One day Carl's mother was making a roast. Carl entered the kitchen for a drink when the oven started to form ice crystals! As Carl's mom pulled out the roast she saw the roast ice up. That is when she noticed Carl's sweater smoldering. Carl's skin was so hot you would have thought he sat in the oven instead of the roast.
Finally, in his junior year of High School, during a graduation dance, Carl burst into flames while most of the people around him got hypothermia, and a few cases of frostbite. Carl's thermodynamic energy powers were manifesting too fast for him to control. The dance was the first time his powers directly drained heat energy from a living person. The dance reported to affect about 50 people that night, dropping their body temperatures about 10 degrees. His prom date, who had been standing next to him at the time, was the one that suffered the most of the heat transfer.
Carl then spent a lot of time in various labs trying to figure out how to stabilize his thermic shifts. The only thing effective so far has been a thermic stabilizer suit that was designed to help Carl regulate his body temperature from the extremes of heat energy entering and leaving his body. His powers mutated to a point that his body could not handle the amount of heat energy he could absorb.
After years of research, and no real breakthrough, Carl escaped the institute. Carl took to being a criminal to fund more research on his condition feeling that he never got the proper care due to various budget cutbacks and other bureaucratic red-tape. His powers made him particularly effective as a safe cracker has he could freeze joints and delicate mechanisms and then applying intense heat to those now weakened areas.
Had Carl been a more ruthless person he could have thrived as a criminal, but that was not in Carl's nature. He only robbed to pay for repairs and upgrades to his thermic suit and to hopefully fund more research on his condition. As it was, he was caught more often then not. Going in and out of jail quite a few times.
These thermic shifts allows Thermite to create simple constructs of fire and ice, such as fireballs or ice slides, and is also able to generate waves of intense heat or cold.