Why doesn’t the United States care about global warming? That’s a common question nowadays. Poll after poll has found that concern about the climate has tumbled. On the policy front, the United States is doing less than even China and India at this point, as a recent report from HSBC details. Over the weekend, Elisabeth Rosenthal tried to explain America’s carbon exceptionalism in a great piece in the New York Times. As you’d expect, it’s a complex, multi-layered story. But two factors — the Senate and the recession — seem worth highlighting here.

(Jonathan Hayward/AP)

Australia offers an interesting comparison here. On many of the underlying structural dynamics, Australia resembles the United States pretty closely. Coal and agricultural interests wield a lot of clout. Per-capita carbon emissions are high. There’s a well-developed network of climate denialism — the country’s best-selling newspaper, the Australian, regularly gives voice to skeptics of global warming. When the Labor Party, led by Prime Minister Julia Gillard, proposed a carbon tax recently, it faced a well-funded and well-organized opposition. Yet the tax managed to squeak through the lower house of parliament (its biggest hurdle) on a 74-72 vote. That wouldn’t have been a large enough supermajority to survive the Senate. It was good enough for Australia.

Meanwhile, the second question is: “Institutions aside, why has public concern about global warming dropped in the United States?” And the recession has arguably played an important role here. Economists Matthew Kahn and Matthew Kotchen have teased out this relationship in more detail. An increase in a state’s unemployment rate is associated with a significant decline in the probability that residents think global warming is real. In California, you can see this effect county-by-county: When local unemployment rises, there’s a drop in the number of residents who see global warming as the most important policy issue. Meanwhile, Google searches for “global warming” plummet sharply in a downturn in favor of searches about the economy:

The same thing occurs with media coverage. Graphs like these don’t explain everything about climate policy in the United States. They can’t account for why the Republican Party has rapidly adopted an anti-scientific stance on the issue, for instance. But the recession is a major part of the story.

Update: Note that there’s one other big difference between Australia and the United States. Newspaper coverage of global warming in Australia actually went up dramatically in the past year, possibly because the country experienced so many climate-related disasters (floods, droughts, wildfires). That’s one data point in favor of Drexel sociologist Robert Brulle’s theory that dwindling media coverage of the issue is a big factor here.