Every new scientific report adds to the body of evidence that global warming is taking place and human activity is a contributing factor. Yet every report is greeted by skeptics who, while conceding warming might be occurring, disagree that human activity is a cause. It’s due to natural earth cycles, they maintain.

But is this the prudent stance to take in light of the evidence?

This is a question the U.S. Catholic bishops have raised on several occasions — first in a statement on global climate change six years ago and again in a recent letter to members of Congress from Bishop Thomas G. Wenski, chairman of the bishops’ Committee on International Policy.

Noting that prudence allows us to discern what is the common good in a particular situation, the bishops said in a 2001 statement that what a scientific consensus says about the reality of global warming cannot be easily dismissed. And it justifies taking action to avert potential dangers, the statement said.

In brief, the bishops wrote, “if enough evidence indicates that the present course of action could jeopardize humankind’s well-being, prudence dictates taking mitigating or preventative action.”

Bishop Wenski put it this way in a Feb. 7 letter to congressional leaders: “The traditional virtue of prudence suggests that we do not have to know with absolute certainty everything that is happening with climate change to know that something seriously harmful is occurring. Therefore, it is better to act now than wait until the problem gets worse and the remedies are more costly.”

He added, “Prudence sometimes keeps us from acting precipitously. In this case, it requires us to act with urgency and seriousness.”

Bishop Wenski’s letter to Congress was prompted by a new report from the Intergovernmental Panel on Climate Change of the United Nations. This report from the leading international network of climate change scientists found that global warming is “unequivocal” and that human activity is very likely causing the rise in temperatures around the globe.

Here are some of the main conclusions of the report:

• The global atmospheric concentrations of carbon dioxide, methane and nitrous oxide “have increased markedly as a result of human activities.” The increases in carbon dioxide concentration are due primarily to fossil fuel use and land-use change, and the increases of methane and nitrous oxide are primarily due to agriculture.
• The warming of the climate is evident from observations of increases in global average air and ocean temperatures and widespread melting of snows and ice and rising global sea levels.
• Numerous long-term changes in climate have been observed. These include “changes in Arctic temperatures and ice, widespread changes in precipitation amounts, ocean salinity, wind patterns and aspects of extreme weather,” such as droughts, heavy precipitation, heat waves and the intensity of tropical cyclones.
• Most of the increase in global average temperatures since the mid-20th century is “very likely” due to the observed increase in greenhouse gases. “Discernible human influences now extend to other aspects of climate, including ocean warming, continental-average temperatures, temperature extremes and wind patterns.”

The report said these trends are likely to continue. But it also noted that the warming can be blunted if prompt action is taken.

The question is how we — as citizens and policymakers — respond to this scientific data. Do we adopt a skeptical view that the climate changes are only natural occurrences and that human activity is not a primary factor in what is taking place?
Or do we take a more prudent approach based on the scientific data and consider that human activity is a driving force in the global climate change?

One of the difficulties in addressing climate change is that the issue has become so politically charged and, in some instances, ideologically polarized. Perhaps we can counteract these forces by adopting the attitude expressed by the U.S. bishops in their 2001 statement on climate change.

“At its core, global climate change is not about economic theory or political platforms, nor about partisan advantage or interest group pressures,” they said. “It is about the future of God’s creation and the one human family. ... It is about our human stewardship to God’s creation and our responsibility to those who come after us.”

It’s about making prudent judgments and decisions.