It may be the most alarming report on climate change yet.

The third U.S. National Climate Assessment draft describes the Earth’s future: rising temperatures, melting glaciers, disappearing coastlines, rising sea levels, extreme weather, frequent heatwaves.

It warns unequivocally that if we don’t do a lot more to curb greenhouse gas emissions, the warming will “accelerate significantly.”

Climatologists say the data is frightening — they also say it won’t change naysayers’ minds.

“As we get more numbers and data, reports get scarier … it feels we have been underestimating the kind and amount of problems we will face,” said John Smol, who holds the Canada Research Chair in Environmental Change at Queen’s University in Kingston.

But he said it won’t be enough to convince climate change deniers.

“Some may change their minds a bit, but that’s about it,” said Smol.

Climate change deniers dismiss the scientific consensus on global warming and its significance. Some are contrarians, some are involved with think-tanks and some are scientists, climatologists say. There aren’t many of them but they are organized, they add.

It is unclear how long they have been around but Clive Hamilton, an Australian author who wrote Requiem for a Species, believes climate change denial dates back to the early 1990s. He says after the collapse of the Soviet Union, conservatives who had put their energy into opposing communism sought other outlets.

Climate change deniers are effective, Smol said. “They have been good at confusing scientific issues with the public.”

Why do they resist “data” and “facts” about climate change? It’s a conundrum, say scientists.

The evidence is there: what was predicted is happening, says Gordon McBean, director of research at Western University’s Centre for Environment and Sustainability. Temperatures are already rising and glaciers are melting, he said.

McBean noted that the National Climate Assessment draft was written by “top-notch people who have looked at every sector that will be impacted by climate change.”

A paragraph in the summary of the draft says: “Evidence for climate change abounds, from the top of the atmosphere to the depths of the oceans. This evidence has been compiled by scientists and engineers from around the world, using satellites, weather balloons, thermometers, buoys and other observing systems. The sum total of this evidence tells an unambiguous story: the planet is warming.”

Data and facts — there are plenty of both in the draft report.

But McBean says deniers have never let scientific information interfere with their line of thought. “I doubt they will ever disappear.”

Deniers have modified some of their ideas. Some now accept the Earth is getting warmer “but they are now saying it is not caused by greenhouse gases,” he said. They blame the sun.

McBean and other climate change scientists believe some deniers do it for attention, others because they are being funded and a miniscule number because they believe climatologists are wrong.

In a blog post on davidsuzuki.org in August, environmental activist David Suzuki said climate change deniers are almost extinct.

But Harry McCaughey, a climatologist at Queen’s University in Kingston, disagrees; he says their number has increased in the past two decades.

“They are also more vocal now,” said McCaughey. “What we have in the denier community is a group of highly organized message managers who take ideas and break them up in a way so they are easily understood and heard frequently.”

It doesn’t help that scientists are hopeless at communicating ideas to the media, he added.