The Global Change Research Act of 1990 mandates that the U.S. Global Change Research Program deliver a report to Congress and the President on global change, human-induced and natural, at least every four years. The Fourth National Climate Assessment (NCA4) is the latest report to fulfill this mandate. Volume II of this report (NCA4-II) was just released and focuses on the observed and projected impacts of climate change in the US, with special consideration given to risk reduction. The news media reacted to NCA-II with alarm. Some typical headlines:
Climate report warns of grim economic consequences, worsening weather disasters in US /Fox News
The latest report on global warming makes grim reading/The Economist
Climate change will have dire consequences for US, federal report concludes/CNN
In Post I of this series, I argued that such news stories misrepresented the actual report. The dire and grim consequences cited in the headlines weren’t true predictions but worst-case scenarios that assumed “high emissions and limited or no adaptation”. Why would NCA4-II use unrealistic scenarios? Because doing so fits its purpose, which is to “inform decision-makers, utility and natural resource managers, public health officials, emergency planners, and other stakeholders by providing a thorough examination of the effects of climate change on the United States.” The scenarios are basically a risk management tool whose use-value matters more than its predictive utility. As explained by Wikipedia:
A worst-case scenario is a concept in risk management wherein the planner, in planning for potential disasters, considers the most severe possible outcome that can reasonably be projected to occur in a given situation. Conceiving of worst-case scenarios is a common form of strategic planning, specifically scenario planning, to prepare for and minimize contingencies that could result in accidents, quality problems, or other issues.
NCA4-II notes repeatedly that a lot is already being done to mitigate and adapt to climate change in the US and the worst possible outcomes are unlikely simply given current trends. Since the goal is more ambitious than merely to avoid the worst possible outcomes, NCA4-II provides lots of guidance on what more can be done. But they do go on at length (as in hundreds of pages) on progress to date. Check out some of the report on your own and you’ll see what I mean, e.g., Chapter 1: Overview, Chapter 21: Midwest, Chapter 28: Reducing Risks Through Adaptation Actions, and Chapter 29: Reducing Risks Through Emissions Mitigation.
Another theme in NCA4-II is that mitigation and adaptation efforts often yield near-term benefits unrelated to their value in reducing risks associated with climate change. Drought-resistant crops help poor farmers now. Increased energy efficiency makes business sense now. Coastal marsh restoration protects against flooding now. Even climate change skeptics could appreciate these co-benefits. Spreading the good news about them would probably do more for the cause of climate change mitigation and adaptation than yet another apocalyptic news story.