My immediate response when asked to respond to this title was that climate change (or global warming) is not about belief. For a scientist, one might equally well be asked to respond to “Can Christians believe in gravity?” And no, I do not mean that the science of climate change is as well understood as the science of gravity, but both processes operate in our world independently of our personal beliefs. The realm of science does not address belief; it addresses observations and measurements, the logical constructions or theories¹ that can be built upon these data using mathematics as our primary tool, and predictions that can be drawn from our constructions. The distinction that I draw here is somewhat sharper than that drawn by Professor Mouw in his introduction. While I am in firm agreement with the statements he makes about the commitment to a capital-C Creation, I would phrase statements about “belief” in the context of carbon-dating or geology or ultra-sound tests much more carefully – these are science issues that are conditioned by knowledge more than by belief. I do want to acknowledge that beliefs can influence science, but that occurs primarily through the questions that we choose to ask rather than impacting the methods and results that we obtain, particularly in the physical sciences.

The physics of climate change has been examined in great detail over the past 40 years. As a result of human activity during the last 150 years, we have increased the carbon dioxide concentration of the atmosphere by more than 40%, which has increased the greenhouse capacity of the atmosphere; consequently, surface temperatures are increasing. Simply put, there is no scientific uncertainty about the basic physics of global warming, the resulting warming of planet Earth, and the human driver of this change.² This does not mean that there is no genuine scientific debate about the issue. Scientists are uncertain about whether all the warming observed over the last century is due to human activity (up to perhaps 30% may be due to natural variations); in addition, model simulations of the expected global temperature increase over this century vary from 4 ⁰F to more than 10 ⁰F depending on the model being used. But these are uncertainties about the relative size of the effect, rather than uncertainties about the basic science.

If science is not really about belief and I (and the vast majority of my colleagues) am so certain of the facts of climate change science, then why do non-scientists (and the media) continue to talk about “belief” in climate change? Why was I as a scientist asked to address the topic of “belief” in climate change when this is not the language of science?  I don’t have a complete answer to that question, but let me suggest two broad areas for consideration: complexity and motivated reasoning.

Climate is a wonderfully rich subject that involves physics, chemistry and biology, all woven together with elaborate mathematics. Our study of climate is informed through the use of an extraordinary array of measurements from satellites, research aircraft, and ground-based instruments, as well as intricate computer codes that stress the largest computers in the world. Despite amazing advances in our understanding of climate during the past 50 years, there is still much more to be learned.

In part because of its complexity, science, when done well, includes estimations of uncertainty and careful articulation of what we scientists do not know.³ Regrettably, scientists all too often give the impression that we know less than we do because we are trained to be cautious in stating our conclusions and to include ranges of uncertainty. We most often talk about what we do not know because that is what we are interested in – solving the next step of the problem. The result is that we scientists fail to provide an adequate statement, particularly for the non-scientists, of what we do know and what we are sure of.

When we as individuals are faced with a very complex subject, especially when much of the discussion about the issue lies outside our intellectual comfort zone, and are forced to rely on experts that are not known to us personally, our response is often to simply “shut down” and move on to something else. When faced with a decision that is based on a complex subject, we as individuals can be paralyzed by all the complexity and we allow inertia to take over. We continue on our current path because it is too difficult to resolve the complex subject and make a decision to change. We then justify our inertia by declaring our disbelief in the information that we have. In other words, we rationalize our lack of action by shifting blame in one way or another to the facts or the purveyors of those facts.

Motivated reasoning,⁴  in a nutshell, states that our reasoning is convolved with emotion and we tend to accept information that is consistent with our beliefs and discard information that is not, regardless of the quality of the information itself. Furthermore, our acceptance of facts is conditioned by the acceptability of those facts to the community around us. Over the last decade or so, research has repeatedly shown that the best predictor of one’s belief in (or, depending on phrasing, acceptance of) climate change science is political party or ideology;⁵ there is a much higher correlation with politics than with Christian faith or membership in a religious denomination.

I suggest that the disbelief in climate change of many Christians is not so much about the science itself, but rather about its complexity and the moral dilemma that it poses. The consequences of a warming world are falling, and will continue to fall, upon the poor, particularly those in less-developed countries, who are precisely the people least responsible for the problem and least able to cope. If a Christian accepts the scientific reality of climate change due to human activities, then Christian morality demands working to mitigate the impacts of that change. In short, it demands changes to our resource-intensive lifestyle. So, many Christians are motivated to disbelief in the scientific facts because the issue is complex, the predictions and suggested outcomes are perceived as murky, and accepting the science threatens our lifestyles with change.

So, let me flip the question around and ask “is it right for Christians to not believe in climate change”? Not believing in (what I mean here is the sense of “not accepting the science of”) climate change requires dismissing the accumulated knowledge and understanding of physical science in general and climate science in particular as scientifically wrong and ethically biased. Not believing requires dismissing the very highly probable outcomes of a warmer world and increased incidence of extreme weather. Not believing requires ignoring the potentially devastating impacts of these changes on the poor among us and on our children and grandchildren.⁶

I believe that God has created us in the image of God, with mind and heart. Our minds allow us to read the world around us and understand the complexity of science. Our hearts convict us of the need to live a life that shows our love for the world that God has given us and for our neighbors who share this world with us. Disbelief in climate change science disavows the understanding of our minds and rationalizes our unwillingness to love our neighbors. I think that we Christians must believe and that belief must move us to action.