There are many stark differences between presidential candidates Hillary Clinton and Donald Trump. One of those differences happens to be about the most significant challenge facing humanity in the 21st century.

As a member of Wake Forest College Democrats and Cultivate Consciousness, I believe that this challenge is climate change.

The overwhelming majority of the world’s scientific community agrees that climate change is a serious threat accelerated by the excess amounts of carbon dioxide we are emitting into the atmosphere. This is a result of the industrialized world’s addiction to hydrocarbon fuels, like oil, coal and natural gas. Our reliance on these fuels is at the root of our ecologically destructive activities in agriculture, transportation, electricity generation and more.

Scientists have elaborated the numerous consequences of these unsustainable practices. Climate change risks pushing the Earth beyond its limits. The Earth does warm naturally, but our excess CO₂ emissions have disrupted the delicate balance on which our climate depends (CO₂ traps heat, preventing solar radiation from returning back to space). As a result, ecosystems will not flourish, sea levels will rise and threaten coastal communities, and extreme weather (heat waves, droughts, natural disasters, etc.) will result in devastating crop failures. All of this is already happening as a consequence of climate change, demonstrating that the time for action is not.

The science is pretty clear, and I encourage everyone to learn as much about it as possible. This is something that Donald Trump has very clearly failed to do. That is because Trump, unlike Clinton, is a climate denier. His utter lack of a scientifically valid opinion on this subject is evidenced by his outrageous tweet that climate change was a hoax made up by China to undercut U.S. manufacturing. Trump may have backpedaled from this comment in the most recent debate, but he still utterly lacks an actual solution to climate change, one that would have helped the U.S. meet its commitments under the Paris climate deal. The framework of the Paris deal was agreed to last December by virtually the entire world; like others, the U.S. and China jointly ratified the deal last month.

In a speech given in May to the North Dakota Petroleum Council, Trump claimed that the Paris agreement “gives foreign bureaucrats control over how much energy we use right here in America.”

Not only is this a flat-out lie as the climate goals for each country were defined individually, not by an over-weening UN, but it’s also clear that Trump believes we have a fundamental right to exploit the Earth’s natural resources with no limits.

In this same speech, Trump claimed that “these actions have denied millions of Americans access to the energy wealth sitting under our feet.” The idea that we should take advantage of our “energy wealth” is uncontroversial, but our real wealth does not come from the fuel sitting under our feet. Our real wealth comes from other forces of nature — wind and the sun.

At some point, our natural reserves of oil, coal and natural gas will have been depleted to zero. We cannot indefinitely exploit nature’s finite resources.

Things do not have to be the way they are. The world has made substantial progress toward the development of renewable energy from wind turbines and solar panels. Germany, Sweden, China and even the U.S. have been trailblazers in renewable technology, so there’s hope for the world.

That being said, there is much more which can be done. We are still far too reliant on fossil fuels, and consequently carbon pollution, to power the globe. With human ingenuity, we can meet and exceed the targets set by the Paris climate deal and preserve our future.

Unlike Trump, Clinton has a plan of action. Clinton recognizes the validity of climate science, has expressed support for Obama’s Clean Power Plan and called for a major boost in solar panel construction according to “The Washington Post.” This isn’t to say that Clinton’s climate record is perfect.

As Secretary of State, Clinton wrongfully promoted hydraulic fracturing. (“fracking”) an unsustainable practice which seriously contributes to climate change. However, it’s the job of committed voters, thinkers and activists to pressure her to make real progress on climate change when she’s president. If we don’t, we have failed the planet and ourselves.

At least Clinton, unlike Trump, is not in denial about a real problem which needs a solution.