reality, it’s both finite and exhaustible.

Because we don’t respect water as remarkable, we use needless quantities for frivolous purposes, such as growing grass in the desert. And because we don’t pay the real cost of water (only the cost of the infrastructure to provide it), we remove the incentive to conserve. Perhaps most important, our innovation economy has encouraged engineers and inventors to create water-saving technologies that extend our supply; but the price of water is so low that few of them have viable business plans.

Reason for hope: We have a suite of options to confront the crisis and prevent it from becoming a catastrophe. These options include conservation, which remains the low-hanging fruit; reuse of treated municipal effluent; and desalination of ocean or brackish water. We can also price water sensibly to encourage conservation, while protecting access to water for persons of modest means. Finally, we can use the power of market forces to encourage a modest reallocation of water from low to higher-value uses. A low single-digit percent reduction in agricultural water consumption would solve the municipal and industrial water-supply problem. Modernization of farm irrigation systems, paid for by cities and industry, would protect the viability of rural communities and secure needed supplies for the urban sector.

None of these options requires a radical change in our behavior, but they will require the moral courage and the political will to act.

Margo Oge, former director of the Office of Transportation and Air Quality of the Environmental Protection Agency

Reason for despair: Climate change is the biggest challenge our planet faces. The science is clear, the risks are real, and the phenomenon’s impact on every part of our planet is increasingly visible. In mid-December, nearly 200 countries met in Paris to secure a historic agreement to reduce the impacts of the global threat. The negotiators for every single country involved have accepted that we need to take immediate and substantive action on this threat. Back at home, however, Congressional Republicans continued their decades of denial. In a symbolic rebuff of global urgency on the issue, both the House and Senate voted to repeal President Obama’s Clean Power Plan. By the time our legislators—a few hundred people—finally accept the overwhelming scientific evidence about the threat, I despair that time will have run out for future generations. I fear that killing, or endlessly delaying, the nation’s serious efforts to mitigate this threat will be catastrophic: rising seas swallowing island nations, floods wiping out towns and villages, unprecedented heat waves and drought destroying crops and lives, and even global instability that provokes wars.

Reason for hope: What gives me optimism is watching our country take a positive role in the Paris international-climate agreements after decades of foot dragging on the issue. When the United States leads, other countries follow. This means that the U.S. efforts to secure strong climate actions in Paris and at home will make a hugely positive impact globally on carbon emissions. The United States has, in fact, long been a leader on environmental technology innovation. In the 1970s, it was American car-emission standards that led to the development of catalytic convertors. These devices were the first to ever clean up the toxic soup coming out of cars’ tailpipes.

The rest of the world followed America. Today you can’t find a car without one.

After we banned leaded gas, Europe and the rest of the world came along. In 2009 we initiated another world-leading effort, regulations that will cut automotive carbon pollution in half as well as double the fuel efficiency of passenger vehicles by 2025. For decades, American environmental efforts have led to innovation, saved lives, and created jobs. As a result of these regulations, our car industry is today undergoing a technological and economic revolution. Our automakers are building the most fuel-efficient vehicle fleet in history and are already ahead on a trajectory to doubling fuel economy by 2025. The world needs the United States to continue and expand its technological leadership in mitigating climate change.

Peter Singer, professor of bioethics at Princeton University

Reason for despair: One thing that brings me close to despair is the fact that, just in the West, we seemed to have turned a corner in regard to meat eating and factory farming—both are now on the decline—the resulting reduction in animal suffering and greenhouse gas emissions is being swamped by the growth in meat eating in China and other parts of Asia. Nevertheless, I don’t despair because the situation is not hopeless. As long as there is hope of change for the better, I’m too busy trying to bring about that change to lose myself in despair.

Reason for hope: More and more people are seeking fulfillment in their lives by turning away from the consumer lifestyle and instead living in accord with their values. The emerging movement known as effective altruism is one outcome of that, and it is having an impact. I’m encouraged by the tremendous progress made over the past 25 years in reducing extreme poverty and improving life expectancy worldwide. Infant mortality, for example, has been cut by more than half since 1990, despite rising population. If we continue to put more resources—our intelligence and our skills, as well as our money—into using reason and evidence to make the world a better place, then I am confident that we can make even more progress over the next 25 years.

Elizabeth Marino, assistant professor of anthropology​ at Oregon State Unviersity

Reason for despair: As an anthropologist working alongside indigenous communities in the United States, it’s hard not to see climate change as another wave of violence inherent in the colonial ideal. Colonized geographies like communities in Alaska, small nation states in the Pacific, and large nations in sub-Saharan Africa all share the heaviest burdens of a rapidly changing climate, all share vulnerabilities to those changes produced by unjust economic and political systems, and all are limited in social and cultural expression by the narrow-mindedness of what is deemed culturally acceptable by the “West.” These burdens are all part of climate injustice.

But even aside from this new form of colonial violence, I despair because, more than any other crisis, climate change needs alternative cultural models for framing problems and non-Western solutions.  Unfortunately, many accept as “natural” merely one set of ideas borne from very particular “Western” worldviews: the necessity of growth; monetary value as determinant of inherent value; the nature/culture dichotomy; competition as the driver of production; technological “fixes” as paramount. I despair when the solutions and rhetoric around climate-change mitigation and climate justice are embedded in these presuppositions; when the world stays narrow.

Reason for hope: The rest of the world is talking back. We see organizers using hashtags such as #pachamama, #indigenouscop21, #AOSIS, and #indigenousenvironmentalnetwork. We have growing innovative collaborations among scientists and Native American leaders and we see strong non-state-based international alliances, political organization, and advocacy by non-Western leaders. It's going to be an interesting century.

Juliet B. Schor, professor of sociology at Boston College​

Reason for despair: Despair? Yes, it is there. Not because I don’t think that eventually we will have a low- or zero-carbon world. We will. But how can one not despair at the certain destruction we’ve already ensured with the warming and chaos that is now built in to the climate system? This month flooding in my husband’s home city of Chennai reached second floors, with more than 1.8 million people displaced. In one 24-hour period there was nearly 11 inches of rainfall. California remains in the grip of a powerful drought. It is 60 degrees in Boston, in  December, in what’s likely the world’s warmest recorded year, a distinction which may be eclipsed 12 months from now. All the while, the politics of hatred are rising, like the sea levels.

Reason for hope: COP21, the UN talks in Paris, ended with a degree of hope that is unprecedented in the world of climate. Despite the absence of a binding agreement or emissions promises that have any hope of avoiding catastrophe, there has been almost delirious optimism, even from many environmental activists. (Not from all, of course. James Hansen and Bill McKibben have been outspoken in their criticisms of the weaknesses of the treaty, and they’re right.)

But I find four major reasons to be hopeful. The first is that China is acting decisively to reduce emissions from coal. The second is that renewable energy is now an economically viable alternative to fossil fuels, and will be even more so if we can eliminate the $450 billion a year in subsidies for the dirty fuels. The third is that the fossil-fuel companies are without doubt on the defensive. From the cancellation of the Keystone XL pipeline to government investigations into Exxon’s cover up of its own climate research, the behavior of this industry is finally on view. True, it is still quite powerful in Congress, but the combination of science, economics, and exposure is sounding the industry’s death knell. As we’ve already seen with coal, I predict that oil and gas won’t survive the mounting pressure to “keep it in the ground.” And that brings me to my fourth reason for hope: the growth of a global grassroots movement for climate justice and ecological sanity. It has taken a long time for us to get here, but it’s now unstoppable.

Robin Bronen, executive director of the Alaska Institute for Justice and a senior research scientist at the Institute of Arctic Biology at the University of Alaska, Fairbanks​

Reason for despair: Living in Alaska, the only Arctic state in the United States, I am witnessing the fast-forward of geologic time. My despair increases as I watch Arctic ecosystems collapse. The recently negotiated Paris Climate Agreement includes aspirational language to limit the global temperature increase to 1.5 degrees Celsius.

But in Alaska, winter temperatures have already increased 3.5 degrees Celsius since 1975. Ice and snow, iconic elements of the land and sea in the Arctic, are disappearing. The winter of 2014-2015 was the lowest snow season on record in Anchorage, Alaska’s largest urban center. Glaciers are losing 75 billion tons of ice annually. Arctic Ocean sea ice has decreased by 36 percent in the last three decades.   

For indigenous communities in Alaska, these changes are life-threatening. Kivalina, Shishmaref, and Newtok, are three of the most imperiled communities. Each has chosen to relocate as a long-term adaptation strategy because sea ice no longer protects their communities from hurricane-force storms that eat the land on which they live. In presentations to U.S. government agencies and Congress, Shishmaref residents plead:

The no action option for Shishmaref is the annihilation of our community …

We are unique, and need to be valued as a national treasure by the people of the United States. We deserve the attention and help of the American people and the federal government ... Shishmaref, we are worth saving.

Due to intense and prolonged advocacy efforts, Interior Secretary Sally Jewell and President Obama traveled to Alaska this past summer. Despite these visits, no community knows when or if it will be able to relocate to higher ground to protect their unique way of life and connection to the land of their ancestors. The gross injustice of their experience adds to my despair because those who have done the least to cause our climate crisis are bearing enormous losses. Their experience also shows that we are completely unprepared to respond to the humanitarian crisis which will be caused by rising seas forcing millions of people from their homes, their heritage, and the places they love.

Reason for hope: Solidarity—the recognition that all of humanity is connected to each other and to the Earth—gives me hope. This understanding that we are one people living on a shared homeland is embedded in the climate-justice movement.

The Arctic, the harbinger of dramatic environmental changes, reminds us of this connection. Decreased Arctic sea ice affects the polar jet stream and contributes to the drought in California and the epic flooding and snowfall events in lower latitudes. The melting of Greenland threatens coastal communities all over the world. More than 50 percent of Greenland was melting in July 2015. In protests across the planet, people are standing together, across countries, Indigenous nations, ethnicities, age, gender, and class to demand that our human rights be protected, that the Earth’s ecosystems be protected and that those least responsible for our climate crisis be provided the resources to adapt and protect their lives.

Gernot Wagner, senior economist at the Environmental Defense Fund

Reason for despair: Climate change. It’s the perfect problem: more global, more long-term, more irreversible, and more uncertain that virtually any other public-policy problem facing us. Climate change is a lot worse than most of us realize. Almost regardless of what we do on the mitigation front, we are in for a whole lot of hurt.

On the policy front, we have now talked for more than 20 years about how we need to turn this ship around “within a decade.” Not unlike the ever-elusive fusion technology, that hasn’t happened yet. Global carbon emissions declined slightly this year—for the first time ever without a global recession—but the trends are still pointing in the wrong direction. Worse, turning around emissions is only the very first step. It’s not enough to stabilize the flow of water going into the bathtub when the goal is to prevent the tub from overflowing. We need to turn around atmospheric concentrations of greenhouse gases. That means turning off the flow of water into the tub—getting net emissions to zero and below. It doesn’t help our efforts that many people seem to confuse the two. A study involving over 200 MIT graduate students faced with this same question revealed that even they confuse emissions and concentrations—water flowing into the tub and water levels there. If MIT graduate students can’t get this one right, what hope is there for the rest of us?

Reason for hope: Climate change. Many signs point to some real momentum to finally tackle this momentous challenge.

The Paris Climate Accord builds an important foundation. It enables transparency, accountability, and markets to help solve the problem. Many governments are moving forward with pricing carbon: from California to China, from Sweden to South Africa, we see ambitious action to reign in emissions in some 50 jurisdictions. Meanwhile, lots is happening on the clean-energy front. That’s particularly true for solar photovoltaic power, which has climbed up the learning curve—and down the cost curve—faster than most would have expected only five years ago. That has also provided an important jolt for sensible climate policy. Then there’s R&D for entirely new technologies. Bill Gates leading an investment coalition with $1 billion of his own money is only one important sign of movement in that direction. The excitement for self-driving, electric vehicles is palpable up and down Silicon Valley, to name just one potentially significant example. In the end, it’s precisely this mix of Silicon Valley, Wall Street, and, of course, Washington that will lead—and, in part, is already leading—to the necessary revolution in a number of important sectors, energy and transportation chief among them.