Why Climate Change "Alternatives" Aren't

Although the anthropogenic basis of climate change has been the conclusion from multiple Intergovernmental Panel on Climate Change (IPCC) assessment reports, there continue to be scientists who challenge this conclusion. Some of these scientists are reputable in their own fields, and thus their criticisms carry a lot of weight for reasonable people as well as politicians who feel threatened by the moral imperative to action that such a conclusion demands. That bloggers, social activists, and politicians continue to be climate deniers is no surprise; we still have plenty of opponents of evolution populating government executive offices, legislatures, and school boards, not just pulpits or church hierarchies. I never paid much attention to these critical scientists because the evidence was overwhelming, and regardless, the main driver of anthropogenic climate change-fossil fuel burning-is demonstrably harmful on so many levels that we have a moral imperative to move to a renewable energy future even without the devastating effects on the climate.
However, a conversation with a reasonable and well-educated person led to him providing me a list of what appear to be the most credible scientists and alternative theories. I felt compelled to investigate this list as a personal response, but that response has general relevance, so I adapted it for this blog entry.

First, let's reflect briefly on the 4th IPCC assessment report (reports available here), in particular, the Summary for Policymakers. The report summarizes the estimated effects of various large-scale influences on regional and global climate, called "forcings", and incorporates them into model predictions of various climate-related phenomena, such as average temperature, sea level, snow cover, etc. These forcings include greenhouse gases (GHGs), ozone, surface albedo, and others that are influenced by human activity, i.e. have an anthropogenic component. It also includes solar irradiance, which is outside our control. Some forcings were left out as they were not considered to have an important effect on climate. The basic but overwhelming conclusions of the reports are that global warming is real, and that anthropogenic increases in GHGs (i.e. "we") are responsible.

Despite all of this, there are plenty of PhD-trained scientists openly questioning the theory itself, not just its internal particulars. At this point, however, to engage in credible external criticism requires a credible alternative that deals with the perceived flaws of the accepted theory. There are a number of alternatives out there, and I suggest those interested in them check out realclimate.org for a cogent scientific discussion of many of them. In general, most of the alternatives are really attempts to propose that specific climate forcings, many of which are considered in the IPCC assessments, are more important than the scientific consensus suggests they are. Thus, they primarily represent areas where new research and understanding can improve the models we have (and improve future IPCC assessments) rather than displace the well-established theory based on increased GHGs.

For a theory to pose a true alternative, it must be a radical break from our current understanding. Think of Einstein's general theory of relativity compared to Newtonian mechanics. Think of Darwin's theory of evolution. These are clearly far-reaching scientific revolutions, but they epitomize what a real alternative would look like in climate science. The models we have now are based on such a wide array of evidence, theory, mechanisms, and understanding that a true alternative must posit a new conceptual basis for understanding how climate works and then show how it better handles the problems, flaws, and inconsistencies of the current theory. That's not to say our current theory is perfect or that predictions won't change; they will. However, it is highly unlikely that we will discover or conclude that the earth isn't actually warming or that it isn't caused by anthropogenic GHG emissions. In a similar fashion, we are unlikely to conclude that natural selection doesn't lead to changes in population genetics or long-term speciation, but we do hope to improve our understanding and ability to predict those changes.

The fact that reasonable people still refuse to accept the IPCC assessment conclusions or point to alternative theories as plausible explanations has more to do about grappling with the moral implications of climate change than of the science itself (see former post). And that's the value and mission of the IPL network: to help people deal with the moral dimensions and practical actions. But every so often, we do need to address the scientific questions to reassure people that the theory is sound and the rational basis for action is well-supported.