<p>The image below (apparently from &quot;physicalgeography.net&quot; is somewhat instructive:</p>
<p>Notice that even in the middle of summer, India (at about 30 °N) still gets slightly more sun than the Britain (at 60 °N). That's because although the days are longer in Britain, the sun is lower in the sky and so its heat is spread out over a wider area.</p>
<p>But the North Pole gets even more sun than either Britain or India in June, and the equator gets substantially less. So there is something to explain. The reason is thermal inertia.</p>
<p><a href="https://i.sstatic.net/9CSGe.png" rel="noreferrer"><img src="https://i.sstatic.net/9CSGe.png" alt="Graph of insolation per month at different latitudes" /></a></p>
<p><sub>This graph shows insolation averaged over 24 hours at four different Latitudes. This shows the theoretical insolation. The model used to calculate these curves includes the effects of Earth's elliptical orbit, but do not take account of any atmospheric effects, such as the energy absorbed by the atmosphere, nor any weather effects such as clouds. It shows that a perfectly black disc with an area of 1 m² placed just above the atmosphere and oriented horizontal to the Earth surface would receive an average of about 515 Joules per second at the North Pole on June 21st and an average of about 380 Joules per second at the Equator.  The main reason for the Equator value being so low is that it is night time for about 12 hours at the equator.</sub></p>
<p>Imagine pushing a heavy ball. It can take some time for it to begin to move quickly because it has inertia. Similarly, it takes time for the ground and water to heat up when the sun shines upon them. India gets much more sun in winter, and so the ground and water remain warm.  When summer comes, it heats up further and ends up much hotter than Britain.  In Britain there is very little sun in winter, and the ground and water cool down (and freeze). Then, even when the sun comes in summer, it takes time to warm up. By the time the ground and water have warmed up, the sun is already starting to weaken. And so the temperature never rises as much as it can in India.</p>
<p>There are lots of details and local effects (the gulf stream in Britain, and the monsoon in India are significant) but the basic reason that India is hotter <em>in summer</em> is that it gets more sun <em>in winter</em>!</p>
<p><a href="http://www.physicalgeography.net/fundamentals/6i.html" rel="noreferrer">Pidwirny, M. (2006). &quot;Earth-Sun Relationships and Insolation&quot;. Fundamentals of Physical Geography, 2nd Edition.</a></p>

CC BY-SA 4.0
2022-04-17T21:32:40.963Z
Also, Earth goes through its aphelion in early July.
Spencer
CC BY-SA 4.0
2022-04-18T07:48:43.997Z
This "inertia" is called seasonal lag and is explained here: https://earthscience.stackexchange.com/a/4512/18081
Jean-Marie Prival
CC BY-SA 4.0
2022-04-18T07:57:09.443Z
@Spencer I don't think I understand how the Earth being furthest from the Sun in July makes a difference. The eccentricity of the Earth's orbit is very low. Also we could equivalently ask about the situation with Patagonia and southern Brazil. Would Earth being at perihelion around January then account for this difference?
Jordi Vermeulen
CC BY-SA 4.0
2022-04-18T12:58:26.910Z
@JordiVermeulen It has a _small_ effect. It's definitely not the major driver. But it explains,  for example, the equatorial dip in June-July being bigger than the December-January one.
Spencer
CC BY-SA 4.0
2022-04-18T19:37:28.443Z
I double-checked the values in diagram: the shown insolation is for [extraterrestrial irradiance](https://en.wikipedia.org/wiki/Solar_irradiance). Basically, the amount of solar energy you'd get on an horizontal surface, just above the atmosphere. That's why the curves are smooth (weather isn't taken into account) and have high values compared to what's available on the surface.
Eric Duminil
CC BY-SA 4.0
2022-04-18T19:52:35.310Z
I agree.  These are extra terrestrial values.  But this particular spherical cow will do fine for illustrating the point:  *India is hotter in summer because it gets more sun in winter!*
James K
CC BY-SA 4.0
2022-04-18T20:25:16.643Z
But this spherical cow doesn't take the atmosphere into account. At higher latitudes, the sun is lower in the sky, and therefore the light goes through more of the atmosphere, more light (and thus heat) gets scattered and less of it reaches the ground.
Cris Luengo
CC BY-SA 4.0
2022-04-18T20:31:59.307Z
Which doesn't change the quality of my answer: which isn't based on particular values of insolation but on the effect of thermal inertia.
James K
CC BY-SA 4.0
2022-04-19T07:04:01.903Z
Yes, your point about thermal inertia still stands, even if the shown diagram doesn't take weather into account. UK vs India isn't the best example, though (I known it was picked by OP): New Delhi gets more irradiance than London every month of the year. Another way to show thermal inertia is to compare monthly irradiance vs temperature. In London, October gets less irradiance than March, but is 5°C warmer, May gets more irradiance than August, but is 5°C colder.
Eric Duminil
CC BY-SA 4.0
2022-04-19T08:31:55.850Z
@JordiVermeulen: "The eccentricity of the Earth's orbit is very low.". Well, it's 0.0167, which doesn't seem like much. But it means the that the longest radius is ~3.4% longer than the shortest radius. And according to the inverse square law, the irradiance at perihelion is ~6.9% higher than at aphelion. 6.9% of [175PW](https://bionumbers.hms.harvard.edu/bionumber.aspx?id=100943&ver=3) is nothing to sneeze at.
Eric Duminil
CC BY-SA 4.0
2022-04-19T10:35:49.437Z
@Eric The user asked about NH pole vs equator. Sure the NH poles would be *very slightly* slower to recover against the tropics in summer vs SH because the magnitude of the solar difference is that little bit less... except NH has much more ice turning to open water and land, making that 6.9% a rather minuscule factor in the entire picture, and the NH summer high lats quicker to recover, yes? But bringing up aphelion for a question on why polar temps are colder in summer seems sort of like alluding to the surrounding grass as the reason your car slowed down when you hit a wall...
JeopardyTempest
CC BY-SA 4.0
2022-04-19T10:37:22.897Z
Decrease each of those latitude curves on James' figure by 7%... doesn't help answer OP's question.  Sure it explains some things in other areas as Spencer notes, but it doesn't really seem to go towards answering the phenomena Leo asked about to any notable degree :)
JeopardyTempest
CC BY-SA 4.0
2022-04-19T11:02:39.293Z
@JeopardyTempest: Sorry, I don't get your point. I was simply answering Jordi's comment, who noted that "The eccentricity of the Earth's orbit is very low".
Eric Duminil
CC BY-SA 4.0
2022-04-19T11:47:55.983Z
Low in terms of magnitude regarding how it contributes to this question at least.  Perhaps we should nix the whole discussion about aphelion, as it honestly doesn't mean anything to the question at hand.
JeopardyTempest
CC BY-SA 4.0
2022-04-19T11:48:03.777Z
@Cris On your thought, I always thought the atmospheric angle to be overrated and of the same order to the areal ground spread already included.  But some scalene triangle calculations suggests at 60N, it does spend nearly double the distance in the atmosphere, increasing to almost 5 times as far by 80°, and 11 times as far by the Pole (using 100 km deep atmosphere... #s drop by ~25% for 50 km atmosphere depth).  So I was wrong to fully dismiss that.
JeopardyTempest
CC BY-SA 4.0
2022-04-19T12:05:12.637Z
Though it still not have as much influence as you'd think... only 23% of solar radiation is removed vs TOA by the atmosphere on average via a Trenberth Diagram).  Digging around personal weather stations, it looks like reasonable stations had fairly similar radiation between [Alaska](https://www.wunderground.com/dashboard/pws/KAKNORTH74/graph/2021-06-22/2021-06-22/daily) and [Mexico](https://www.wunderground.com/dashboard/pws/ILLERA3/graph/2021-06-25/2021-06-25/daily) last June, with a few hundred W/m^2 * hrs in the early/late day mostly making up for the shortage at peak time.
JeopardyTempest
CC BY-SA 4.0
2022-04-19T12:18:05.940Z
But then the poster only asked why polar locations are colder.  Highs gets into the mid 20s C (mid 70s F) regularly in both Alaska and Siberia in the summer.  So they aren't a ton cooler, just a bit... which should be explained by a mix of James' answer and yours.  And other cooler locales, like much of the UK, are better explained by local weather/cloudcover/temperature advection/elevation and such, a mix of the thermal inertia seas, cloudcover's big albedo, and such.  So hopefully in the end, we've reached something reasonably substantive.
JeopardyTempest
CC BY-SA 4.0
2022-04-19T14:17:23.310Z
@JeopardyTempest: The atmospheric angle you're talking about is called [*Air mass*](https://en.wikipedia.org/wiki/Air_mass_(solar_energy)).
Eric Duminil
CC BY-SA 4.0
2022-04-19T14:20:48.207Z
@JeopardyTempest The angle of the sun makes a difference by itself.  The amount of 'rays' per unit area are less in the north.  The [tropic of cancer](https://en.wikipedia.org/wiki/Tropic_of_Cancer) is only at 23.5 degrees.  Anything farther north than that never has the sun directly overhead.
JimmyJames
CC BY-SA 4.0
2022-04-19T14:49:28.363Z
"basic reason that India is hotter in summer is that it gets more sun in winter!"  I think this overstates things a bit.  Based on the chart you show, The 60 line never goes above the 30 line i.e. there are no periods when Britain gets more sun than India.  No inertia needed.  And for the 90 line, it only goes above the 30 for 2 months-ish.
JimmyJames
CC BY-SA 4.0
2022-04-19T15:31:53.153Z
Can you clarify: does the figure show the average power over a 24-hour period?  It can't be local noon, because then it would be much higher at the equator than at the pole.  As for thermal inertia: don't underestimate the effect of the most powerful greenhouse gas, H₂O.  The tropical atmosphere has _a lot_ more of it than at high latitudes, which is one of the reasons why temperatures drop more in a sunny Arctic night than in a dark tropical night.  We need to consider incoming and outgoing radiation. Thermal inertia is a factor, but I'm not sure if it's the biggest reason.
gerrit
CC BY-SA 4.0
2022-04-19T15:35:13.987Z
We could use a (toy) climate model to calculate this.  Suppose that, magically, the Earth stops revolving around the Sun in June (but it still turns on its axis, so we still have day and night).  Fast-forward 3–6 months.  Is the Arctic now the hottest place on Earth, or are the tropics still hotter?  My gut feeling is that the tropics would still be hotter, but I'm not sure if it's true.
gerrit
CC BY-SA 4.0
2022-04-19T19:40:32.143Z
@gerrit I wonder if the relative areas help explain things.  For example, the area between 60° and 90° is much smaller than the area between 0° and 30°.
JimmyJames
CC BY-SA 4.0
2022-04-19T21:22:10.597Z
@gerrit yes, the diagram shows daily averages of extraterrestrial irradiances on horizontal surfaces. Instantaneous values would go above 1400W/m**2, but also to 0 half of the time.
Eric Duminil
CC BY-SA 4.0
2022-04-20T15:16:04.653Z
@EricDuminil You called that diagram "extraterrestrial radiation." It is typically called "Top Of the Atmosphere" (TOA) radiation. Air mass, to which you alluded, exaggerates the TOA effect.
David Hammen
CC BY-SA 4.0
2022-04-20T17:18:29.100Z
@DavidHammen: I guess it depends on the field. *Extraterrestrial radiation* is a well-known term in solar energy, e.g. in Duffie Beckman "Solar Engineering of Thermal Processes", which has apparently been cited 20000 times according to google scholar. I don't know what you mean with "TOA effect". I'd be interested to know how it's linked to the air mass coefficient.
Eric Duminil
CC BY-SA 4.0
2022-04-17T20:18:14.383Z
2022-04-19T17:17:03.250Z
2022-04-19T17:17:03.250Z
James K
<p>Hours of sunlight are not the only factor that determines insolation (solar energy at the surface).</p>
<p>Thought experiment: spread a bed sheet on the floor, switch the lights off, and shine a flashlight directly down on that bed sheet from about one foot above it. You will get a small, fairly bright spot of light on the sheet.</p>
<p>Now tilt the flashlight, and shine it across it at a flat angle - say, 45 or 60 degrees - still keeping it about one foot away from the spot it's illuminating. As you flatten the angle, that spot elongates to cover a larger and larger area. But the amount of light coming out of the flashlight is still the same, spread over a larger area, which means lower intensity on the sheet. The same amount of light that was previously hitting a 100 cm<sup>2</sup> spot might now be spread across 500 cm<sup>2</sup>.</p>
<p>This is part of what's happening at the high latitudes. During the summer months they are getting many hours of sunlight, but they're not getting a lot of energy per square metre compared to the tropics. In early April, the North Pole is getting sunlight 24 hours a day, but much <em>less</em> sunlight (in terms of energy/m<sup>2</sup> etc.) than the equator gets in 12.)</p>

CC BY-SA 4.0
2022-04-20T00:57:00.493Z
@JeopardyTempest Looks like I may have misunderstood sources, apologies. I've deleted the content on circulation.
G_B
CC BY-SA 4.0
2022-04-20T03:25:11.253Z
Sounds good, no worries, I withdrew my comments as they weren't pertinent anymore.  Will just leave a summary for future visitors who may also get confused (I've certainly had to think through things carefully many times): circulation cells in the atmosphere (the Hadley/Polar, and even the Ferrel via eddies) transports heat (and moisture and momentum) from the tropics towards the poles, so it as a whole aids in warmup not opposes it :-)
JeopardyTempest
CC BY-SA 4.0
2022-04-18T02:18:59.433Z
2022-04-20T00:55:59.333Z
2022-04-20T00:55:59.333Z
G_B
<p>As the Earth's axis is inclined, during summer in the northern hemisphere places in the north are exposed to the Sun's rays for longer, so days are longer during summer (say in June - Aug). Yet, countries like the UK have a lower summer temperature than countries like India, particularly given that the UK is to the north of India and has longer days in summers). I was just wondering about this. Feel free to share your insights.</p>

<meteorology><climate><earth-rotation><sun>
In the northern hemisphere summer, why are places in the north cooler than those in the south?
Leo
# In the northern hemisphere summer, why are places in the north cooler than those in the south?

(Asked by: username_0 on 2022-04-17)

As the Earth's axis is inclined, during summer in the northern hemisphere places in the north are exposed to the Sun's rays for longer, so days are longer during summer (say in June - Aug). Yet, countries like the UK have a lower summer temperature than countries like India, particularly given that the UK is to the north of India and has longer days in summers). I was just wondering about this. Feel free to share your insights.

**Tags:** meteorology, climate, earth-rotation, sun


---

## 2 answers

### Answer by username_1 on 2022-04-17. Score: 32

The image below (apparently from "physicalgeography.net" is somewhat instructive:

Notice that even in the middle of summer, India (at about 30 °N) still gets slightly more sun than the Britain (at 60 °N). That's because although the days are longer in Britain, the sun is lower in the sky and so its heat is spread out over a wider area.

But the North Pole gets even more sun than either Britain or India in June, and the equator gets substantially less. So there is something to explain. The reason is thermal inertia.

[![Graph of insolation per month at different latitudes](https://i.sstatic.net/9CSGe.png)](https://i.sstatic.net/9CSGe.png)

This graph shows insolation averaged over 24 hours at four different Latitudes. This shows the theoretical insolation. The model used to calculate these curves includes the effects of Earth's elliptical orbit, but do not take account of any atmospheric effects, such as the energy absorbed by the atmosphere, nor any weather effects such as clouds. It shows that a perfectly black disc with an area of 1 m² placed just above the atmosphere and oriented horizontal to the Earth surface would receive an average of about 515 Joules per second at the North Pole on June 21st and an average of about 380 Joules per second at the Equator. The main reason for the Equator value being so low is that it is night time for about 12 hours at the equator.

Imagine pushing a heavy ball. It can take some time for it to begin to move quickly because it has inertia. Similarly, it takes time for the ground and water to heat up when the sun shines upon them. India gets much more sun in winter, and so the ground and water remain warm. When summer comes, it heats up further and ends up much hotter than Britain. In Britain there is very little sun in winter, and the ground and water cool down (and freeze). Then, even when the sun comes in summer, it takes time to warm up. By the time the ground and water have warmed up, the sun is already starting to weaken. And so the temperature never rises as much as it can in India.

There are lots of details and local effects (the gulf stream in Britain, and the monsoon in India are significant) but the basic reason that India is hotter *in summer* is that it gets more sun *in winter*!

[Pidwirny, M. (2006). "Earth-Sun Relationships and Insolation". Fundamentals of Physical Geography, 2nd Edition.](http://www.physicalgeography.net/fundamentals/6i.html)

> **Comments:**
> **username_2**: Also, Earth goes through its aphelion in early July.  
> **username_3**: This "inertia" is called seasonal lag and is explained here: https://earthscience.stackexchange.com/a/4512/18081  
> **username_4**: @username_2 I don't think I understand how the Earth being furthest from the Sun in July makes a difference. The eccentricity of the Earth's orbit is very low. Also we could equivalently ask about the situation with Patagonia and southern Brazil. Would Earth being at perihelion around January then account for this difference?  
> **username_2**: @username_4 It has a _small_ effect. It's definitely not the major driver. But it explains,  for example, the equatorial dip in June-July being bigger than the December-January one.  
> **username_5**: I double-checked the values in diagram: the shown insolation is for [extraterrestrial irradiance](https://en.wikipedia.org/wiki/Solar_irradiance). Basically, the amount of solar energy you'd get on an horizontal surface, just above the atmosphere. That's why the curves are smooth (weather isn't taken into account) and have high values compared to what's available on the surface.  
> **username_1**: I agree.  These are extra terrestrial values.  But this particular spherical cow will do fine for illustrating the point:  *India is hotter in summer because it gets more sun in winter!*  
> **username_6**: But this spherical cow doesn't take the atmosphere into account. At higher latitudes, the sun is lower in the sky, and therefore the light goes through more of the atmosphere, more light (and thus heat) gets scattered and less of it reaches the ground.  
> **username_1**: Which doesn't change the quality of my answer: which isn't based on particular values of insolation but on the effect of thermal inertia.  
> **username_5**: Yes, your point about thermal inertia still stands, even if the shown diagram doesn't take weather into account. UK vs India isn't the best example, though (I known it was picked by OP): New Delhi gets more irradiance than London every month of the year. Another way to show thermal inertia is to compare monthly irradiance vs temperature. In London, October gets less irradiance than March, but is 5°C warmer, May gets more irradiance than August, but is 5°C colder.  
> **username_5**: @username_4: "The eccentricity of the Earth's orbit is very low.". Well, it's 0.0167, which doesn't seem like much. But it means the that the longest radius is ~3.4% longer than the shortest radius. And according to the inverse square law, the irradiance at perihelion is ~6.9% higher than at aphelion. 6.9% of [175PW](https://bionumbers.hms.harvard.edu/bionumber.aspx?id=100943&ver=3) is nothing to sneeze at.  
> **username_7**: @username_5 The user asked about NH pole vs equator. Sure the NH poles would be *very slightly* slower to recover against the tropics in summer vs SH because the magnitude of the solar difference is that little bit less... except NH has much more ice turning to open water and land, making that 6.9% a rather minuscule factor in the entire picture, and the NH summer high lats quicker to recover, yes? But bringing up aphelion for a question on why polar temps are colder in summer seems sort of like alluding to the surrounding grass as the reason your car slowed down when you hit a wall...  
> **username_7**: Decrease each of those latitude curves on username_1' figure by 7%... doesn't help answer OP's question.  Sure it explains some things in other areas as username_2 notes, but it doesn't really seem to go towards answering the phenomena Leo asked about to any notable degree :)  
> **username_5**: @username_7: Sorry, I don't get your point. I was simply answering username_4's comment, who noted that "The eccentricity of the Earth's orbit is very low".  
> **username_7**: Low in terms of magnitude regarding how it contributes to this question at least.  Perhaps we should nix the whole discussion about aphelion, as it honestly doesn't mean anything to the question at hand.  
> **username_7**: @username_6 On your thought, I always thought the atmospheric angle to be overrated and of the same order to the areal ground spread already included.  But some scalene triangle calculations suggests at 60N, it does spend nearly double the distance in the atmosphere, increasing to almost 5 times as far by 80°, and 11 times as far by the Pole (using 100 km deep atmosphere... #s drop by ~25% for 50 km atmosphere depth).  So I was wrong to fully dismiss that.  
> **username_7**: Though it still not have as much influence as you'd think... only 23% of solar radiation is removed vs TOA by the atmosphere on average via a Trenberth Diagram).  Digging around personal weather stations, it looks like reasonable stations had fairly similar radiation between [Alaska](https://www.wunderground.com/dashboard/pws/KAKNORTH74/graph/2021-06-22/2021-06-22/daily) and [Mexico](https://www.wunderground.com/dashboard/pws/ILLERA3/graph/2021-06-25/2021-06-25/daily) last June, with a few hundred W/m^2 * hrs in the early/late day mostly making up for the shortage at peak time.  
> **username_7**: But then the poster only asked why polar locations are colder.  Highs gets into the mid 20s C (mid 70s F) regularly in both Alaska and Siberia in the summer.  So they aren't a ton cooler, just a bit... which should be explained by a mix of username_1' answer and yours.  And other cooler locales, like much of the UK, are better explained by local weather/cloudcover/temperature advection/elevation and such, a mix of the thermal inertia seas, cloudcover's big albedo, and such.  So hopefully in the end, we've reached something reasonably substantive.  
> **username_5**: @username_7: The atmospheric angle you're talking about is called [*Air mass*](https://en.wikipedia.org/wiki/Air_mass_(solar_energy)).  
> **username_8**: @username_7 The angle of the sun makes a difference by itself.  The amount of 'rays' per unit area are less in the north.  The [tropic of cancer](https://en.wikipedia.org/wiki/Tropic_of_Cancer) is only at 23.5 degrees.  Anything farther north than that never has the sun directly overhead.  
> **username_8**: "basic reason that India is hotter in summer is that it gets more sun in winter!"  I think this overstates things a bit.  Based on the chart you show, The 60 line never goes above the 30 line i.e. there are no periods when Britain gets more sun than India.  No inertia needed.  And for the 90 line, it only goes above the 30 for 2 months-ish.  
> **username_9**: Can you clarify: does the figure show the average power over a 24-hour period?  It can't be local noon, because then it would be much higher at the equator than at the pole.  As for thermal inertia: don't underestimate the effect of the most powerful greenhouse gas, H₂O.  The tropical atmosphere has _a lot_ more of it than at high latitudes, which is one of the reasons why temperatures drop more in a sunny Arctic night than in a dark tropical night.  We need to consider incoming and outgoing radiation. Thermal inertia is a factor, but I'm not sure if it's the biggest reason.  
> **username_9**: We could use a (toy) climate model to calculate this.  Suppose that, magically, the Earth stops revolving around the Sun in June (but it still turns on its axis, so we still have day and night).  Fast-forward 3–6 months.  Is the Arctic now the hottest place on Earth, or are the tropics still hotter?  My gut feeling is that the tropics would still be hotter, but I'm not sure if it's true.  
> **username_8**: @username_9 I wonder if the relative areas help explain things.  For example, the area between 60° and 90° is much smaller than the area between 0° and 30°.  
> **username_5**: @username_9 yes, the diagram shows daily averages of extraterrestrial irradiances on horizontal surfaces. Instantaneous values would go above 1400W/m**2, but also to 0 half of the time.  
> **username_10**: @username_5 You called that diagram "extraterrestrial radiation." It is typically called "Top Of the Atmosphere" (TOA) radiation. Air mass, to which you alluded, exaggerates the TOA effect.  
> **username_5**: @username_10: I guess it depends on the field. *Extraterrestrial radiation* is a well-known term in solar energy, e.g. in Duffie Beckman "Solar Engineering of Thermal Processes", which has apparently been cited 20000 times according to google scholar. I don't know what you mean with "TOA effect". I'd be interested to know how it's linked to the air mass coefficient.  

---

### Answer by username_11 on 2022-04-18. Score: 12

Hours of sunlight are not the only factor that determines insolation (solar energy at the surface).

Thought experiment: spread a bed sheet on the floor, switch the lights off, and shine a flashlight directly down on that bed sheet from about one foot above it. You will get a small, fairly bright spot of light on the sheet.

Now tilt the flashlight, and shine it across it at a flat angle - say, 45 or 60 degrees - still keeping it about one foot away from the spot it's illuminating. As you flatten the angle, that spot elongates to cover a larger and larger area. But the amount of light coming out of the flashlight is still the same, spread over a larger area, which means lower intensity on the sheet. The same amount of light that was previously hitting a 100 cm2 spot might now be spread across 500 cm2.

This is part of what's happening at the high latitudes. During the summer months they are getting many hours of sunlight, but they're not getting a lot of energy per square metre compared to the tropics. In early April, the North Pole is getting sunlight 24 hours a day, but much *less* sunlight (in terms of energy/m2 etc.) than the equator gets in 12.)

> **Comments:**
> **username_11**: @username_7 Looks like I may have misunderstood sources, apologies. I've deleted the content on circulation.  
> **username_7**: Sounds good, no worries, I withdrew my comments as they weren't pertinent anymore.  Will just leave a summary for future visitors who may also get confused (I've certainly had to think through things carefully many times): circulation cells in the atmosphere (the Hadley/Polar, and even the Ferrel via eddies) transports heat (and moisture and momentum) from the tropics towards the poles, so it as a whole aids in warmup not opposes it :-)  

---

