When framers of the Declaration of Independence outlined those famous truths they believed self-evident, we can imagine they unanimously agreed that logic, wisdom, and knowledge are unassailable, rooted — as they wrote — in the "laws of nature and of nature's god." Writing during an intellectually exuberant period of change later referred to as the Age of Enlightenment, or Age of Reason, their words reflected the essential ideal of this movement: Reason provides understanding of the natural and political worlds.

With far more evidence at hand than our forefathers might ever have imagined possible, scientists and educators in the 21st century study Earth's systems with an array of data. Using logic and many lines of evidence that build upon centuries of learning and scientific advances, we continually grow the knowledge and wisdom needed to comprehend nature's laws in a complex and changing world.

The 2006 documentary film An Inconvenient Truth was hailed by many for its reasoned account, and yet it was vilified by "climate-change deniers" as if the laws of nature are mutable or deniable. To be sure, these laws can be refined in light of new evidence, but it is the weight of scientific evidence in support of human-induced climate change that is unassailable.

Regardless of political rhetoric today, An Inconvenient Truth has had a profound impact on the under-30 generation, which has the most at stake in Earth's future climate.

According to a 2015 Pew Research Center survey, a record number of Americans view global warming as a serious threat (72 percent), and think that human activity is the cause (46 percent). This survey shows that the younger generations (18 to 29 years), of all political leanings, are more prone to believe global warming is real (73 percent) and caused by human factors (60 percent) than the over-65 generation (61 percent and 36 percent, respectively).

The new film An Inconvenient Sequel: Truth to Power could not come at a more appropriate or crucial time in modern culture. The world is looking to the United States for climate-change leadership, but finding precious little. The Trump administration's decision to pull out of the Paris Climate Agreement unfortunately reflects the opinion in the United States that climate change is not seen as an immediate threat to global welfare.

A 2016 Pew Research Center report on what the world thinks about climate change found that majorities in all 40 nations polled say climate change is a serious problem, and a global median of 54 percent believe it is a very serious problem. Opinion in the United States (41 percent), however, lags behind Latin America (77 percent), Europe (60 percent), Africa (52 percent), and Asia (48 percent) in concern that climate change is harming and will harm global populations.

So, what's to be done?

Whether you grasp the scientific logic underpinning human-induced climate change or not, why not prepare for the worst and hope for the best? We do the same in purchasing insurance for our homes or lives. No one believes they will get into an accident or get cancer, yet we all recognize the value of insuring for the worst, particularly when much is at stake.

It's the same with climate change, although we must think beyond our own lives and homes, to the broader common good.  We'd rather not think that seas will rise and inundate much of the world's population, and yet we are facing that very problem due to global warming.

That opening passage in the preamble of the Declaration of Independence has come to represent a moral calling for which the nation should strive.

We hold these truths to be self-evident, and invite you to build upon the work started by our country's founders. They held logic so dear, to advance the common good through scientific understanding and achievement.

Robert C. Walter (robert.walter@fandm.edu) is an associate professor of geosciences and Dorothy J. Merritts (dorothy.merritts@fandm.edu) is professor of geosciences and chair of the environmental studies program at Franklin & Marshall College. Their 2008 article Natural Streams and the Legacy of Water Powered Mills won the 2011 Kirk Bryan Award from the Geological Society of America for outstanding research. Merritts is coauthor of the textbook Environmental Geology.