July 12, 2015
In Laudato si’ Pope Francis tells us that the “climate is a common good, belonging to all and meant for all. At the global level, it is a complex system linked to many of the essential conditions for human life.”  Thus, the challenge of global warming is, at bottom, a life issue.
While there are a large number of politicians who express doubts about global warming, this is not the case among relevant scientists. “A very solid scientific consensus indicates that we are presently witnessing a disturbing warming of the climatic system.” 
“The U.S. Global Change Research Program, the National Academy of Sciences, and the Intergovernmental Panel on Climate Change (IPCC) have each independently concluded that warming of the climate system in recent decades is ‘unequivocal.’ This conclusion is not drawn from any one source of data but is based on multiple lines of evidence, including three worldwide temperature datasets showing nearly identical warming trends as well as numerous other independent indicators of global warming (e.g., rising sea levels, shrinking Arctic sea ice).” 
What’s more, human “influence on the climate system is clear. This is evident from the increasing greenhouse gas concentrations in the atmosphere, positive radiative forcing, observed warming, and understanding of the climate system….Human influence has been detected in warming of the atmosphere and the ocean, in changes in the global water cycle, in reductions in snow and ice, in global mean sea level rise, and in changes in some climate extremes….It is extremely likely that human influence has been the dominant cause of the observed warming since the mid-20th century.”  As the Holy Father tells us, humanity “is called to recognize the need for changes of lifestyle, production and consumption, in order to combat this warming or at least the human causes which produce or aggravate it. It is true that there are other factors (such as volcanic activity, variations in the earth’s orbit and axis, the solar cycle), yet a number of scientific studies indicate that most global warming in recent decades is due to the great concentration of greenhouse gases (carbon dioxide, methane, nitrogen oxides and others) released mainly as a result of human activity.” 
The fact is, changes “in atmospheric concentrations of greenhouse gases (GHGs) and aerosols, land cover and solar radiation alter the energy balance of the climate system,” and global “GHG emissions due to human activities have grown since pre-industrial times, with an increase of 70% between 1970 and 2004….Carbon dioxide (CO2) is the most important anthropogenic GHG. Its annual emissions grew by about 80% between 1970 and 2004.”  “The problem is aggravated by a model of development based on the intensive use of fossil fuels, which is at the heart of the worldwide energy system. Another determining factor has been an increase in changed uses of the soil, principally deforestation for agricultural purposes.”  “Global increases in CO2 concentrations are due primarily to fossil fuel use, with land-use change providing another significant but smaller contribution.”  Scientifically speaking, there “is very high confidence that the net effect of human activities since 1750 has been one of warming.” 
The pope warns us that that global warming is having a negative impact on “essential resources like drinking water…and agricultural production in warmer regions….”  “With higher temperatures, the water-holding capacity of the atmosphere and evaporation into the atmosphere increase, and this favours increased climate variability, with more intense precipitation and more droughts….While temperatures are expected to increase everywhere over land and during all seasons of the year, although by different increments, precipitation is expected to increase globally and in many river basins, but to decrease in many others.”  “Sea-level rise will extend areas of salinisation of groundwater and estuaries, resulting in a decrease in freshwater availability for humans and ecosystems in coastal areas….”  Overall, the “negative impacts of climate change on freshwater systems outweigh its benefits….”  As to agricultural production, “low-latitude areas are most at risk of having decreased crop yields”  due to global warming.
“Across developing countries, millions of the world’s poorest people are already being forced to cope with the impacts of climate change. These impacts do not register as apocalyptic events in the full glare of world media attention. They go unnoticed in financial markets and in the measurement of world gross domestic product (GDP). But increased exposure to drought, to more intense storms, to floods and environmental stress is holding back the efforts of the world’s poor to build a better life for themselves and their children.”  And so the Holy Father warns us that the worst effects of global warming “will probably be felt by developing countries in coming decades. Many of the poor live in areas particularly affected by phenomena related to warming, and their means of subsistence are largely dependent on natural reserves and ecosystemic services such as agriculture, fishing and forestry. They have no other financial activities or resources which can enable them to adapt to climate change or to face natural disasters, and their access to social services and protection is very limited.” 
These and other concerns, the pope tells us, make climate change “one of the principal challenges facing humanity in our day.”  Unfortunately, many “of those who possess more resources and economic or political power seem mostly to be concerned with masking the problems or concealing their symptoms, simply making efforts to reduce some of the negative impacts of climate change.”  Instead, what is needed is “to develop policies so that, in the next few years, the emission of carbon dioxide and other highly polluting gases can be drastically reduced, for example, substituting for fossil fuels and developing sources of renewable energy.” 
In the United States we confront a number of politicians who are denying either the existence of global warming, or its anthropogenic nature. But the science on the issue is clear, and cannot be credibly denied. Thus, Pope Francis has spoken out on the matter. It is critical that he be heeded, particularly by our political class. For ordinary citizens to deny the existence of anthropogenic global warming is simply ignorance. For our political leadership to do the same is dereliction.