My brother Rex, unlike me, is a pretty tough dude.

Retired military, living outside Jacksonville, Florida, grew up on the mean streets of South Portland and Cape Elizabeth. In the Navy, he flew submarine reconnaissance missions as a radio operator, trained other tough dudes in wilderness combat in the woods of western Maine and elsewhere, and possibly most brutal of all, headed up quality control departments in aircraft hangars.

He is paranoiacally skeptical of everything the government does and says. I’m pretty sure he voted for Trump in 2016. His tune, however, has changed radically the last couple of years on several points. One sweltering morning last month at Sebago Lake, he told me why.

He was driving from his suburban house to downtown Jacksonville, a trip of 16 miles. Sixteen miles, he was thinking. A 20-minute or so flat drive. If you tip that 16 miles vertically, you have a rough idea of how high the atmosphere reaches above the Earth’s surface. Actually it reaches to about 300 miles, but almost all of it is packed in the lower 10 miles.

Holy crap, he thought. Sixteen miles, in the big picture of things, is a sliver at best and I’ve been pouring smoke into it from my cars for 45 years. And from the planes I’ve flown. And from my oil-burning heaters. And so has everybody else in the industrialized world, including billions of cars and trucks, millions of factories, coal-burning plants and stoves, chemical facilities, war explosions, and so on and on, decade after decade. At some point, he thought, this sliver of air will reach some kind of saturation of CO2. Figuratively speaking.

Holy crap squared, it’s reaching that point now, he thought. The unusually long spell of withering heat in Florida this May and the goddamn hurricanes and rainstorms that have been swamping his backyard and Puerto Rico are just the first wave of the inevitable result. We have to knock this off. Now.

Reality is that which, when you stop believing in it, doesn’t go away, a science fiction writer once said. If you’re in the dwindling minority of people who think Rex is merely a casualty of an arcane kind of egghead trickery, try out some of these facts from reality:

HEAT REPORTS

• July’s average temperature was the highest ever recorded in Maine (when adjusting for two years of bad data from the 19th century), according to WCSH meteorologist Keith Carson.

• Globally, July was the hottest month ever recorded on Earth, according to the Copernicus Climate Change Service, a program of the European Union.

• Globally, June’s average land and ocean surface temperature was the warmest ever recorded for that month, according to NOAA. Nine of the 10 warmest Junes have occurred since 2010.

• On June 6, Helsinki, Finland, reached 84 degrees, a record for that early in the season.

• In June, parts of France reached that country’s highest temperature ever recorded, 114.8 degrees Fahrenheit.

• In July, a town in Germany broke that country’s high temperature record four times in two days, topping out at 108.7.

• On July 24, towns in the Netherlands and Belgium hit a record high of 105.3.

• London had its hottest day ever for July, 98.4.

• As a result of the same heat wave, Greenland’s ice sheet lost about 197 billion tons of ice in July, enough to raise global sea level by about two one-hundredths of an inch. On Aug. 1 alone, 12.5 billion tons of ice went to the ocean as surface melt. Ten billion tons of ice were lost July 31.

• In Alaska, July 6 was the warmest day statewide ever recorded. On July 4 Anchorage hit its highest temperature ever, 90.

• On July 15, San Francisco reached its highest temperature ever recorded for June, July or August, 100.

• On June 10, New Delhi, India, reached its highest temperature ever recorded in June, 118.4. In the heat wave of May and June, temperatures reached 123 and dozens of people died of the heat.

• A recent study predicts that if global warming trends continue as they are now, severe heat waves that produce temperature-humidity index readings in which the human body cannot cool itself enough to survive more than a few hours are likely to increase in South Asia, the Middle East and eastern China. Such heat killed 3,500 people in Pakistan and India in 2015.

• Researchers in China reported that severe heat waves in Fujian province (where I lived for a while years ago) are starting earlier, ending later, becoming more frequent and intense, and lasting longer. They say urbanization in southeastern China contributes to approximately half of the increasing heat waves.

• Since 1980, there has been a 50-fold increase in dangerous heat waves worldwide, David Wallace-Wells notes in his alarming book, “The Uninhabitable Earth.”

• If carbon emissions stopped increasing today, Earth’s overall temperature rise would exceed 1.5 degrees Celsius by 2040. Best-case scenarios for temperature rise by 2100 are about 2 to 2.5 C. If the Paris Accord goals were met, the rise would be about 3.2 degrees. The Paris Accord goals are not expected to be met. If things continue as they are, a rise of 4 C is likely, according to the Intergovernmental Panel on Climate Change. A 4-degree rise would probably reduce crop yields by half, worldwide. A 5-degree rise would make whole regions uninhabitable for humans. A 6-degree rise would make New York City hotter than present-day Bahrain. A rise of 5 or 6 degrees by 2100 is unlikely, Wallace-Wells reports, but possible.

ONE ITEM TO THINK ABOUT

• In June, White House officials prohibited a State Department intelligence agency from including in a report to the House Intelligence Committee a warning that human-caused climate change could be “possibly catastrophic.”

A layer of atmosphere less than 16 miles thick. Humans put 40 billion tons of carbon dioxide, a greenhouse gas, into it every year. Reality. Think about it.

Dana Wilde lives in Troy. You can contact him at naturalist1@dwildepress.net. His recent book is “Summer to Fall: Notes and Numina from the Maine Woods,” available from North Country Press. Backyard Naturalist appears the second and fourth Thursdays each month.