In order that this your grave and pernicious error and transgression may not remain altogether unpunished and that you may be more cautious in the future and an example to others that they may abstain from similar delinquencies, we ordain that the book of the “Dialogues of Galileo Galilei” be prohibited by public edict.
--Sentence of Galileo June 22, 1633
Pope Francis has announced that he intends to issue an encyclical on climate change , “urging all Catholics to take action on moral and scientific grounds.” We will have to see what this encyclical actually says. But there are some questions which we might ask in advance. I am agnostic about climate change. This is a matter in which I do not have sufficient information to make a decision.
“An objective analysis of the factors which contribute to climate change” (http://www.palisad.com/co2/) provides a helpful summary of the issues which are still unsettled: “Many facts are not in dispute. One is that climate change occurs. The evidence indicating a wide range of long term climate variability is indisputable. It's also reasonable to consider that climate change is happening now. What's in dispute, is the magnitude and cause of any recent change.
The reason is that there are no medium term measurements of worldwide climate from which to draw conclusions. There are detailed measurements of the slow change in 100 to 1000 year average temperatures going back millions of years as well as 25 years of detailed satellite measurements providing a very accurate indication of the hourly change for each 50 or so square kilometer patch of the Earth's surface, but nothing in between. Adding to the confusion, is that the satellite data is inconclusive regarding any discernible trends in the global yearly average temperature over the last 25 years!
Other indisputable facts that are that CO2 is a greenhouse gas and that man has been adding CO2 to the atmosphere. It's quite clear that the current CO2 levels are as much as 25% higher than they would be without mans contributions. What's in dispute, is the magnitude of the forward effect incremental CO2 has on the global mean temperature. The physics of atmospheric absorption tells us that this effect, while finite, is so small as to be inconsequential. The ice core data shows a correlation between average temperature and CO2 levels which many have interpreted to imply that CO2 change drives temperature change. However, the ice core data also tells us that CO2 and methane changes in response to temperature changes and not the other way around. It also tells us that all of the observed changes are periodic and highly correlated to known variability in the Earth's orbit and axis. This variability affects climate in the same way as the Earth's axial tilt results in periodic seasonal variability. A controversy arises because some sort of amplification is required to match temperature data to solar variability. The satellite data illustrates how the hemispheric asymmetry in the ebb and flow of surface ice as a function of temperature provides enough amplification, while the alarmists insist that some sort of unqualified positive feedback effect from CO2 provides it.
Since so many have unconditionally embraced the idea that CO2 variability drives the climate, there's a great reluctance to consider anything else. So much so, that those who challenge CO2 forcing are considered heretics and ridiculed just for being objective”.
This last point is the most troubling one. Much has been written about the Galileo ‘legend’ and what really happened in the 17th century Papal condemnation of Galileo. But what is happening right now to those scientists who dare to disagree with the so-called climate change ‘consensus' is not legend. Many of those who are most adamant about the theory, facts, and solutions surrounding climate change would welcome a condemnation of the climate dissenters like the condemnation of Galileo. Will Pope Francis put on the Index all books, writings, research and opinions which argue against global warming or that it is not as catastrophic as some have claimed or that there nothing we can do about it in any case? Maybe, we will have to see, Pope Francis will turn out to be more traditional than we expect and follow his predecessors who shut down Galileo.