A recent Brunswick summit on climate change (“Climate panel’s vision is ominous,” Page A1, June 13) focused on how global warming will harm Maine’s economy.

The Southwest is facing a “megadrought,” and California is severely rationing water supplies.

Science predicts dire consequences for the entire planet if CO2 emissions continue to climb. Indeed, climate change is the pre-eminent threat facing our planet today.

The Republican Party, however, is led by climate-change deniers, including virtually all current candidates seeking the party’s nomination for president. Sen. Susan Collins, R-Maine, is not a denier, but what role does she play in the climate debate, and why is her role important?

Ninety-seven percent of professional climatologists are convinced warming is happening and that human behavior is a significant factor, yet a third of Americans believe there’s no solid evidence for global warming, and among those who do, 60 percent deny human activity as a factor (“Maine Voices: Warming denial proves science under siege, much like 17th century,” Nov. 8, 2014).

This ignorance is obviously affirmed when one of our two major political parties conspicuously denies the science behind this dangerous reality.

Sen. Collins is widely praised as an independent-minded Republican in the tradition of Margaret Chase Smith. But is she really?

Sen. Smith courageously challenged the extremism of Sen. Joe McCarthy; thus far Sen. Collins has failed to “call out” the extremist science-deniers, who pose a far greater threat than did McCarthy. Failing to do so lends a silent or indirect credibility to their uninformed, irresponsible “thinking.”

Scientists tell us the time for avoiding climate catastrophe is short. The senator’s silence, therefore, is not only disappointing; it’s dangerous. Let us hope she will one day soon speak up and serve us as wisely and courageously as did Sen. Smith.

Bob Schaible