One scientific question that has relevance for every person on the planet is whether the global climate is changing in response to human activities. The major causative agents of the change, if indeed there is change, are the so-called greenhouse gases. Some of them, such as carbon dioxide, methane and nitrous oxide, are naturally occurring components of the atmosphere, but humans have caused their concentrations to increase greatly. Other greenhouse gases are substance that humans have learned to make and use for various purposes. These include the so-called chlorofluorocarbons and hydrofluorocarbons.
Not everyone is convinced that human activities are the driving force for some of the climate changes we have been seeing in recent years, or that the scientific models for climate reliably predict what may happen in the future if we continue to consume fossil fuels and add increasing amounts of other greenhouse gases such as methane to the atmosphere. In one sense this is not entirely surprising, because climate is not a well-defined entity, not easily described in terms of just a few critical measurements. Weather, something that happens at the local level, and climate, which extends over large regions and ultimately to the entire planet, are easily confused in many peoples’ minds. Although seasonal weather changes from one year to the next are not reliable indicators of climate change, they are frequently brought into discussions as though they were. Thus, a cold spring in the northwestern states of the United States are taken by many as evidence that global warming is not occurring. It seems that nearly everyone is an expert of some sort on climate. Political entertainers such as Glenn Beck and Rush Limbaugh, who have not a shred of expertise, don’t hesitate to declare that global warming is a massive hoax perpetrated by an establishment that wants to use it as a pretext for sinister incursions into private rights and freedoms.
This is a big topic, because if climate changes are occurring as a result of human activities to date, those changes will accelerate greatly over the next few decades as more and more greenhouse gases are pumped into the atmosphere. I need not rehearse here again, as I have in earlier blogs, the vast range of studies performed by scientists working in many different disciplines, and in a host of environments all over the planet, to attempt to learn about past climates and the changes occurring now in our own climate. Those studies have all gone into formation of the successive reports of the Intergovernmental Panel on Climate Change (IPCC), and the information collected there is continually updated as new evidence is produced. All of this scientific work, and the inferences drawn from it by the best minds working in all the areas of science related to climate change, have led to the conclusion that the climate is indeed changing as a result of human activities, and that the changes are accelerating. For example, the Greenland ice mass is decreasing; the latest evidence is that the loss is accelerating.
This past March, a group of about 2000 climate scientists gathered in Copenhagen to assess the current views on climate change. Because the group was not brought together under the auspices of the IPCC or any other single governmental agency, participating scientists were more free to offer frank appraisals and prescriptive statements. Many factors that bode ill for our prospects were either not considered in the IPCC report or were very conservatively estimated. For example, it is only now becoming evident that permafrost holds vast amounts of carbon that is becoming “unlocked” as the permafrost warms. The upshot is that the prospects look worse than the projections of the IPCC would lead one to expect.
The evidence for global warming and the role of human activities in the process, is at this point overwhelming. One way of putting this is that there is a strong consensus in the scientific community on these matters, of the same sort that exists with respect to many widely held bodies of evidence in chemistry, physics, genetics, and other branches of science. The National Academies of Science have produced a very nice video, America’s Climate Choices, that reveals the degree of consensus that obtains in the scientific world, and describes the organization of groups of experts that are being convened to assist the government in addressing the challenges that lie ahead. I urge you to watch this, to sense how deep and widely felt are the views of outstanding scientists and other citizens on this matter. Yet there are scientists, mostly without credentials in any of the relevant areas of science, and lacking acceptable scientific evidence that contravenes the current understanding, who continue to reject the consensual scientific position. Some seem to think it is a conspiracy of some kind, an attempt to somehow put something over on society. I can understand how some politicians, entertainers, entrenched interest groups such as those representing certain segments of the energy industry and the like, might find it convenient to resist the existing scientific evidence, but what is going on in the heads of deniers who have a supposedly scientific training? It must have to do with a deep-seated unease with the implications of greater governmental oversight as society comes to grip with the steps that must be be taken to reduce greenhouse gas emissions and at the same time begin to deal with mitigating global warming effects.
In a letter published in a recent issue of Chemical and Engineering News a writer reluctantly seems to agree that Earth’s climate is getting warmer, though he cites the low spring temperatures in the northeast as evidence that might contradict the global warming hypothesis (!). But he thinks that “blaming it (global warming) on human activities seems to be speculative.” What blows my mind is that this person can’t seem to imagine that the virtual army of scientists working on this problem would not have held this very question at the fore in all their work! What does that say about this person’s understanding of how science works? Apparently the means by which science establishes its epistemic authority, within the scientific community and outside it, is not clear to some scientists. We have a long way to go.