Americans rarely cite environmental concerns when asked in polls to name the most important problem facing the country. In the last several years, the economy, jobs, the budget deficit and health care garnered the most mentions, with the environment barely registering. In the Pew poll, fewer Americans cited climate change as a top threat than cited financial instability, Islamic extremism, Iran’s nuclear program or North Korea’s nuclear program.

The Middle East was the only other region that did not have a majority seeing the issue as a major threat. Fewer than 20 percent of respondents in Egypt or Pakistan viewed it as a big threat, and 30 percent in Israel did.

In many other middle-income or poor countries, concern over climate change was higher than in rich countries or as high. Scientists predict that climate change will cause larger problems for poor countries than rich ones, partly because many poorer countries are already naturally hot or prone to extreme weather. But all countries will be affected, scientists say.

A scientific report issued Tuesday on the effects of climate change in the United States concluded, “Climate change, once considered an issue for a distant future, has moved firmly into the present.”