 Scientists predict that if we continue on our current path, we'll see around 4 degrees Celsius warming by the end of this century. That's because we're burning more and more fossil fuels and emitting heat-trapping greenhouse gases into the atmosphere. Carbon dioxide is the main control knob for the Earth's climate. Other factors act like fine-tuning knobs, but it's carbon that causes the big changes. Over the last few decades, the sun has been getting cooler. What if it kept getting cooler? This has happened before. From about the year 1450 to 1850, Europe and North America went through little ice age. Around this time, there were two periods when the sun was relatively quiet. These two periods are known as the Mondromenum and the Dalton Minimum. The Mondromenum occurred from 1645 to 1715. Astronomers like Galileo and Christoph Scheiner kept records of the number of sunspots starting in 1600s. Sunspots are a good indicator of how active and energetic the sun is at any given time. If there are lots of sunspots, there's also more sunlight reaching the Earth. During the Mondromenum, astronomers observed very few sunspots. The sun was quiet. Toward the end of the little ice age, there was another period between 1790 and 1830 known as the Dalton Minimum. During that time, again, there were relatively few sunspots. In other words, less energy from the sun was warming the Earth. What would happen to future global warming if the sun's output fell down to Mondromenum levels? Several teams of scientists have investigated this question. All the studies agree. Even if the sun entered another quiet period like the Mondromenum, the drop in sunlight would only be enough to offset about one decade's worth of human-caused global warming. In other words, a quieter sun would cause global cooling of no more than 3 tenths of a degree Celsius or about half a degree Fahrenheit. To put that into perspective, global temperatures are already more than 1 degree Celsius or about 2 degrees Fahrenheit hotter than the little ice age. The planet will warm another 1 to 5 degrees Celsius this century depending on how much more carbon pollution you put into the atmosphere. That slight cooling would also only be temporary. As soon as the sun entered another more active phase, the cooling from the solar minimum would be erased by the solar warming. Compared to the greenhouse warming, the sun's role in the current climate is a minor blip. One myth argues that rather than see global warming in the future, we're heading into an ice age. Why? The myth argues it'll happen because of the cooling sun. This myth represents the role of the sun in climate change. Over the past several thousand years, changes in the sun have not been the main driver of climate change. Rather, it's been changes in carbon dioxide in the atmosphere and volcanic eruptions that have been the two main factors. Recent research suggests that the sun has played less of a role than scientists previously thought and volcanoes a larger role. Once, climate scientists thought the sun was a major contributor to the little ice age. However, scientists have discovered that the sun is more stable than we used to think. The best recent estimates suggest that the amount of sunlight now is only about one tenth of one percent higher than during the little ice age. So what caused the little ice age? First, it's important to understand that the little ice age really was little. The planet just wasn't that cold outside of Europe and North America. The average global surface temperature was only about half a degree Celsius or one degree Fahrenheit cooler than the medieval warm period that happened 500 years earlier. That half a degree cooling took several centuries. In comparison, human greenhouse gas emissions have caused more than half a degree Celsius global warming in just the last 40 years. There were a lot of volcanic eruptions during the little ice age. When volcanoes erupt, they send tiny particles into the atmosphere that block sunlight. During periods of high volcanic activity, this can cool the planet. Recent research has found that high volcanic activity during the little ice age played a bigger role than cooling from the quiet sun. So unfortunately, the sun isn't coming to our rescue. It's up to us to prevent the worst impacts of global warming. Until we dramatically reduce our greenhouse gas emissions, they'll continue to be the main factor driving global warming.