According to Johannes Gutenberg University Mainz (JGU), an international team "has published a reconstruction of the climate in
northern Europe over the last 2,000 years based on the information
provided by tree-rings." Their reconstruction is illustrated in the adjascent graph.According to the article, the group "used tree-ring density measurements from sub-fossil pine trees originating from Finnish Lapland to produce a reconstruction reaching back to 138 BC. In so doing, the researchers have been able for the first time to precisely demonstrate that the long-term trend over the past two millennia has been towards climatic cooling."
The authors also suggest that "the large-scale climate reconstruction shown by the Intergovernmental Panel on Climate Change (IPCC) likely underestimate this long-term cooling trend over the past few millennia."
While one study is hardly ever sufficient to change an entire scientific theory, this data raises an important issue to be considered by those in the sustainability community, viz., is "global warming" a necessary component of sustainability?
In my personal opinion, the answer is a resounding "no." Sustainability efforts are justified regardless of whether global warming is a valid phenomenon. Behaviorally speaking, people are much more motivated by short term consequences than by long term consequences. In addition, when consequences are a cumulative product of macrobehavior -- that is, the behavior of many people acting concurrently over time, rather than the behavior of one particular individual -- those consequences are even less likely to change behavior. Global warming, whether "real" or not, suffers from these behavioral shortcomings.
The philosophical foundation of behavior analysis is one of pragmatism. It's functional contextualist underpinnings suggest that if the scientific enterprise and it's products are intimately tied to the verbal behavior of scientists acting in context, then "what is real" is unimportant and indeterminate because "reality" is relative to one's history of interacting with the world. Rather, what we should focus on is "what changes behavior." Thus, worrying about whether global warming is "really" happening is a non-issue. While there are many individuals motivated by "global warming" there are many more who aren't and a sizable portion of those who are flat out skeptical.
Alternatively, what most people do care about are the more immediate and tangible products of unsustainable behavior such as (a) pollution which can be seen, smelled, and felt, rising from factories and emitted from vehicles, (b) trash, which are eye sores on our sidewalks, rivers, and parks, and (c) chemical contaminants in our lakes, rivers, and water supply which impair our health.
