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Earth Was Furthest From The Sun On July 4th - Why This Is Counterintuitive

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It is very hot in parts of the Northern Hemisphere right now. Heat records are being shattered in Asia, Europe, and North America. On July 4th, the National Weather Service in Anchorage tweeted:

The Anchorage International Airport has just reached 89 degrees. The all time record high temperature for #Anchorage has officially been broken. The previous record of 85 degrees was set on June 14, 1969 (period of record 1952-2019). #AKwx #RecordHeat

An hour later was a "hold my drink" moment because the reading went to 90 degrees. When a heat record is broken, it is typically by a degree or so not 5 degrees. In the Olympics, a runner breaking a long-standing world record by 5 seconds would immediately raise concerns about doping. I discussed this in a recent Forbes article about temperature records shattered in Europe recently so I will not linger on the topic here. July 4th was a national holiday in the United States, but it was also the aphelion, the point at which Earth is furthest from the sun. How can it be so hot if we are at the furthest point from the Sun?

NASA

Before I answer that question about aphelion, it is useful to define perihelion also. My colleague Phil Plait does a masterful job explaining it in a 2016 Slate article:

perihelion, the point in its orbit where it’s closest to the Sun. At that moment the center of the Earth will be 147,100,176 km (91,403,811 miles) from the center of the Sun...........Why are we closer to the Sun now than other times? Well, if the Earth orbited the Sun in a circle, we’d always be the same distance from it (in one way, that’s the definition of a circle). But our orbit is ever so slightly elliptical, so sometimes we’re closer to the Sun, sometimes farther.

Aphelion was on July 4th, 2019 this season. The Earth was approximately 152.1 million kilometers (94.5 million miles) from the Sun. As a professor and scientist, I often notice concepts that are very counterintuitive to the public. For example, many people struggle with understanding that a snowy day represents weather not climate or that it can actually get pretty cold in a desert. I suspect some people wonder how it can be so warm right now in the Northern Hemisphere when the Earth is furthest from the Sun.

NOAA

The National Oceanic and Atmospheric Administration (NOAA) website provides the context for the answer to that question:

The Earth is tilted 23.5 degrees on its axis, which affects the distribution of the sun’s energy across the surface of the planet. As the Earth orbits the sun every 365 ¼ days, the axis is always pointing in the same direction into space, with the North Pole toward Polaris, the North Star. Around June 22, the northern hemisphere is angled towards the sun, and receives the most direct radiation and the most energy. This is the start of astronomical summer in the northern hemisphere and winter in the southern hemisphere. 

To be completely accurate, even the axial tilt angle can vary through the action of Milankovitch cycles. Most globes lie to us  by showing a fixed axial tilt of 23.5 degrees, but it is certainly a good average approximation.

During the aphelion, Earth may be at its furthest point from the Sun, but the Northern Hemisphere is receiving more direct solar radiation. If you need a way to conceptualize this process, shine a flash light directly onto the floor. You should see a very concentrated circle of light. If you shine the flashlight to the floor at an angle, the spot is broader and more diffuse. In a nutshell, this explains why summer temperatures are warmer. Meanwhile, the Southern Hemisphere is tilted away from the Sun right now. It is winter.

NOAA

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