When released into the atmosphere, certain gases act like a blanket, preventing heat from escaping. One of the most important heat-trapping gases is carbon dioxide (CO2), which is released when we burn fossil fuels like oil, coal, and natural gas.
Once released, carbon dioxide stays in the atmosphere for roughly 40 years, though its effects stay much longer; other gases, like methane, are even longer-lived. The cumulative effect is to raise the planet’s temperature.
The "doldrums" is a descriptive adjective for the corridor from around Earth closer to the equator when ships can become stuck in windless seas. In the horse elevations, where even the air moves down to towards the Earth's surface, the increasing jet stream eventually subsides.