Baseball legend Yogi Berra once quipped, “It’s tough to make predictions, especially about the future.” This humorous statement is especially true regarding climate. It goes without saying that the earth’s climate is an incredibly complex system with countless variables. Meteorologists struggle to predict the weather just a few days in advance. Predicting the earth’s climate far into the future is virtually impossible. The Intergovernmental Panel on Climate Change (IPCC) admitted as much in its 2001 assessment report: “In climate research and modelling, we should recognize that we are dealing with a coupled non-linear chaotic system, and therefore that long term prediction of future states is not possible.” When the panel speaks of the earth’s climate as “a coupled non-linear chaotic system,” this sounds like scientific gobbledygook. But they’re really just saying the same thing as Yogi Berra. The earth’s climate system is so complicated that predicting future climate is extremely difficult.
The corollary to this principle is that making claims of certainty about future climate based on one variable are deeply dishonest. It is quite remarkable how the entire discussion about global warming has effectively boiled down to carbon dioxide. Yes, it’s true that carbon dioxide is a greenhouse gas and that increasing levels of atmospheric CO2 should result in a slight warming effect. But it’s important to keep in mind that CO2 is only one factor among many. Our climate is influenced by countless factors including things like changing solar activity and cloud patterns. Yet the constant carbon drumbeat from climate alarmists has resulted in a situation whereby most people think our entire climate system is entirely dominated by carbon dioxide. Many have the impression that carbon dioxide is like a giant thermostat which has complete control over our temperatures. This is simply not the case. Remember, carbon dioxide comprises only a tiny fraction of our atmosphere! All the human carbon emissions since the dawn of the industrial revolution have only increased the amount of atmospheric carbon dioxide from roughly 0.03% to 0.04%.
Moreover, as the chart below illustrates, the greenhouse effect of CO2 decreases rapidly as the concentration of CO2 increases. So, for example, below 100 parts per million, adding additional CO2 to the atmosphere results in a strong greenhouse effect whereby a relatively large amount of energy is retained in the form of heat. However, our current concentration of atmospheric CO2 is about 420ppm. At this concentration, adding additional CO2 to the atmosphere results in a relatively weak greenhouse effect – and this effect will only diminish further at higher concentrations.
All this doesn’t mean that scientists shouldn’t make predictions. In fact, it could be said that the fundamental purpose of science is to give mankind the ability to make accurate predictions about the natural world. The scientific method is all about developing a hypothesis and then testing that hypothesis. A hypothesis is essentially a prediction – a prediction about the nature of reality. But a hypothesis is only the starting point of the scientific method. Further investigation and rigorous experimentation are then required to test the hypothesis. If the hypothesis matches up to reality, we can have growing confidence that it is indeed true. Now many scientists have indeed hypothesized that carbon dioxide is the dominant factor controlling climate. They have created models which attempt to predict future temperatures based on increasing levels of atmospheric CO2. Over the last 30 years, we’ve all had the opportunity to see how these models hold up to reality. And the plain fact is that these models have spectacularly failed to make accurate predictions.
Perhaps the most famous model in the history of climate science was proposed by James Hansen. Hansen is considered one of the leading climate scientists in the world. In 1988, he published a highly influential paper in the Journal of Geophysical Research. The paper proposed a temperature model based on three different scenarios. Scenario A he called “business as usual” – meaning rapidly rising CO2 emissions correlating with continued worldwide industrialization. Scenario B was a middle ground whereby there would be modestly increasing CO2 emissions. Scenario C would involve severe restrictions in CO2 emissions such that atmospheric CO2 would cease to rise. It turns out that CO2 emissions have tracked midway between scenario A and B. Yet actual temperature measurements have lagged far below Hansen’s expectations.
Hansen is far from alone in crafting a model which fails to accurately predict future temperatures. In 2016, John Christy, a climatologist from University of Alabama – Huntsville testified before the U.S. House Committee on Science, Space and Technology. Christy displayed the chart shown below in order to illustrate the difference – or “divergence” -between climate models and actual observed temperatures. The green and blue boxes represent actual temperatures as measured by satellites and balloons. The red line represents the average of 102 climate models which the Intergovernmental Panel on Climate Change (IPCC) had been relying upon in their reports. The models predicted over 2.5 times the actual amount of observed warming.
Now I certainly am not attempting to personally insult or smear James Hansen or the other scientists who developed these models. In fact, even in failure, their models are an essential part of the scientific endeavor. As we’ve noted, the scientific method is all about developing a hypothesis and then testing that hypothesis to see how well it correlates with reality. My main point is to recognize the objective fact that the models have manifestly not correlated with reality; they have completely failed to accurately predict future temperatures. This failure should be helpful in that it tells the scientists that something is missing. They need to go back to the drawing board and try to understand where they went wrong. Unfortunately, this is not at all what has happened. Instead of admitting failure, many in the scientific community – along with politicians and the media – have continued to trumpet their absolute certainty that increasing CO2 levels will bring about climate disaster.
So where did the models go wrong? Everyone agrees that carbon dioxide is a greenhouse gas and that increasing concentrations of atmospheric CO2 should have a slight warming effect. However, the models often assume various powerful positive feedback loops. In other words, the small increase in temperatures caused by rising CO2 triggers other processes which magnify this warming effect. For instance, we’ve noted that water vapor is itself an important greenhouse gas. Many scientists have speculated that as CO2 levels warm the atmosphere, it will hold more water vapor which will in turn drive further warming. However, there is a great deal of uncertainty surrounding these positive feedback loops. Moreover, there are potential negative feedback loops as well. For example, increasing atmospheric water vapor may condense into clouds. Greater cloud coverage results in more solar energy being reflected out of the atmosphere without reaching the earth’s surface. In this scenario, increased water vapor would result in an overall cooling effect. Many scientists believe that the climate models have failed because they have assumed strong positive feedback loops and ignored or minimized potential negative feedback loops.
Remember that the earth’s temperatures have been increasing since the depths of the Little Ice Age in the late 1600’s. This naturally occurring warming trend began long, long before any significant rise in CO2 levels due to human activity. It is very possible that the gentle warming we have continued to observe in recent times is simply a continuation of the natural warming observed over the last 300+ years. After all, the same forces which were warming the planet since the end of the Little Ice Age did not suddenly cease to operate in recent decades. Therefore, from a scientific perspective, it’s impossible to say with any certainty whether human CO2 emissions are making a significant contribution to global warming. Based upon the known greenhouse effect, it is quite reasonable to believe that increasing atmospheric CO2 is indeed contributing at least a small amount of warming. But it’s equally reasonable to believe that the warming resulting from human CO2 is so small as to be insignificant relative to natural factors. But the evidence does not allow anyone to parade around proclaiming that CO2 will cause certain catastrophic warming.
Often times, people ask, “Is climate change real?” And of course the correct answer is yes. We know that the earth’s climate has always been changing. Specifically, we know that there has been natural warming for the last several hundred years. The key question is not whether global warming is real, but to what extent humans are driving global warming. Science is not about opinion or belief but about evidence. And the evidence we have suggests that humans are making very little contribution to current warming. The claim that humans are the main or sole cause of recent warming is simply not supported by the facts.
Even more importantly, we must ask ourselves what will be the results of any future warming. We are constantly bombarded by claims that future warming will result in climate catastrophe. Very few people consider the possibility that rising CO2 and warmer temperatures might very well be beneficial for humanity. Yet there is substantial evidence that this might very well be the case. We’ve noted already how warmer temperatures and CO2 fertilization have already benefited the growth of forests and crops. The graph above shows the results of a recent satellite study evaluating world-wide leaf coverage from 1982 until 2015. This study found that 25-50% of the earth’s surface was greening while only 4% of the earth’s surface was browning. This is fantastic news! Larger and healthier trees and forests provide more habitat for animals. More abundant crops to help feed hungry people. The truth is that humanity has historically suffered greatly during times of cold and flourished during times of warmth. So if we desire to see greater flourishing for humanity and all creation, we should consider that more warmth and more carbon dioxide might help us achieve that goal.
