As a result between the people from the European continent and the people from the North American and South American continents, most of the native populations had died out.
Even though there's the general opinion that the main cause for this were the battles and the killing in them, even though they were numerous and there were casualties, the reason for the mass dying out was totally different, diseases.
The Europeans brought new diseases with them, and the Native Americans were not immune to them, so they spread around them very quickly and they were dying very quickly, which lead to a depopulation of large ares of the continents.
The correct answer is cooler. It is because those locations that are near to the equator are having hotter climates than those who are much farther because the equator has receives the sun's energy most of the times, making those near it exhibit the hottest climates.
Global warming is what scientists conclude has caused the massive rise in temperature. Greenhouse gases are in the atmosphere, keeping heat trapped around Earth. The more these gases build up, the warmer or the more significant rise in temperature will take place. Greenhouse gases are released when we use fossil fuels, burn fires, etc. We are using more of these than ever, especially with the world's growing population.
I hope this helps!
~kaikers
