<p>I get 40.4%</p>
<p>With a workflow using a tiny bit of Python.</p>
<ol start="0">
<li><p>After <a href="https://earthscience.stackexchange.com/questions/6515/in-the-northern-hemisphere-only-what-percentage-of-the-surface-is-land/15139#comment49016_15139">Polygorial‘s comment</a> I am adding (<strong>Updated on Feb 17, 2021</strong>) point zero to state more explicitly that this method requires a map like the one I used (Gall-Peters projection) with equal area projection, as regions of same area on the Earth’s surface will have the same area on the map, and therefore same number of pixels.</p>
</li>
<li><p>Invert and import B/W <a href="https://mycarta.files.wordpress.com/2018/09/peters_projection_black_north.png" rel="nofollow noreferrer">image</a> of equal area projection for the Northern hemisphere (land = white pixels). Source of original image (full globe): <a href="https://commons.wikimedia.org/wiki/File:Peters_projection,_black.png" rel="nofollow noreferrer">Wikimedia Commons</a>.</p>
</li>
<li><p>Store as Numpy array.</p>
</li>
<li><p>Calculate total number of pixels in image array (black + white).</p>
</li>
<li><p>Calculate total number of white pixels (1s) by summing the entire array (black pixels (0s) will amount to zero).</p>
</li>
<li><p>Calculate percentage of white pixels.</p>
</li>
</ol>
<p><a href="https://i.sstatic.net/2ivd9.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/2ivd9.png" alt="enter image description here" /></a></p>
<p><strong>UPDATE September 20, 2018</strong></p>
<p>As suggested by @JeopardyTempest in a comment, as a validation test I run the script for the full image with both hemispheres, and got the expected 30%</p>
<p><a href="https://i.sstatic.net/KtjF5.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/KtjF5.png" alt="enter image description here" /></a></p>

CC BY-SA 4.0
2018-09-20T17:13:15.017Z
Love your answer, shows a simpler/ingenious way to solve it, and explains your work process, so very useful.  It's of course a bit of a rough estimate depending upon the pixel resolution of the image... but for many purposes, that's plenty fine. 
 Stack Exchange can always use more thoughtful answers like these.  Thanks!
JeopardyTempest
CC BY-SA 4.0
2018-09-20T20:20:36.757Z
(For good measure, happen to be easy to get the Southern Hemisphere number, since it sort of naturally goes with the question?  [Plus serves as a further check in how close it is in methodology given the full-Earth values are pretty well publicized])
JeopardyTempest
CC BY-SA 4.0
2018-09-20T22:34:57.563Z
Thanks for your comment. Yes, the resolution of the image may limit the accuracy. I was hoping to get high resolution data like the Global Land One-km Base Elevation from the US National Geophysical Data Center (https://www.ngdc.noaa.gov/mgg/topo/gltiles.html), but it would have meant merging 8 huge arrays, threshold work, and then reproject. As you imply probably beyond the scope of a Stack Exchange answer. Also we might want to subtract the estimated rivers and streams coverage in @farrenthorpe 's answer.
MyCarta
CC BY-SA 4.0
2018-09-20T23:09:16.617Z
Always a fan of keep it simple, unless it's something really asking for intense precision :-)
JeopardyTempest
CC BY-SA 4.0
2018-09-21T03:30:06.880Z
I run the code using the full globe and got the expected 30% land coverage. Updated answer with the details. Thanks for suggesting it.
MyCarta
CC BY-SA 4.0
2020-02-04T01:32:20.220Z
This is a great solution, though I wonder how much error results from 1) lack of small features, and 2) plot line width for features in the image.  It would also be great to know what the definition of "land" is for this scenario, in regards to seas on continental shelves or ice shelves on oceanic continent.
f.thorpe
CC BY-SA 4.0
2020-02-04T21:52:24.773Z
all good points @farrenthorpe ! I was just happy to suggest an approach, but agreed, it should be tried on highest resolution images one can find, so as to accurately account for some coastline complexity, at least major rivers and lakes, etcetera
MyCarta
CC BY-SA 4.0
2021-02-17T04:06:24.210Z
@Polygorial. Good point! As a prerequisite for this approach I used a map drawn with Gall–Peters projection, which preserves relationship between areas. I will update my answer so it is stated clearly.
MyCarta
CC BY-SA 4.0
2018-09-19T18:17:58.367Z
2022-06-02T04:06:50.053Z
2022-06-02T04:06:50.053Z
MyCarta
<p>The <a href="https://en.wikipedia.org/wiki/Northern_Hemisphere" rel="nofollow noreferrer">Northern Hemisphere</a> is 40% land and 60% water. The Southern Hemisphere is 20% land and 80% water.</p>

CC BY-SA 3.0
2016-03-23T23:22:05.013Z
Your answer would benefit from citations. Also, it does not make sense to say that the Southern Hemisphere is 80% land and 20% water and call it the water hemisphere.
Isopycnal Oscillation
CC BY-SA 3.0
2017-01-10T15:42:53.567Z
Fixed the typos so the info on southern hemisphere is correct now.
f.thorpe
CC BY-SA 3.0
2016-03-23T22:56:42.887Z
2017-07-04T10:48:38.090Z
2017-07-04T10:48:38.090Z
Dr.Ravikant Pagnis.
<p>From <a href="http://www.physicalgeography.net/fundamentals/8o.html" rel="noreferrer">http://www.physicalgeography.net/fundamentals/8o.html</a> and <a href="http://www.eoearth.org/view/article/154984/" rel="noreferrer">http://www.eoearth.org/view/article/154984/</a></p>

<blockquote>
  <p>The spatial distribution of ocean regions and continents is unevenly arranged across the Earth's surface. In the Northern Hemisphere, the ratio of land to ocean is about 1 to 1.5. The ratio of land to ocean in the Southern Hemisphere is 1 to 4. This greater abundance of ocean surface has some fascinating effects on the environment of the southern half of our planet. For example, climate of Southern Hemisphere locations is often more moderate when compared to similar places in the Northern Hemisphere. This fact is primarily due to the presence of large amounts of heat energy stored in the oceans.</p>
</blockquote>

<p>This equates to a measurement of ~40% land in the northern hemisphere.  This agrees with the northern hemisphere azimuthal equal-area map image below.</p>

<p><a href="https://i.sstatic.net/gBOwC.png" rel="noreferrer"><img src="https://i.sstatic.net/gBOwC.png" alt="enter image description here"></a></p>

<p>The surface area of the Earth covered by lakes and rivers is a fraction of a percent, so their classification does not really change the answer.  However, you would get a slightly different answer if you consider land to be any continental crust (including seas not on ocean crust).  If you define a year and a definition of "land" that you are satisfied with, an exact calculation could be made with GIS software.</p>

<p>From <a href="https://www.fba.org.uk/journals/index.php/IW/article/viewFile/502/327" rel="noreferrer">https://www.fba.org.uk/journals/index.php/IW/article/viewFile/502/327</a></p>

<blockquote>
  <p>Rivers and streams are likely to cover 0.30–0.56% of the land surface [of Earth]</p>
</blockquote>

CC BY-SA 3.0
2015-09-10T11:58:06.657Z
So close to a quantitative answer! I hope someone can follow up on your last sentence.
Matt Hall
CC BY-SA 3.0
2015-09-10T19:53:57.370Z
Are you sure rivers and lakes make up only a tiny fraction? Rivers in particular can be very long and can branch all over the place. All those gullies might add up.
DrZ214
CC BY-SA 3.0
2015-09-11T20:39:33.117Z
I've added some more info to address this.
f.thorpe
CC BY-SA 3.0
2015-09-09T22:44:52.687Z
2015-09-11T20:40:59.697Z
2015-09-11T20:40:59.697Z
f.thorpe
<p>Across the whole Earth, about 70% of the surface is water and 30% is land.</p>

<p>What I want, though, is to restrict the scope to the <strong>northern hemisphere (NH) only.</strong> What percentage of NH surface is land?</p>

<p>It would also be good to clarify exactly how we define "land". If I'm not mistaken, the 70/30 split of water/land actually places inland rivers and lakes as land area.</p>

<p>Please also cite a source for this. The only google result I found with an answer was yahoo questions.</p>

CC BY-SA 3.0
2015-09-10T11:57:33.850Z
Good question! The best answer will give you a quantitative estimate, and show you how this was done in a GIS or programming language. I hope someone can give you this.
Matt Hall
<geography><land-surface>
In the northern hemisphere only, what percentage of the surface is land?
DrZ214
# In the northern hemisphere only, what percentage of the surface is land?

(Asked by: username_0 on 2015-09-09)

Across the whole Earth, about 70% of the surface is water and 30% is land.

What I want, though, is to restrict the scope to the **northern hemisphere (NH) only.** What percentage of NH surface is land?

It would also be good to clarify exactly how we define "land". If I'm not mistaken, the 70/30 split of water/land actually places inland rivers and lakes as land area.

Please also cite a source for this. The only google result I found with an answer was yahoo questions.

**Tags:** geography, land-surface

> **Comments:**
> **username_1**: Good question! The best answer will give you a quantitative estimate, and show you how this was done in a GIS or programming language. I hope someone can give you this.  

---

## 3 answers

### Answer by username_4 on 2015-09-09. Score: 13 | Accepted answer

From <http://www.physicalgeography.net/fundamentals/8o.html> and <http://www.eoearth.org/view/article/154984/>

> The spatial distribution of ocean regions and continents is unevenly arranged across the Earth's surface. In the Northern Hemisphere, the ratio of land to ocean is about 1 to 1.5. The ratio of land to ocean in the Southern Hemisphere is 1 to 4. This greater abundance of ocean surface has some fascinating effects on the environment of the southern half of our planet. For example, climate of Southern Hemisphere locations is often more moderate when compared to similar places in the Northern Hemisphere. This fact is primarily due to the presence of large amounts of heat energy stored in the oceans.

This equates to a measurement of ~40% land in the northern hemisphere. This agrees with the northern hemisphere azimuthal equal-area map image below.

[![enter image description here](https://i.sstatic.net/gBOwC.png)](https://i.sstatic.net/gBOwC.png)

The surface area of the Earth covered by lakes and rivers is a fraction of a percent, so their classification does not really change the answer. However, you would get a slightly different answer if you consider land to be any continental crust (including seas not on ocean crust). If you define a year and a definition of "land" that you are satisfied with, an exact calculation could be made with GIS software.

From <https://www.fba.org.uk/journals/index.php/IW/article/viewFile/502/327>

> Rivers and streams are likely to cover 0.30–0.56% of the land surface [of Earth]

> **Comments:**
> **username_1**: So close to a quantitative answer! I hope someone can follow up on your last sentence.  
> **username_0**: Are you sure rivers and lakes make up only a tiny fraction? Rivers in particular can be very long and can branch all over the place. All those gullies might add up.  
> **username_4**: I've added some more info to address this.  

---

### Answer by username_2 on 2018-09-19. Score: 16

I get 40.4%

With a workflow using a tiny bit of Python.

0. After [Polygorial‘s comment](https://earthscience.stackexchange.com/questions/6515/in-the-northern-hemisphere-only-what-percentage-of-the-surface-is-land/15139#comment49016_15139) I am adding (**Updated on Feb 17, 2021**) point zero to state more explicitly that this method requires a map like the one I used (Gall-Peters projection) with equal area projection, as regions of same area on the Earth’s surface will have the same area on the map, and therefore same number of pixels.
1. Invert and import B/W [image](https://username_2.files.wordpress.com/2018/09/peters_projection_black_north.png) of equal area projection for the Northern hemisphere (land = white pixels). Source of original image (full globe): [Wikimedia Commons](https://commons.wikimedia.org/wiki/File:Peters_projection,_black.png).
2. Store as Numpy array.
3. Calculate total number of pixels in image array (black + white).
4. Calculate total number of white pixels (1s) by summing the entire array (black pixels (0s) will amount to zero).
5. Calculate percentage of white pixels.

[![enter image description here](https://i.sstatic.net/2ivd9.png)](https://i.sstatic.net/2ivd9.png)

**UPDATE September 20, 2018**

As suggested by @username_3 in a comment, as a validation test I run the script for the full image with both hemispheres, and got the expected 30%

[![enter image description here](https://i.sstatic.net/KtjF5.png)](https://i.sstatic.net/KtjF5.png)

> **Comments:**
> **username_3**: Love your answer, shows a simpler/ingenious way to solve it, and explains your work process, so very useful.  It's of course a bit of a rough estimate depending upon the pixel resolution of the image... but for many purposes, that's plenty fine.   Stack Exchange can always use more thoughtful answers like these.  Thanks!  
> **username_3**: (For good measure, happen to be easy to get the Southern Hemisphere number, since it sort of naturally goes with the question?  [Plus serves as a further check in how close it is in methodology given the full-Earth values are pretty well publicized])  
> **username_2**: Thanks for your comment. Yes, the resolution of the image may limit the accuracy. I was hoping to get high resolution data like the Global Land One-km Base Elevation from the US National Geophysical Data Center (https://www.ngdc.noaa.gov/mgg/topo/gltiles.html), but it would have meant merging 8 huge arrays, threshold work, and then reproject. As you imply probably beyond the scope of a Stack Exchange answer. Also we might want to subtract the estimated rivers and streams coverage in @farrenthorpe 's answer.  
> **username_3**: Always a fan of keep it simple, unless it's something really asking for intense precision :-)  
> **username_2**: I run the code using the full globe and got the expected 30% land coverage. Updated answer with the details. Thanks for suggesting it.  
> **username_4**: This is a great solution, though I wonder how much error results from 1) lack of small features, and 2) plot line width for features in the image.  It would also be great to know what the definition of "land" is for this scenario, in regards to seas on continental shelves or ice shelves on oceanic continent.  
> **username_2**: all good points @farrenthorpe ! I was just happy to suggest an approach, but agreed, it should be tried on highest resolution images one can find, so as to accurately account for some coastline complexity, at least major rivers and lakes, etcetera  
> **username_2**: @Polygorial. Good point! As a prerequisite for this approach I used a map drawn with Gall–Peters projection, which preserves relationship between areas. I will update my answer so it is stated clearly.  

---

### Answer by username_5 on 2016-03-23. Score: 2

The [Northern Hemisphere](https://en.wikipedia.org/wiki/Northern_Hemisphere) is 40% land and 60% water. The Southern Hemisphere is 20% land and 80% water.

> **Comments:**
> **username_6**: Your answer would benefit from citations. Also, it does not make sense to say that the Southern Hemisphere is 80% land and 20% water and call it the water hemisphere.  
> **username_4**: Fixed the typos so the info on southern hemisphere is correct now.  

---

