Environmental advocates have a compelling story to tell, but it has been hard to get people to listen. The advocates argue that the ever increasing burden of human activitiesâ€” reflected in rising world population, coupled with rising per capita GDPâ€” is taking an increasingly heavy toll on the global environment. The impacts encompass climate change, ocean acidification, destruction of terrestrial ecosystems, the appropriation of most of the worldâ€™s great river systems for hydroelectric power projects, the depletion of fossil aquifers, the loss of topsoil, water and air pollution, and the squandering of irreplaceable resources. On a global scale, environmental capital is being liquidated at a much faster rate than it is being renewed.
Some of the consequences of our abuse of the environment are imminent. With world agricultural production leveling off, grain prices are rising. Water tables in parts of India, China, and the Middle East are dropping precipitously in response to the unsustainable use of ground water for irrigation. Without ground water as a backup, even a quite ordinary drought could trigger acute water shortages that would threaten food security. Irreversible species extinctions are occurring parts of the tropics due to the combined effects of habitat destruction and global warming. Human health is threatened by the buildup of toxic wastes in water and soils and by declining air quality.
In todayâ€™s globalized economy, environmental disruptions in populous countries anywhere in the world could profoundly affect us all.
In their efforts to warn the public that a global environmental crisis is at hand, some environmental advocates are increasingly exploiting the shock value of extreme weather events. For example, columnist Thomas Friedman has been talking about the â€śglobal weirdingâ€ť of the weather. Activist/author Bill McKibben stated recently in a Youtube video: â€śPretty much every day, somewhere on this planet we are breaking records that have stood for centuries…”
Many scientists and policy advisers endorse this strategy of making global warming the flagship of the environmental movement and extreme weather events the ship symbols. They argue that it gets climate changeâ€”the â€śsmoking gunâ€ťâ€” onto the front page of the newspapers and it plays into Americansâ€™ proclivity to be more concerned about what is happening here and now than about issues that they perceive as affecting people in distant countries far off on the future. But I wonder if this strategy might have a downside.
Establishing a linkage between extreme weather events and climate change is not as easy as it might seem. The power of statistical inference is limited by sample size.Â Memorable weather events occur far less frequently than, say, lung cancer cases, so attribution of extreme events to climate change is far less convincing than the attribution of lung cancer to smoking. Even when the linkage is statistically significant, as in the case of heat waves, the more extreme the event, the smaller the relative contribution of global warming to the observed anomaly. That doesnâ€™t detract from the statistical significance of a record breaking high temperature, but it places a damper on its shock value.
The limitations imposed by sample size would not be such a serious issue if the mechanisms that link extreme weather events to climate change were well understood, but unfortunately, they are not. These ambiguities confront scientists and science writers with a dilemma. Nuanced stories that reflect the true state of the science are rarely simpleÂ and dramatic enough to qualify as front page news. But stories that exaggerate the human contribution to extreme weather events detract from the credibility of climate science.
Has the strategy of focusing the discussion of the global environmental crisis on extreme weather events been effective in raising public awareness? Opinion polls indicate that there does, in fact, tend to be a discernible upswing in the level of public concern about climate change in the wake of particularly damaging extreme events such as Hurricanes Katrina and Sandy. But there is no evidence of a robust, sustained upward trend.
At no time in the recent past have Americans ranked climate change as their highest priority environmental issue. According to the report â€śPublic Support for Climate and Energy Policies in November 2013â€ť, published by the Yale Project on Climate Change Communication,Â Americans rank the leading environmental issues as follows: water pollution (62% say it should be a â€śhighâ€ť or â€śvery highâ€ť priority), developing sources of clean energy (61%), toxic waste (56%), air pollution (54%), climate change (44%).
If the polling results are any indication, it would require a series of extreme weather events much more disruptive than the ones weâ€™ve experienced during the past decade to bring about a real sea change in public opinion on climate change. I donâ€™t think we can afford to wait for that to happen. Raising public awareness of the multiple threats to our planetâ€™s life support system is too important to be subject to the whims of the weather.
The author,Â John Michael Wallace, is a professor of atmospheric sciences at the University of Washington.