The Earth, The Sun, and Our Weather

The Earth at any given time is about 93 million miles from the Sun, give or take 1.5 million miles. Our planet sits in the so-called “habitable zone,” a region of space around a star that astrophysicists have determined a planet receives enough energy to maintain a livable temperature and for moisture to be prevalent in the air. Too close, and the temperature is too hot to support liquid water: too far away, and water (if any) freezes.

The Sun’s energy output and the Earth’s orbit around the sun has varied over millions of years. These changes in orbit explain how the Earth’s climate have transitioned from icy to equally hot periods. Science has found that during periods where the orbit has wobbled outward ice ages occurred, while closer passes have caused polar ice to melt and created planet-wide warmth.

Known as the Milankovitch Cycle, these kinds of changes in orbit occur over time cycles of nearly 100,000 years. Solar radiation also varies on cycles even longer than that, which can worsen or diminish the effects of the either the hot or cold portions of that cycle. The effects on the weather you experience during your lifetime are barely noticeable, so we focus on much shorter cycles in the Earth’s orbit and distance around the Sun that do influence our weather.

The Earth wobbles on its axis as it orbits the Sun. When one hemisphere points towards the sun during a wobble it is summer, and when it points away it is winter. This is where our seasons come from (the distance from the Sun has nothing to do with it).

If you’re reading this from the Northern Hemisphere, you might be surprised to find out that the Earth’s distance to the sun is closest in the winter, called aphelion, then it is in the summer, which is called perihelion. Because of the differences in the amount of land mass in either hemisphere, summers aren’t appreciably warmer than one another.

This is because the vast oceans of the Southern Hemisphere take longer to heat up as they absorb the extra solar energy. The Northern Hemisphere has much more land mass, which even at perihelion heats up fast enough to keep summers warm. It’s a perfect balance for life to evolve and thrive.

While its role is still controversial and not well understood, some scientists believe that sunspot activity may play a role in changes in weather over longer time periods. Sunspots are magnetic storms on the Sun’s surface, so when sunspot activity is high, the Sun emits more solar radiation. 

Long periods of little solar activity may be behind short periods throughout history when portions of the Earth experienced colder weather. The last low sunspot period, known as the Maunder Minimum, occurred from about 1645 to 1715, and roughly coincided with what is known as the Little Ice Age.

During this period, portions of Europe and North America experienced some of the coldest winters on record. In London, the River Thames froze regularly in the winter, and the 1780 winter in New York City was so severe New York Harbor completely froze over, allowing people to walk on the ice between Manhattan and Staten Island.

Other areas of the world did not see such pronounced changes, so it is not clear whether the lack of sunspot activity causes enough of a drop in the amount of solar radiation to affect global weather and climate. The changes in the amount of energy are very small, but natural cycles of the Sun do affect weather patterns here on Earth

Furthermore, the Earth’s rotation gives storms their spin and movement. It causes winds to turn right in the Northern Hemisphere and left in the Southern. This spin forms storm systems like low pressures and hurricanes. These larger spinning storms create smaller ones, so Earth’s spin is indirectly responsible for severe storms and tornadoes. These basic concepts form the basis of the science of weather.