It has been almost a quarter century since the majority of nations signed the United Nations Framework Convention on Climate Change, agreeing to “limit dangerous anthropogenic [human] interference with the climate system.” And yes, nearly 25 years since the world agreed to prevent serious impacts on global food supply, the natural environment and the economy.

This December, 195 nations will be heading to Paris for the 21st Conference of the Parties (COP21) to discuss yet again how to accomplish what they all promised nearly a generation ago. As you can imagine, the question on everyone’s mind is, “Will this time be any different?”

Climate science has certainly advanced across this time frame. Our global climate models zoom down to finer and finer resolutions; our satellites reveal remote corners of the globe; we increase our understanding of the response of giant ice sheets and deep ocean currents to a warming planet.

But more science is not the answer to global action. The first observations of human-induced climate change were published in 1938. The first U.S. president to be formally warned of the dangers of climate change was Lyndon B. Johnson, in 1965. The diplomatic arguing has not been about the science; it has been about what we are willing to do to prevent that danger. And that has a lot more to do with the values in our hearts than the facts in our heads.

For many of us—including more than 75 percent of people in the U.S.—what is in our hearts is often directly related to our faith. And what is different about this year, leading into COP21, is how faith leaders have stepped up to the plate.

Pope Francis’s encyclical, released in June, leaves nothing to the imagination in laying out the attitudes that the world’s more than two billion Christians should have toward climate change. It speaks eloquently of stewardship of God’s creation and care for the poor, those already affected by the exacerbating impacts of climate change on droughts, floods, heat waves, hurricanes and other extreme weather.

The same themes of stewardship and care for the poor have been raised by the World Evangelical Alliance and the National Association of Evangelicals in recent years. The Islamic Declaration on Climate Change presented in August goes further, connecting the issue of climate change to humans’ relentless pursuit of economic growth and consumption and encourages the world’s 1.6 billion Muslims to support global action on climate. Today faith leaders from every corner of the world are connecting the dots between our heads and our hearts, between the scientific facts about climate change and our human response.

By bridging the perceived divide between religion and science, these unique voices have the potential to fundamentally alter the climate debate. What if, in the international discussions, we weigh our own personal short-term gain against the well-being of our brothers and sisters around the world? What if we value not only the resources we have today but also the wealth of diversity across the planet tomorrow? What if we can use both our science and our faith to move forward into an increasingly uncertain future?

New research suggests this approach may be making a difference. U.S. Catholics, mainline Protestants and Evangelicals are all more concerned about climate change now than before the pope’s encyclical was published. Not only that, but now more agree than just six months ago that climate change is an issue of morality and social justice.

Faith communities are taking action too: hosting community solar gardens on church roofs, helping individuals cut their carbon footprints, and raising their voices here in the U.S. and around the world in advance of COP21. These examples, and many more, highlight how science and faith can work hand in hand: science quantifying the nature of the challenge and faith-based values informing sustained, hopeful action.

That is why this year I am taking both my head and my heart to COP21. As a scientist, I value the observations, data and facts that have been collected in many years of climate science research. As a person of faith, I am motivated by love for others and for this amazing world in which we live.

We need both our heads and our hearts to make good choices at COP21 and to agree on actions that demonstrate our love and respect for our fellow humans—today and into the future. Could that be the change we have been waiting for?

Katharine Hayhoe is a climate scientist and professor at Texas Tech University. She studies what climate change means to us in the places where we live. In 2014 she was named one of TIME’s 100 Most Influential People in the World and one of Foreign Policy’s 100 Global Thinkers.