WASHINGTON — As we marked Earth Day earlier this week, it is natural to ask: What do Americans think of global warming? Is it a big worry? Is government doing enough? The answers seem conclusive but, on closer inspection, are frustrating. They reveal the limits of public opinion surveys in judging public opinion.

Karlyn Bowman and Eleanor O’Neil, the public opinion experts at the right-leaning American Enterprise Institute, recently took a look at some global-warming polling. What they found suggests — superficially — that most Americans want tougher action against global warming.

One question on a 2018 Gallup Poll asks whether “the effects of global warming have already begun.” A stunning 60 percent said “yes,” up substantially from 48 percent in 1997. When the question was presented in a slightly different way — “Do you think global warming will pose a serious threat to you or your way of life in your lifetime” — the answer was even more dramatic; 45 percent said “yes,” up from 25 percent in 1997.

Gallup’s answers were not flukes. Two-thirds of respondents (64 percent) attributed the rise in global temperatures mainly to human activity. When asked whether they worried about this, two-fifths (43 percent) said “a great deal” and one-fifth (20 percent) said “a fair amount,” report Bowman and O’Neil. As for combating global warming, a 2018 Pew poll found that 46 percent of respondents thought it should be a “top priority” of government and 24 percent said it was “important” but a lower priority.

It seems all of a piece. Large majorities of Americans accept the reality of global warming, blame economic activity and think government should act. Case closed.

Not so fast, caution Bowman and O’Neil.

For starters, there is no bipartisan consensus. By and large, Democrats accept global warming and urge tougher policies to stop it, while many Republicans are skeptics. In a March poll, Gallup found that 91 percent of Democrats worried “a great deal/fair amount” about global warming; the comparable Republican figure was only 33 percent. The gap has grown. In 2000, it was 78 percent to 64 percent. Moreover, fighting global warming doesn’t rate high on Americans’ priorities, Bowman and O’Neil note.

There are 19 public priorities that Pew asked about in the January poll. Dealing with climate change ranked next to last. Fighting terrorism was first. The “other” category includes priorities that are opposed or considered not important.

What the table suggests is that Americans want government to do almost everything, from fighting terrorism to strengthening the economy to helping the poor…and on and on. Public opinion polls can be used selectively to create the impression that grass-roots pressure for action is overwhelming. One obvious way to do this is to merge the responses of those who believe a chosen issue is a “top” priority with those who think it’s merely “important.”

For example: In the Pew poll, 94 percent of respondents rated fighting terrorism as the top priority (73 percent) or an important priority (21 percent). Way down the list at number 12 is “improving transportation.” Only 49 percent consider this a “top priority,” but when that is combined with those who think it is important (39 percent), the total is 88 percent-not far from the combined score of fighting terrorism.

The reality is that government can’t do everything for everybody. Practical politicians judge where public pressure demands action — and where it can be minimized or ignored. Combating global warming seems to be in a gray area. It bothers more and more people, but it hasn’t reached a critical mass of public opinion that would compel Congress and the White House to act decisively.

Robert Samuelson is a columnist with The Washington Post.