# Do the Perigee and Apogee of the Earth's orbit affect the temperature of our summers?

#### philip porhammer

does the Perigee and Apogee of the earths orbit relative to the seasons affect the temperature of our summers?

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#### Bystander

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does the Perigee and Apogee of the earths orbit relative to the seasons affect the temperature of our summers?
What's your conclusion, given that the sun is approximately constant in its radiation output? Have you considered northern and southern hemispheres?

#### lomidrevo

You probably mean perihelion and aphelion instead of perigee and apogee when we talk about Earth orbiting Sun.
The reason why we have seasons on Earth is due to the fact that axis of Earth's rotation is not perpendicular to the orbital plane, it is tilted by about 23 degrees. As Earth orbits Sun, one of the hemispheres is getting more sunlight than the other, except equinoxes, of course.
However, the orbit is slightly eccentric, and indeed it plays some role. Perihelion occurs at beginning of January, and as Earth is slightly closer to Sun than a mean distance, the winters on northern hemisphere are bit warmer than winters on southern hemisphere (aphelion occurs in July). Similarly, the summers are bit colder on northern hemisphere.

#### OmCheeto

Gold Member
Interesting question. From my calculations, if the Earth were not tilted, and had no atmosphere, the variation in temperature would be ≈4.5°C (≈8°F).

Wiki lists:
a. Earth's tilt
b. Higher concentration of land masses in the northern vs southern hemispheres​
as two reasons this is hard to figure out.

"...summers are 2.3 °C (4 °F) warmer in the northern hemisphere than in the southern hemisphere under similar conditions."

Which is backwards, if temperature were based on apsides.

#### lomidrevo

You are right! I made it too simple in my previous post, I didn't consider the difference in surface of the hemispheres. What I wrote would be the case if the Earth's surface is homogeneous.
The surface of the southern hemisphere is covered by more ocean and less land comparing to northern hemisphere. That influences how is the heat absorbed and transported over the surface. I found this link interesting.

One can learn something new every day!

#### davenn

Gold Member
Perihelion occurs at beginning of January, and as Earth is slightly closer to Sun than a mean distance, the winters on northern hemisphere are bit warmer than winters on southern hemisphere (aphelion occurs in July).

No, that is very incorrect and you only need to look at the data to see that.
The southern hemispheres have VERY mild winters compared to the northern hemisphere.
We don't get the massive snowfalls, ice storms, rivers freezing over etc etc

"...summers are 2.3 °C (4 °F) warmer in the northern hemisphere than in the southern hemisphere under similar conditions."
yeah ... under similar conditions, which of course they are not

Dave

#### lomidrevo

No, that is very incorrect and you only need to look at the data to see that.
Yes, I thought I made it clear in my post #5, that I admit I was wrong in my first post. Although the difference of solar irradiance between perihelion and aphelion is almost 7%, the Earth's climate system (including distribution of land and ocean) has a more significant influence on the surface temperatures.

The southern hemispheres have VERY mild winters compared to the northern hemisphere.
We don't get the massive snowfalls, ice storms, rivers freezing over etc etc
If you compare the mean temperatures at comparable (opposite) latitudes (e.g Sydney and Los Angeles), the difference is not very big. Daily mean in Sydney 13 °C (in July) vs. 14.4 °C in LA (January) could even suggest colder winter in Sydney. Of course, this is very simplified comparison, as we do not take into account any effects due to regional climate conditions (we could also try to compare Europe and Patagonia). I just want to point out that differences might not be so big as you suggest.

"Do the Perigee and Apogee of the Earth's orbit affect the temperature of our summers?"

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