How global warming will increase religious strife.

When John of Patmos listed the four horsemen of the apocalypse, he didn't have access to climate-modeling software or any of the technology used by the Intergovernmental Panel on Climate Change. If he had, he might have described the end of times in slightly more specific terms. And, to know what those terms would be, you just have to look at the area approximately between the latitudes of 23 degrees north and 23 degrees south over the next 50 or so years.

Over the next half-century, this equatorial swath will be broiling from global warming. Droughts will kill crops, and warming oceans will cripple the fishing industry (decimating the populations of fishing villages that will be disappearing, anyway, because water from the melting ice caps will drown them). By midcentury, water shortages could force countries already suffering from generations of ethnic and religious conflict to explode. A country like Nigeria, for example, where Christians and Muslims have self-segregated to the Southeast and the North, might erupt in a violent tug-of-war over limited water supplies. The Coptic Christians in Egypt could become a lost people, as ethnic cleansing in the name of resource protection becomes common. By the same token, Muslim minorities in places like Uganda and Kenya might be annihilated or driven out, creating vast waves of refugees that will swarm the more prosperous countries looking for aid (in response to which Western countries could see a new era of harsh border enforcement). Gradually, whole areas would become arid, uninhabitable wastelands.

The ramifications for the global warming-driven destruction of equatorial nations are frightening for everyone--but they should be especially frightening for Christians, whose numbers have been growing so explosively in those very areas. By 2050, although the world's largest Christian population will still be found in the United States, many of the other most populous communities will belong to the global South, in places like Brazil, Mexico, Nigeria, the Congo, Ethiopia, Uganda, and the Philippines. Christianity is no longer synonymous with the West, and that equation will become ever less plausible as time passes. What Christianity is becoming synonymous with, however, is the most volatile and the most ecologically threatened area of the world--and the coming temperature changes could have serious consequences for the future of the religion.

The connection between climate change and religious violence is not that tenuous--in fact, there's a historical indicator of how it could unfold, the Little Ice Age. Between the ninth and thirteenth centuries, the Northern Hemisphere actually went through a modest warming phase: With a longer growing season, harvests were bountiful, Europe's population boomed, and the relative prosperity inspired a burst of creativity in the arts and in the new university system. But, in the late thirteenth century, what's known as the Little Ice Age began: Pack ice grew in the oceans, making trade routes more dangerous, and summers became cooler and wetter, harming crops. Populations swollen by the earlier boom came up against steep food shortages. The Great Famine, beginning in 1315, led to rumors of widespread cannibalism within a few years. At least one-third of Eurasia's weakened population died in the Black Death of the 1340s.

In a climate of death and horror, people cast about for scapegoats, even before the Black Death struck. The Church formally declared witchcraft a heresy in 1320, and people were soon being executed for devil-worship and black magic. And governments, desperate to find a safe outlet for their subjects' rage, condoned mob attacks on religious minorities.

Bigots of whatever faith rarely referred explicitly to the climatic catastrophe in progress around them, but the very close correlation between the cooling and a regionwide heightening of violent intolerance makes such a linkage likely. Jews were among the favorite targets of the Little Ice Age's hate criminals: England expelled its Jews in the 1290s, and pogroms were common in the 1320s and '30s and accelerated during the Black Death, forcing an eastward migration that ended up concentrating most of Europe's Jews in modern-day Poland, Lithuania, and Russia by the end of the fourteenth century.

But Christians suffered as well, at the hands of Muslims in Asia and the Middle East strained by some of the same circumstances that were affecting Europe. In 1250, Christians were still substantial minorities in many African and Asian countries. But, during the Little Ice Age, old-established Christian communities began to get the same treatment their coreligionists were dishing out to Jews in Europe. Egyptian Muslims accused Christians of arson and plotting terrorist attacks against mosques, using the newly popular weapon of gunpowder. Elsewhere, in Mesopotamia and modern-day Turkey, churches were destroyed and Christians were massacred. When modern jihadis look for intellectual role models, they turn back to precisely this era, to hard-line scholars like Ibn Taymiyya, who loathed infidels and condemned moderate Muslim regimes for not being tough enough on them.

It is not outlandish to say that we are heading toward a future very much like our fourteenth-century past, particularly in the areas of the global South where Christian populations are rising drastically. As the Little Ice Age did in the fourteenth century, global warming will redraw the world's religious maps, making it more and more difficult for religious or ethnic minorities to survive under a majority-led government and forcing splinter groups to concentrate in nations with sympathetic governments. The resource-driven genocide in Darfur, for example, although it involves competing Muslim communities and not Muslim-Christian warfare, is a foretaste of conflicts that could soon be sweeping the whole area, as nations implode in sectarian violence, pulling neighboring countries down with them.

But the greater globalization of Christianity, while it heightens some of the religious tensions in resource-poor countries and may put the religion at risk of pogroms and genocides, might also help prevent some of the worst scenarios. As morally conservative churches in America form relationships with like-minded churches in the global South, especially Africa, they are becoming vastly more sensitive to African and Asian issues and values, and among these is a greater sympathy toward international cooperation on climate change.

In fact, the looming crisis has provoked some surprisingly radical actions by conservative Christians. The most famous of these is probably Richard Cizik, vice president of governmental affairs for the National Association of Evangelicals, an umbrella organization whose affiliate groups claim 30 million members. In the past five years, Cizik has become an outspoken advocate of "creation care," a doctrine rooted in the Bible that urges environmental protection, with global climate change as the clear and present danger. Cizik has called climate change "a phenomenon of truly Biblical proportions"--and one, therefore, that demands action on a similarly Biblical scale. Recognizing the pivotal importance of Africa in the Christian future, prominent evangelicals such as Rick Warren have become deeply committed to global South issues.

Once the connection between climate change and the fate of many of the world's Christians becomes self-evident (as, sadly, it will begin to before very long), we can expect an even greater involvement from the Christian community. Combining the themes of world stewardship and protecting Christian minorities could lead to a whole new synthesis of religious and political action, a kind of latitude politics that could represent a potent new element in U.S. foreign affairs. It's that, of course, or a return to medieval levels of misery and doom for the majority of Christians worldwide.

Philip Jenkins is the author of God's Continent: Christianity, Islam and Europe's Religious Crisis.

By Philip Jenkins